Home
About Us
Services and Tools
Membership
Telemedicine
  • Glossary of Terms
  • Policy and Legislation
  • International
     Activities
  • Telemedicine
     Documents
  • Key Organizations
e-Health Forum
Schedule an Event
News and Archives
Submit a Comment
Contact Us

Glossary of Terms

The following is a comprehensive summary of acronyms, terms and definitions often utilized in telemedicine and telehealth. If you can’t find it here, let us know by submitting a comment.

A - B - C - D - E - F - G - H - I - J - K - L - M - N - O - P - Q - R - S - T - U - V - W

Access Control
Protection against unauthorized access to a computer network. A less restrictive tool than a firewall. Using access controls, a HIN will check its access control list to see if a computer requesting service from the outside world is permitted to use that service. See also Encryption.
ACR-NEMA
American College of Radiology and the National Equipment Manufacturers Association. They have jointly developed standards for teleradiology practice. For CT, MRI, ultrasound, nuclear medicine, digital fluoroscopy: images must be scanned at 500 pixel x 500 line resolution by 8 bit depth (256 gray scale) or better; for diagnostic X-rays: 2,000 x 2,000 ("2K by 2K") by 12 bit depth (4,096 gray scale).
ADSL
Asymmetric Digital Subscriber Line. DSL refers to a pair of modems connected by a copper line that yields asymmetrical transmission of data. Currently under trial in several metropolitan areas. Uses existing copper phone lines. With proper retooling by phone companies, these can supply 6 Mbps downstream delivery of data.
Algorithm
A mathematical coding scheme for compressing digitized broadband video or audio signals so that the signals can be transmitted over a lower (and less expensive) bandwidth. Standards-based algorithms are those which enable communication with standards-based systems from disparate manufacturers. Proprietary algorithms are unique to individual manufacturers and enable communications only between equipment from that manufacturer. Current practice strongly encourages standards-based systems.
Amplifier
Electronic devices that strengthen a signal as it passes along a communications channel.
Analog Signal
A wave shaped electrical symbol, which continuously changes with respect to size and shape depending on the information source. Differences in volume, voice and pitch are a result of signal variations.
Analog
An electrical signal that varies constantly in voltage, unlike a digital signal which varies between two constant values (typically denoted as 0 and 1). The value of the analog signal varies all the time during transmission, whereas a digital signal changes only between two set values without intermediate variations. Information (electronic or otherwise) that is created and transmitted as a continuous stream. Wave forms (e.g., on oscilloscopes) are analog. Compare this to digital information generated by computers. Modems are used to convert digital computer data to analog form for sending over standard POTS lines.
Annotation
Simultaneous shared annotation of captured (or, less commonly, live video) images allows conference participants to clearly point out the areas in question on an image, and may provide significant instructional value.
ANSI
American National Standards Institute
Applications as a video input source. Indicates whether a separate PC application (e.g., PowerPoint, MS Word) can be run on the system during a video conference and sent as the video picture to the far end.
Architecture
The selection, design, and interconnection of the hardware of a computer system.
Archiving
A method of transferring information created during operations into a more permanent form. Systems vary from manual backups, through periodic transfer to audio cassettes, to real-tune storage onto WORM (Write Once Read Many) disks.
DARPA
Defense Advanced Research Projects Agency. Governed under the Department of Defense, this agency is involved with the use of telemedicine, its development, and continuing research. The ARPA is responsible for establishing the network, which later became known as the Internet.
ARPANET
Advanced Research Projects Agency Network. The original developer of the Internet.
Asynchronous
Refers to systems of communication where there is a lapse in time from when a message is sent and when it is received.
ATLS.
Advanced Trauma Life Support. The basic skills for resuscitation employed by emergency care workers.
ATM.
Asynchronous Transfer Mode. A way of transmission where a start signal precedes individual characters and one or more stop signals follow it. Due to this start/stop system, delays may occur between characters. Also denotes the complete system of protocols and equipment associated with cell based communications network. These networks have the ability to transmit voice, data, and video traffic simultaneously using a statistical multiplexing scheme. This type of switching is expected to bridge the gap between packet and circuit switching. ATM uses packets referred to as cells that are designed to switch cells so rapidly that there is no perceptible delay.
Audio only conference add-ins.
The ability to add another site into a video conference via an audio connection only. This feature uses a regular phone line connected to the codec to conference in someone who is not near a video site but needs to be part of the conversation.
Audio-teleconferencing
Two way communications between multiple people at various locations.
Authentication
A method of verifying the identity of the person sending or receiving information by use of passwords, keys and other automated identifiers.
Automated Data Collection
The direct transmission of physiological information from monitoring devices to either a bedside display system or a computer-based patient record.
B-CDMA
Broadband Code Division Multiple Access. A form of wireless technology where digital information is sent over communication networks.
Backbone Network
A high-speed, high capacity transmission facility created to interconnect lower speed distribution channels from smaller branches of the computer or telecommunication network.
Backbone
The high-traffic density connectivity portion of any communications network. In packet-switched networks, a primary forward-direction path traced sequentially through two or more major relay or switching stations. Note: In packet-switched networks, a backbone consists primarily of switches and interswitch trunks.
Bandwidth
The capacity of an electronic transmission medium to transmit data per unit of time. The higher the bandwidth, the more data can be transmitted. Typically measured in kilobits or megabits per second, (Mbps). Standard telephones are low bandwidth devices (maximum bandwidth = 33.6 Kbps). Cable television uses high bandwidth (up to 140 Mbps).
BRI
Basic Rate Interface. An ITU-T Integrated Services Digital Network (ISDN) multipurpose user interface standard that denotes the capability of simultaneous voice and data services provided over two clear 64 kilobits/second (Kbps) channels and one clear 16 kbps channel (2B+D) access arrangement to each user location.
Baud
A unit of digital transmission that indicates the speed of information flow. The rate indicates the number of events able to be processed in one second and is expressed as bits per second (bps). The baud rate is the standard unit of measure for data transmission capability. Typical rates are 1200, 2400, 9600, and 14,400 baud.
BBS
Bulletin Board Service. A computer service that allows users in an isolated location to access a central host computer through a computer in order to read and send electronic messages.
Beam splitter
For tele-oto/ophthalmoscopes. Allows direct visualization through the device into the eye or ear by the clinician, while still routing a portion of the image to the video camera. This is usually preferred by the clinician who is accustomed to looking directly through the device rather than at a video monitor.
Bit depth
The number of colors or levels of gray scale a scanner or monitor supports. An 8-bit scanner can differentiate between 256 (28) levels of gray. A 12-bit scanner supports 212 = 4,096 levels of gray.
Bit
Binary digit. The basic 0-1 unit of information used by computers for information entry, storage, and transmission. Data rates in telecommunications are often referred to in bits (abbreviated “b”) per second. See Mbps, Kbps, Byte, Bandwidth. This is the smallest piece of digital information that a computer handles. This system limits this information to an 'on' or 'off', represented by a 0 or 1. All characters, numbers and symbols are translated into electronic strings of bits.
BOCs
Bell Operating Companies. Grouped under the seven Regional BOCs.
Bps
Bits per second. The number of binary digits transmitted per second. This transmission particularly applies to a modem. Common modems transmit at either 14.4 Kbps (14,400 bps) or 28.8 Kbps (28,000 bps), but newer modems are capable of 33.6 Kbps and 56Kbps, and in some cases, transmission speed may extend to 128 Kbps.
Bridge
Device connecting two separate networks at the OSI Data Link Layer (Level Two Media Access Control Layer). Once bridging is accomplished, the bridge makes interconnected LANs look like a single LAN, passing data between the networks and filtering local traffic. There are two key classifications of bridge: those supporting Spanning Tree and, for Token Ring networks, those supporting Source Routing. Bridges connect networks using dissimilar protocols and do not interpret the data they carry. They control network traffic and security, filtering where necessary to boost network, performance and contain sensitive data to particular LAN areas. See also MCU.
Brightness
The perception of luminance by the human eye. Although many use luminance and brightness interchangeably, they are not exact synonyms.
Broadband
A general term for a telecommunications medium of sufficient capacity to transmit high quality voice, data, and video transmissions. Broadband has been defined in many ways; e.g., a Wide Area Network (WAN) providing bandwidth greater than 45 Megbits/sec (T3); voice, data, and/or video communications at rates greater than 1.544 Megabits/sec (T-1), but has been Federally defined as data transmission each way, of 200 kilobits/second or more. Television, microwave, and satellite transmission are all example of this medium.
Browser
Also known as a Web browser. Any program that permits access and uses the World Wide Web.
Bundle(d)
A group of optical fibers or electrical conductors, such as wires and coaxial cables, usually in a single jacket. Note: Multiple bundles of optical fibers or electrical conductors may be placed in the same cable.
Bursty data
Short, intense transmissions of grouped, related information. Sometimes called “boluses of data” by medical clinicians.
Byte
A string or cluster of eight bits to represent a character. Each data character, such as the letter A, is composed of 8 bits, called a “byte” (abbreviated “B”). Units of storage are often referred to in terms of the number of bytes (e.g., a “100 MB hard drive”).
C-mount
See Universal C-mount
Cable Modem
In CATV systems, a bidirectional high-speed digital communications interface located on a subscriber's or user's premises and used, for example, for Internet access or other digital communications.
CATV
Cable television. A transmission system that distributes broadcast television signals and other services by means of a coaxial cable.
Cable
An assembly of one or more insulated conductors, or optical fibers, or a combination of both, within an enveloping jacket. Note 1: A cable is constructed so that the conductors or fibers may be used singly or in groups. Note 2: Certain types of communications cables, especially long submarine cables but also terrestrial cables, whether the communications media are metallic or optical fiber, may contain metallic conductors that supply power to repeaters (amplifiers).
CAD
Computer-aided Design.
Camera control
May be near end (local control of local pan/ tilt/ zoom/ iris/ focus) or far end (local control of p-t-z at the remote site). May be quite useful in consultations if the examiner wants to control the remote camera’s view without having to provide verbal directions to the assistant at the remote site.
CCD
Charge coupled device = “chip”. A 1-CCD (“1-chip” camera contains a single charge coupled device with specialized semiconductors. These contain photosensitive cells that generate voltage when struck by photons of light. One photosensitive cell equates to one pixel in the displayed image. The number of cells on a chip determines the number of pixels of resolution the camera can display. The larger the chip the greater the image resolution. Increased resolution is accomplished either by using larger chips or by using more of them. Single chip cameras do a good job. 2-CCD cameras use one chip for chrominance and one for luminance. Three chip cameras do an even better job because they have more total cells and because they use one chip each to capture red, green and blue light. Three chip cameras provide images with higher resolution and better color representation, and can cost 10 times as much as 1-CCD cameras. A 1-CCD camera can support 640 pixels x 480 lines and 24 bit color. A 3-CCD camera may cost $10,000 (for 1,524 x 1,012 x 36 bit) up to $30,000 (for 3,060 x 2,036 x 14 bit). CCD scanners for teleradiology are less expensive than laser scanners, and may not have the same ability to detect contrast. This may or may not affect their ability to transmit diagnostic quality images.
CCITT
Consultative Committee for International Telegraphy and Telephony. The forerunner of the ITU’s Telecommunications Standardization Sector (TSS). Currently, the International Telecommunications Union Consultative Committee for Telecommunications (ITU-T). An international agency responsible for developing standards for telecommunications, as well as FAX and video coder-decoder (CODEC) devices.
CD-ROM
Compact Disk, Read Only Memory. A device used for storing large amounts of information, the equivalent of about 220,000 pages of text.
CDC
Center for Disease Control and Prevention. United States organization.
CDS
Clinical Decision Support. Information regarding a patient, his or her health problems, and alternative tests/treatments used to aid a clinician in diagnosis and treatment. Also referred to as Clinical Decision Support Systems (CDSS).
CEN
European Technical Committee for Normalization. An international agency responsible for setting standards in health care informatics.
Channel
A radio frequency assignment designed depending on the frequency band being used and the geographic location of the sending/receiving sites.
CHIN
Community Health Information Network. A popular system of communication created for common use by health professionals, patients and the community. This system fuses hospital information systems (HIS) with medical databases, community health information, and on-line computer services.
Chip
See CCD. An integrated circuit.
Chrominance.
Hue and saturation (color) on a video monitor.
CIF
Common Intermediate Format. An international standard for video display formats developed by the TSS (see ITU-T). See FCIF, QCIF.
Ciné loop.
Also called “paging.” The rapid, repeating display of sequential images in movie fashion. This display method plays a limited number of frames, at a limited frame rate, but gives the impression of dynamic motion. Often used in telecardiology applications.
Circuit Switched Network.
Also may be called line switching and dial-up service, this network temporarily links multiple channels between multiple points that permits the user to exclusive use of an open channel to exchange information.
Clinical Information System.
Relating exclusively to the information regarding the care of a patient, rather than administrative data, this hospital-based information system is designed to collect and organize data.
Closed
Refers to a type of mailing list that allows only members of that mailing list to send messages to it. Distinctive from 'open' or 'moderated'.
CME
Continuing Medical Education.
CMHCs
Community Mental Health Centers.
Co-processor
A device within a computer to which specific processing operations are assigned, like mathematical computation or video display. This device accelerates processing speed significantly.
Coaxial Cable
A single or dual transmission wire covered by an insulating layer, a shielding layer, and an outer jacket. Because it contains a high bandwidth, this cable may be a broadband carrier with the ability to transmit data, voice, and video.
CODEC
COder/DECoder (also COmpression/DECompression) hardware and/or software used with interactive video systems that converts an analog signal to digital, then compresses it so that lower bandwidth telecommunications lines can be used. The signal is decompressed and converted back to analog output by a compatible CODEC at the receiving end. The compression method (algorithm) may be proprietary or (much preferred) standards-based.
COM port
Serial port for connecting a cable to an IBM PC-compatible computer, usually, but not exclusively for data communications. They are referred to by the operating system as COM1, COM2, COM3, etc.
Common Carrier
A telecommunications company, charging published and nondiscriminatory rates and regulated by the government, which offers communications relay services to the general public by means of shared circuits.
Communication Multiplexer.
An instrument that permits data from multiple, lower speed communication lines to share a single higher speed communication path.
Compatibility
Refers to the ability of two pieces of hardware (a personal computer and a printer, for example) to work together. Standards, published specifications of procedures, equipment interfaces, and data formats are essential to decreasing and possibly eventually extinguishing incompatibility.
Component video
Compared to composite video, keeps the chrominance and luminance parts of the video signal separate, yielding better image quality, higher lines of resolution, and better color. See also S-video.
Composite video
Color TV evolved from black/white systems that were developed more than 50 years ago. A separated red, green, and blue color broadcast used in RGB would have taken three times the bandwidth of existing black/white approaches. An ingenious solution to conserve bandwidth was to create a separate chrominance signal for color that could be overlaid onto the existing luminance signal, without increasing bandwidth. The result: composite video. Because of potential interference between the chrominance and luminance, composite video requires periodic adjustment to assure “true” color. Used with NTSC and PAL systems. See Component video, S-video.
Compressed Video
Video images that have been processed to reduce the amount of bandwidth adequate for capturing the necessary information so that the information can be sent over a telephone network.
Compression ratio
The amount that an image is “compressed” using mathematical algorithms to decrease the amount of data that needs to be stored or transmitted. The ratio of the number of bits in an original image to the number in a compressed version of that image. For example, a compression ratio of 3:1 would signify a compressed image with a third of the number of bits of the original image. An uncompressed NTSC (broadband, broadcast quality) signal transmits at about 90 Mbps; this can be compressed using a CODEC to 384 Kbps (more than 200:1 compression); the resulting image is adequate for most clinical applications. “Lossless compression” loses no data; generally data compressed more than three times (3:1) is considered “lossy.” This is true of the JPEG compression algorithm. Some compression algorithms (wavelets) support a higher compression ratio (10:1 or higher) before becoming lossy. See also MPEG.
CR
Computed Radiography. A system of creating digital radiographic images that utilizes a storage phosphor plate (instead of film) in a cassette. Once the plate is exposed, a laser beam scans it to produce the digital data which are then translated to an image.
Computer Conferencing
Communications within groups through computers, or the use of shared computer files, remote terminal equipment, and telecommunications channels for two-way communication.
CPR
Computer-based Patient Record. A compilation in electronic form of individual patient information that resides in a system designed to provide access to complete and accurate patient data, alerts, reminders, clinical decision support systems, links to medical knowledge, and other aids.
Conference Multiple public messages found on a system, usually specific to a particular topic and sometimes moderated by a conference host who leads the discussion. Also called "Folder," "SIG" (Special Interest Group), or "Echo." Very much like the newsgroups on the Internet.
Connectivity
The ability to send and receive information between two locations, devices, or business services.
CPRI.
Computer-based Patient Record Institute, Inc. An independent institute that develops and recommends standards for computerized patients records.
CPU.
Central Processing Unit. The device in a computer that executes directions in software programs and performs calculations and other operations.
Crawlers
The software used to index the World Wide Web. Also referred to as "robots" and "spiders."
CRT.
Cathode Ray Tube. The monitor or other means of displaying data in a computer system.
CSU/DSU
Channel Service Unit / Data Service Unit. A hardware device that is needed to terminate a high speed telecommunications connection. It is inserted between the telemedicine system (i.e., CODEC) and the communications line. It conditions and strengthens the signal, and supports the necessary link protocols, for transmission of data from LANs, video systems, and other applications over leased or switched communications lines (T1, fractional T1, leased or switched 56, ISDN). Some models allow the allocation and sharing of bandwidth with other traffic, such as digitized voice from a PBX, and act as a multiplexer.
Data Compression
Method to reduce sheer volume of data by more efficient encoding practices, thereby reducing image processing, transmission times, bandwidth requirements, and storage space requirements. Some compression techniques result in the loss of some information, which may or may not be clinically important.
Data Repository
The element of an information system that accepts, files, and stores data from various sources.
Data
Units of information that can be stored and analyzed.
DAX
Digital Exchange. A computerized digital cross connection that permits specific channels from high capacity lines to split out separately so that they may be directed elsewhere.
DBS
Direct Broadcast Satellite. A satellite designed with adequate power so that inexpensive earth stations, or downlinks, may by used for direct residential or business reception.
DDS
Digital Data System. A system for transmitting telephone traffic in digital format between major switching hubs. This system allows digital transmission of voice and data as a component of the analog telephone system (POTS).
Dedicated Line
A permanent telephone line reserved exclusively for one patient, accessible all hours of the day. These lines usually offer better quality than standard telephone lines, but may not significantly augment the performance of data communications. May also be known as 'leased,' or 'private' lines.
Dedicated T1.
A permanent telephone line reserved exclusively for one patient, accessible during all hours of the day. These lines usually offer better quality than standard telephone lines, but may not significantly augment the performance of data communications. May also be known as "leased," or "private" lines.
DDN
Defense Data Network. Used generally to refer to Milnet, Arpanet and the TCP/IP protocols those networks use. More specifically refers to Milnet and associated parts of the connected Internet that link military installations.
Dental HPSA
Dental Health Professional(s) Shortage Area. An area is so designated if the following three criteria are met: 1. The area is a rational area for the delivery of dental services. 2. One of the following conditions prevails in the area:(a) The area has a population to full-time-equivalent dentist ratio of at least 5,000:1, or(b) The area has a population to full-time-equivalent dentist ratio of less than 5,000:1 but greater than 4,000:1 and has unusually high needs for dental services or insufficient capacity of existing dental providers. 3. Dental professionals in contiguous areas are over-utilized, excessively distant, or inaccessible to the population of the area under consideration (See http://bhpr.hrsa.gov/shortage/hpsacritdental.htm).
DICOM
Digital Imaging and Communications in Medicine. A set of protocols describing how radiology images are identified and formatted that is vendor-independent and developed by the American College of Radiology and the National Electronic Manufacturers Association. The standard emphasizes point-to point connection of digital medical imaging devices. DICOM 3.0 is the current version.
Digital Camera
An image producing lens system made up of one or more light-sensitive integrated circuits, a myriad of light sensitive elements, and circuits for timing, nonlinear amplification, and encoding color. Captures images (still or motion) digitally and does not require analog-to-digital conversion before the image can be transmitted or stored in a computer. The analog-to-digital conversion process (which takes place in CODECs) usually causes some degradation of the image, and a time delay in transmission. Avoiding this step theoretically provides a better, faster image at the receiving end.
Digital Image
An image formed by independent pixels, each of which is characterized by a digitally represented luminance level. For example, a popular screen size for digital images is a 1024 by 1024 matrix of pixels x 8 bits, representing 256 luminance levels.
Digital Signal
An electrical signal in the form of discrete voltage pulses. These signals transmit audio, video, and data as bits, which are either on or off, differing from analog signals, which are continuously varying. Communications signals may be compressed using digital technology, allowing efficient and reliable transmission rotes.
DSL
Digital Subscriber Line. In Integrated Services Digital Networks (ISDN), equipment that provides full-duplex service on a single twisted metallic pair at a rate sufficient to support ISDN basic access and additional framing, timing recovery, and operational functions. Note: The physical termination of the DSL at the network end is the line termination; the physical termination at the customer end is the network termination.
DS
Digital telecommunications channels. These channels are capable of transmitting high volume voice, data or compressed video signals. DS1 and DS3 are also known as T1 and T3 carriers. Transmission rates are 64 Kbps for DS0, 1.544 Mbps for DS1, and 45 Mbps for DS3.
Digital
Information coded in discrete numerical values (bits). Digital data streams are less susceptible to interference than analog data streams. Also, because they are made up of zeros and ones (bits) than can be manipulated and integrated easily with other data streams (voice/video/data).
Digitize
The process by which analog, or continuous, information is transformed into digital, or discrete, information. Because most computers are only capable of processing digital information and visual information is inherently in analog format, this process is essential in computer imaging applications.
Digitizer
A device that converts an analog signal into a digital representation of the analog signal. A digitizer usually samples the analog signal at a constant sampling rate and encodes each sample into a numeric representation of the amplitude value of the sample.
DBS
Direct Broadcast Satellite. A satellite designed with sufficient power so that inexpensive earth stations, or downlinks, can be used for direct residential reception.
Direct Capture
A procedure by which image data are formed directly from the original source allowing a high quality image reproduction. In this process, images created from image files are identical to the original, regardless of the device used to capture them, such as a CT or an MRI. In direct video capture, the video signal is digitized from the display, which creates a higher quality image and is more efficient than acquisition through scanning.
Direct Digital Imaging
Involves the capture of digital images so that they can be electronically transmitted.
Dish
An antenna shaped like a parabola that is the essential component of a satellite earth station, or downlink.
Document camera
See Graphics stand.
Domain
The last two parts of an e-mail address or an URL signifying an organizations name on the Internet. For example, "aol.com" refers to America OnLine.
Downlink
The path from a satellite to the Earth stations that receive its signals.
Download
The process of transferring files or software from another computer to your computer.
Dpi
Dots per inch. The number of dots or pixels per inch used in film resolution. In conventional radiography resolution is given in line pairs per millimeter (lp/mm).
DS0, DS1, DS2
Digital telecommunications channels. These channels are capable of transmitting high volume voice, data or compressed video signals. DS1 and DS3 are also known as T1 and T3 carriers. Transmission rates are 64 Kbps for DS0, 1.544 Mbps for DS1, and 45 Mbps for DS3.
DS1 (T1)
A digital carrier capable of transmitting 1.544 Mbps of electronic information; the general term for a digital carrier available for high-value voice, data, or compressed video traffic.
DS3 (T3)
A carrier of 45 Mbps bandwidth. One DS3 channel can carry 28 DS1 channels.
DS3
A leased line (non-switched) running at 45 Mbps. Compare OC3, T1, ISDN.
DSU
Digital Service Unit. See CSU/DSU.
Duplex audio
Full duplex describes the ability of both ends of a conference to speak and be heard simultaneously (like a regular phone call). Half duplex audio supports only one site speaking at a time; other speakers will be cut off.
Duplex
A transmission system permitting data to be transmitted in both directions simultaneously.
Dynamic Range
The characteristic of a communications or imaging system to reproduce or transmit various brightness levels.
e-Health policy
A set of statements, directives, regulations, laws, and judicial interpretations that direct and manage the life cycle of e-health.
e-Health
‘e-Health’ was first introduced as a term that distinguished web-based telehealth activities from the use of videoconferencing. It is now gaining in popularity as an over-arching term for the use of information and communications technology in health care.
Earth Station
The ground equipment essential for receiving and/or transmitting satellite telecommunications signals.
Echo cancellation
Prevents a system from picking up the sound from its own speakers and transmitting it back to other conference sites. Highly desirable for acceptable audioconferencing.
EDI
Electronic Data Interchange. Refers to any transmission of information without paper or human intervention between two devices or application, using a standard data format.
E-mail
An electronic system of transmitting messages through a computer system. Data can be transmitting to anywhere in the world for the price of a local telephone call. An email address is typically made up of a part of your name (your account name), the 'at' sign (@), and your domain name.
Encryption
A mathematical transposition of a file or data stream so that it cannot be deciphered at the receiving end without the proper key. Encryption is a security feature that assures that only the parties who are supposed to be participating in a video conference or data transfer are able to do so. This has not been an essential feature for telemedicine systems, but with the growing concern about patient privacy in telemedicine networks it may become one. See Firewall.
Equal Access
The ability to choose between various long distance carriers. However, in more remote areas, some local exchange carriers are still serviced by only one long distance carrier.
Ethernet
A communications protocol that utilizes various types of cable at a rate of 10 Mbps to 100 Mbps LAN data link protocol.
FCIF
Full Common Intermediate Format (“Full sif”). A measure of video resolution. Considered by some a requirement of telemedicine video. See QCIF.
FDA 510K approval
Product has met the FDA’s approval criteria, or is similar to a product that has.
FDDI
Fiber Distributed Data Interface. A high-speed fiber optic network containing a state-of-the art bandwidth.
Fiber Optic Cable
Cable that is insulated, flexible and consists of a glass core that relies on light sources rather than electricity to transmit audio, video, and data signals. This system permits high capacity transmission at extreme speeds, sometimes billions of bits per second, with very low error rates.
Fiber optics
Hair-thin, flexible glass rods encased in cables that use light to transmit audio, video, and data signals.
Film Alternator
A device powered by a motor that displays multiple films for interpretation and moves them under the control of an operator. This device may be thought of as multiple banks moving view boxes.
Film Digitizer
A device that allows scanning of existing static images so that the images can be stored, manipulated, or transmitted in digital form.
Filmless Radiology
Use of devices that replace film by acquiring digital images and related patient information and transmit, store, retrieve, and display them electronically.
Firewall
A computer connected both to the Internet and the local HIN that prevents the passing of Internet traffic, in the form of IP packets, to the internal hospital network. Provides an added layer of protection against “hackers.” There are two kinds of firewalls: external, which protect all hospital systems form the outside world, and internal, which protect only selected systems. Firewall disadvantages: it restricts information transfer in both directions, and makes file transfer (ftp) and telnet (remote login) more difficult. See Access control, Encryption.
Firewall
Computer hardware and software designed to prevent unauthorized communications between an institution's computer network and external networks.
Footprint
The geographic range on the earth beneath a satellite that is in the scope to receive that satellites information.
FPS
Frames per second. See Frame rate
Fractional T1
A portion of the 1.544 Mbps (T1-aggregate) bit stream; the available fractions being determined by the type of multiplexer used to achieve the T1 aggregate bit stream.
Frame grabber
Captures, into a computer, the analog display output of cameras, VCRs, etc.
Frame rate
Frames per second (fps) displayed on a video monitor. A frame rate of 25-30 fps is consider “full motion” and is what most broadcast video operates at. A frame rate of 15 fps is noticeably “jerky.” Slower frame rates may be inadequate for gait and motion observations and analysis. See NTSC, PAL, SECAM.
Frame relay
A service that supports data rates in the range of 56 Kbps to 1.54 Mbps. The Frame Relay circuit often comes in different levels of committed information rates (CIR). A 1.54 Mbps Frame Relay circuit with a 768 Kbps CIR would indicate that you would never drop below 768 Kbps transmission capability, and could burst up to 1.54 Mbps. RBOCs can offer Frame Relay cheaper since they can oversubscribe these circuits to users and share the bandwidth.
Frame
Also known as "framed." A website with this characteristic is one that divides your Web browser's screen into smaller sections. Each area displays different data, usually to help the user navigate the website, or to display advertisements.
Freeze Frame
One way to transmit still images over regular telephone lines. A single image is transmitted every 8 to 30 seconds. This method may also be known as slow scan.
Frequency Response
Measured in cycles/second (Hz); a relative measure of audio quality. Generally the broader the response the better. To approximate a standard acoustic stethoscope, an electronic stethoscope should be able to send and receive sounds as low as 30 Hz (for low-pitched heart murmurs) and as high as 1000 Hz (for squeaks, wheezes and pops heard in lung sounds). Many electronic stethoscopes can have their frequency response optimized for either heart or lung sounds by flipping a switch.
Frequency
The rate at which an electromagnetic signal alternates, denoted in Hertz.
FTP
File transfer protocol. The typical process for transferring files over the Internet or the software program that uses this procedure. Using this program, the user is permitted to connect to another computer online to transfer files to his/her desktop computer using a GET command. An 'anonymous' ftp is usually allowed, where the user would enter 'anonymous' as the login name, and his/her e-mail address as the password, enabling the user to access a limited number of public directories where files can be retrieved.
Full duplex
A channel used for communication that is capable of both transmitting and receiving in two directions at the same time. A standard telephone line is one example of this because both parties can simultaneously speak while listening to the voice on the opposing end.
Full Motion Video
Video running at 25 (PAL, SECAM) or 30 (NTSC) frames per second, down to 1015 fps. Any frame rate less than about 10 fps is approaching slow-scan video.
Full T1
See T1.
Full-motion Video
A standard video signal, conventionally requiring 6 Mhz an analog format and 90 Mbps when digitally encoded, that is able to be transmitted by a variety of ways including television broadcast, microwave, fiber optics, and satellite.
Gateway
A computer used to provide translations between different types of standards. Generally refers to computers that translate complex protocol suites; for example, different E-mail messaging systems. Currently, it has been used to describe a 'door' from a private data network to the Internet.
GB
Gigabyte. A measure of the storage capacity and memory of a computer. One gigabyte is equivalent to 1.074 billion bytes or 1,000 Mb. Usually used to express a data transfer rate, (1 gigabit/second=1 Gbps). The bandwidth of optical fiber is often in the gigabit or billion-bits-per second range.
Gbps
Gigabits per second. A measure of bandwidth and rate of data flow in digital transmission.
GEO
Geostationary Orbit. Refers to the orbit of a satellite whose location relative to the earth's surface is constant so it seems to hover over one sport on the earth's equator.
Ghosting
A motion artifact in monitor displays of compressed video images. As an image moves quickly across the field of view (e.g., an arm waving) it leaves a trail of “ghost” images that resolve as the movement stops. See tiling.
Ghz
Gigahertz. One billion cycles per second. It measures analog signal transmission.
GIF
Graphical Interface Format. A typical graphics or image file commonly used on the Web that is most effective when the graphic or image is not a photograph.
Global e-Health
The sustainable global integration of information and communications technologies into the practice of protecting and promoting health across geo-political, temporal, social, and cultural barriers - including research and education - to facilitate health, public and community health, health systems development, and epidemiology.
Globalization
The integration of international markets as a result of advances in communications and transportation, the liberalization of trade, and the emergence of new competitors in the developing world.
Gopher
A predecessor to the World Wide Web. A method of storing and retrieving text and software files on the Internet. More user friendly than ftp, but less so than the Web.
Graphic Equalizer
Allows user to accentuate or de-emphasize selected frequencies within an audio sample. An example is the different “tuning” for heart and lung sounds in electronic stethoscopes. See frequency response.
Graphics stand
Document stand. Typically used for capturing and transmitting images of documents. Can be used for skin lesions and the like. Typically uses a 1-CCD (1-chip) camera. At a minimum, a graphic camera should have color and black and white modes, manual iris, zoom, focus, and color adjustments, additional overhead lights for uniform illumination, and a large (at least 8.5 x 11 inch) back-lighted base. The last feature is useful for capturing images of transparencies and X-ray, CT, and MRI images.
Gray Scale
Refers to the quantity of various tones or levels of gray than can be stored and displayed by a computer system. The number of gray levels, or gray scale, is directly related to the number of bits used in each pixel, with the number of gray levels doubling for each added bit. For example, there are 64 gray levels in a 6 bits system, 128 gray levels for 7 bits, 256 gray levels for 8 bits, and so forth.
Gray-scale Monitor
A visual display with varying shades of gray, extending up to thousands, making it capable of displaying an image. May also be known as a monochrome monitor.
GUI
Graphical User Interface. A method of controlling computers using graphic images or icons, to which the user accesses using a mouse.
Guide
A list of online resources, usually websites, which may be generalized or specific, compiled by human editors. This index is generally less comprehensive than search engines, but often more specific. May also be known as a 'search' or 'subject guide.'
H channel
The ISDN packet switched channel on Basic Rate Interface, designed to carry user information streams at different speeds, depending on type: H11=1536Kbit/s, H0=384Kbit/s and H12= 1920Kbit/s.
H.26, H.256, H.324, H.263, H.242... . see ITU-T, video format, standards
Half-duplex
A communication channel over which both transmission and reception are possible, but only in one direction at a time.
Hard Drive
The storage device within a computer used to save data, files, and programs.
Hard Wired
Refers to the permanent connection of two devices by a communications link.
Hardware
Used to refer to all the tangible equipment related to information technology, including the computers, peripheral devices, such as printers, disks, and scanners, and the cables, switches, and other components of the telecommunications infrastructure that binds everything together.
HCII
Health Care Information Infrastructure. A subset of the National Information Infrastructure.
HDTV
High-definition television. A television system with 1125 lines of horizontal resolution, with the ability of creating high quality video images.
HPSA
Health Professional(s) Shortage Area. Means any of the following which the Secretary determines has a shortage of health professional(s): (1) An urban or rural area (which need not conform to the geographic boundaries of a political subdivision and which is a rational area for the delivery of health services); (2) a population group; or (3) a public or nonprofit private medical facility (See http://bhpr.hrsa.gov/shortage/hpsacrit.htm).
Hertz
A measure of radio frequency. One Hz = one cycle per second.
HF
High frequency. Frequencies from 3 MHz to 30 MHz.
High pass filter.
See Low pass filter.
HIN
Hospital Information Network
HIS
Hospital Information System. One that supports all hospital functions and activities such as patient records, scheduling, administration, charge-back and billing, and often links to or includes clinical information systems such as an RIS
HISPP
Health Care Information Standards Planning Panel. Established by the ANSI, this panel coordinates the evolution of standards using standard-setting organizations in health care.
Hit
Recorded each time a Web browser displays a page, a hit refers to a single access of a Web page. It is common for a user's homepage to display the number of hits it has received, and this number is used by Webmasters to determine the popularity of any given Website and thus how much attention it should receive.
HL7
Health Level 7 Data Communications Protocol. Used at the applications level, this communication protocol outlines the guides to transmitting health-related information. Usually used within a single institution, HL7 allows the synthesis of various applications, such as bedside terminals, radiological imaging stations, hospital census, order entries, and patient accounting, into one system.
HMO
Health Maintenance Organization.
Home page or Homepage In a hierarchical collection of linked HTML documents, this term refers to the top-level hypertext document. It is typically the document implied in a WWW site's address.
Hot link
Hypertext link. A highlighted word, phrase, or graphic within an Internet document that, when selected, automatically links to another site (URL) on the Internet.
HPCC
High Performance Computing and Communications. A program of research coordinated by the Federal Government focused on research and development, created to expedite the introduction and use of the next generation of high performance computer systems.
HTML
HyperText Markup Language. A simple computer language used for formatting and presentation of Internet hypermedia documents. It is used to embed hypertext links (“hot links”) into documents. The guides to publishing used on WWW pages. It defines the events when the user clicks on a hypertext link embedded in the page. HTML is a publishing standard, not a programming language. HTML document comprise the core of a website, and can be identified by an .shtml or .shtm suffix.
HTTP
Hypertext Transport Protocol. The standard by which the World Wide Web operates.
Hub
Provides a cost-effective single point of connection to the network for workstations and other devices.
Hypertext Link
Sometimes known simply as a "link". This visual aid, usually signified by highlighting, underlining or graphics, instructs the computer to display a specific Web document. This system permits users to move easily within a website or across websites residing on different computers. A "bad" link, which refers to one that does not work properly, will display an error message rather than the Web page the user was attempting to visit. Bad links are generally caused because a website has changed location without leaving a forwarding address or because the page was simply removed from the Web. See Hot link, html
IATV
InterActive TeleVideo (=ITV)
IEC (IXC)
InterExchange Carrier. The long distance companies in the U.S. that provide inter-LATA telephony services. E.g., Sprint, AT&T, MCI. See LEC.
IEEE
Institute of Electrical and Electronic Engineers.
IITF
Information Infrastructure Task Force. This organization, established by the Clinton Agency, is comprised of the Federal agencies specializing in information and telecommunications technology development and application, with the goal of outlining and implementing a plan for the National Information Infrastructure (NII).
Image capture
See Freeze frame.
Image management
Stored image management denotes the ability to sort, arrange, and manipulate stored images into functional groups. Some systems allow the user to store images, but once done they cannot be arranged and are permanently stored in the order in which they were saved. This may be cumbersome.
Image Processing
Use of algorithms to modify data representing an image, usually to improve diagnostic interpretation.
Image Technology
The component of computer applications that transform documents, illustrations, photographs, and other images into data that computers and special-purpose workstations are capable of storing, distributing, accessing, and processing.
IMUX.
Inverse multiplexer. Re-aggregates split subchannels in a data stream into a single channel. See ISDN
Independent Telephone Company.
A local exchange carrier that is independent of the Bell system of operating companies (BOCs). In rural locations, many of the independent telephone companies are cooperative.
Informatics
The deployment of systems that collect, organize, and report health data to improve the quality and cost-effectiveness of health care, public health, and providers and consumers decision-making about health care management (e.g., electronic medical record, integrated health care management systems, disease tracking systems). The use of computer science and information technologies to the management and processing of data, information and knowledge.
ICT
Information and Communications Technology. The application of modern electronic and computing capabilities (technology) to the creation and storage of meaningful and useful facts or data (information), and to its transmission to users by various electronic means (communication). The ultimate goal is for ICT to transform data into information, and information into knowledge.
Information Economy
A knowledge-based economy dominated by knowledge-based industries such as computers, pharmaceuticals and consulting services.
INMARSAT
An international global telecommunications satellite network established by government treaty in 1979, with 79 member countries. Land Earth Stations (fixed or portable, even to suitcase-sized) provide links between rural sites and telecom networks. Can provide low-bandwidth digital services anywhere on the earth’s surface for as little as $1/minute.
Integrated Circuit
A solid state microcircuit comprised of interconnected semiconductor components diffused into a single instrument.
ISDN
Integrated Services Digital Network. A completely digital telephone system that is slowly enjoying more popularity throughout the United States which permits the integrated transmission of voice, video, and data to users at a higher speed than would be possible over typical telephone lines. It also provides connections to a universal network. It currently requires special installation and equipment.
Integrator
A vendor that uses retail parts from other manufacturers to produce a product that other vendors might make and assemble within the company. See VAR, OEM.
Interexchange carrier
See IEC.
Interface
How the system enables information to be accessed and modified. A graphical user interface (GUI) is typically simple to use, with mouse controlled point-and-click onscreen icons. See Primary user interface.
Interface
The connection between two devices; applies to both hardware and software.
Internet (1).
A group of networks that are interconnected so that they appear to be one continuous network, and can be addressed seamlessly at the Network Layer Three of the OSI model. Typical internets are built using routers, either to form a backbone network comprised of routers, or to link together LANs at the Network Layer.
Internet (2)
A collection of networks and gateways, including the Milnet and NSFNET, all using the TCP/IP protocol suite. It functions as a single, cooperative virtual network. The Internet provides universal connectivity and three levels of network services: connectionless packet delivery; full duplex stream delivery, and application level services, including electronic mail and EDI.
IP
Internet Protocol. The messenger protocol of the TCP/IP (Transmission Control Protocol/Internet Protocol), describing software that tracks the Internet address of nodes, routes outgoing messages, and recognizes incoming messages. It facilitates the identification of the Internet Protocol Address (IP Address) of a computer or other device on the Internet (normally printed in dotted decimal form, such as 128.127.50.224).
Internet
A loose aggregation of thousands of computer networks forming an enormous worldwide WAN (although some would not use the term WAN for this generally low-bandwidth system).
Interoperability
The condition achieved among communications and electronics systems or equipment when information or services can be exchanged directly between them, their users, or both.
Intranet
A “private Internet” that employs TCP/IP communications protocols used over the Internet. The intranet may be linked to the public Internet through a tightly managed, controlled gateway.
ISDN
Integrated Services Digital Network. A completely digital telephone system that is slowly enjoying more popularity throughout the United States which permits the integrated transmission of voice, video, and data to users at a higher speed than would be possible over typical telephone lines. It also provides connections to a universal network. It currently requires special installation and equipment. A low-to-medium speed technology for digital telephony. Usually transmits at 64-128Kbps, although higher speeds are possible. ISDN is broken into 64 Kbps bearer channels (B-channels) and 16 Kbps data channels (D-channels) . Basic Rate Interface (BRI) generally provides a 128 Kbps data rate (“2B+D”), while Primary Rate Interface (PRI) can provide up to 1.54 Mbps (the equivalent of a T1 circuit). To combine channels to provide a virtual circuit at greater than the basic 64 Kbps an inverse multiplexer may be needed.
ISO
International Organization for Standardization is an international organization composed of national standards bodies from more than 75 countries. ISO has defined a number of important computer standards, the most significant of which is perhaps OSI (Open Systems Interconnection), a standardized architecture for designing networks. Note that ISO is not an acronym; the name derives from the Greek word iso, which means equal.
ISO/OSI
International Organization for Standardization/Open Systems Interconnections. The typical reference archetype for local area network (LAN) architecture. The model is made up of several hierarchical levels (physical, data link, network, transport, session, presentation, and application) that address LAN design, from the specification of the physical transmission medium to the abilities of user interaction with LAN services.
ISP
Internet Service Provider. The local, regional, or national (AOL, CompuServe, etc.) company that provides dial-up connections to the Internet, as well as hosting of home pages
IT
Information Technology. Using a variety of techniques, it refers to the storage, manipulation, and communication of information in audio, data, and video formats.
ITU-T Standards
International Telecommunications Union (the T is for TSS). Founded in 1865 as a telegraphy standards body. Now a United Nations agency. H series (videoconferencing): H.320 defines how the whole H series works together & contains instructions for ISDN and some G (audio) algorithms as well; H.323 are LAN standards; H.324 permits video, voice, and data over a single analog phone line; H.261 is a video compression protocol for dissimilar CODECs; H.230 for multipoint control; H.263 is a video coding interface subset of H.324 and supports html; H.723 is a dual speech coder that transmits at 6.4 and 5.3 Kbps; H.242 is an audio conference setup and termination protocol. T.120 series: image capture, annotation and transfer in video conferences. G series (G.721, G.722, G.728): audioconferencing. See CCITT, TSS.
ITU-T
International Telecommunications Union Consultative Committee for Telecommunications. Formerly the Consultative Committee on International Telephone and Telegraph (CCITT). An international agency responsible for developing standards for telecommunications, including FAX and video coder-decoder devices.
ITU
International Telecommunications Union. This union, governed by a treaty and comprised of government telecommunications agencies, is responsible for setting standards for radio, telegraph, telephone, and television.
ITV
Interactive TeleVideo (=IATV)
IXC
Interexchange Carrier. Also referred to a long-distance carrier, a telephone company that carries long-distance calls.
Java, Javascript
Two independent, but related programming languages that are largely Web-based. They permit augmented functionality of and enhancements to a website. If one's browser is unable to use these languages, the enhancements or features found in the website will usually not be displayed. Netscape and Microsoft support both types of languages.
JCAH
Joint Commission on Accreditation of Healthcare Organizations.
JPEG
Joint Photographic Experts Group. This international group, a joint effort of the ISO and TSS, has developed standards for still image compression. Motion JPEG applies JPEG compression to each frame of a video clip. An algorithm and standard for compressing digital photographic images. Related to GIF.
KB
Kilobyte. A measure of computer storage and memory capacity. Equivalent to 1,024 bytes; often applied to 1,000 bytes as well.
Kbps
Kilobits (thousands of bits) per second. A typical compressed video clinical interaction is transmitted at 385 Kbps.
LAN Connectivity
The ability to connect the video system to a LAN within the health care facility. This can allow access to and sharing of patient records, test reports, demographics, etc. during a videoconference. Currently few institutions are capitalizing on this potential.
LAN
Local Area Network. A computer network linking computers, printers, servers, and other equipment within an enterprise. Can support audio, video, and data exchange. Typically runs at 10-100 Mbps.
Laser digitizer
Laser scanner. Employs a laser to capture image information to digital form. Very high resolution and wide gray scale range are possible. Because it uses coherent light, the laser scanner can penetrate thick films (an ability measured in units of optical density) and extract information better than CCD scanners. Serves the same function as CCD X-ray scanners, but generally at higher resolution, better contrast, and much higher price.
LATA
Local Access and Transport Areas. The areas within which the RBOC and LEC can provide telephony services. Inter-LATA connections are provided by IECs. The local telephone districts that were created by the divesture of the Regional Bell Operating Companies (RBOCs) formerly associated with AT&T.
Lavaliere
A small microphone that is typically clipped to clothing at breast pocket level. May be wired or wireless. Coined from the Duchesse de La Vallière (1644-1710), a mistress of Louis XIV, who wore a jeweled pendant on a chain around her neck.
LDC
Long Distance Carrier. Also referred to as Interexchange Carrier (IEC).
Leased 56
A leased line providing a transmission rate of 56 Kbps.
Leased line
Private line. A point-to-point connection that is logically similar to two cans tied together with a dedicated piece of string. You pay for the sole use of the circuit and the price does not vary as a function of usage, as with switched lines. A line rented from a telephone company by a customer so that s/he may have exclusive rights to it. May also be called a dedicated line.
LEC
Local Exchange Company. The local telephone office that bridges between the long-distance carrier and the customer site. May be part of an RBOC or an independent telephone company. See LATA, IEC.
Leveling
A software manipulation technique, using mathematical algorithms, to compensate for a teleradiology monitor’s inability to provide the same contrast and bit depth as the original hardcopy X-ray. The great variation in the density of X-ray exposure within an image can lead to seriously over- and underexposed portions of a monitor (screen) image. Thus, a chest film may have very high density (white) portions, such as the spine, and very low density portions (such as the lungs). Using locally adapted histogram leveling, bit depth (contrast; gray scale) can be selectively adjusted for different portions of the image, or for different pixel depths. This yields much more useable clinical information.
Lossless compression
See Compression ratio.
Lossless
A format of data compression, typically of an order of less than 2:1, in which none of the original data information is lost when the image is reproduced.
Lossy compression
See Compression ratio.
Lossy
A process of data compression at a relatively high ratio, which leads to some permanent loss of information upon reconstruction.
Low pass filter
A filter for leveling out the borders in the screen display of a radiology image. The image is altered by placing a value on each pixel which is the weighted sum of the pixels in a small square surrounding the pixel in the original image. The weights or filter coefficients determine how the new image will look, and the borders of the image can be leveled out (“low pass filter”) or sharpened (“high pass filter”).
LSTAT
Luminance Life Support for Trauma and Transport. The amount of light an object gives off. Perceived luminance is denoted as brightness. Although the terms brightness and luminance are sometimes used interchangeably they are not equivalent.
Luminance
Characteristics of brightness for a video monitor. See Composite video
Lux
A unit of illumination. Generally, lighting levels of 1000-3500 lux are satisfactory for telemedicine applications, while newer “low lux” cameras produce quality pictures at levels as low as 750 lux. Having a lux level above 1000 enables the camera to keep more of the image in focus, since the trade-off for low light conditions is lower depth of field.
Mailing List
Conducted exclusively through e-mail this is a discussion group open to the public. Once a user subscribes to a mailing list, all messages s/he sends to the list and copied and sent to all other members of the mailing list. A popular method of engaging in on-line topic-specific discussions. Mailing Lists are sometimes referred to as 'listservs' or majordomos,' named after the types of software used to maintain them.
MAN
Metropolitan Area Network. A network of computers whose reach extends to a metropolitan area. MANs may be used to link telemedicine applications at a data rate similar to DS1. In some cases, MANs may be used by cable companies to offer links to off-network services such as the internet, airline reservation systems, and commercial information services, in addition to data exchange abilities. Compared to LAN and WAN, MAN is in between the two.
MB
Megabyte. A measure of computer storage and memory capacity. One Mb is equivalent to 1.024 million bytes, 1,024 thousand bytes, or 1.024 kbs. However, this term is also applied to the more rounded term of 1 million bytes.
Mbps
Megabits (millions of bits) per second. A typical uncompressed video signal requires 45 Mbps (or more) to transmit. A measure of bandwidth and rate of data flow in digital transmission. One Mbps is equivalent to one million bits per second.
MCU
Multipoint Control (or Conferencing) Unit = Bridge. A device that enables participants at more than two sites to participate in voice or video calls.
MCU
Multipoint Control Unit. Offered by switched network providers, this centrally located service allows three or more user to be connected, allowing audio and video teleconferencing.
Medical Informatics
A system comprised of computer science, information science, and health sciences created to assist in the management and processing of data to support the execution of health care.
MUA
Medically Underserved Areas. May be a whole county or a group of contiguous counties, a group of county or civil divisions or a group of urban census tracts in which residents have a shortage of personal health services. (see http://bhpr.hrsa.gov/shortage/)
MEDIX
Medical Data Interchange Standard. Established by the IEEE, this data communication protocol is utilized at the applications level.
Megahertz (Mhz)
A measure of bandwidth and rate of information flow for analog transmission. One Mhz equals 10 to the sixth power cycles per second.
MHPSA
Mental Health Professional(s) Shortage Area. An area is so designated if the following criteria are met: 1.) The area is a rational area for delivery of mental health services; 2.) One of the following conditions exists within the area: a.) population-to-core mental health professional ratio greater than or equal to 6,000:1 and a population-to-psychiatrist ratio greater than or equal to 20,000:1;  b.) a population-to-core-professional ratio greater than or equal to 9,000:1, or c.) a population-to-psychiatrist ratio greater than or equal to 30,000:1; 3.) The area has unusually high needs for mental health services, and has: a.) a population-to-core mental health professional ratio greater than or equal to 4,500:1, and a population-to-psychiatrist ratio greater than or equal to 15,000:1; b.) a population-to-core professional ratio greater than or equal to 6,000:1; or c.) a population-to-psychiatrist ratio greater than or equal to 20,000:1; 4.) An area will be considered to have unusually high needs for mental health services if one of the following criteria is met: a.) 20 percent of the population (or of all households) in the area have incomes below the poverty level; b.) the youth ratio, defined as the ratio of the number of children under 18 to the number of adults of ages 18 to 64, exceeds 0.6; c.) the elderly ratio, defined as the ratio of the number of persons aged 65 and over to the number of adults of ages 18 to 64, exceeds 0.25; d.) a high prevalence of alcoholism in the population, as indicated by prevalence data showing the area's alcoholism rates to be in the worst quartile of the Nation, region, or State; or e.) a high degree of substance abuse in the area, as indicated by prevalence data showing the area's substance abuse to be in the worst quartile of the Nation, region, or State (See http://bhpr.hrsa.gov/shortage/hpsaguidement.htm).
Message Switching
A message either in image or text form that is separated into multiple parts that are then transmitted independently to the receiver where they are put back together to form the message.
MAN
Metropolitan Area Network. A network of computers whose reach extends to a metropolitan area. MANs may be used to link telemedicine applications at a data rate similar to DS1. In some cases, MANs may be used by cable companies to offer links to off-network services such as the Internet, airline reservation systems, and commercial information services, in addition to data exchange abilities. Compared to LAN and WAN, MAN is in between the two.
Mhz. Megahertz
A measure of bandwidth and rate of information flow for analog transmission. One Mhz equals 10 to the sixth power cycles per second.
Mic level inputs
The input jacks available for microphones. Some applications may require multiple microphones. A mixer can be added if there are not enough mic level inputs.
Microphone audio overlays playing tape audio.
The ability to talk to the other end while using the VCR as the audio/video input source. In a telemedicine consult, this feature is valuable when playing a pre-recorded tape of a procedure or examination and the providers want to discuss what is being seen at the same time.
Microsoakable camera
An oddball term meaning that the camera can be sterilized by soaking in disinfectant solutions. This adds significantly to the camera’s expense but may be necessary.
MW
Microwave. Loosely, an electromagnetic wave having a wavelength from 300 mm to 10 mm (1 GHz to 30 GHz). Note: Microwaves exhibit many of the properties usually associated with waves in the optical regime, e.g., they are easily concentrated into a beam.
Microwave Link
A system of communication using high frequency radio signals, exceeding 800 megahertz, for audio, video, and data transmission. These links require line of sight connection between transmission antennas.
Mini-PACS
An image management system that focuses one or more of the digital modalities, such as an ultrasound mini-PACS, or one application areas such as neuroradiology.
Mirror
A website identical to another website at a different physical location. This process is typically used to expedite access because the original site resides on another continent. For example, a website may be set up in America duplicating an already existing website in Europe so that Americans can quickly access the site.
Mixer
Enables multiple audio or video inputs to a processor. See mic level inputs.
Modem access for remote diagnostic support. Indicates that a technical support center can call into the system on a separate modem line to perform remote diagnostics.
Modem
Modulator/De-modulator. A device that translates digital signals to pulse tone (analog) signals to enable transmission over telephone lines and reconverts them to digital form at the point of reception, thus permitting a computer to communicate with another computer over a regular telephone line. These devices are usually identified by the speed (in bits per second or bps) of communication they permit. The higher the bps, the faster the modem. Enables transmission of digital data (by transforming it to and from analog waveforms) over standard analog phone lines and cable video systems.
Moderated
Used to refer to either mailing lists or newsgroups, a moderated forum is one in which every message sent to the forum is first analyzed by an individual called the 'moderator.' If the message is germane to the forum's topic, and is appropriate, it will be approved and published on that forum. If it is not acceptable, the message is returned to the author. Distinguished from open and closed.
Monochrome Monitor
Also known as a gray-scale monitor. A visual display on a computer that presents images as various shades of gray, ranging from black to white.
MPEG
Moving Picture Experts Group. A group of standards for compression and storage of motion video. MPEG-1 provides images of 240 lines x 360 pixels/line, digital transfer rates up to 1.5 Mbps, and compression ratios of about 100:1. MPEG-2 provides a higher quality picture - 720 horizontal lines x 480 vertical lines (pixels/line). The MPEG-2 standard is used for HDTV, and will be used for cable broadcasts.
Multimedia
A term which broadly applies to the transmission and manipulation of any form of information, including words, pictures, videos, music, numbers, or handwriting. This information is regarded as simply digital bits-zeroes and ones-as it is to a digital telecommunications link that carries information in bit form. The substantial increase in computing power permits integrated patient records with audio and video clips.
Multiplexer
By combining and interweaving low-capacity channels in discrete time or frequency slices, this equipment allows transmission of multiple lines of audio, video or data information in one high-capacity communications channel.
MCU
Multipoint Control Unit. A multiport device, by means of which two or more audiovisual terminals may intercommunicate in a conference call. Note: A "principal MCU" has been assigned a superior controlling function in a call where two or more MCUs in that call are termed "satellite MCUs". The physical realization of an MCU may be such that two or more independent conferences may be set up within the same unit; logically, however, there is no relationship between these conferences; the text of this definition refers to an MCU only as a logical entity pertinent to the particular call of concern.
Narrowban
A telecommunications medium that uses low frequency signals, not exceeding 1.544 Mbps.
NCHSR
National Center for Health Services Research. Former name of the Agency for Health Care Policy and Research (AHCPR).
NEMA
National Electrical Manufacturers Association.
Netiquette
Rules of etiquette for online interactions.
NetPhone
Commonly referred to as the "Internet telephone." Refers to the equipment used to permit two users to talk to one another using the Internet as the connection.
Network interface
Connectivity options for the system.
Network
A set of nodes, points or locations which are connected via data, voice, and video communications for the purpose of exchanging information. Interconnected telecommunications equipment used for data and information exchange. Consists of different types, LAN, MAN, and, WAN being examples.
Newsgroup Reader
The software used to access, read, and post to newsgroups.
Newsgroups
Sometimes referred to collectively as "Usenet." Discussion groups open to the public where users can read the information posted and add new messages, or articles. Uses a hierarchical topic structure to make it easy for the user to find the information. Messages posted to newsgroups are sent to every computer connected to the Internet, where it is stored for a few days to give interested users the chance to read it. Individual users have the option whether they would like to subscribe to newsgroups. Currently, over 18,000 newsgroups exist and are available for subscription, although most users only subscribe to, read, and respond to a few of them.
NHSC
National Health Service Corps program.
NII
National Information Infrastructure. A United States government policy developed by the Clinton Administration that involves the synthesis of hardware, software, and skills that will make it easy and affordable to connect people with each other, with computers and with a wide variety of services and information resources.
NIMH
National Institute of Mental Health.
NLM
National Library of Medicine.
Node
A branching or exchange point for networks.
NTIA
National Telecommunications and Information Administration. The federal agency in the Department of Commerce responsible for the National Information Infrastructure initiative.
NTSC
National Television System Committee. An independent panel that is involved in setting the standards for broadcast television in the United States. The standard for the NTSC is sometimes considered a "composite video," because all video information is combined into one analog signal.
NTSC
National Television Systems Committee. This body adopted a video signaling standard for black and white television in 1953 (EIA RS-170 specification). The NTSC standard defines all of the parameters that allow television sets in N. America to receive broadcast signals. NTSC has a display rate of 30 frames per sec (fps) in interlaced fashion: odd lines in one pass, even lines in the next. The vertical resolution is determined by the number of rasters (scan lines). It actually consists of 525 scan lines, but due to “vertical blanking intervals” many of these drop out, resulting in 484 lines. In actual practice this is usually reduced to 352 lines. Thus, many systems advertise “352 x 288 lines of resolution.” Horizontal resolution is determined by how small the scanning point is in the camera and the number of vertical lines that can alternate between white and black in an area as wide as the overall image is tall. (see PAL, SECAM, Video format)
OC3
A high-speed digital transmission capability of 155 Mbps. Compare DS3, T1, ISDN.
OCR
Optical Character Recognition. Automatic scanning the translation of printed characters to computer-based text.
Ocular tube adapter
Allows a camera to be mounted to any microscope. This feature is needed to adapt a telepathology system to an existing ocular microscope without a camera port. Capturing images through an ocular tube has some disadvantages that must be weighed against the cost of a new scope.
OEM
Original equipment manufacturer. Compare VAR, integrator.
Open Systems Architecture
A design that permits the interconnection of system elements provided by many vendors. The system elements must conform to interface standards.
Open
Refers to a type of mailing list. Signifies a system which permits anyone to post a message to it, independent of their member status. Different than closed or moderated.
Operating System
The underlying system software which enables a computer to operate. Common operating systems include DOS, Windows, and Macintosh System 7x.
Operator
A character used to limit or broaden a search. Operators such as and, or, and not are referred to as a "Boolean operator."
Optical Carrier (OC)
The nomenclature for the line rate of the optical transmission signal.
Optical Disk
A computer storage disk used solely for large quantities (Gbs) of data.
Optical Ring (Disk)
A computer storage disk used solely for large quantities (Gbs) of data.
OSI
Open Systems Interconnect. The standard reference model for local area network (LAN) systems.
OTA
Office of Technology Assessment. Agency established by the United States congress, it was terminated in 1996.
Packet Network
A network that gives out data bits in packets.
PSN
Packet Switching Network. Refers to the transmission of digital information using addressed packets that are transmitted along various routes in a network. This system is more efficient than modem transmission where the channel is occupied throughout the transmission, because the occupation in the channel is limited to packet transmission.
Packet Switching
The procedure of transmitting digital information via an addressed packets so that a channel is occupied only during the transmission of the packet.
Packet
A basic message unit for communications in networks. A short block of data comprised of data, call control signals and error control information and containing information on its source, content and destination that is transferred in a packet switched network.
PACS
Picture Archiving and Communication System. An image system that embraces all modalities (X-ray, CT, MR, nuclear medicine, ultrasound) and links users with display workstations over a high speed network to an image server, an archive, printers, and radiology information systems (RISs). A system capable of acquiring, transmitting, storing, retrieving, and displaying digital images and relevant patient data from various imaging sources and communicates the information over a network.
Paging
See Ciné loop.
PAL
Phase Alternation Line. A European alternative to NTSC composite video signaling used in N. America, adopted in 1967. Provides greater bandwidth for chrominance, yielding better color resolution. Also, the number of scan lines is increased to 625 over NTSC’s 525 (or less on the monitor). However, the frame rate is reduced to 25 fps from NTSC’s 30. See SECAM, video format. A European alternative to NTSC composite video signaling used in N. America, adopted in 1967. Provides greater bandwidth for chrominance, yielding better color resolution. Also, the number of scan lines is increased to 625 over NTSC’s 525 (or less on the monitor). However, the frame rate is reduced to 25 fps from NTSC’s 30. See SECAM, video format.
PBX
Private Branch Exchange. A computerized private telephone switchboard with an extended scope of data and voice services. This exchange generally serves one organization and is connected to the public telephone network. A telephone switch, typically located at the customer site, connected to the public telephone network but operated by the customer. PBXs may be digital rather than analog.
PC applications conferencing. Describes the ability to run a PC application on one end of a video conference and to share that application with the PC at the other end of the video conference. This computer sharing application allows the monitors and keyboards to simultaneously interact with the computer program while in a conference. It has use primarily in administrative applications when working in a financial spreadsheet or database, and in distance learning environments when using educational software.
PC platform for data/applications access and storage.
Indicates if a personal computer (PC) is integrated into the system and is available for use by PC applications.
PC
Personal Computer. Generally, but not necessarily, IBM-compatible (as opposed to Macintosh).
PCM
Pulse Code Modulation. A process of encoding audio signals.
PDF
Portable Document Format. Permits the user to read a document and print it out using Adobe's Acrobat reader, a free piece of software. PDF files may only be read or printed using this software.
Peripheral Devices
Attachments to telehealth systems that augment their communications or medical capabilities. Examples include: electronic stethoscopes, blood pressure monitors, oxygen saturation monitors, oto-/ophthalmo-scopes, dermascopes, graphic stands, and scanners.
Peripheral
Any device that is attached to a computer externally. Scanners, mouse pointers, printers, keyboards, and monitors are all examples of peripherals. Scales, blood pressure cuffs, spyrometers, and glucometers are also examples.
PET
Position Emission Tomography.
Phosphor
The coating on the inside of a cathode ray tube (CRT) or monitor that produces light when hit by an electron beam.
PIP
Picture-In-Picture allows both ends of the videoconference to be viewed simultaneously on a single monitor. Picture in picture swap allows the two video pictures to change positions so that the local video fills the largest portion of the screen. On some two monitor systems, PIP allows both live video images to be seen simultaneously on one screen while higher resolution graphic images are seen on the other.
Pixel
Picture element. This is the smallest piece of information that a CRT is able to display, and is symbolized by a numerical code in the computer. Pixels appear on the monitor as dots of a specific color or intensity. There are many, many pixels in a single image. The smallest unit of a raster display. A picture cell with specific color and/or brightness. The more pixels an image has, the more detail, or resolution, it can display. The pixel size in a high-end computer monitor's screen (a “1K x 1K monitor”) is approximately 0.28 x 0.28 mm. The pixel size for diagnostic teleradiology monitors (“2K x 2K”) is much smaller than this.
Platform
The type of computer on which a given operating system or application runs; the operating system in use on a given computer; or the application program in use on a given computer and operating system. The term cross-platform may be used to characterize an application program or operating system that may be run on more than one platform.
Post
The process of adding a new message or article to a newsgroup, conference, or mailing list discussion area online.
POTS
Plain Old Telephone System. The analog, public switched telephone network in common use throughout the world. Also known as Public Switched Telephone Network (PSTN). Enables voice phone calls and data transmission of up to 33.6 Kbps, as well as limited videoconferencing.
PPO
Preferred Provider Organizations.
PPP
Point to Point Protocol. A type of computer protocol used by modems for online communication.
PPRC
Physician Payment Review Commission.
Presets
Determines how many predefined camera positions can be set. Presets are useful for rapid changes in camera position - for example, to quickly move from a close up of a patient to a larger view of both the patient and the physician.
PRI
Primary Rate Interface. An integrated services digital network (ISDN) interface standard that is designated in North America as having a 23B+D channels, in which all circuit-switched B channels operate at 64 kb/s, and in which the D channel also operates at 64 kb/s. Note: The PRI combination of channels results in a digital signal 1 (T1) interface at the network boundary.
Primary user interface device
Indicates what type of device is used to control the video conferencing system. Hardwired and wireless, keyboard, mouse, and touchscreen options each have advantages and disadvantages. The user should seriously consider in what setting and for what application the system will be used to determine which is the preferred interface.
Printer interface
Allows data and images sent or received via the PC to be sent to a printer. This enables reports, images, and data shared in a videoconference to be rendered as hard copy for record keeping and teaching purposes.
Protocol
A system of guidelines and procedures, applying to both hardware and software, that oversees communications between two computer devices. They are primarily concerned with three aspects of the communication process: how data are symbolized and coded, how data are transmitted, and, in file transfer protocol, how errors and failures are recognized and corrected.
PSTN
Public Switched Telephone Network. The public telephone network.
Push
In networking, to send data from a server to a client in compliance with a previous request from (via) the client, as soon as the data are available.
Px64
“P time 64.” Synonymous with the ITU H.261 standard.
QCIF
Quarter Common Intermediate Format (“Q-sif”). A measure of video resolution, displaying 176 pixels by 144 lines. Has half of the CIF spatial resolution of FCIF. This is the “default” minimum H.261 format. Typically used in desktop videoconferencing.
RAID
Redundant Array of Inexpensive Disks. Any of six arrangements of conventional disk drives to increase data transmission speed and reliability, and better assure safe backup.
RAM
Random Access Memory. The temporary memory area on a computer that permits the user to run software, process images, and store information. The amount of RAM needed varies according to the application. Increasing the amount of RAM in a computer can improve computer performance. Information stored in the RAM is lost when the power is shut off.
RANs
Rural Area Networks Shared-usage networks. Designed to include a wide scope of users in rural communities, such as educational, health, and business entities.
Raster
Scan line. See NTSC.
RBOC
“R-BOCK.” Regional Bell Operating Company. The Bell companies (SW Bell, PacBell, Nynex/Bell Atlantic, Bell South, Ameritech, US West, Pacific Telesis) that were the result of the AT&T breakup of the 1970s. See LEC.
Real-time
Sends and receives audio / video / data simultaneously, without more than a fraction of a second delay. Applications that are transmitted within a few seconds are sometimes called near real-time. Compare store-and-forward, slow scan. The capture, processing, and presentation of data, audio, and/or video signals at the time the data is originated on one end and received at the other end. When signals are received at rates of 30 frames per second, real time is achieved.
Redundant or Redundancy
Known as fault-tolerance, in data transmission, refers to characters and bits that can be removed from a transmission without affecting the message. In data processing and data communications, it means providing backup for components: should one of them fail, the system continues to run without operation. Total redundancy is usually impractical, but organizations with mission-critical applications attempt to install a high level of redundancy on the basis that downtime loses money, or possibly lives, depending on the business.
Repeater
A bi-directional instrument used to amplify or regenerate signals.
Resolution
Refers to the ability of a device to distinguish between various factors. For example, spatial resolution is the ability to distinguish between adjacent structures. Contrast resolution is the ability to discriminate between shades of gray.
Resolution
The level of detail that can be captured or displayed. For video displays (teleradiology or interactive video) resolution is measured in pixels x lines x bit depth.
RGB
Red Green Blue. A coding language that controls the electron gun in CRT (Cathode Ray Tube) monitors. The video signal that comes into the monitor is separated into its component parts and converted to RGB; the video images are then rendered on the monitor’s screen.
RIS
Radiology Information System. A synthesized system for the electronic processing, storage and transmission of radiographic images. RIS allows the remote interpretation of radiographic image-teleradiology-and may be connected to Hospital Information Systems (HIS) and Laboratory Information Systems (LIS).
RJ-11 Jack
The connector jack used for standard telephone and FAX lines.
RMDS
Navy Remote Medical Diagnosis System.
ROC
Receiver Operating Characteristic. A procedure involving statistics used to analyze the ability of a diagnostic tool to determine whether an individual is healthy or diseased. ROC serves are most often used in observer performance evaluations of the feasibility and performance of diagnostic imaging systems.
Rollabout unit
Common term for a teleconferencing/ telemedicine unit where the monitor, CODEC, camera, etc. are placed in a cabinet with wheels that can be rolled from room to room. Often a somewhat ludicrous misnomer, since some rollabout units weigh more than 500 pounds. Compare to room unit.
ROM
Read Only Memory. The permanent memory capacity for a computer. Programs and information stored in ROM are not lost when power is extinguished.
Room unit
Common term for a large teleconferencing/telemedicine unit, usually with two large monitors, that is placed more or less permanently at a single site.
Router
In data communications, a functional unit used to interconnect two or more networks. Routers operate at the network layer (layer 3) of the ISO Open Systems Interconnection Reference Model. The router reads the network layer address of all packets transmitted by a network, and forwards only those addressed to another network.
Routing
The assignment of a path of communication.
RTFv
Rich Text Format. A series of word processing directions that are able to be read by the majority of word processing programs in order to retain the formatting rules of the document.
S-Video
Similar to component video, but closer to the RGB signaling required by monitors.
S&F
Store-and-forward. A telemedicine interaction type that creates a multimedia electronic medical record. Data and images are captured and stored for later transmission, consultation or downloading. These static images or audio-video clips may be transmitted to a remote data storage device, from which they may be retrieved by a medical practitioner for review and consultation at any time, obviating the necessity of simultaneous availability of the consulting parties and reducing transmission costs due to low bandwidth requirements.
Satellite Connections
A system of communications that uses radio signals sent to and from a satellite orbiting the Earth. The benefits of this mode of communication are that it allows connection between points at a great distance from each other on the Earth's surface, between which direct transmission is difficult, as well as to remote areas that lack cables for telephone lines.
Satellite
An electronic retransmission instrument serving as a repeater, which is a bi-directional device used to amplify or regenerate signals, placed in orbit around the earth in geostationary orbit for the purpose of receiving and retransmitting electromagnetic signals. It typically receives signals from a single source and retransmits them over a wide geographic area, known as the satellite's 'footprint.'
Scan line Raster
See NTSC.
SCSI
Small Computer Systems Interface. An interface system of rules and procedures used to connect peripherals such as disk drives, scanners, and tape back-up units, to computers. SCSI is also referred to as "scuzzy."
SDM
Shared Decision Making. A style of decision-making in health care where the patient is able to take a more active role in decision making, especially by offering them increased control over the choice of treatment, and, as a result, giving them a greater sense of responsibility for their care and health. Also called SDP, or Shared Decision Programs.
Search Engine
A website that indexes an online resource and makes that index available to other users for searching. This term is typically applied to a site that has indexed Web documents, but search engines also index mailing lists and other online resources. An 'internal' search engine index only includes the documents of that particular website, which permits the user to find information on that site more easily and quickly.
SECAM
Sequential Couleur Avec Memoire. A color television signaling standard with 625 scan lines and 25 interlaced frames/second. Used in France, the Newly Independent States (NIS) of the former Soviet Union, and parts of the Middle East. See PAL, NTSC.
Security - Data Security
The result of effective data protection measures. Data security exists when data are protected from accidental or intentional disclosure to unauthorized persons and from unauthorized or accidental alteration.
Security - System Security
The totality of safeguards including hardware, software, personnel policies, information practice policies, disaster preparedness, and oversight of these components.
Server
A computer designated to providing specific services to other computers. For example, print servers only accept, store, and print out documents sent to them by other computers, and nothing else. Web servers permit users from around the world to access the websites and documents stored on them.
Shareware
Computer software that the author gives license to the user to 'try before you buy.' Users are encourages to try the software, copy it and distribute it to other users. If the user continues to use the software after the initial sampling, a voluntary payment of a specific sum of money is required. Failure to pay the requested fee is a legal violation of the author's copyright.
Simultaneous playing of pre-recorded tape and recording of conference
Concerns the ability to have one VCR playing a pre-recorded tape into the system as a video source, while simultaneously having another VCR connected and recording the videoconference in progress. This is necessary for those telemedicine programs that maintain a policy of recording all consults and which periodically use pre-recorded tapes of patient procedures or educational tapes as part of a videoconference.
Site
An area or location online, typically on the Web, where an organization, individual or business stores its information.
SLIP
Serial Line Internet Protocol. A kind of computer protocol used by modems for online communication.
Slow-scan Video
The device that transmits and receives still video images over a narrow communications channel, such as a standard telephone line.
SONET
Synchronous Optical Networks. A broadband, wide area communications service capable of transmitting extremely high capacity data, such as interactive video, at very high speeds ranging from 150 Mbps to 10 Gbps. SONET services are convenient for real-time digital telemedicine applications.
Spam
Messages which are topic irrelevant usually taking the form of advertisements and are sent to wide variety of discussion forums (mailing lists or newsgroups), or e-mail addresses online. This practice, known as "spamming" is discouraged in the online world.
Spatial Resolution
Characteristic of being able to distinguish two equal sized adjacent objects in the same place. Represents the number of pixels in a specified area of a matrix.
SPEC
Single-photon emission computed tomography.
Spooling
As one image or data set is being reviewed, additional images can be received and stored for sequential review without “locking up” the computer.
SS7
Signaling System 7. A recent development in control systems for the public telephone network enabling faster processing and more efficient telephone service, plus making more services available to consumers.
Standards
Agreements on how to implement technologies.
Store-and-forward
Captured audio clips, video clips, still images, or data that are transmitted or received at a later time (sometimes no more than a minute). E-mail is a store-and-forward system. Enables dissynchronous communication, with the advantage of not needing concurrent participant involvement. Compare to real time. Transmission of static images or audio-video clips to a remote data storage device, from which they can be retrieved by a medical practitioner for review and consultation at any time, obviating the need for the simultaneous availability of the consulting parties and reducing transmission costs due to low bandwidth requirements.
Streaming
A technique for transferring data (usually over the Internet) in a continuous flow to allow large multimedia files to be viewed before the entire file has been downloaded to a client's computer.
Structured Data Entry
A method of data collection that constrains the content and format of clinical descriptions for the purpose of ensuring consistent, unambiguous, interchangeable messages.
Switch
In communications systems, a mechanical, electro-mechanical, or electronic device for making, breaking, or changing the connections in or among circuits. Also known as the process by which one transfers a connection from one circuit to another. In a computer program, a conditional instruction and a flag that is interrogated by the instruction or a parameter that controls branching and that is bound, prior to the branch point being reached.
Switched 56
A dial-up 56 Kbps digital line, billed at a monthly rate + cost/minute, as with a regular POTS phone line.
Switched line or network
A telecommunications option that operates like a dial-up phone line (which is, in fact, a switched line-as are ISDN, ATM, switched 56). There is often a usage charge for switched services, particularly for long distance connections such as phone lines. Compare to leased line, where the connection is continuously open and charges are usually on a flat, monthly rate.
Switched Line
Communication link for which the physical path, established through dialing, may change with each use.
Switched Network
A system of telecommunications where each user has a separate address and any two points can be linked directly, using any combination of available routes in the network.
Switched Service
A telecommunications service, often based on telephone technology, that switches circuits to connect multiple points.
Synchronous Transmission
The method by which bits are transmitted at a fixed rate with the transmitter and receiver synchronized, extinguishing the need for start/stop elements, with the result of providing increased efficiency.
T-carrier
A series of transmission systems using pulse code modulation technology at different channel capacities and bit rates to transmit digital information over telephone lines or other transmission medium.
T.120
A standard for audio and graphics exchange, supporting higher resolutions and pointing and annotation (which the H.320 standard does not).
T1 (DS1)
A leased T1 line, marketed and serviced by LECs, that provides 1.544 Mbps data rate (in N. America; the European T1 provides 2.048 Mbps). T1 is available almost everywhere, and can be fractionated. Fractional T1 services are less expensive than full T1. Typical interactive video-mediated telemedicine programs transmit video images at “1/4 T1” rates (384 Kbps).
T3 (DS3)
A digital transmission system for high volume voice, data, or compressed video traffic, with a transmission rate of 44.736 Mbps. It is also known as D3.
Tariff
The cost of telecommunications set by either a federal or state regulatory body.
TB
Terabyte. A measure of computer memory and the quantity of storage capacity available on a computer. One Tb is equivalent to one trillion bytes, or ten to the twelfth power bytes. See also gigabyte, kilobyte, and megabyte.
Tbps
Terabits per second. A measure of bandwidth and rate of information flow in digital transmission. One Tbps is equivalent to one trillion bits per second.
TD
Time Division Multiplexing. Transmission of more than one lines of information in one high-capacity communications channel using time as the means to separate channels.
TELCO
Telephone Company
Telecommunications
The use of wire, radio, visual, or other electromagnetic channels to transmit or receive signals for voice, data , and video communications.
Teleconferencing
Interactive electronic communication between multiple users at two or more sites which facilitates voice, video, and/or data transmission systems: audio, audiographics, computer and video systems.
Teleconsultation
The physical separation between multiple providers during a consultation.
Telediagnosis
The detection of a disease as a result of evaluating data transmitted to a receiving station from instruments monitoring a remote patient.
Telehealth
Telehealth is the use of information and communication technology (ICT) to deliver health services, expertise and information over distance. It includes Internet or web-based “e-health” and video-based applications, and can be delivered “real-time” or through “store-and-forward” mode. Telehealth is unique in having the capability to cross-geographical, temporal, political, social and cultural barriers within the health sector; and The electronic provision of health care and information services for the direct benefit of individual patients and their families. It includes actual physician-patient interactions via telemedicine, and the provision of education and information services designed to increase awareness of (and where applicable, compliance with) diagnoses and medical conditions, treatments, and good health practices; and The use of electronic communications networks for the transmission of information and data focused on health promotion, disease prevention, diagnosis, consultation, education, and/or therapy, and the public's overall health including patient/community education and information, population-based data collection and management, and linkages for health care resources and referrals. Although telehealth is sometimes considered broader in scope than telemedicine, there is no clear-cut distinction between the two; and The use of electronic information and telecommunications technologies to support and promote long-distance clinical health care, patient and professional health-related education, public health, and health administration.
Telematics
The use of information processing based on a computer in telecommunications, and the use of telecommunications to permit computers to transfer programs and data to one another.
Telemedicine
Telemedicine is often used interchangeably with telehealth, however, the term telemedicine generally implies a physician mediated interaction with patients, and is used more in the USA; and The provision of health care and education over a distance, using telecommunications technology; and The use of audio, video, and other telecommunications and electronic information processing technologies for the transmission of information and data relevant to the diagnosis and treatment of medical conditions, or to provide health services or aid health care personnel at distant sites; and the use of electronic communication and information technologies to provide or support clinical care at a distance. Included in this definition are patient counseling, case management, and supervision/preceptorship of rural medical residents and health professions students when such supervising/precepting involves direct patient care.
Telementoring
The use of audio, video, and other telecommunications and electronic information processing technologies to provide individual guidance or direction. An example of this help may involve a consultant aiding a distant clinician in a new medical procedure.
Telemetry
The science and technology of automatic measurement and transmission of data via wires, radios, or another medium from stations based in remote locations to receiving stations for recording and analysis.
Telemonitoring
The process of using audio, video, and other telecommunications and electronic information processing technologies to monitor the health status of a patience from a distance.
Telepresence
The method of using robotic and other instruments that permit a clinician to perform a procedure at a remote location by manipulating devices and receiving feedback or sensory information that contributes to a sense of being present at the remote site and allows a satisfactory degree of technical achievement. For example, this term could be applied to a surgeon using lasers or dental handpieces and receiving pressure similar to that created by touching a patient so that it seems as though s/he is actually present, permitting a satisfactory degree of dexterity.
Teleradiology
A system that transmits images over a distance, using leased or switched transmission lines. See also PACS and RIS.
Teletext
A broadcasting service utilizing several otherwise unused scanning lines (vertical blanking intervals) between frames of TV pictures to send data from a central database to receiving television sets.
Telnet
An application program that permits users to logon to any computer on the Internet for interaction with other users. For example, a telnet program may be used to peruse library holdings and receive results.
Terrestrial Carrier
A telecommunication transmission system using land-based facilities such as microwave towers, telephone lines, coaxial cable, or fiber optic cable as differentiated from satellite transmission.
Thread
Messages on an individual topic that appear in the order they were sent in an online discussion forum, such as on a newsgroup. This system makes reading of a particular subject easier, because all of the relevant messages are grouped together.
Throughput
The amount of data that is actually transmitted over a network in a given period of time, expressed in bits per second. Throughput rates are related to baud rates, but are generally little lower due to imperfect transmission conditions. Usually, higher baud rates will permit higher throughput.
Thumbnails
Miniature pictures of images using very small, low resolution data files. These download for display very quickly, and can be compared on-screen to select the proper high-resolution image.
Tie Line
A telephone circuit leased or dedicated to an individual which is provided by common carriers that connect two points together without using the switched telephone network.
Tiling
An artifact of digitization and compression. Portions of the on-screen video image break into smudged squares. Tends to happen when there is too much on-screen motion, overwhelming the ability of the compression algorithm adequately to apportion system resources to both motion handling and resolution. See Ghosting.
Translator
A broadband network operation. A translator is an instrument, located in a central retransmission facility to filter incoming microwave signals and retransmit them in a higher frequency band.
TCP/IP
Transmission Control Protocol/Internet Protocol. The underlying communications rules and procedures that allow computers to interact with each other on the Internet.
Transmission rate
Amount of information / unit of time that a technology such as a regular (POTS) or digital (ISDN or T1) phone line, satellite or wireless technology, or local area network (LAN) can transmit. A typical POTS-based modem can transmit 33.6 thousand bits (Kbps) of information/second.
Transmission Speed
The speed at which information passes over a communications channel; generally given in either bits per second (bps) or baud.
Transponder
A microwave receiver and transmitter in a satellite that receives signals being transmitted from Earth, amplifies them, and sends them back down to Earth for reception purposes.
Trunk
A large capacity, long-distance channel that common carriers use to transfer information between its customers.
TSS
Telecommunications Standardization Sector of the ITU (International Telecommunications Union).
Turn-key System
A system of telecommunications in which all of the installation services and components needed for operational teleconferencing have been provided by a single vendor or contractor.
Twisted Pair
The most common type of medium in PSTN's (public switched telephone network) local loops, insulated copper wires are wrapped around each other to void the effects of electrical noise. It can transmit voice, data, and low-grade video.
UHF
Ultrahigh Frequency. A radio frequency in the second highest range of the radio spectrum, from 300 to 3,000 MHz.
Universal C-Mount
Enables a video camera to be attached to any medical peripheral device that uses the same connector. These are increasingly common.
Unsharp Mask
Despite the name, this is an edge-enhancing filter frequently used in teleradiology. It is created by first generating a low-pass filtered image, which is then subtracted from the original image. This effectively removes part of the background, leaving an image where contours are emphasized.
Uplink
The link, or path, from a transmitting earth station to the satellite. The term is typically referring to a transmitting earth station.
Upload
Transferring files or software from one computer to another.
URL
Uniform Resource Locator. The standard form for an address on the Internet. For example, http://www.vase.org/ indicates a Hypertext Transport Protocol (http) address on the World Wide Web (www) with location 'vase' and the type of owner (org). Other valid guidelines may include ftp and gopher. Unlike most e-mail addresses, URLs are always case sensitive, that is, whether a character is upper or lower case does make a difference.
User Interface
The graphic and design components of a Web page that directs users on how to access the information contained in that website.
V.32 bis
International standard for data communications using a modem at speeds of up to 14,400 bits per second.
V.34 bis
International standard for data communications using a modem at speeds of up to 28,800 bits per second. When purchasing a modem, the user should look for this feature.
Validity
The extent to which a situation observed reflects the actual situation.
VAR
Value Added Reseller. Adds functionality to product(s) from OEM(s). Compare integrator.
VCR record source control
One-source control indicates if the system allows the user to push one button and start or stop recording either end of the video conference. Several systems require entering a complex series of commands (multiple button pushes) to initiate or stop recording the conference, or to change which end of the conference is being recorded. This is very cumbersome when a user only remembers shortly after the start of a conference to turn the tape on, or when trying to record sequential segments of the participants at both ends of a video conference. We have not found an off the shelf system that allows the user to record both ends of a video conference simultaneously on one tape.
VCR Simultaneous
Concerns the ability to have one VCR playing a pre-recorded tape into the system as a video source, while simultaneously having another VCR connected and recording the videoconference in progress. This is necessary for those telemedicine programs that maintain a policy of recording all consults and which periodically use pre-recorded tapes of patient procedures or educational tapes as part of a video conference.
VCR
Video Cassette Recorder
VFC
V-Fast Class. Introduced prior to the V34, this proprietary modem modulation used for 28.8 Kbps connections, is no longer a supported standard.
VGA
Videographics Array. A measure of image size, representing the capacity to display 640 X 480 lines, such as on viewing monitors for personal computers.
VHF
Very High Frequency. A radio frequency in the very high range of the radio spectrum, from 30 to 300 MHz.
Video format
NTSC, PAL, HDTV, SECAM
Video Frame Grabber
An instrument that changes an analog video signal into a set of digital values.
Video on Demand
The ability to provide instantaneous access to remotely stored sources of video. A video server stores and manages large amounts of multimedia data and delivers it on demand to one, or many, users. Limitations to deployment are bandwidth availability, video server price, and video compression protocols.
Video Output
Composite, S-video.
VTC
Video teleconferencing. A teleconference that includes video communications, specifically pertaining to a two-way electronic communications system that permits two or more persons in different locations to engage in the equivalent of face-to-face audio and video communications. Note: Video teleconferences may be conducted as if all of the participants were in the same room.
Videoconferencing
Actual-time, generally two way transmission of digitized video images between multiple locations; uses telecommunications to bring people at physically remote locations together for meetings. Each individual location in a videoconferencing system requires a room equipped to send and receive video.
Videophone
Small, stand-alone video appliance with a small camera and circulation, not part of a computer or larger videoconferencing system, that enables interactive audio-video communications over POTS or ISDN.
Virtual Circuit
Packet switched network facilities that appear to be an actual end-to-end circuit.
VLAN
Virtual Local Area Network. A computer network using inter-networks as data links that are transparent for users and that do not have restrictions on protocols, so that the network has the characteristics of a local area network.
VPN
Virtual Private Network. The provision of private voice and data networking from the public switched network through advanced public switches. The network connection appears to the user as an end-to-end, nailed-up circuit without actually involving a permanent physical connection, as in the case of a leased line. VPNs retain the advantages of private networks but add benefits like capacity on demand.
Virtual Reality
A computer-based technology for simulating visual, auditory, and other sensory aspects of complex environments to create an illusion of being a three-dimensional world. The world is designed by the computer and viewed through a special headset that responds to head movements while a glove responds to hand movements. For example, while in a virtual room a person may move their hand up in order to fly or tap to change the color of a wall.
VoD
See Video on Demand.
Voice Grade Channel
A telephone circuit of adequate bandwidth to carry signals in the voice frequency range of 300 to 3400 Hertz. This is the bandwidth of a POTS line.
Voice Recognition
The ability of a computer to interpret auditory information in the form of spoken words.
Voice Switching
An electronic method for opening and closing a circuit, such as changing form one microphone to another microphone or from one video camera to another video camera, responding to the presence or absence of sound.
Voxel
Volume Element. A voxel is like a pixel in a three-dimensional version and is generated by computer-based imaging systems, such as CT or MRI.
VRAM
Video Random Access Memory
VTC
Video Teleconferencing
WAN
Wide Area Network. Data communication networks that links together distant networks and their computers to provide long-haul connectivity between separate networks located in different geographic areas. Wide Area Network. Wider in geographic scope than a LAN. Provides digital communications (voice / video / data) over switched (ISDN, switched 56) or unswitched (fractional T1, T1) networks. Some consider commercial dial-up networks (America OnLine, the Internet) to be WANs
WATS
Wide Area Telephone Service. A telephone service with a flat rate for measured bulk-rate, long distance services given on an incoming or outgoing basis. WATS allows a consumer, by use of an access line, to make telephone calls to any telephone number that is able to be dialed in a specific zone for a flat or bulk monthly rate using an 800 number.
Wavelets
An image compression technique that enables more or less lossless compression ratios of 10:1 or even 20:1, compared to the standard 3:1 maximum for lossless JPEG compression.
Whiteboard
Shared notebook. The shared whiteboard feature provides the electronic equivalent of an onscreen blackboard. This feature’s greatest utility is when a video call is established but the audio portion is not functioning. One can then write a note on the white board for one end to make a phone call to the other to discuss the problem. May have modest utility.
Wildcard
Typically represented by an asterisk (*), a wildcard symbol permits the user to conduct an open-ended search. It may be used to ensure a search turns up all forms or derivatives of a word. For example, chil* will turn up both child and children.
Window Width
The range of the gray scale of the image seen on a screen. The middle value is the 'window level.'
Windowing
A software manipulation technique, using mathematical algorithms, to compensate for a teleradiology monitor’s inability to provide the same contrast and bit depth as the original hardcopy X-ray. Pixels within a certain range of bit-depth values are assigned the full range of possible grayscale values, while those outside that range are either white or black. This allows emphasis of contrast for those structures that lie within the grayscale “window.”
Wireless
Descriptive of a network or terminal that uses electromagnetic waves (including rf, infrared, laser, visible light-and acoustic energy) rather than wire conductors for telecommunications.
Workstation
A grouping of computer hardware and software (e.g. monitor, keyboard, hard drive) functioning for individual uses such as word, information, and image processing.
WWW
World Wide Web. The universe of accessible information, including graphics, sound, text and video accessible through the Internet. The Web has a body of software, a set of protocols and defined conventions for accessing such information, including HTML (HyperText Markup Language), the Web's software language, and TCP/IP, a family of networking protocols providing communication across interconnected networks. Also known as "the Web." An Internet information resource for international hypertext linking which offers graphics, sound, text, and in some cases video clips giving information. This is the newest (1993) and fastest growing aspect of the Internet because of its ability to offer more than just plain text online.
WRAIR
Walter Reed Army Institute for Research.
WWW
World Wide Web.
Zip
An extension for a file name indicating the file is indexed and compressed using Phil Katz's PKZIP compression utilities. A program, called 'pkunzip.exe' is needed to decompress and extract the programs within this file.

Sources:
Health Resources and Services Administration, US Dept of HSSA
http://www.hrsa.gov/telehealth/granteedirectory/glossary.htm
Health Telematics Unit, University of Calgary
http://www.fp.ucalgary.ca/telehealth/Glossary.htm
TelehealthNet
http://telehealth.net/glossary.html
The Association of Telehealth Service Providers
http://www.atsp.org/telemedicine/glossary.asp
Telemedicine Information Exchange
http://tie.telemed.org/professional/glossary.asp