- Joint Photographic Experts Group (JPEG)
- 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.
- A video frame in which all of the video information is recorded in
compressed fashion. If the clip has a large amount of motion, better
playback will occur with every frame being a Key Frame. If there is very
little motion, such as a narrator, a higher number of Delta Frames will
give satisfactory playback. In general, making every 3rd frame a Key Frame
is a good choice with the current Indeo technology algorithm. Also see
- A telephone system in which multiple
phones share a set number of outside lines
and a currently open line must be selected by pushing the corresponding
button on the phone.
Laboratory Information System (LIS)
- An integrated system for the processing of laboratory data. While
electronic lab reports are becoming more commonplace, the proprietary
nature of commercial lab systems has limited the changeover to a paperless,
- 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 video
conference. Currently few institutions are capitalizing on this potential.
- A storage device similar to an optical disk but in a card form.
- 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.
- In a LAN used for videoconferencing for
example, latency refers to delays which may be experienced by some data,
causing intermittent cessation of the audio and/or visual communications.
Similarly, the sound might arrive before the image or vice versa
under some high-latency conditions. The cause is often poorly designed
networks with utilization greater than 30 per cent or single users
accessing or originating multi-megabyte-sized files.
- a data compression algorithm named after its developers.
- 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
- The maintenance of sound (i.e., speech) exactly in step with movement in
a visual image (i.e., faces). Because the processing time for the video
portion of the signal in a low-speed codec is about 100 times longer than
the audio processing time, codecs usually incorporate adjustable audio
delay circuitry to delay-equalize the two signals, to regain lip sync.
Liquid Crystal Display (LCD)
- A very low-power device capable of displaying characters, words and
symbols, often built into a codec or videoconferencing room control panel.
Local Area Network (LAN)
- 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.
- See compression ratio.
- See compression ratio
Low bit rate or low data rate video
- Video that we are doing over the satellite at 56 kpbs. It is live video,
but not FULL MOTION Video. There
is now technology to do low bit video at 16 kpbs...
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").
- That portion of a composite
video signal which represents the monochrome or brightness part of
- 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.