contrast

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con·trast

(kon'trast),
1. A comparison in which differences are demonstrated or enhanced.
2. In radiology, the difference between the image densities of two areas is the contrast between them; this is a function of the number of x-ray photons transmitted or the strength of the signals emitted by the two regions and the response of the recording medium.
4. Performed with a contrast medium.
[L. contra, against, + sto, pp. status, to stand]
Farlex Partner Medical Dictionary © Farlex 2012

contrast

Imaging An MRI term for the relative difference of signal intensities in two adjacent regions of an image. Image contrast heavily depends on the chosen imaging technique (i.e., TE, TR, TI), and reflects such parameters as proton density and T1 or T2 relaxation times.
Segen's Medical Dictionary. © 2012 Farlex, Inc. All rights reserved.

con·trast

(kon'trast)
1. A comparison in which differences are demonstrated or enhanced.
2. radiology The difference between the image densities of two areas.
[L. contra, against, + sto, pp. status, to stand]
Medical Dictionary for the Health Professions and Nursing © Farlex 2012

Contrast (agent, medium)

A substance injected into the body that illuminates certain structures that would otherwise be hard to see on the radiograph (film).
Gale Encyclopedia of Medicine. Copyright 2008 The Gale Group, Inc. All rights reserved.

contrast 

1. Subjective sense: subjective assessment of the difference in appearance of two parts of a field of view seen simultaneously or successively. Hence, luminosity contrast, lightness contrast, colour contrast, simultaneous contrast, successive contrast.
2. 
Objective sense: quantities defined by the formulae for luminance contrast.
Note: Example (c) is better known as luminance ratio (CIE). L2 is the maximum luminance and L1 is the minimum luminance. See spatial frequency; contrast sensitivity; differential threshold.
brightness contrast The enhanced apparent darkening of an area when viewed near, or following a lighter stimulus (or lightening, near or after a darker stimulus).
colour contrast 1. A difference in the appearance of surfaces based on hue or saturation. 2. The enhanced difference in the colour of two surfaces induced by their proximity (simultaneous colour contrast) or successive stimulation (successive colour contrast). The appearance of the smaller area shifts towards the complementary colour of the surround or background. Example: a yellow area appears reddish when surrounded by a green background.
contrast sensitivity function See contrast sensitivity function.
contrast sensitivity test See contrast sensitivity chart; contrast sensitivity.
simultaneous contrast A difference in the appearance of two adjacent areas occurring at the same time.
successive contrast A difference in the appearance of stimuli following each other.
contrast threshold See contrast sensitivity; differential threshold.
Millodot: Dictionary of Optometry and Visual Science, 7th edition. © 2009 Butterworth-Heinemann

con·trast

(kon'trast)
1. A comparison in which differences are demonstrated or enhanced.
2. In radiology, the difference between the image densities of two areas is the contrast between them.
3. Contrast medium.
4. Performed with a contrast medium.
[L. contra, against, + sto, pp. status, to stand]
Medical Dictionary for the Dental Professions © Farlex 2012

Patient discussion about contrast

Q. Has anyone had an allergic reaction to gadolinium dye, MRI contrast agents, I have had a severe reaction. I would like to know the long term effects of this dye. And if anyone else has had or heard of problems and reactions to it. Please answer me. Thank you

A. In 1969 I almost died from the IVP dye. I had no idea I was allergic and when I awoke I was in a "recovery room." The doctor told me to always tell any physicians/paramedics etc of my allergy status regarding the dye. I now have chronic back pain, have a history of cancer in the family and the doctor wants to do a scan (including dye) but when I emphasized that I was allergic he backed off. Now I am wondering if there is anything else that can be done to test the bone (scan) without the dye. Any answers? Thanks

More discussions about contrast
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References in periodicals archive ?
By improving the contrast ratio of LCDs, light leakage caused by LC retardation in the bump region can be reduced.
The relationship of perceived phase against interocular contrast ratio (previous fellow eye/previously amblyopic eye) is plotted for 14 treated anisometropic amblyopes (S1-S14).
With 33mn sub-pixels, the advanced display produces an infinite contrast ratio and lifelike perfect colours
PLC-XK2600 has XGA resolution, a 2,000:1 contrast ratio and 2,600 Lumens brightness
The C2 Fine technology that enabled high contrast ratios in transmissive HTPS panels has been optimized for the reflective HTPS panels, and Epson's unique planarization technology is used to make the reflective layer almost perfectly flat so as to control the scattering of light.
SANYO, Chatsworth, Calif., one of the world's largest manufacturers of LCD and DLP projectors introduces the PLV- Z3000 a super-fast 120Hz Full HD 1080p LCD Projector that features SANYO's exclusive 3D color management system, an ultra-high contrast ratio of 65,000:1, an advanced lens shifting function and a quiet fan system.
After JVC developed the initial 7.86-megapixel (3840 x 2048 pixels) 4K2K D-ILA device in the summer of 2003, it subsequently further evolved the technology for highly realistic, high-definition images through a range of test viewings and verification testing, resulting in the development of JVC's first commercial 4K2K D-ILA device (1.7-inch device size, 5,000:1 device contrast ratio) and the 4K2K D-ILA projector incorporating that device in September 2004.
Featuring innovative Dynamic Contrast Ratio (DCR) technology that enhances the LCD contrast ratio up to 3000:1, exceptional speed and the best in reliability and performance, the new CASA LCD series includes a collection of screens ranging in size from 17-inches to 22-inches at a competitive price point.
A spokesman from General Dynamics Itronix of Spokane Valley, Wash., says the technology mutes "internal reflections that wash out touch screen displays." It also improves the sunlight contrast ratio, which he says permits better "view and fine details definition."
With a patent-pending design approach that focuses on contrast ratio and polarization techniques, DynaVue technology optimizes viewability in all lighting conditions, including direct sunlight, and will be featured as the standard touchscreen on General Dynamics Itronix's full line of rugged and semi-rugged notebooks and tablet PCs.
The ViewSonic VA1716w features 250 nits of brightness, 1440x900 native resolution, and 500:1 contrast ratio; the ViewSonic VA1916w offers a 1440x900 native resolution and 2000:1 dynamic contrast ratio, while the ViewSonic VA916 features 2000:1 dynamic contrast ratio and 1280x1024 native resolution.
The GD-19L1GU is a 19-inch monitor with a contrast ratio of 1000:1 and a wide viewing angle of 178 degrees both horizontally and vertically.