contrast

(redirected from contrasts)
Also found in: Dictionary, Thesaurus, Legal, Idioms, Encyclopedia, Wikipedia.

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]

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.

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]

Contrast (agent, medium)

A substance injected into the body that illuminates certain structures that would otherwise be hard to see on the radiograph (film).

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.

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]

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
References in periodicals archive ?
Key topics discussed include: the declining utilization of barium contrast agents due to the emergence of endoscopy and CT colonography as favorable alternatives for gastrointestinal imaging, and the effects that recent safety concerns surrounding paramagnetic contrast media may have on the MRI contrast media market.
Before presenting the interdialectal and intradialectal contrasts subject to analysis, it is necessary to make a methodological remark.
Take a look at the selected works of art; which ones have areas of high contrast? Listen to a few of the podcasts available at the following link to hear how students interpret these works: americanart.si.edu/education/activities/podcasts.
One of the most important visibility factors is luminance contrast, but there are few luminance contrast concepts and application of each is specific.
One nanoparticle evaluated is a new class of uniform, biodegradable, and non-toxic superparamagnetic contrast agent, [Fe.sub.3][O.sub.4].
In contrast, they more easily linked an array of foreigners, from the celebrated Albert Einstein to the despised Adolf Hitler, to unpleasant words.
By contrast, workers trapped in the life-long monotony of wage-earning and routine office work and under the thumb of employers sought a very different sort of release in vertigo, simulated violence, and the empowering experience of crowds free of any authority.
Hence the design is contemporaneous with MJP's extension to St John's, Oxford (AR October 1994), to which it offers an instruct:re contrast St John's continues the typical Oxbridge courtyard form and draws obvious inspiration flora John Soane.
Using ironic juxtaposition, Walker contrasts Traynor's other-defined "deacon-imposed" television image (his on-camera appearance) with the more "presentable" self which he brings to Gracie Mae's (his off-camera appearance): "On the TV he was inclined to dress like the deacon told him.
That is why it is important that residents should be able to see the colors clearly, to find their way without getting lost, to see the handrail contrasted against the wall, to be able to see where the wall starts and the floor ends (at the baseboard), and to be able to find and differentiate the furniture and fixtures that they use everyday.
Contrasts must exceed a particular minimum level in order to be perceptible.