contrast

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Related to double contrast: double contrast radiography

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 ?
In the double contrast cases, the expected alternative is given by the contrastive topic of the second conjunct, that is, in (23) wash the dishes.
In general, the picture is as follows: in the simple as well as the double contrast cases, but is associated with a focus in the second conjunct which provides the expected alternative (EA).
Double contrast barium enema sensitivity: a comparison of studies by radiographers and radiologists.
Complications of radiographer performed double contrast barium enema examinations.
A study conducted in 1989 at the Cleveland Clinic[21] revealed that technologists competently performed gastrointestinal studies with an average fluoroscopy time of 4.1 minutes for esophagrams and 3.2 minutes for a double contrast barium enema.
Single-contrast examination may require the use of secondary double contrast. Infusion with water may be used to achieve better distension and to help delineate the ileocecal region.
* Feczke et al[8] reported that compensating filters reduced radiation exposure during double contrast barium enema examinations by 14% to 19%.
PAUL Hanagan's double contrasted with a major net loss for Silvestre de Sousa on a day when all three champion jockey aspirants were in direct competition at Nottingham.
Also on the program were Choo San Goh's Double Contrasts, which provided an adequate showcase for the company's command of classical technique and resident choreographer Lynn Cote's Icare.