contrast

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Related to Contrast agents: Contrast MRI

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 ?
Cardiologists also reported safety as the most important factor in selecting a contrast agent and identified safety as the greatest area for improvement.
With healthy kidney function, Gd contrast agents should be excreted within a short time.
The first contrast agent approved for in vivo usage was Gd-DTPA (Magnevist[R]), which is still among the most frequently used contrast agents.
"The alternative for patients having MRI scans is to not use a gadolinium-based contrast agent at all as part of the scan.
The longitudinal relaxation time (T1, ms) and transverse relaxation time (T2, ms) of the synthesized PEG contrast agent solutions were measured using a 300 MHz (7.1 T) NMR spectrometer with a combination of measurements obtained in a large NMR tube (650 [micro]L of deuterium oxide to dilute the synthesized PEG contrast agents to different concentrations from 0.05 mM to 0.8 mM) and in a small tube (containing 50 [micro]L of benzene-D6).
Respiratory system, while it works together with the cardiovascular system for oxygen homeostasis, can be directly affected by cardiovascular disorders [5] or indirectly by diagnostic contrast agents. There are scarce data on the adverse effects of angiographic contrast agents on respiratory functions.
Nontargeted SPIO MR contrast agents have been reported to wash out from tissues a few hours following injection [28], which is also observed for the MIC6-injected animals.
Baseline Characteristics and Positive Detection Rate of Different Contrast Agents. The baseline characteristics of the population included in this study are shown in Table 1.
TEHRAN (FNA)- Ordinary sugar could become a contrast agent of the future for use in magnetic resonance tomography examinations of tumors, as malignant tumors show higher sugar consumption than surrounding tissue, report scientists.
Conclusion: The results show that bare and coated MNPs are suitable as [T.sub.2]-weighted MR imaging contrast agents. Also, the obtained [r.sup.2]/[r.sub.1] values (59.3 and 50) for bare and coated MNPs were in agreement with the results of other previous relevant works.
Chemists, radiologists, and physicists from the US, Europe, Asia, and Canada discuss the chemistry of imaging contrast agents, probes, and biomarkers in these modalities, the methodology in which the agent becomes bound to its intended target, and how it acts in in vitro and in vivo environments.
As with other iodinated contrast agents, Visipaque is often associated with sensations of discomfort, heat or pain.