A REQUEST FOR A CAT SCAN READS LIKE THIS: Tomografia computadorizada de cabeza y con contraste. What does "contraste" mean here?

contrasting agent that enables his scan to register in a more pronounced manner. If the oral agent does not work sufficiently, he takes IV.

https://www.proz.com/kudoz/spanish_to_english/medical/31886-...

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Note added at 25 mins (2017-10-01 15:15:09 GMT)
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It is generally accepted that contrast is not indicated in cases of suspected retroperitoneal bleeding or renal stones. Otherwise, in patients who are tolerant, contrast agents are usually used during routine abdominal CT scans to help identify the internal contents of hollow organs, to visualize spaces in the abdomen, and/or to delineate surrounding blood vessels. These agents can be broadly categorized in terms of their route of administration, either through the gastrointestinal tract or intravenously, and further described by their relative density to the surrounding tissues.
Proprietary names of contrast agents used and protocols detailing the specifics of their administration vary from institution to institution.

http://emedicine.medscape.com/article/2114236-medication

Sometimes a dye (contrast agent) is injected into the bloodstream via a vein in your arm. The dye may give you a flushing feeling and an odd taste in your mouth, which soon goes.

https://patient.info/health/ct-scan

I've seen that 'contrast agent' is better than 'contrasting agent'.