Contrast is a substance that highlights structures of the body in the images, such as blood vessels, organs and some lesions. It helps the radiologist tell tissues apart and reach a more accurate diagnosis. The doctor who ordered the exam decides whether it will be done with or without contrast, according to the clinical indication.
CT and MRI use different contrasts
| CT | MRI | |
|---|---|---|
| Type of contrast | Iodinated | Gadolinium based |
| How it is given | Into a vein; in some exams, by mouth | Into a vein |
| How it leaves the body | Through the kidneys | Through the kidneys |
What to tell us before the exam
- Allergies (to medicines, to contrast or others) and asthma: let us know when booking, so the nursing team can contact you beforehand.
- Kidney disease, diabetes or regular use of medication.
- Pregnancy or possible pregnancy. During pregnancy, CT is only done on some areas of the body, with the abdomen protected.
- Breastfeeding: tell the team and your doctor.
For CT, patients aged 70 or older who will receive contrast should bring their urea and creatinine results, tests that show how the kidneys are working.
What you feel at the time
With CT contrast, it is common to feel a warm sensation through the body or a metallic taste in the mouth for a few seconds, right after it is given. Allergic reactions can happen, but they are uncommon, and the team is prepared to act if they do.
After the exam, follow the team’s instructions.
Informational content. It does not replace your doctor’s advice.
