Imaging scans are a standard part of medicine. In addition to the familiar X-rays or ultrasound, your doctor may perform computed tomography (CT) or magnetic resonance imaging (MRI). Imaging tools use X-rays, radio waves, sound waves, or a magnetic field to produce images of your internal structures. The scans are invaluable in monitoring your health, guiding surgery, or diagnosing some medical conditions.
Sometimes, these tests need help to produce clearer images. That's where contrast for scans comes in.
What Is a Contrast Medium?
Contrast materials are substances you take before an imaging test that help produce contrast in the pictures. For example, X-rays ordinarily pass through your body's tissues, except for bone. With a contrast medium, those X-rays don't pass through soft tissue, making it clearer in the images. The contrast may help visualize blood vessels, blood flow, organs, and tissue.
Contrast can be used in most types of diagnostic imaging, including ultrasound, CT, MRI, and X-ray. There are a few different types of contrast used for scans, according to the Radiological Society of North America:
- Iodine-based contrast, which is usually administered by injection for enhancing X-ray and CT images.
- Barium sulfate, which is often taken orally, but sometimes rectally with an enema, used to enhance CT and X-rays.
- Gadolinium, which is usually injected to enhance MRI exams.
- Saline or air, which are most often used for ultrasounds to get clearer pictures in areas such as the uterus or heart.
The type of contrast you're given depends on the type of imaging test and what structures your doctor needs to view. For example, you may take an oral or enema barium sulfate solution for a CT scan of your gastrointestinal tract. You may need an intravenous (IV) injection of a gadolinium-based agent for an MRI of the brain.
Contrast for scans is sometimes called dye, but it doesn't actually dye your internal organs or tissues. Instead, it changes the way the imaging tools interact with your body, leading to clearer pictures.
What Can I Expect From Contrast for Scans?
Contrast agents are safe to use during scans, and your body naturally rids you of them within a day or two when you urinate or have a bowel movement. When the contrast is first administered, you may have some surprising feelings, so it helps to know what to expect.
When contrast for scans is injected, it sends a warm, tingly sensation throughout your body. This can also leave a warm feeling between your legs that sometimes feels like you urinated. But don't worry, you didn't have an accident. The warm feeling fades within a minute or two.
You may also have a metallic taste in your mouth for a short while from the contrast.
If you take the contrast by enema, you may immediately feel the need to void it back out, but that will pass. An enema can also make you feel temporarily bloated and a little uncomfortable until the dye begins to work its way out of your system.
After the scan, drink lots of water or fluids to help your body pass the contrast sooner. Most people do not have any severe adverse effects from the different contrast agents. Be sure to tell your doctor if you have any allergies or kidney problems.
Your radiologist or technician will help prepare you for what to expect during your exam. The contrast is a normal part of many tests and will help your doctor develop the most accurate diagnosis possible.