WHAT IS CONTRAST MATERIAL AND WHY IS IT USED IN MEDICAL IMAGING?

Medical imaging allows radiologists to see inside the body, helping them detect potential concerns and share those findings with your physician. For certain exams, such as computed tomography (CT) and magnetic resonance imaging (MRI), a contrast material (also called contrast dye or contrast agent) may be used. The contrast material helps highlight specific structures, making it easier to identify abnormalities. 

The type of contrast material depends on the type of medical imaging your physician has requested. It is not a permanent colouring agent, but a temporary substance that changes how X-rays or magnetic fields are absorbed or reflected by tissues. This creates clearer separation or “contrast” between different areas of the body, improving the visibility of organs, blood vessels, and tissues. 

CT WITH CONTRAST 

A CT scan uses a combination of X-rays and computer technology to produce comprehensive images of specific areas of your body, including your bones, chest, head, joints, lungs, and spine. CT scans provide more detail than regular X-rays and can detect conditions that may not be visible with other imaging methods. 

If a CT scan requires contrast, it may be administered either intravenously or orally:   

• An injected iodine-based contrast helps highlight blood vessels and organs by blocking X-rays, making the targeted areas appear brighter on the scan. Some patients may notice a very warm feeling that spreads throughout their body for about 20 seconds during and after the injection. This is often concentrated around the groin area, and you might think that you are passing urine, but you are not. This is very common and is nothing to worry about and the feeling goes away quickly (10–20 seconds). If IV contrast is required, you will need to fast for two hours prior to your appointment. 

• If your exam requires oral contrast, you’ll be asked to drink 1500 ml of water mixed with a small amount of iodine-based contrast. This helps the scan clearly show the esophagus, stomach, intestines, and colon. If oral contrast is prescribed, you will need to fast for four hours prior to your appointment and arrive two hours prior to your exam, unless otherwise specified at the time of booking.  

MRI WITH CONTRAST 

MRI uses a strong magnetic field to provide very clear images of the body and is often ordered to help diagnose stroke, aneurysms, or multiple sclerosis. Using magnets and radiofrequency waves MRI can help find diseases of the brain, spine, skeleton, abdomen, and soft tissues. 

An MRI uses a different type of contrast material, gadolinium-based compounds. Gadolinium alters the magnetic properties of nearby water molecules, enhancing the visibility of tissues on MRI scans. It is administered intravenously. Most patients do not notice any sensation, although a few will experience a cold feeling in the arm during the injection.  

CONTRAST SAFETY 

Contrast materials are safe and rarely produce side effects, such as allergic reactions. However, certain allergies and medical conditions, such as kidney disease, can increase your risk of side effects. While reactions are rare, we are well-equipped to deal with them.  

When booking your exam, you will be asked about your allergies, medical conditions, and any previous reactions to contrast materials. This information helps us identify if you may be at higher risk for complications. Please answer these questions carefully, and include details about your current medications, health conditions (including allergies or pregnancy), and any past contrast-related reactions. 

WHAT HAPPENS AFTER MY EXAM?  

After your exam, your body will absorb or naturally eliminate the contrast material through urine or bowel movements. Drinking plenty of water can help this process along. Most people feel completely fine afterward, but if you notice unusual symptoms, such as diarrhea, nausea, or vomiting, contact your doctor. If you ever experience signs of an allergic reaction, like difficulty breathing, itching, or hives, call emergency services immediately. 

 We do our best to have our radiologists interpret the imaging and forward the results to your doctor in a timely manner. Please consult with your doctor regarding your results and any follow up exams or questions. 

HOW MUCH WILL IT COST? 

In Calgary, CT and MRI exams are provided at our Mayfair Place location as private pay exams and are not covered by Alberta Health Care. Prices are per body area. If additional body areas are scheduled within the same appointment, discounts apply. For example, the abdomen is one body area, while the spine is divided into three body areas. We also offer CT Health Assessment packages. 

In Saskatchewan, we provide MRIs as a publicly funded, community-based service under contract with the Saskatchewan Health Authority and as a private pay exam. Private MRI services in Saskatchewan are provided in accordance with and under the legislation of the Province of Saskatchewan. Prices are per body area. If additional body areas are scheduled within the same appointment, discounts apply. 

We offer a 10% Seniors discount (65+) that can be applied to the first exam. 

Your health spending account or group medical insurance plan may cover the cost of a private CT or MRI that is prescribed by a qualified health care practitioner. You will need to check with your plan administrator for coverage details. 

REFERENCES 

Radiology Info (2024) “Contrast Materials.” www.radiologyinfo.org. Accessed August 15, 2025
Inside Radiology (2017) “Iodine-containing contrast medium.” www.insideradiology.com.au. Accessed August 14, 2025. 

Inside Radiology (2017) “Gadolinium Contrast Medium (MRI Contrast agents).” www.insideradiology.com.au. Accessed August 14, 2025.