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MRI stands for magnetic resonance imaging; it basically uses powerful magnets and radio waves to create detailed images of the interior of your body. It can be done with or without contrast. Contrast is a type of dye that is injected intravenously either right before, or during the procedure. Certain abnormalities, such as tumors, will absorb the dye and show up very clearly on the MRI with contrast. Your doctor will determine whether you need an MRI with contrast or without, and may order both tests.
An MRI scan is different than a regular x-ray or a CT scan, which both use ionizing radiation to create images. MRI scans generally produce clearer images with much more detail than an x-ray or CT scan. Small tumors, which may be invisible on an x-ray or CT scan, may be detected by MRI. In the case of most cancers, the earlier treatment is begun, the better the outcome of treatment, so an early MRI scan of any suspicious area can literally mean the difference between life and death.
As good as a standard MRI image is, the image can be improved even further by adding contrast. Tumors and other abnormalities will absorb the contrast dye as it progresses through your blood vessels, and on the MRI scan this area will glow. This allows for the detection of even the smallest tumors, and it also gives your doctor a clearer idea about the location and size of a tumor and which organs or tissues are involved. In addition, contrast allows a doctor to observe functional abnormalities that are not visible on a regular scan, particularly problems with how well your blood is flowing through your vessels.
The contrast medium used in MRI, generally gadolinium, is different than the contrast dyes used in x-rays or CT scans. Adverse reactions to gadolinium are much rarer than iodine-based dyes. However, if you have abnormal kidney function, you may be at increased risk for nephrogenic systemic fibrosis caused by the MRI dye. This complication is extremely rare, but always be sure your doctor and radiology technician are aware of any medical problems or allergies you may have, before you are injected with any type of contrast dye. Most people tolerate MRI with contrast just fine, and the benefits of early tumor detection generally outweigh the minor risks associated with the dye.
An MRI with contrast is generally painless, but you may experience some discomfort with the IV or needle used to inject the dye. You will be placed on a table and positioned so that the scan will show the affected area most clearly. You may be slid inside a long narrow tube in a closed MRI, or you may have an open MRI, in which the scanning equipment is shaped like a large doughnut and only scans a certain portion of your body at a time. The imaging process itself may take 45 minutes up to two hours, and you may be offered headphones so you can listen to music during the scan. Once the scanning is complete, a radiologist will read and interpret the scan and your doctor will discuss the results with you.