MRIs do not use ionizing radiation, so there is no issue of raising cancer risk. But they take much longer to complete than CTs. MRIs require the person to lie still within a closed space for about 20 to 40 minutes. This can affect some people with claustrophobia, and the procedure is noisy, which is why we provide ear protection.
This helps the radiologist see organs and other tissues within the body more clearly. For CT, I hear anxiety about exposure to radiation, especially if it is being done repeatedly. For example, certain early-stage cancers can be cured. But you might be coming back every few months or every year for a CT scan. The question is: Do we have an alternative? For MRI, people who have trouble with claustrophobia or are unable to hold their breath, which may be required for certain abdominal imaging tests, may not be able to tolerate the procedure.
Some MRI machines can be configured in ways that may reduce claustrophobia. Medical implants, such as a pacemaker, brain stimulator, or other devices, are another complicating factor. The radio waves used with MRI can heat up devices made of metal. It is an injectable dye. When you are scheduled to have contrast, there are no restrictions, meaning you may eat, drink and take any medications you are on. After your exam, you will be reminded to drink extra water throughout the day.
This aids in flushing the contrast from your system. This includes areas of the brain, spine, abdomen, chest, pelvis, and joints like knees and shoulders.
The MR image offers unique information to help your doctor better plan your treatment and care. Inform your doctor if you have any of these items: a pacemaker, aneurysm clips, metallic implants, metal fragments in your eyes or any other electronic or magnetically activated implant.
If you have any of these items it may not be possible, or safe, to have an MRI scan. If your MRI requires the injection of a contrast agent, blood work may need to be done before your MRI to make sure your kidneys are working well.
If you are claustrophobic or experience pain when lying on your back ,let your doctor know before the day of your MRI. Your doctor can prescribe a relaxant or pain medication. If your doctor has you take a relaxant medication, arrange for a companion family member or friend to pick you up after your MRI. You will not be able to drive or take a taxi home after the test if you take a relaxant medication.
When you arrive in radiology you will be asked to fill out a screening form asking about anything that might create a health risk or interfere with imaging. You will be given scrubs to change into before your exam. For imaging of the brain, spine, heart and blood vessels and cancers in particular, contrast can help doctors pick up things that would otherwise not be visible.
For certain conditions, contrast can effectively highlight areas of interest and help in making a more accurate, and more specific diagnosis. The particular type of contrast dye used in an MRI scan is different to other x-ray based tests. In MRI, the contrast used contains a naturally occurring substance called Gadolinium, which is typically attached to other compounds so that it can be used in the human body without causing any harm.
Contrast dyes are designed so that healthy kidneys recognise the contrast as something the body does not need, and excrete the agent before the complex bonds of the contrast itself have a chance to break down.
For this reason, gadolinium is generally considered to be very safe, and due to the design of modern day contrast agents, allergic-type reactions to gadolinium are very rare indeed. The vast majority of patients will feel nothing after receiving an injection of contrast and only a very small number of people will have any adverse effects.
As with all injections, whatever the substance being injected, doctors and radiology staff are always conscious of the risks vs the benefits of performing the injection.
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