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Magnetic resonance imaging (MRI) is a way of viewing the inside of the body, especially the soft tissues, without using any invasive procedures. Instead, a magnetic field combines with radio frequency pulses to create an image that is displayed on a computer. In many cases a contrast substance such as gadolinium or iodine is administered to the patient, typically to make the blood vessels, intestines or another area of the body appear opaque during the MRI procedure. Not all tests require this, and in some cases the patient may be given a brain MRI without contrast substances being used.
A brain MRI is used to diagnose many different conditions. Some of these include aneurysms, strokes and tumors. The procedure is also used to identify multiple sclerosis lesions and to locate injuries from accident or illness. There are times that the use of a contrast substance is essential, but many times it is possible to get the desired results from a brain MRI without contrast. It generally depends on the condition being investigated.
When problems with blood vessels, tumors or inflammation are suspected, it is likely that the doctor will choose to use a contrast material with the brain MRI. The contrast substance is usually injected just prior to the MRI procedure itself. In some cases it may be injected during the test, especially if areas of the brain are being investigated for problems with blood flow, such as after a stroke. Trying to get images of blood vessels from a brain MRI without contrast is often unsuccessful.
People that are allergic to the contrast substances or who are suspected of having conditions that will readily be visible anyway may be given a brain MRI without contrast. Typically anyone with serious kidney problems will also not be given a contrasting agent, since in some cases the contrast can cause further kidney problems. Certain types of MRIs used for investigating multiple sclerosis (MS) can also be administered without contrast.
Both a patient that is undergoing a brain MRI without contrast and one that has had a contrast injection will be required to hold absolutely still during certain parts of the test. This allows the machine to get a clear, focused image of the patient’s brain. If the subject moves, the results will not be clear enough to show the level of detail normally required of MRI results. Not everyone is a good candidate for a brain MRI, especially people who are very overweight, who have a pacemaker or who are claustrophobic. In such cases other tests may be used to diagnose a patient’s condition.