Magnetic resonance imaging (MRI) is a way to see inside the body, especially the soft tissues, without using any invasive procedures. Instead, a magnetic field is combined with radio frequency pulses to create an image that is displayed on a computer. In many cases, a contrast agent such as gadolinium or iodine is given to the patient, typically to make blood vessels, intestines, or another area of the body appear cloudy during the MRI procedure. Not all tests require this, and in some cases the patient may receive a brain MRI without the use of contrast agents.
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 disease. There are times when the use of a contrast agent 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 blood vessel problems, tumors, or inflammation are suspected, the doctor will likely choose to use a contrast material with the brain MRI. The contrast substance is usually injected just before the MRI procedure. 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 the blood vessels from a brain MRI without contrast is often unsuccessful.
People who are allergic to contrast agents or who are suspected of having conditions that will be easily visible anyway may receive an MRI of the brain without contrast. Typically, anyone with severe kidney problems will also not receive a contrast agent, as in some cases the contrast can cause additional kidney problems. Certain types of MRI used to investigate multiple sclerosis (MS) can also be given without contrast.
Both the patient undergoing a brain MRI without contrast and the one receiving a contrast injection will be required to remain absolutely still during certain parts of the test. This allows the machine to obtain a clear, focused image of the patient's brain. If the subject is moving, the results will not be clear enough to show the level of detail normally required from MRI results. Not everyone is a good candidate for a brain MRI, especially people who are overweight, have a pacemaker, or are claustrophobic. In such cases, other tests may be used to diagnose a patient's condition.