What the risks are:

There is no ionizing radiation involved in MRI. To date, there have been no documented significant side effects of the magnetic fields and radio waves used on the human body during an MRI scan.

The most common MR intravenous contrast agent, gadolinium, is very safe, and although there have been documented allergic reactions to it, it is an extremely rare occurrence. However, gadolinium should not be given if you are pregnant because of potential harm to the fetus.

If sedation is used, there are associated risks of over-sedation. The technologist monitors the patient's vital signs, including heart rate and breathing as needed.

People have been harmed in MRI machines when they did not remove metal objects from their clothes or when metal objects were left in the room by others.

Special considerations:

MRI is superior to computed tomography (CT) in most cases where differentiation of soft tissues is necessary. It can view organs without obstruction by bone and foreign bodies. It is capable of showing the tissues from multiple viewpoints and is a noninvasive way to evaluate blood flow.

A CT scan may be preferred for:

• Acute trauma of the head and face
• Acute (less than 72 hours) neurological dysfunction
• Early symptoms of stroke
• Subarachnoid or intracranial hemorrhage (within the first 24 - 48 hours)
• Skull bone disorders, disorders involving the bones of the ear