Brain Imaging

There are a number of tests that give the doctor information about the structure of the skull and the inside of the brain.

These include conventional x-rays and x-rays taken after the injection of dye into the vessels leading into the brain (angiograms). In babies, high-frequency sound waves may also be used to produce a picture of the brain (echoencephalogram). All these tests help the doctor find any brain tumors, blood clots, malformations or scar tissue that might be causing seizures.

Magnetic resonance imaging (MRI, fMRI) techniques use magnetic fields instead of x-rays to produce detailed pictures of the brain. A magnetoencephalogram (MEG) measures magnetic fields of the brain and can pinpoint the source of signals of seizure activity as well as the site of normal functions such as vision, hearing, or sense of touch.

Computerized tomography (CT) and other imaging techniques also produce images of brain structures inside the head.

Brain imaging is performed by special equipment that looks somewhat like a very large front-loading washing machine, although there are variations in structure.

Typically, if you have a CT or MRI scan, you will lie on an examination table with your head resting on a curved support directly in front of the machine. You and the table will then be moved gently towards the machine so your head is inside its circular opening.

A person having a CT scan may be given an injection of what's called a contrast medium. This is a fluid that goes up to the brain and makes the scan easier to read. After the injection, some people may feel flushed, have a metallic taste in the mouth, or feel a brief nausea. The scanning process is controlled and monitored by a technologist in an outer room nearby.

Again, a child should be told what to expect and shown how this big round camera will take a picture of the brain.

Another type of machine which produces images of the brain is the positron emission tomography (PET) scanner. It produces color-coded pictures of brain processes at work -- including blood flow, use of glucose, and the presence of oxygen.