Helpful Definitions

Some definitions to help you understand the procedures discussed in this section:

Aneurysm: A bulging section in the wall of a blood vessel that has become stretched out, thin and weak. If an aneurysm ruptures (bursts), it may result in death if not treated immediately.

AVM (Arterial Venous Malformation): A tangle of blood vessels in the brain that can invade healthy tissue, restrict blood flow to the brain and cause a brain hemorrhage.

CAT (Computerized Axial Tomography): CAT scans use X-rays and computers to produce images of the soft tissue within the body, including the brain.

MRI (Magnetic Resonance Imaging): MRI produces very clear images of the body without X-rays. Instead, MRI uses a large magnet, radio waves, and a computer to produce these images.

PET (Positron Emission Tomography): During a PET scan, a radioactive substance called a tracer is combined with a chemical substance (such as glucose) and either inhaled or injected into a vein (usually in the arm). The tracer emits tiny, positively charged particles (called positrons) that produce signals. A special camera records the tracer's signals as it travels through the body and collects in organs. A computer then converts the signals into three-dimensional images of the examined organ. The three-dimensional views can be produced from any angle and provide a clear view of an abnormality. A PET scan is often used to detect and evaluate tumors, and examine brain function.