Your doc has asked that you go for a medical scan to take a closer look at what's ailing you-likely one of these tests: a CAT scan, a SPECT scan, a PET scan, an ultrasound, an MRI-or some combination of these. So how will it help you? Here's an overview of what each medical imaging device does and what information it captures:

CT scans (aka CAT scans)

A computed tomography scanner is an X-ray device. As a large doughnutlike ring moves over and spins around the body, the beams are sent through the body from one side and the emerging radiation is detected and forms images on the other. "When patients go through a CAT scanner," says Scott Daniel Flamm, M.D., head of cardiovascular imaging at the Cleveland Clinic in Cleveland, "it takes a series of 3-D pictures or axial slices very quickly. It's much like getting a chest X-ray-just a whole lot faster and more sophisticated."

SPECT scans

In a single-photon emission computerized tomography (SPECT) scan, a camera photographs the travels of a radioactive tracer that is injected into the body. Dr. Flamm explains: "How it moves in different areas of the body can highlight possible problems, such as inadequate blood supply."

PET scans

Positron emission tomography (PET) scanners use a different kind of radioactive tracer and are considered a more powerful imaging tool. Both SPECT and PET scans usually produce no side effects, but PET scans are considered better because they are more sensitive to some metabolic activities, such as the amount of glucose or oxygen used in different parts of the brain. A SPECT scan focuses more on blood flow.

Combo scans

SPECT and PET scanners can be combined with CAT scanners (at which point they're called SPECT-CT scanners or PET-CT scanners). SPECT and PET scans give some physiological and functional information that the CAT scan doesn't, while CAT scans provide more structural information-about the heart, for instance. Together, they can provide the most detailed picture of what may be going on inside of you.

Nonradioactive scans

The two most common are ultrasound and MRI (magnetic resonance imaging). Ultrasound uses sound waves to take pictures inside the body. MRI can acquire images both in 2-D and in 3-D; it can look at the beating of the heart in real time, as ultrasound can; and it is able to tell tissues apart in ways other technologies can't.

Mind-Reading: EEG Reports

An electroencephalogram (EEG) can detect problems in the brain's electrical system that may indicate the presence of a tumor, head injury or diseases, such as epilepsy and migraine. In the test, up to 25 electrodes are placed on the patient's scalp; they record changing patterns of electrical activity and convert the electrical signals into a series of spiky lines drawn on a moving piece of graph paper. The doctor can then read the print-out to see if there are any abnormalities.

During an EEG, patients often have to stay motionless, because any movement may alter the results. Sometimes a patient is asked to breathe deeply and rapidly or to look at a bright flickering light.

The procedure is very safe. If it happens to trigger a seizure, the person performing the EEG is trained to ensure the patient's safety.

It's useful to know how medical imaging tools work. After viewing your scan results, a doctor obtains precise information that could help make a diagnosis or guide treatment. And that's what really matters: getting the care you need.

©REMEDY, Summer 2007