Medical Imaging | All About Medical Scans: CT, MRI, PET and SPECT

Your doc has asked that you go for a medical scan toinformation that the CAT scan doesn't, while CAT
take a closer look at what's ailing you-likely one ofscans provide more structural information-about the
these tests: a CAT scan, a SPECT scan, a PET scan,heart, for instance. Together, they can provide the
an ultrasound, an MRI-or some combination of these.most detailed picture of what may be going on inside
So how will it help you? Here's an overview of whatof you.
each medical imaging device does and whatNonradioactive scans
information it captures:The two most common are ultrasound and MRI
CT scans (aka CAT scans)(magnetic resonance imaging). Ultrasound uses sound
A computed tomography scanner is an X-ray device.waves to take pictures inside the body. MRI can
As a large doughnutlike ring moves over and spinsacquire images both in 2-D and in 3-D; it can look at
around the body, the beams are sent through the bodythe beating of the heart in real time, as ultrasound can;
from one side and the emerging radiation is detectedand it is able to tell tissues apart in ways other
and forms images on the other. "When patients gotechnologies can't.
through a CAT scanner," says Scott Daniel Flamm,Mind-Reading: EEG Reports
M.D., head of cardiovascular imaging at the ClevelandAn electroencephalogram (EEG) can detect problems
Clinic in Cleveland, "it takes a series of 3-D pictures orin the brain's electrical system that may indicate the
axial slices very quickly. It's much like getting a chestpresence of a tumor, head injury or diseases, such as
X-ray-just a whole lot faster and more sophisticated."epilepsy and migraine. In the test, up to 25 electrodes
SPECT scansare placed on the patient's scalp; they record changing
In a single-photon emission computerized tomographypatterns of electrical activity and convert the electrical
(SPECT) scan, a camera photographs the travels of asignals into a series of spiky lines drawn on a moving
radioactive tracer that is injected into the body. Dr.piece of graph paper. The doctor can then read the
Flamm explains: "How it moves in different areas ofprint-out to see if there are any abnormalities.
the body can highlight possible problems, such asDuring an EEG, patients often have to stay motionless,
inadequate blood supply."because any movement may alter the results.
PET scansSometimes a patient is asked to breathe deeply and
Positron emission tomography (PET) scanners use arapidly or to look at a bright flickering light.
different kind of radioactive tracer and are consideredThe procedure is very safe. If it happens to trigger a
a more powerful imaging tool. Both SPECT and PETseizure, the person performing the EEG is trained to
scans usually produce no side effects, but PET scansensure the patient's safety.
are considered better because they are moreIt's useful to know how medical imaging tools work.
sensitive to some metabolic activities, such as theAfter viewing your scan results, a doctor obtains
amount of glucose or oxygen used in different partsprecise information that could help make a diagnosis or
of the brain. A SPECT scan focuses more on bloodguide treatment. And that's what really matters: getting
flow.the care you need.
Combo scansWriter: John McIntosh
SPECT and PET scanners can be combined with©REMEDY, Summer 2007
CAT scanners (at which point they're calledGet a FREE 2-year subscription to REMEDY, one of
SPECT-CT scanners or PET-CT scanners). SPECTMediZine, LLC's award-winning health magazines. Sign
and PET scans give some physiological and functionalup today!