Fall 2009

A Look INSIDE

CT and MRI Explained

Each year, millions of patients in the American health care system will undergo a computed tomography (CT) or magnetic resonance imaging (MRI) diagnostic exam, many of them apprehensive, frightened, or simply unsure about what these tests involve.

The imaging process is vital in the diagnosis of many diseases because it gives physicians the extraordinary capability to see details in the human body that may result in earlier and more accurate diagnoses and a broader range of treatment options for patients.

“CT and MRI exams are two critical, non-invasive tools in analyzing potential disease, allowing us to look inside the patient,” said AAMC radiologist Timothy S. Eckel, M.D., of Annapolis Radiology Associates. “But it’s important for our patients to know why their physician has ordered one exam over the other, and how the exams work. CT and MRI exams provide us images in very different ways.”

The CT scan

A CT scanner uses a single beam of x-radiation to create a cross-section picture of the body. A computer processes the results in two- or three-dimensional pictures shown on a monitor. It is used to diagnose acute brain disorders such as a hemorrhage or stroke as well as to examine the lungs, bowel, abdominal organs and bones. The scanner looks like a large doughnut. During the scan the patient lies on a table that moves slowly forward while the scanner takes pictures of the body part to be examined. The beam rotates around the patient as the patient and the table move through the scanner.

Magnetic Resonance Imaging
(MRI)

Magnetic resonance imaging, or MRI, is a newer technique that uses a powerful magnetic field and radio waves to produce images without the use of radiation. MRIs are used to evaluate the diseases of the central nervous system (brain and spine) and joints but can also be used for further evaluation of soft tissue. In this exam, the patient lies on a table that is surrounded by a cylinder-shaped or open configuration magnet. The strong magnetic field forces the protons in the body into a different position. As they move back into place they send out radio waves of their own. A computer turns these signals into a picture.

Dr. Eckel said, “Both CT and MRI are extremely useful tests. The best imaging choice for a patient depends on a number of factors, including the patient’s clinical complaints, working diagnosis, and individual patient factors (prior surgery, allergies, medical problems, etc.). When needed, the radiologists are always available to help your physician determine which imaging test would be best in any circumstance.”

Your AAMC primary care physician or medical specialist may order an MRI or CT exam for many reasons. Anne Arundel Diagnostics Imaging, part of Anne Arundel Health System, offers a full range of CT, MRI and other imaging services. For more information about Anne Arundel Diagnostics, visit www. annearundeldiagnostics.com or call 1-800-909-XRAY (9729).

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