Posted by Article on 2/25/2002, 9:49 am

Diagnostic Imaging: Getting the inside view The main players Other imaging tests Remember how neat and tidy medical practice was in the original Star Trek television series? Dr. McCoy ("Bones") could instantaneously diagnose a crew member's malady simply by waving a hand-held tricorder over whatever hurt. Real-life diagnostic imaging has not quite progressed to the Star Trek level. But the growth of technology has allowed for astounding changes in how the human body can be viewed. Today, physicians have available to them more and better imaging tools than ever before. Not only have the X-ray and today's sophisticated, computerized imaging techniques reduce the need for exploratory surgery, they've also made it possible to detect disease earlier. The main players More than 100 years after its discovery, X-ray remains a valuable diagnostic tool. Chest X-ray is still among the most commonly used imaging techniques. X-ray (roentgenograms) can detect changes in body tissues, such as bone problems or tumors in the lungs or breast. X-rays also are used to view the gastrointestinal tract. In addition to X-ray, today's computerized scanning equipment makes it possible to record more precise images of what lies within the human body. Among the most commonly used scanning tests are ultrasound, computed tomography (CT) and magnetic resonance imaging (MRI). Ultrasonography (also called ultrasound or sonography) — Ultrasound uses no radiation. Instead, it combines high-frequency sound waves and computer processing. This makes it possible to view internal organs in motion, a fetus during pregnancy or the flow of blood through a vessel. Ultrasound is especially good for providing information about the shape, texture and makeup of tumors and cysts. Typically it's used to examine abdominal organs (such as the kidneys, liver, pancreas and gallbladder) as well as the breast, uterus, ovaries, prostate and thyroid gland. It's also used to view the heart's movements (echocardiography). There's a growing trend to use ultrasound to look for narrowing (stenosis) of blood vessels. For example, the large neck (carotid) arteries leading to the brain are commonly examined to screen for stroke risk. It's also useful in detecting enlarged arteries, such as an aortic aneurysm. Ultrasound exams are painless. While you relax on a bed or examining table, a wandlike device (transducer) is placed on your body. It emits inaudible sound waves that are reflected back to the transducer (like sonar). Those reflected sound waves are then translated into a moving image by a computer. Typically, an exam takes less than 30 minutes. Computed tomography (CT) — A CT scan allows your doctor to see your organs in two-dimensional "slices." Split-second computer processing creates these images as a series of very thin X-ray beams are passed through your body. CT can provide detailed, cross-sectional images of extremities, the brain and organs of the chest and abdomen. CT images are especially useful in diagnosing tumors, bleeding or infection deep within large organs. To help visualize the area of interest, a "dye" (contrast medium) is almost always used. The dye can be injected into a vein or, for abdominal scans, swallowed. CT scans are painless and generally take less than 10 minutes. You simply lie still on a movable table that's guided into what looks like an enormous doughnut where the images are taken. Even faster imaging is possible with spiral (helical) CT scanners that can scan the entire body in as little as 30 seconds. Magnetic resonance imaging (MRI) — The cylinder-shaped MRI scanner uses no X-rays. Instead, a computer creates tissue slice images from data generated by a powerful magnetic field and radio waves. These images can be viewed from any direction or plane. Examinations of the brain, neck, spinal cord and soft tissues are MRI's strong suit. It's also especially good for evaluating joint, muscle and bone problems. During your exam — which may take 15 minutes to an hour — you lie on a movable table inside the scanner. Exams are noisy, so you may be given earplugs. In some instances, a contrast medium is injected into a vein to enhance certain images. Because of the magnetic field, MRI usually is not appropriate for people with pacemakers or other implanted electrical devices. People who have claustrophobia may find having an MRI difficult. However, medications are available that can help. Other imaging tests In addition to MRI, CT, ultrasound and X-ray, there are other diagnostic imaging tools. Among them are nuclear scans (radionuclide imaging). These are used to visualize the function of tissue and organs instead of their structure. This is done by introducing small amounts of radioactive materials (usually by injection) and then making images as the material passes through a certain location or organ. Nuclear scanning techniques include, among others, positron emission tomography (PET) and single photon emission computed tomography (SPECT).

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