Your physician might order one of several diagnostic imaging tests.
Diagnostic imaging tests are tools your doctor uses to help determine a diagnosis of a medical condition. The type of disorder your doctor suspects dictates which type of test will be ordered. These tests are usually conducted in a hospital or clinic and are interpreted by a physician called a radiologist. The radiologist reads the tests and reports his findings back to the physician who ordered them. Most diagnostic imaging tests are non-invasive and therefore not painful. The most common tests are X-rays, CT scans, magnetic resonance imaging, mammography, ultrasound and nuclear medicine scans.
X-Rays
.A common X-ray test image is called a radiograph.
The most common and well know diagnostic imaging test is the X-ray. X-rays typically image bones to look for fractures. The chest X-ray might be ordered if the doctor suspects damage to or disease of the lungs. The image is formed from a small amount of radiation projected into the specific body part to be imaged, and the rest of the patient's body is covered with protective draping. The resulting images are "negatives" of the internal structures. An X-ray does not show soft tissues or organs.
CT Scans
A CT scan is useful in imaging bone structures.
To better image bone structures, your physician might order a CT scan, or a CAT scan. This stands for Computed Axial Tomography. In this test, the patient lies down into a cylinder that then rotates around the body to capture the images. These images come out as "slices" of the section being imaged, much like slices of bread. A CT scan is particularly useful also in imaging the brain and the inner ear. At certain times, a contrast agent might be injected into the patient to provide better results. These agents are iodine-based, so let your physician know if you are allergic to iodine or shellfish.
MRI
An MRI is used to vary images of tissues, similar to those of a CT scan.
Another diagnostic test used by physicians is the magnetic resonance imaging (MRI) scan. This test is useful in providing more detailed images of soft tissues. The patient is placed inside a cylindrical tube that uses powerful magnets and radio waves to produce the images. The machine can be noisy, and patients are required to lie still, so a mild sedative might be prescribed beforehand for people with claustrophobia. Like the CT scan, an MRI images tissues in slices; a change in the radio waves and the magnetism of the machine provide different image contrasts. Contrast agents might be used in conjunction with an MRI, but they are not iodine-based.
Utlrasound
Ultrasounds are most commonly used to image the developing fetus in the womb.
An ultrasound is mostly used to let the physician see an unborn fetus as it develops in the womb. The test uses sound waves to produce images, and there is no harm to either the baby or the mother. Ultrasounds are used to image other "hollow" organs as well, such as the bladder. The test can be performed with three-dimensional images, or four-dimensional, which is an ultrasound in motion. To image blood flow through arteries and veins, the doctor might use an ultrasound with Doppler capability.
Mammography
A mammogram is a test used to study breast tissue. It is similar to an X-ray but images the density of the breast to look for any abnormalities. This test uses no contrast agents and is relatively painless.
Nuclear Medicine
A doctor will order a nuclear medicine test to scan the bones, thyroid or heart. A contrast medium is injected, and the test is conducted over a period of time as the contrast moves through the body. The doctor might order a cardiac stress test, which will include the use of the radioisotope thallium during the test. The test itself is painless.
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