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The field of nuclear medicine is expanding quickly, and the number of scans as well as their general availability seem to be growing every year. There are many different types being used at any given time, though some of the most popular options include bone scans; whole-body scans like positron emission topography (PET); scans that focus on specific tissues and glands; and scans that are designed specifically to identify and detect tumors. In the broadest sense, the goal of all of these is to help doctors and other medical professionals see inside the body to get a precise sense of problems, growths, or abnormalities in a way that is far less invasive than surgery, but much more accurate than X-ray or most other imaging option. Patients usually have to either ingest or inject a specialized tracker that the scanning machines and related procedures will use to map things like bone density, organ thickness, and tumor size, among other things. Some tests are highly specialized while others are more general. A lot depends on the problem being diagnosed, as well as the technology available.
Nuclear medicine scans typically make use of radioactive isotopes to diagnose internal problems. Most of the time, scans are conducted in hospitals or clinics and are usually an important part of making a diagnosis. They’re usually considered relatively safe, but just the same they’re not usually performed without cause, and usually only after a patient has presented with a range of symptoms consistent with an expected diagnosis.
The patient must usually remains motionless for a period of minutes or hours while the scanning device measures how the body processes the isotope. Results can be immediate, but in other cases they take quite a bit of time to process. In some cases patients need to make a series of tracker-related appointments before the actual scanning even happens.
As their name suggests, bone scans produce skeletal images that allow medical professionals to gauge how bones are growing and to see any tumors or lesions that are forming on them. Radioactive tracers are usually injected deep into the veins before these tests begin, and they are usually programmed to illuminate or “latch on” to any problem spots on the bones. The test itself is painless, and within a few hours the tracers will pass naturally out of the body, normally through the urine.
One of the most common reasons for any nuclear medicine scan is to detect the presence of tumors, abnormal masses that often indicate cancer or other problems. Doctors can suspect tumors based on a patient’s symptoms, but these growths can be very difficult to place without some sort of imaging tool. In positron emission topography (PET) scanning, tracers attach not to problem areas of the bone but to irregular growths anywhere in the body. Like bone scans, these are usually full-body scans that look for tumors and cysts wherever they occur. The machine involved in this sort of test tends to be somewhat cavernous, and patients must usually lie on their backs and be inserted into or covered completely by the scanning device.
A test called the metaiodobenzylguanidine (MIBG) scan is another option in this category. It uses an isotope to identify and bind to MIBG, which is a growth hormone in most tumors. It illuminates these growths on results, making them much easier to locate and measure.
Other types of scans look for problems within tissue material. The body’s soft tissues are often places where beginning infections lurk, and can also support tumors and other growths. Scans intended to measure tissue density and abnormality are normally called gallium scans, and usually involve specialized cameras that have been programmed to detect areas of the body that are emitting higher then normal radioactivity a day or two after a tracer has been placed.
Nuclear medicine scans can also detect the presence of glandular dysfunctions, one example being hyperthyroidism. To test for this disorder, a patient ingests a pill containing a small amount of radioactive iodine and returns for testing several hours later. Instead of lying down for an hour or more, a technician simply places a sensor plate against the neck for about four minutes. The plate records the amount of radioactive iodine the thyroid has absorbed since ingestion. Above normal levels indicate hyperthyroidism.
One of the oldest and most “classic” scans is the cholescintigraphy, also known as the hepatobiliary iminodiacetic acid (HIDA) scan. In a healthy patient, the radioactive isotope travels through the liver and into the gallbladder within one hour of injection. If the isotope does not appear in the gallbladder, it indicates a duct obstruction between the liver and gallbladder. Due to advances in ultrasound technology, the number of HIDA scan procedures performed in developed countries is falling; when available, ultrasound if often the preferred method for this sort of diagnosis. Ultrasound is less invasive in that it requires no injection, is usually faster, and is almost always less expensive, too.
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