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Nuclear Medicine Imaging
A Diagnostic Procedure
Note: This section has health/medical information. It was not written by a health care professional. References:
- Everything You Need to Know About Medical Tests, edited by Breanndan Moore (1996).
- The People's Book of Medical Tests, by David S. Sobel, MD, and Tom Ferguson, MD, (1985).
The Technical Facts
Nuclear medicine imaging provides images of internal organs not possible with conventional X-ray machines. X-rays can only distinguish between dense (bone) tissues and less dense (muscle) tissues in the body. In nuclear imaging, the body is not bombarded with X-rays, instead, a radioactive compound is injected, swallowed, or inhaled and after a suitable amount of time, detected in the body using a special camera. The dose of radiation received from the radioisotope in a nuclear imaging procedure is usually comparable to that obtained in a dental X-ray. The imaging camera may look like an X-ray machine, but it is actually only a detector, as it does not emit radiation.
The challenge to a child undergoing a nuclear imaging procedure will depend on the test. One consideration is the administration of the radioactive compound, whether it is one more needle prick, gulping down a yucky-tasting liquid, or inhalation. (IV injections can likely be given through their port.) Other considerations are whether a lot of water needs to be consumed during the test, or whether an enema will be required. Often there is a delay between the administration of the radioactive compound and the imaging, from minutes to hours or days. The actual imaging procedure will require the child to remain still for a varying amount of time. Since the imaging doesn't emit radiation, the parent can be next to their child during the procedure.
The different nuclear imaging procedures which children with cancer might need are discussed below. Most of them are used in conjuction with other tests to obtain a definitive diagnosis.
Bone scans show abnormalities in the skeleton long before the problems are detectable by X-rays (3-6 months before, according to one reference). The doctor may order bone scans to determine whether or not cancer is present in the bones or to evaluate unexplained bone pain.
The radioactive tracer is administered intraveneously and the it travels through the body and is absorbed by the bones. During the 1-3 hours after the isotope is injected, the child will need to drink a lot of water or juice, otherwise there are no restriction on activities. The fluids clear the body of radioactive material that is not picked up by bone tissue. When the scan is about to begin, the child must empty his/her bladder to prevent the radioisotopein the bladder from obscuring the pelvic bones.
The child must lie still on the table for about an hour while the gamma camera moves back and forth above his/her body. He/she may be asked to change position several times to obtain different views.
The radioactive tracer concentrates in areas of increased bone metabolism, both normal growing bone or in bone tumors or bone infections. These areas will show up as "hot spots" on the scan. Results are usually available in a day or two.
Liver and Spleen Scan
Liver and spleen scans can be used to detect tumors in the liver and spleen. The radioactive substance is called technetium and most of it is absorbed by the liver, some by the spleen, and some by the bone marrow. The technetium is injected into a vein and the abdomen is scanned 10-15 minutes later. Tumors show up as "cold spots"; results are usually available in 1-2 days.
Kidney scans are used to evaluate kidney function as well as tumors. A combination of radionucleotides is used and after IV injection, pictures are taken every few minutes for about 20 minutes. The test shows blood flow through the kidneys, which in turn can signify the presence or absence of tumors, cysts, or other kidney disease.
Gallium Scan of the Body
A gallium scan is a whole body scan. It helps detect tumors and inflammations. The radioactive substance is "gallium citrate" and it tends to accumulate in areas where there is rapid cell growth, such as tumors and sites of infection.
The gallium is injected IV. There are no special concerns such as drinking water or fasting. The imaging is done 24-48 hours later; sometimes scans are taken at several different times after injection. The scan itself takes 30-60 minutes, during which time the child must lie still. Results are available in a day or two.
Generally more than X-rays, less than CT.
These pages are intended for informational purposes only and are not intended to render medical advice. The information provided on Ped Onc Resource Center should not be used for diagnosing or treating a health problem or a disease. It is not a substitute for professional care. If you suspect your child has a health problem, you should consult your health care provider.