What is Nuclear Medicine?
Nuclear Medicine is a medical subspecialty that involves the use of small amounts of radioactive materials (radiopharmaceuticals or tracers) to help diagnose and treat a variety of diseases.
Unlike an x-ray, which provides information on the presence of disease based on structural appearance, nuclear medicine determines the cause of the medical problem based on the function of the organ, tissue or bone. In a nuclear medicine test, the radioactive material is introduced into the body by injection, swallowing, or inhalation. Different tracers are used to study different parts of the body. The amount of radioactive material used is carefully selected to provide the least amount of radiation exposure to the patient while ensuring an accurate examination. In treating diseases, the radiopharmaceuticals destroy diseased tissues.
What are some common Nuclear Medicine procedures?
Scans of the thyroid, heart, lungs, GI tract, kidneys, and bones are common. Other tests such as localization of infection or tumors and serum measurements (radioimmunoassay) of thyroid function are also performed. The images from the abovementioned scans provide physiologic information other imaging modalities cannot give.
Thyroid Scan and Uptake provides a means of documenting the location, shape, and functional characteristic of thyroid tissue. The radioactive iodine (RAI) uptake complements the thyroid scan and answers specific questions regarding thyroid function. Combined with serum measurements of thyroid function (radioimmunoassay), thyroid scan and uptake permits a quick diagnosis and logical approach to therapy or further diagnostic procedures. The test takes 60 minutes for imaging while the radioactive iodine uptake will be taken at 2 and 24 hours post-administration.
Myocardial Perfusion Imaging (Nuclear Cardiac Stress Test) provides information about the function of the heart and the extent and severity of any abnormality relating to blood flow to the heart muscle. A radiopharmaceutical (Thallium 201 or Technetium 99m-Sestamibi) is injected into a vein and goes to the heart. It is usually performed while the patient is on a treadmill or during pharmacologic stress test. The test requires two sets of pictures of the heart and may take 4-5 hours depending on the protocol used and the need for extra pictures. The staff can tell you more about how long you need to stay or if delayed imaging will be needed after 24 hours.
Ventilation/Perfusion Lung Scan provides information about ventilation and blood flow patterns in the lungs. Scans can be used to detect blood clots blocking the blood flow in the lungs. The test may also show which areas of the lungs are functional and which are not. The patient breathes in a small amount of radioactive gas or aerosol for the ventilation lung scan while the perfusion lung scan is done through intravenous administration of the radiotracer. The test may take about 60 to 70 minutes.
Gastrointestinal Bleeding Scan is most commonly used to locate suspected bleeding in the lower gastrointestinal tract. It involves “tagging” a radiotracer to the patient’s red blood cells. Serial images of the abdomen in the supine position are taken up to 2 hours. Delayed imaging may be done after 6 and 24 hours if initial study is negative or continued blood per rectum is noted.
Hepatobiliary (HIDA) Scan evaluates the patency (openness) of the cystic duct in suspected acute cholecystitis (inflammation of the gallbladder). Other applications include potential biliary obstruction, leaks and biliary atresia (congenital absence of biliary duct opening), as well as other problems involving biliary dynamics.
A small amount of radiotracer is injected through a vein, which will be taken up by the liver and passed into the gallbladder and bowel. The series of images usually takes about 2 hours. Delayed images may be taken at 3, 6, and 24 hours after injection. Pediatric patients may be sedated.
GFR/Renal Scan provides important diagnostic and prognostic information for patients with known or suspected kidney disease. Basic renogram is generated, which includes a series of images of the kidney as the radiotracer is removed from the blood, transits the kidneys, and enters the bladder. A measurement of relative function is also obtained. The test may take approximately 60 minutes.
Bone Scan detects possible bone problems by depicting blood flow to bone and bone metabolism or turnover. The entire skeletal system can be surveyed for presence of bone metastasis. Bone scan is also used to evaluate suspected osteomyelitis, fracture, tumor, and treatment response. After injection of the radiotracer into the vein, you will be asked to return for scanning after 3 hours. A series of images will be taken for up to 1 hour. Sometimes, images are acquired during the initial phase of injection (three-phase bone scan) to survey for presence of bone infection.
Leukocyte Scan (99mTc-HMPAO-labelled white blood cells) is the most sensitive and specific radionuclide imaging tool for detecting infection. It localizes in sites of soft tissue infection, abscesses, and osteomyelitis. After labeling leukocytes from the patient’s own blood and injecting it to the peripheral vein, the imaging is performed after a few hours.
Gallium Scan is highly useful in staging, detecting relapse or progression, and monitoring and predicting therapeutic response and outcome for Hodgkin’s disease and non-Hodgkin’s lymphoma. It involves intravenous injection with delayed imaging up to 7 days after injection.
How safe are Nuclear Medicine procedures?
Nuclear Medicine procedures are generally safe because the radioactive tracers or radiopharmaceuticals used are quickly eliminated from the body through natural functions. Moreover, the tracers rapidly lose their radioactivity through time. The amount of radiation in a nuclear imaging procedure is comparable with that received from a diagnostic CT x-ray.
Are there any side effects?
Minor discomfort may arise from the intravenous injection but is similar to the one you’d have for a routine blood test. Side effects in diagnostic scans are rare. The overall prevalence of adverse reaction has been documented at 2.3/100,000 administrations or less than 1%. In radioactive iodine therapy, minor side effects such as nausea or swelling of the salivary glands may be experienced but the latter can be prevented.
How should I prepare for a nuclear medicine procedure?
No special preparation is usually needed. However, if the procedure involves the heart or stomach, you may have to skip a meal before the test. You may also be asked to stop or avoid certain medications that might interfere with the test. If the procedure involves the kidneys, you may need to drink plenty of water before the test.
How is the procedure performed?
The radiopharmaceutical is usually administered into a vein or given orally, depending on which organ system is being studied. The organ system also determines what kind of radiopharmaceutical will be used for the study. The imaging may be done immediately, a few hours later, or even several days after administration of the radiopharmaceutical. The wide range in scanning times is attributed to the time it takes for the radiopharmaceutical to concentrate in the organ system of interest.
Images obtained are acquired through a Gamma Camera, which detects the emitted light or radioactivity of the radiopharmaceutical in the body. A computer enhances the acquired images. The series of images reflect how a certain organ functions over time.
After the procedure, the Nuclear Medicine physician checks the quality of images to ensure that an optimal diagnostic study has been performed and makes the report for the referring physician.
Who interprets the results and how do I get them?
When the exam is completed, a physician specially trained in Nuclear Medicine will review the images, prepare a report, and discuss the results with your doctor. Your doctor will then explain the results to you and discuss what further procedures, if any, are needed.
What are common therapeutic indications of Nuclear Medicine?
The most common conditions treated by nuclear medicine are hyperthyroidism (overactive thyroid) and thyroid cancer. Newer indications include relief of pain from arthritis non-responsive to medications, certain tumors that have spread to bones, and inoperable liver cancer.
Precautionary Information Nuclear medicine procedures are not recommended for pregnant and/or lactating women unless absolutely needed. If you are, or suspect you may be, pregnant or if you are breastfeeding, discuss the matter with your physician before undergoing any procedure.
The Department of Nuclear Medicine is located at the Upper Ground Floor. For inquiries, please call us at (632) 771-9000 ext. 8141.