Nuclear Medicine

Nuclear medicine is a medical specialty that uses safe, painless, and cost-effective techniques both to image the body and treat disease. Nuclear medicine imaging is unique in that it documents organ function and structure, in contrast to diagnostic radiology, which is based upon anatomy. It is a way to gather medical information that may otherwise be unavailable, require surgery, or necessitate more expensive diagnostic tests.

As an integral part of patient care, nuclear medicine is used in the diagnosis, management, treatment, and prevention of serious disease. Nuclear medicine imaging procedures often identify abnormalities very early in the progression of a disease -long before some medical problems are apparent with other diagnostic tests. This early detection allows a disease to be treated early in its course when there may be a more successful prognosis.

Nuclear medicine uses very small amounts of radioactive materials or radiopharmaceuticals to diagnose and and treat disease. Radiopharmaceuticals are substances that are attracted to specific organs, bones, or tissues. The radiopharmaceuticals used in nuclear medicine emit gamma rays that can be detected externally by special types of cameras: gamma or PET cameras. These cameras work in conjunction with computers used to form images that provide data and information about the area of body being imaged. The amount of radiation from a nuclear medicine procedure is comparable to that received during a diagnostic x-ray.

Today, nuclear medicine offers procedures that are helpful to a broad span of medical specialties, from pediatrics to cardiology to psychiatry. There are nearly one hundred different nuclear medicine imaging procedures available and not a major organ system which is not imaged by nuclear medicine.

• Careers in Nuclear Medicine
• Fast Facts about Nuclear Medicine
• Terminology Commonly Used in Nuclear Medicine
• Nuclear Medicine, X-Rays, CT, and MRI

Careers in Nuclear Medicine

Nuclear physicians are usually based in a university or hospital, or both, and have limited involvement in direct patient care. Nuclear Medicine physicians participate in the intellectual challenge presented in assisting with the formulation of patient diagnoses and treatment wherever indicated. This specialty offers clinical variety, freedom to conduct research and make original observations.

A nuclear pharmacist specializes in the procurement, compounding, quality control testing, dispensing, distribution, and monitoring of radiopharmaceuticals. They also provide consultation regarding health and safety issues as well as the use of non-radioactive drugs and patient care.

Fast Facts about Nuclear Medicine

• An estimated 10 to 12 million nuclear medicine imaging and therapeutic procedures are performed each year in the United States.
• Nuclear medicine procedures are unique, safe, and cost-effective.
• There are nearly 100 different nuclear medicine imaging procedures available today.
• Nuclear medicine uniquely provides information about both the function and structure of virtually every major organ system within the body.
• Nuclear medicine procedures are among the safest diagnostic imaging tests available.
• The amount of radiation in a nuclear medicine procedure is comparable to that received during a diagnostic x-ray.
• Nuclear medicine procedures are painless and do not require anesthesia.
• Children commonly undergo nuclear medicine procedures to evaluate bone pain, injuries, infection, or kidney and bladder function. Common nuclear medicine applications include diagnosis and treatment of hyperthyroidism (Grave's Disease), cardiac stress tests to analyze heart function, bone scans for orthopedic injuries, lung scans for blood clots, and liver and gall bladder procedures to diagnose abnormal function or blockages.
• There are approximately 2,700 full-time equivalent nuclear medicine physicians and 14,000 certified nuclear medicine technologists nationwide.

The following techniques are used in the diagnosis, management, treatment, and prevention of disease. Nuclear medicine is unique in that it often allows for diagnostic information to be discerned prior to the onset of physical symptoms.

Planar - Provides a two-dimensional view of the process or function of the organ being imaged.

SPECT - (Single Photon Emission Computed Tomography) Provides 3-D computer-reconstructed images of multiple views and function of the organ being imaged.

PET - (Positron Emission Tomography) Produces high energy, 3-D computer-reconstructed images measuring and determining the function or physiology in a specific organ, tumor, or other metabolically active site.

Tomography - From the Greek words "to cut or section" (tomos) and "to write" (graphein). A method of separating interference from the area of interest by imaging a cut section of the object.

Nuclear Medicine Scan - The images produced as the result of a nuclear medicine procedure, often referred to as the actual procedure, examination or test.

Radiopharmaceutical - Also referred to as tracer or radionuclide. The basic radioactively tagged compound necessary to produce a nuclear medicine image.

Gamma Camera - The basic instrument used to produce a nuclear medicine image.

In Vitro - In vitro procedures are done in test tubes. Radioimmunoassay (RIA) is a special type of in vitro procedure that combines the use of radiochemicals and antibodies to measure the levels of hormones, vitamins, and drugs in a patient's blood.

In Vivo - In vivo procedures are when trace amounts of radiopharmaceuticals are given directly to a patient. The majority of nuclear medicine procedures are in vivo.

Nuclear medicine began approximately 50 years ago and has evolved into a major medical specialty for both diagnosis and therapy of serious disease. More than 3,900 hospital-based nuclear medicine departments in the United States perform over 10 million nuclear medicine imaging and therapeutic procedures each year. Despite its integral role in patient care, nuclear medicine is still often confused with other imaging procedures, including general radiology, CT, and MRI.

Nuclear medicine studies document organ and function and structure, in contrast to conventional radiology, which creates images based upon anatomy. Many of the nuclear medicine studies can measure the degree of function present in an organ, often times eliminating the need for surgery. Moreover, nuclear medicine procedures often provide important information that allows the physician to detect and treat a disease early in its course when there may be more success. It is nuclear medicine that can best be used to study the function of a damaged heart or restriction of blood flow to parts of the brain. The liver, kidneys, thyroid gland, and many other organs are similarly imaged.

General Radiology

The image, or a x-ray film, is produced when a small amount of radiation passes through the body to expose sensitive film on the other side. The ability of x-rays to penetrate tissues and bones depends on the tissue's composition and mass. The difference between these two elements creates the images. The chest x-ray is the most common radiologic examination. Contrast agents, such as barium, can be swallowed to highlight the esophagus, stomach, and intestine and are used to help visualize an organ or film.

CT

Computed tomography or CT, shows organs of interest at selected levels of the body. They are visual equivalent of bloodless slices of anatomy, with each scan being a single slice. CT examinations produce detailed organ studies by stacking individual image slices. CT can image the internal portion of organs and separate overlapping structures precisely. The scans are produced by having the source of the x-ray beam encircle or rotate around the patient. X-rays passing through the body are detected by an array of sensors. Information from the sensors is computer processed and then displayed as an image on a video screen.

MRI

Like CT, MRI produces images, which are the visual equivalent of a slice of anatomy. MRI, however, is also capable of producing those images in an infinite number of projections through the body. MRI uses a large magnet that surrounds the patient, radio frequencies, and a computer to produce its images. As the patient enters a MRI scanner, his body is surrounded by a magnetic field up to 8,000 times stronger than that of the earth. The scanner subjects nuclei of the body's atoms to a radio signal, temporarily knocking select ones out of alignment. When the signal stops, the nuclei return to the aligned position, releasing their own faint radio frequencies from which the scanner and computer produce detailed images of the human anatomy. Patients who cannot undergo a MRI examination include those people dependent upon cardiac pacemakers and those with metallic foreign bodies in the brain or around the eye.

For more information about any of the above, or if you have questions about Nuclear Medicine, please visit the Society of Nuclear Medicine homepage!

Last updated: August 2001