Nuclear Medicine and the NRC: How it Works for Us, Patients and Health Care Providers

Sophie Holiday
ACMUI Program Manager

One of the more interesting things to emerge from nuclear weapons development was the use of radioisotopes in medicine. Before the end of World War II, there wasn’t much in the way of peaceful uses for radioisotopes. But in 1946, the Manhattan Project found a way to use its weapons technologies for the common good. It used a reactor at Oak Ridge to produce isotopes that could be distributed widely for research, medicine and industrial uses.

The Oak Ridge reactor offered a new family of isotopes created when uranium atoms fission, or split apart. These “byproduct” materials have many uses. It works like this: Radioisotopes give off energy that can be detected as they move through the body, allowing them to be used as “tracers.” This allows technicians to view different processes of the body than can be seen on x-rays. In larger amounts, some isotopes can also be used to target and destroy tumors.

Today, about 17 million patients each year in the U.S. benefit from imaging with radioisotopes or are involved in research, according to the Society of Nuclear Medicine and Molecular Imaging. About 150,000 patients a year undergo radionuclide therapy.

More than half of the diagnostic procedures are cardiovascular studies. But nuclear medicine patients may have cancer, diabetes, even Alzheimer’s disease. Radioisotopes are also used for bone scans, to locate tumors, to treat infections, and for studies of the liver, kidney, and lungs. And new procedures are being developed all the time.

acmuiquoteThe NRC’s job is to review uses of radioisotopes in medicine and determine if they can be safe both for the patient and the medical personnel – as well as the public. To ensure the NRC has access to the best available information for our reviews, we rely on a committee of experts known as the Advisory Committee on the Medical Uses of Isotopes.

This committee is made up of 13 health care professionals from several disciplines, including nuclear medicine, nuclear cardiology, nuclear pharmacy, medical physics, patients’ rights advocacy and health care administration. There are also representatives from the Food and Drug Administration and an NRC Agreement State—a state that has assumed regulatory authority over certain radioactive materials used in their state. They are appointed by the Commission and serve four-year terms. They meet twice and have three teleconferences each year.

These committee members advise the NRC on technical and policy issues related to nuclear medicine. Last year, the committee provided advice on changes needed to our regulations on medical isotopes and trends in a relatively new therapy called Y-90 microsphere brachytherapy. This therapy uses tiny beads containing radioactive material to target and destroy liver tumors while preserving healthy tissue.

We recently named three new members to fill open seats on the committee. For more information, see the committee’s webpage.

Using Radioactive Materials to Help Fido and Fluffy

Betsy Ullrich
Sr. Health Physicist
Region I

Radiation and radioactive materials aren’t just used for human medical purposes. Animals that are sick or hurt benefit as well, in methods similar to those used by medical doctors.

vetBy far, the most common use of radiation in a veterinary practice is from x-ray machines. An x-ray machine uses electricity to produce low-energy radiation that passes through soft substances such as skin and muscle, but not through hard substances like bone or metal. So when a veterinarian suspects your dog has a broken leg, he uses an x-ray machine to obtain a picture, called a radiograph.

Radiographs can also spot objects that animals have swallowed by mistake, such as lead sinkers lost in a pond or stream by a fisherman.

While x-ray machines are regulated by state agencies, not the NRC, other activities performed by veterinarians do require an NRC license. One common radioactive material, technetium-99m or tech-99m as it’s often called, is used to diagnose bone damage too small to be seen by x-rays. This type of diagnosis, called a “bone scan,” is performed often in horses used for racing or jumping.

The horse is injected with a tech-99m-labelled compound that acts like calcium and concentrates in the bones. The compound emits low-energy gamma rays that can be detected by a “gamma camera.” Because most of the gamma radiation will come from the bony areas of the horse, a picture of the bone can be seen. Damaged areas will have high concentrations of the tech-99m, allowing the veterinarian to see what areas are causing pain. The radioactive material decays away in a few days. The horse can then go home and be treated for the problems identified in the bone scan.

Vets commonly use another isotope, iodine-131, to treat feline hyperthyroidism. This disease is caused by an overactive thyroid, catvetand cats with this disease become very thin and sick. One possible treatment involves surgery to remove part of the thyroid, so that the cat’s thyroid activities are reduced to normal levels.

Or a veterinarian can use radioactive iodine-131, known as I-131, to reduce thyroid activity. In this type of treatment, a cat is injected with I-131, which will concentrate in the cat’s thyroid and emit gamma radiation that will damage some of the thyroid tissue and reduce thyroid activities to a more normal level. I-131 has an eight-day half-life, so cats treated with it must remain at the vet hospital for several days. Then owners must follow special handling precautions when they return home.

While technetium-99m and iodine-131 are the most commonly used radioisotopes for treating animals, some large veterinary hospitals may also use lasers, computed tomography scans, positron-emission tomography scans, and magnetic resonance imaging. And animals of all sizes, from hamsters to horses, from owls to elephants, may need x-rays – thus benefitting from the careful medical use of radiation.

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