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Category Archives: Nuclear Materials

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.

The Wonderful World of Radiography: How Radioactive Sealed Sources Check Welds

Betsy Ullrich
Sr. Health Physicist
Region I
 

During construction of pipelines and fabrication of large metal structures, welding is used to join the parts. It is very important to know the welds are structurally sound and the whole piece will be strong enough for its job. For example, the pipes used to transport natural gas must be properly welded together so that the gas does not leak from the pipes.

constructionAnd metal I-beams used in constructing a parking garage must be properly welded so that the structure can hold the weight of the vehicles in the garage. How can this be done? Often, workers perform “radiography” using sealed sources to inspect the weld to see if it is correct.

What is radiography? It is term used to describe using gamma rays or x-rays to inspect the structure of some large dense material. Although x-ray machines may be used for this, they are limited by their need for an electrical source, and because x-rays can only penetrate certain materials. A radiography device (sometimes referred to as a radiography camera) uses sealed sources that emit gamma radiation that can penetrate very dense materials such as metal. Radiography devices can be used without electricity and are portable, making them handy to use at work sites.

Because a radiography source, while small in size, emits gamma radiation that can penetrate several inches of metal, it must be stored in its shielded container. When a weld needs to be inspected, a long guide tube is connected to the device that allows the source to travel to the location that needs to be inspected. A long drive cable also is attached to the other end of the device. This allows the radiographer performing the inspection to stand far away from the radiation source during the inspection. Typically, the source is in the guide tube only a few seconds to a few minutes, depending on what is being inspected.

Radiography is used to inspect welds on pipes for oil rigs; large tanks that hold gasoline; airplane engines; and other large metal structures. So the next time you use natural gas, or park your car in a multi-story garage, you might remember the important role a radioactive source plays in keeping you safe.

Paving the Way To A Better Road

Betsy Ullrich
Sr. Health Physicist
Region I
 

When you mention radioactive material, many people automatically think reactor or medical facility. They’re not aware that radiation could be used right outside their door. One example — portable gauges containing sealed sources of radioactive materials are often used during construction or repair of roads.

roadconstructionWhen paving a new road, construction crews need to know the amount of moisture in a roadbed and the density of the bed so the new road will last for many years. Portable gauges use small quantities of radioactive materials in sealed sources to make these measurements without damaging the roadbed.

To ensure the roadbed is dense enough, a sealed source emitting gamma radiation is lowered from the portable gauge into a small hole drilled into the road bed, at a specific distance from the gauge. Inside the gauge, a detector measures the amount of radiation that travels through the soil from the bottom of the drilled hole. The denser the soil, the more gamma radiation will be absorbed by the roadbed material and not reach the detector. A computer program in the gauge calculates the density of the roadbed based on the amount of radiation that reaches the detector.

Similarly, a sealed source containing a small amount of radioactive material that emits neutrons can be used to determine the amount of moisture in a roadbed. Neutrons are absorbed by water in the roadbed material, and scattered by mineral and other solid materials. The neutron source remains inside the portable gauge, and a shutter is opened to allow the neutrons to be emitted against the road bed surface. A detector inside the portable gauge detects neutrons that are scattered back from the road bed surface. This is why such source-detector combinations are referred to as “backscatter” devices.

In this case, the more moisture in the roadbed, the more neutrons are absorbed and fewer neutrons are available to be scattered back into the detector. A computer program in the gauge calculates the amount of moisture in the roadbed material from the number of neutrons detected by backscatter.

Although there are other ways to obtain this information, they may take more time, or require more invasive methods to obtain samples for analysis.

The radiation from these sources is not detectable even a few feet away, as long as the devices are used as designed. Portable gauges must be used by workers trained in radiation safety and use of the devices. And, workers using the sources are required to keep the gauges with them at all times, unless they are locked or secured as required by regulation.

NRC and Agreement State inspectors periodically inspect the companies that are licensed to operate portable gauges to ensure they’re being used safely.

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.

Reducing Proliferation Risks AND Healing the Sick

Steve Lynch
Project Manager
Research and Test Reactor Licensing Branch
 

It’s a little known fact: One of the most useful radioisotopes in medicine comes mainly from highly enriched uranium (HEU), the very stuff that can be turned into a nuclear weapon. We’re talking about technicium-99m, or Tc-99m—which has been called the world’s most important medical isotope. It’s used to diagnose a variety of illnesses in millions of procedures each year in the United States alone.

Tc-99m is created from another radioisotope, molybdenum-99, which traditionally has been produced abroad from HEU sources. A stethoscopesupply shortage that delayed patient treatments several years ago, coupled with the desire to reduce proliferation risks, prompted the world community to find better ways of securing the future supply of this isotope.

In 2012, Congress passed the American Medical Isotope Production Act to support private efforts to develop medical radioisotope production facilities using other methods and begin phasing out the export of HEU for medical isotope production. The National Nuclear Security Administration, through its Global Threat Reduction Initiative, has been promoting domestic Mo-99 production using different technologies through formal cooperative agreements with four commercial partners.

These partners and several other companies have said they are interested in producing Mo-99 in the U.S. They have proposed using several different technologies, ranging from non-power reactors to accelerator-driven, sub critical solution tanks. To support the transition to new technologies, the NRC is preparing to receive and review applications for construction permits and operating licenses for new facilities. In fact, we are now reviewing the first medical radioisotope production facility construction permit application, received earlier this year.

But not all Mo-99 production facilities will need an NRC license. While reactors fall strictly under NRC regulation, accelerator technologies that do not use enriched uranium or plutonium would be regulated by the states.

Companies, facilities and technicians involved in producing and administering Tc-99m to patients may also need to be licensed by either the NRC or an Agreement State. (There are 37 Agreement States, which have formal agreements with the NRC allowing them to regulate certain nuclear materials, including medical isotopes).

For more information on the role of the NRC and other agencies in regulating the medical use of nuclear materials, visit the NRC webpage.

Kara Mattioli also contributed to this post.

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