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.
![vet]()
By
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,
![catvet]()
and
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.
No comments:
Post a Comment