What is an application of nuclear chemistry in medicine?
The most common nuclear medicine procedure is the use of technetium-99m in the diagnosis of coronary artery disease.
Technetium-99m is used in over forty million diagnostic and therapeutic procedures annually. It accounts for 80 % of all nuclear medicine procedures worldwide.
Technetium-99m has almost ideal characteristics for a nuclear medicine scan. These are:
It decays by emitting gamma rays and low energy electrons. The radiation dose to the patient is low.
The low energy gamma rays are about the same wavelength as medical X-rays, so they are accurately detected by a gamma camera.
It has a half-life of 6 h, which means that 94 % disappears within 24 h. This is long enough to examine metabolic processes, yet short enough to minimize the radiation dose to the patient.
Technetium can form tracers by being incorporated into a range of biologically active substances to ensure that it concentrates in the tissue or organ of interest.
Besides its use in the detection of coronary artery disease, technetium-99m is used mainly to image the skeleton, brain, thyroid, lungs, liver, spleen, kidneys, gall bladder, bone marrow, salivary glands, and numerous specialized medical studies.
In cardiac imaging, for example, a technetium compound is injected intravenously into a patient, where it distributes in the heart muscle in proportion to the blood flow. A gamma camera detects the gamma rays emitted by the technetium-99m as it decays.
Two sets of images are acquired. For one set, the technetium is injected while the patient is at rest, and then the heart muscle is imaged. In the second set, the patient is stressed either by exercising on a treadmill or by administering a drug. The drug is injected at peak stress, and imaging is again performed. The resulting two sets of images are compared with each other to distinguish restricted and blocked blood vessels.