Positive emission tomography, more commonly known as the PET scan, offers seriously ill patients the promise of more effective treatments and physicians a powerful tool against killer diseases like cancer, heart disease, Alzheimer's and Parkinson's disease.
Tomography measures metabolic rate, thereby analyzing the function and physiology of any tissue including tumors, heart muscle and brain matter.
It's a valuable tool helping physicians understand the disease process, thereby aiding in diagnosis, staging, and treatment of most types of cancer, according to Dr. David Landis, radiologist with Great Basin Imaging in Carson City.
During the procedure, a low-level radioactive isotope bound to a simple sugar is injected into the patient. The radiation received is different, but roughly equal, to the amount from two chest X-rays.
All cells consume glucose to produce energy to function, but cancer cells use more energy than neighboring cells and the cancerous tissue appears hot or unusually active in the scan, an important indicator irrespective of the size of the tumor.
"A normal-sized lymph gland could be cancerous and that could be determined by this test," he said. "If a suspicious-looking mass doesn't take up the glucose solution, it's a good indication, though not a guarantee, that it is not malignant."
Some cancers don't exhibit high metabolism, but many do and this method is very effective in staging lung cancers, so critical to determining the type of treatment. Once diagnosed, the scan can be used to determine if malignancies have grown or shrunk following chemotherapy or radiation therapy, Landis said.
The scan is also gaining popularity as a tool in determining the extent of damage following a heart attack. Damaged muscle can create scar tissue, easily differentiated from functional heart muscle on the scan. Landis said patients with functional muscle are sometimes better candidates for surgery.
In addition to being a valuable tool in diagnosing cancers and heart damage, neurological disorders like Alzheimer's disease can be diagnosed long before patients show serious symptoms.
"Now that we have drugs that may slow the progression of Alzheimer's, there is an interest in trying to diagnose it at an early stage," Landis said. "For example, if someone is 50, is forgetting things and has a family history of the disease, the diagnosis is important because treatment is now available."
Currently used in conjunction with more traditional diagnostic tools, this state-of-the-art technology is available Mondays in Carson City through Great Basin Imaging.
The procedure requires no fasting or preparation, though patients must remain very still to minimize the amount of radioactive material taken up by normal tissues. After being injected, patients wait about 45 minutes for the radioisotope to be absorbed by the body's tissues. The procedure takes about 45 minutes.
The radioisotope, known as fluorodeoxyglucose (FDG), has a half-life of 55 minutes, meaning half of it will dissipate in that time and it will completely disappear in a matter of hours.
The procedure can be expensive, about $2,900 for a full-body scan, but medicare and most major insurance companies will help with the cost.
