Before new PET technology came on the scene, physicians could only examine the brains of Alzheimer's disease patients once they died. Now, new PET images can show the brain plaques characteristic of Alzheimer's disease in living patients, technology that, while ground-breaking, is expensive and may not produce useful results for every patient. On Jan. 28, the Society of Nuclear Medicine and Molecular Imaging and the Alzheimer's Association co-released guidelines that give physicians, patients and family members the tools to determine whether the cutting-edge tests are right for a patient.
"Even though it's really exciting new technology, which we are certain will contribute to patient care, because of the expense as well as it's not [being a] perfect test, we want to really carefully integrate this technology for the best care of the patient," said Dr. Satoshi Minoshima, SNMMI member and co-author of the appropriate use criteria. "That's really the reason for creating this appropriate use criteria."
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Dr. Minoshima explained that the test, still in its early stages, has about a 90 to 95 percent accuracy rate. And results can be misleading if used on the wrong patients. Elevated beta-amyloid plaques are one of the defining signs of Alzheimer's disease, but for reasons unknown, the plaques can sometimes appear on seemingly healthy brains as well.
Also, many cases of Alzheimer's can be diagnosed without the use of scans. The guidelines suggest using them for cases when a person younger than 65 is showing symptoms, or if the case is more difficult to diagnose, such as if the patient had a stroke recently and is already showing some cognitive decline.
"In clinical diagnosis, it's very difficult to distinguish Alzheimer's disease if the patient had a stroke," said Dr. Minoshima. "Having PET imaging, that shows really positive amyloid deposition, really helps atypical cases like that."
The guidelines also note that the tests are inappropriate when used to determine the severity of dementia, when requested, based solely on family history of dementia or Alzheimer's disease and for non-medical reasons, such as insurance.
The SNMMI team combed through medical journals and sought comments from nuclear medicine professionals in order to develop the guidelines. Dr. Minoshima hopes the guidelines will help physicians get the most out of the emerging technology.