Introduction
A PET scan (positron emission tomography) is imaging tests that can help reveal how your tissues and organs are functioning. To show this chemical activity, a small amount of radioactive material must enter your body.
The precise type of radioactive material, and its delivery method, depends on which organ or tissue is being studied by the PET scan. The radioactive material may be injected into a vein, inhaled or swallowed.
More radioactive material accumulates in areas that have higher levels of chemical activity. This often corresponds to areas of disease and shows up as brighter spots on the PET scan. A PET scan is useful in evaluating a variety of conditions — including neurological problems, heart disease and cancer.
Recent researches confirmed that a PET scan can show the brain's biological changes attributable to Alzheimer's disease before any other diagnostic test with significant degree of the results reliability. Alzheimer's disease can even be detected several years earlier than the onset of symptoms. Early detection and confirmation of Alzheimer's disease allows for:
- Early drug therapy to slow the loss of the patient's ability to function.
- Future planning before loss of mental capacity.
- Positive and accurate diagnosis of other dementing processes, chronic depression and normal aging.
- Help in the discovery and development of new therapies.
- Hope.
PET scan for Alzheimer’s
PET imaging has been confirmed as being one of the most accurate predictors of Alzheimer’s disease out of all of the different types of medical diagnostic imaging procedures available. A PET scan image of Alzheimers is able to show a physician the biological changes in the brain caused by Alzheimer’s disease. A recent study taken at UCLA, the California based university, have shown that PET imaging improves a doctor’s ability to forecast a patient’s future cognitive functions by up to 30%. This find relates to Alzheimer’s detection as PET imaging increases the ability of a physician to predict, in patients with early memory complaints, whether this condition will significantly worsen in the years following the initial exam.
PET scans for Alzheimer’s disease involves the administration of a radioactive tracer that is a combination of a radioisotope (a radioactive compound whose movements are detectable by a PET scanner) with a natural body compound. In Alzheimer’s diagnosis, the radioactive tracer used in the Positron Emission Tomography procedure is Fluorodeoxyglucose (FDG), which combines the natural body compound glucose with the radioisotope Fluorine-18. This radioactive tracer, or radiopharmaceutical, is used in Alzheimer’s diagnosis as the radioactive compound that it uses has a short half-life and will disappear from the body within hours. Therefore, PET scans for Alzheimer’s are safe and the patient should not have any worry about the radiation content of this procedure.
Additionally, Alzheimer’s PET scans use FDG as it contains the body compound glucose. The use of FDG, which shares a similar structure to glucose, is important, as the absorption of glucose is effective in determining the metabolic activity of the brain. In Alzheimer’s disease and other forms of dementia, the brain produces a metabolic pattern that is significantly different from the metabolic pattern of healthy brain cells. As PET imaging examines the metabolic activity of brain cells by tracing how FDG is absorbed, it is able to detect Alzheimer’s disease and other forms of dementia.
Additionally, recent studies have confirmed the effectiveness of Positron Emission Tomography in distinguishing Alzheimer’s disease from other forms of dementia. This is because Alzheimer’s disease has a metabolic abnormality (bilateral temporoparietal hypometabolism) that is significantly different from metabolic abnormalities found in other forms of dementia.
PET scan of Alzheimer’s have increased in recent years as PET imaging provides a noninvasive, painless way for physicians to confirm the presence of Alzheimer’s in patients. Traditionally, autopsy or biopsy was considered the only methods to absolutely confirm the presence of Alzheimer’s disease. With PET technology, it is now possible to identify Alzheimer’s in its early phase and subsequently use new drug therapies to delay its progression.
Recent medical studies have pointed to the possible effectiveness of using PET scanning of the hippocampus as a way to detect Alzheimer’s disease while in its early stages. It is a well-known medical fact that the hippocampus, a region of the bran that is instrumental in learning and short-term memory, is affected in the early stages of Alzheimer’s disease. It is believed that through a PET scan of hippocampus that it will be possible to see the first signs of Alzheimer’s disease long before it has spread to the cerebral cortex, which damages cognitive function and impairs the memory. Future studies on the viability of a PET scan of hippocampus have been undertaken to further the use of PET scanning for detecting Alzheimer’s disease.
In the latest studies, a new type of PET scan has been used to detect Alzheimer's non-invasively. It also gives results that are as good as doing an autopsy. The brain of a person with Alzheimer's contains abnormal proteins that form deposits and tangles (or more specifically, amyloid senile plaques and tau neurofibrillary tangles) in the cortical region. However, the most reliable method of finding these proteins while the patient is alive is by surgical removal of brain tissue, an invasive and potentially risky procedure. Some scanning methods exist but they are not as reliable. Scientists have now come up with what appears to be a reliable non-invasive method of detecting these Alzheimer "markers" using a PET scan and a new tracer chemical called FDDNP that binds effectively to abnormal protein plaques and tangles. A PET scan gives a three dimensional, computer enhanced and highly colorful "blurry-looking" image of the brain as it traces a positron emitting chemical (in this case FDDNP) after it is injected into the patient and travels through the tiny blood vessels in the brain. Any abnormal protein plaques and tangles show up because the FDDNP will stick to them.
While the usefulness of the PET scan results for early Alzheimer’s detection is already proven, the potential for this method is still huge, so we will see more and more intense research in this direction and hopefully even more promising results.
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