It’s exciting that the new technology is allowing medical professionals to see pictures of amyloid plaque in the brain. But what if you wanted to have such a scan, even if you weren’t experiencing symptoms of memory loss?
That request would probably be denied based on new guidelines related to brain amyloid imaging that were published by the Alzheimer’s Association and the Society of Nuclear Medicine and Molecular Imaging (SNMMI). These guidelines are important to guide the medical professionals because finding elevated beta amyloid plaques using positron emission tomography (PET) scans may indicate Alzheimer’s, but also may be indicative of other conditions.
What is a PET scan?
This type of scan involves injecting a very small dose of a radioactive chemical into the patient’s body. This chemical, called a radiotracer, is absorbed by the organs and tissues that are being studied in the body, according to the Cleveland Clinic. The patient is then asked to lie down on an examination table that is moved into the center of a PET scanner. The scanner detects and records the energy that is emitted from the radiotracer. A computer then converts the findings into three-dimensional pictures that allow physicians to look at cross-sectional images of the organ from any angle in order to identify any functional problems. This particular scan identifies metabolic changes at the cellular level that are occurring in an organ; this is different from other types of imaging such as a computed tomography (CT) scan or magnetic resonance imaging (MRI). “A PET scan can often detect these very early changes whereas a CT or MRI detect changes a little later as the disease because to cause changes in the structure of organs or tissues,” the Cleveland Clinic website states.
The radiotracer takes between 45-60 minutes once it is injected into a vein to travel throughout the body and be absorbed into the organs and tissues to be examined. The scan can take between 30-60 minutes, although brain studies typically take less time for imaging. “Depending on which organ is being examined, there may be additional tests and additional dyes or chemicals used that may lengthen the total appointment time up to 3 to 4 hours,” the Cleveland Clinic added.
To develop these guidelines, the two groups named an Amyloid Imaging Taskforce that consisted of experts in both imaging and dementia. This group was asked to review the scientific literature and then come to a consensus on recommendations for the clinical use of PET scans.
The group’s recommendation was that PET scans can be helpful in diagnosing cognitive impairment as long as they are considered along with information identified during clinical appointments. Furthermore, these PET scans need to be performed by trained staff who follow a standardized protocol. Additionally, the decision to use PET scans needs to be made after a comprehensive evaluation by an experienced physician who is well versed in the assessment and diagnosis of cognitive impairment and dementia. These scans should only be done if the physician believes “the presence of absence of amyloid would increase certainty in the diagnosis and alter the treatment plan,” the Alzheimer’s Association reported.
The taskforce identified which patients would be appropriate candidates for PET scanning in order to check amyloid levels. These groups are:
- Patients who are experiencing persistent or progressive memory problems or confusion that can’t be explained. Furthermore, these patients need to demonstrate impairments using standard tests the assess cognition and memory.
- Patients who have progressive dementia and who are considered as having early onset dementia (before the age of 65).
- Patients whose tests indicate possible Alzheimer’s disease who also are unusual in their clinical presentation.
The taskforce also identified cases when it would be inappropriate to do a PET scan to identify amyloid in the brain. These cases are:
- Patients who are 65 years of age or older who meet standard definitions and tests of Alzheimer’s. The taskforce believed that a positive PET scan would provide little additional value in these cases.
- Patients who do not exhibit symptoms of cognitive impairment or dementia.
- Patients who have a complaint about their cognitive status but whose impairment hasn’t been confirmed by a clinical assessment.
The taskforce also noted that PET imaging to identify amyloid plaques is considered inappropriate in the following circumstances:
- To determine the severity of dementia.
- When requested based only on a patient’s family history of dementia or other risk factors for Alzheimer’s, such as the ApE-e4 gene.
- As a substitute for genetic testing that could identify mutations that cause Alzheimer’s disease.
- For non-medical reasons, which include insurance, legal or employment decisions.
I applaud the taskforce for creating these guidelines. The use of PET scans are a wonderful tool, but they need to be used by physicians in concert with other types of assessments in order to make the appropriate diagnosis.
Primary Sources for this Sharepost:
Alzheimer’s Association. (2013). First guidelines published for brain amyloid imaging in Alzheimer’s.
Cleveland Clinic. (2009). PET scan.
Published On: January 30, 2013