How to differentiate tumor recurrence from radiation necrosis in the brain using an FDG PET scan? Brain tumors, like other cancers, are typically hypermetabolic. While it is sometimes difficult to detect primary brain tumors from underlying cortical metabolism, after treatment with surgery and/or radiation therapy it becomes much easier to detect recurrent tumor. Thus, on …
How does an acetazolamide SPECT scan work to determine cerebrovascular disease? Acetazolamide is utilized sometimes with SPECT imaging to uncover cerebrovascular disease that might potentially result in an eventual stroke. Acetazolamide is a potent vasodilator and can increase cerebral blood flow through vessels that are patent and without cerebrovascular disease. However, vessels with atherosclerotic disease …
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What are the normal patterns of radiotracer uptake for CBF SPECT and FDG PET scans? In most cases, CBF and glucose metabolism correlate or are coupled. Therefore, the pattern of CBF and cerebral metabolism should appear similar. Generally, brain scans should demonstrate uniform and symmetric radiotracer uptake throughout the brain. There should be no cortical …
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How to prepare for a brain scan to assess general brain function? Patients should be informed that the test takes approximately one hour and typically involves the injection of the radiotracer followed approximately 30 minutes later by PET or SPECT imaging depending on the radiotracer. It is important to recognize that virtually everything affects brain …
Radiotracers for functional brain scintigraphy What radiotracers are available for functional brain scintigraphy? There are currently two single photon emission computed tomography (SPECT) radiotracers that are available to evaluate general brain function by measuring cerebral blood flow (CBF): technetium-99m ( 99m Tc) ethylcysteinate dimer (ECD) and 99m Tc hexamethylpropyleneamine oxime (HMPAO). These diffuse passively into the brain shortly after …
How does FDG PET scan help with the diagnosis of myocardial sarcoidosis? Granulomatous disease related to sarcoidosis typically is very FDG avid. Sarcoidosis can therefore easily be detected in affected areas of the body such as lymph nodes and lungs via FDG PET. In addition, FDG uptake in the heart itself may be seen and …
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How does an FDG PET scan of the heart help to evaluate for myocardial viability? The primary energy substrate of the myocardium is free fatty acids rather than glucose. During ischemia, however, there is a switch in the myocardium to use of glucose. If there is decreased perfusion but preserved FDG uptake (i.e., metabolism), then …
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