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Frequently Asked Questions (FAQs) What is an FDG-pet scan?

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Frequently Asked Questions 


What is an FDG-pet scan?




An FDG-PET scan stands for Flurodoxyglucose Positron Emission Tomography scan.  It allows the doctor to have the deepest look into your brain. The scan captures brain activity after the patient has been injected with a glucose tracer.

FDG-PET scan is useful as a diagnostic tool in patients with suspected Autoimmune Encephalitis who have normal MRI. It usually shows medial temporal hypo-(slowing) or (fast moving) hypermetabolic changes in limbic encephalitis.

For example, it can show abnormalities in anti-NMDAR encephalitis at various brain sites, such as frontal, temporal, and occipital lobes, brainstem and cerebellum. The findings range from focal hyper-metabolism and hypo-metabolism.

Anti-LGI1 encephalitis frequently showed basal ganglia and medial temporal hyper-metabolism.

The FDG PET scan can also verify the progression of the disease. The scan can be repeated after 6 months or so of treatment for a visual confirmation of the treatment’s effectiveness.


During a scan


A patient is injected with a radioactive glucose tracer and within hours be scanned. The patient lays down on a table and the table is moved into a donut scanner.

The scan takes a half hour to an hour. The injected medicine is a radioactive tracer. It has a minute amount of radioactive material that binds to the brain. That radioactivity is what the scanner picks up. The radioactive medicine fades within in hours. No significant harmful effects have been documented from PET scanning.

No eating for four hours prior the scan.

Less involved than MRI. (No knocking noises.)

A nuclear medicine doctor will interpret the scans and the neurologist will review the results with the patient. The results are 3-dimensional, color, and can take a day.



The Laboratory Diagnosis of Autoimmune Encephalitis, Sang Kun Lee, Soon-Tae

Dr. Bradley Boeve discusses the PET Scan that patients may be asked to take while visiting Mayo Clinic. He emphasizes the importance, reasoning behind getting a PET Scan, what to expect, and why the test is ordered.

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