{"entity":{"id":"f-18-fdg-brain","kind":"drug","name":"Fludeoxyglucose F-18 (brain metabolism)","aka":["FDG-PET brain","18F-FDG"],"tldr":"The standard PET tracer for measuring how the brain is using energy; a pattern of low activity in particular brain regions can help doctors work out which type of dementia a patient has.","summary":"Fludeoxyglucose F-18 (FDG) is the general-purpose PET metabolic tracer used across oncology, cardiology and neurology; it is not brain-specific as a product, but brain FDG PET is a distinct, well-established clinical application. Reduced glucose metabolism follows a regional pattern that differs by disease: temporoparietal and posterior cingulate hypometabolism is typical of Alzheimer's disease, while frontal and/or anterior temporal hypometabolism points to frontotemporal dementia, and this pattern difference is the main clinical use of FDG-PET in cognitive impairment.\n\nIn the United States, Medicare's national coverage determination for FDG-PET in dementia (NCD 220.6.13) covers a scan specifically to help differentiate Alzheimer's disease from frontotemporal dementia, in patients with a recent dementia diagnosis and at least 6 months of documented cognitive decline whose presentation leaves this distinction clinically uncertain after a comprehensive specialist evaluation; a prior brain SPECT or FDG-PET scan for the same question generally precludes a repeat scan within a year. All other dementia uses of FDG-PET (for example distinguishing other neurodegenerative diseases, or use outside a CMS-approved clinical trial in mild cognitive impairment) remain nationally non-covered under this determination, a materially narrower coverage pathway than the one now in force for amyloid PET.\n\nFDG-PET brain imaging does not require thyroid blockade or specialised handling beyond standard F-18 PET radiopharmacy practice, and dosing follows general oncologic/neurologic FDG protocols (typically around 185-370 MBq IV, imaging beginning about 30-45 minutes later, with the patient resting quietly in a darkened, low-stimulation room during uptake to standardise regional brain activity). Because FDG uptake reflects neuronal activity rather than a specific pathological protein, it complements rather than replaces amyloid and tau PET: FDG shows the functional consequence of neurodegeneration, while amyloid and tau tracers show the underlying molecular pathology.","status":"approved","asOf":"2026-09-22","links":[{"label":"CMS NCD 220.6.13: FDG PET for Dementia and Neurodegenerative Diseases","url":"https://www.cms.gov/regulations-and-guidance/guidance/transmittals/downloads/r24ncd.pdf"},{"label":"CMS coding article: PET scan coverage reference table including FDG dementia indication (A53134)","url":"https://www.cms.gov/medicare-coverage-database/view/article.aspx?articleId=53134"}],"tags":["FDG PET","diagnostic","neurology","metabolic imaging"],"related":["alzheimers-disease","fludeoxyglucose-f18","fdg-pet","tc-99m-hmpao-brain","f-18"],"indications":[],"sections":[],"technologies":[],"targets":[],"drugs":[],"companies":[],"institutions":[],"pathways":[],"terms":[],"trials":[],"people":[],"bottlenecks":[],"keyPapers":[],"journals":[],"dependsOn":[],"notes":[],"modality":"PET tracer","mechanism":"A glucose analogue labelled with fluorine-18 that is taken up by cells in proportion to glucose metabolism and trapped after phosphorylation; in the brain, regional FDG uptake reflects synaptic activity, so characteristic patterns of reduced metabolism can distinguish different neurodegenerative diseases.","approvals":[{"region":"US","year":2004,"indication":"FDG-PET nationally covered by Medicare specifically to differentiate Alzheimer's disease from frontotemporal dementia in patients with an uncertain diagnosis after comprehensive specialist evaluation (NCD 220.6.13)"}],"mechanismSteps":[],"dosing":{"route":"Intravenous injection","schedule":"Typical adult brain FDG-PET protocol: ~185-370 MBq IV, patient rested in a quiet, dimly lit room during the ~30-45 minute uptake phase, then PET imaging","monitoring":"Visual and statistical/voxel-based comparison of regional glucose metabolism against normative databases to identify disease-specific hypometabolism patterns","source":"https://www.cms.gov/regulations-and-guidance/guidance/transmittals/downloads/r24ncd.pdf"},"toxicity":[],"access":[],"regulatoryEvents":[]},"route":"/drugs/f-18-fdg-brain/","neighbours":{"indication":[{"id":"alzheimers-disease","kind":"indication","name":"Alzheimer's disease","route":"/indications/alzheimers-disease/"}],"drug":[{"id":"fludeoxyglucose-f18","kind":"drug","name":"Fludeoxyglucose F-18 (FDG)","route":"/drugs/fludeoxyglucose-f18/"},{"id":"tc-99m-hmpao-brain","kind":"drug","name":"Technetium-99m exametazime (brain perfusion)","route":"/drugs/tc-99m-hmpao-brain/"}],"technology":[{"id":"fdg-pet","kind":"technology","name":"FDG PET","route":"/technologies/fdg-pet/"}],"isotope":[{"id":"f-18","kind":"isotope","name":"Fluorine-18","route":"/isotopes/f-18/"}]}}