Alzheimer's disease Other Imaging Findings

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief:

Overview

Other imaging studies in Alzheimer's include positron emission tomography (PET) and single photon emission computed tomography (SPECT) scan. PET and SPECT scan are not routinely done in Alzheimer's disease. However, patients with atypical presentation may be evaluated with either a PET or SPECT scan to assess for any underlying condition. In these patients, use of amyloid β PET scan will reveal lower FDG (fluorine-18 fluorodeoxyglucose) metabolism and higher PiB ([11 C]Pittsburgh compound B) deposition in areas of the brain affected by Alzheimer's disease.

Other Imaging Findings

• Other imaging studies in Alzheimer's include positron emission tomography (PET) and single photon emission computed tomography (SPECT) scan.
• PET and SPECT scan are not routinely done in Alzheimer's disease. However, patients with atypical presentation may be evaluated with either a PET or SPECT scan to further assess the patient for any underlying condition.
• The Amyloid Imaging Taskforce (AIT) recommends use of amyloid β (Aβ) positron emission tomography (PET) scanning in atypical cases of Alzheimer's.
• The tracer used in PET scan for amyloid β include [11 C]Pittsburgh compound B (PiB) and fluorine-18 fluorodeoxyglucose(FDG).
• Patients with atypical presentation of Alzheimer's and a greater decline in memory function will have lower FDG metabolism and higher PiB deposition in areas of the brain affected by Alzheimer's disease.
• According to the guidelines of AIT, amyloid β PET scan is recommended in cases of:
  • Patients with persistent or progressive unexplained mild cognitive impairment
  • Patients with early age onset
  • Patients with progressive dementia

• In SPECT scan, patients are given a simple word-discrimination task and then observed for gradation of cerebral blood flow (rCBF).
• Patients with Alzheimer disease have low relative regional cerebral blood flow (rCBF) in the parietal and prefrontal cortices.