Small et al evaluated PET scans following injection of [18F]-FDDNP which binds to both amyloid and tau proteins. Higher uptake implies higher concentrations of these abnormal proteins and the greater the likelihood of the patient having Alzheimer's disease (AD). The authors are from the University of California Los Angeles.
[18F]-FDDNP =
= 2-(1-{6-[(2-[F-18]fluroethyl)(methyl)amino]-2-naphthyl}ethylidene)malononitrile
Regions of the brain examined (based on distribution of plaques in patients with AD):
(1) medial temporal region
(2) lateral temporal region
(3) parietal region
(4) posterior cingulate region
(5) frontal region
relative distribution volume = DVR =
= (distribution volume of the FDDNP in the region of interest) / (distribution volume of the tracer in the reference region)
global value =
= SUM(DVR for the 5 regions of interest) / 5
Diagnosis
Range for Global DVR (mean +/- 2 standard deviations
normal controls
1.03 to 1.11
mild cognitive impairment
1.08 to 1.16
Alzheimer's disease
1.14 to 1.18
Global DVR
Interpretation
< 1.08
normal
1.08 to 1.11
normal or mild cognitive impairment (
1.11 to 1.14
mild cognitive impairment
1.14 to 1.16
mild cognitive impairment or Alzhiemer's disease
> 1.16
Alzheimer's disease
Limitations:
• The measurements must be precise and accurate since the differences between the groups are small.
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