Reduced hippocampal metabolism in MCI and AD: automated FDG-PET image analysis.
BACKGROUND
To facilitate image analysis, most recent 2-[18F]fluoro-2-deoxy-d-glucose PET (FDG-PET) studies of glucose metabolism (MRglc) have used automated voxel-based analysis (VBA) procedures but paradoxically none reports hippocampus MRglc reductions in mild cognitive impairment (MCI) or Alzheimer disease (AD). Only a few studies, those using regions of interest (ROIs), report hippocampal reductions. The authors created an automated and anatomically valid mask technique to sample the hippocampus on PET (HipMask).


METHODS
Hippocampal ROIs drawn on the MRI of 48 subjects (20 healthy elderly [NL], 16 MCI, and 12 AD) were used to develop the HipMask. The HipMask technique was applied in an FDG-PET study of NL (n = 11), MCI (n = 13), and AD (n = 12), and compared to both MRI-guided ROIs and VBA methods.


RESULTS
HipMask and ROI hippocampal sampling produced significant and equivalent MRglc reductions for contrasts between MCI and AD relative to NL. The VBA showed typical cortical effects but failed to show hippocampal MRglc reductions in either clinical group. Hippocampal MRglc was the only discriminator of NL vs MCI (78% accuracy) and added to the cortical MRglc in classifying NL vs AD and MCI vs AD.


CONCLUSIONS
The new HipMask technique provides accurate and rapid assessment of the hippocampus on PET without the use of regions of interest. Hippocampal glucose metabolism reductions are found in both mild cognitive impairment and Alzheimer disease and contribute to their diagnostic classification. These results suggest re-examination of prior voxel-based analysis 2-[18F]fluoro-2-deoxy-d-glucose PET studies that failed to report hippocampal effects.
Mosconi
L
L
Department of Psychiatry, New York University School of Medicine, 560 First Avenue, New York, NY 10016, USA.
Tsui
W-H
WH
De Santi
S
S
Li
J
J
Rusinek
H
H
Convit
A
A
Li
Y
Y
Boppana
Madhu
M
de Leon
M J
MJ
D000368:Aged; D000369:Aged, 80 and over; D000544:Alzheimer Disease / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000378:metabolism; D003072:Cognition Disorders / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000378:metabolism; D015331:Cohort Studies; D015536:Down-Regulation / Q000502:physiology; D004734:Energy Metabolism / Q000502:physiology; D005260:Female; D019788:Fluorodeoxyglucose F18; D005947:Glucose / Q000378:metabolism; D006624:Hippocampus / Q000000981:diagnostic imaging / Q000378:metabolism* / Q000503:physiopathology; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008875:Middle Aged; D049268:Positron-Emission Tomography / Q000379:methods*; D011237:Predictive Value of Tests; D015203:Reproducibility of Results; D012985:Software Design
D019788:Fluorodeoxyglucose F18; D005947:Glucose