Although (18)F-FDG PET is an established technique to assess brain glucose use, a shorter imaging time is preferable for patient convenience and increased throughput. The aim of this study was to validate a brain (18)F-FDG PET protocol more rapid than the conventional protocol.
Methods: For comparison of normalized metabolic activities, brain (18)F-FDG PET was performed on 60 healthy subjects and 25 patients with probable Alzheimer's disease (AD), and an additional 20 healthy subjects served as a control group to assess diagnostic performance between the conventional and rapid scanning protocols. Conventional scans were acquired for a total of 20 min (a 10-min emission and a 10-min transmission). Immediately after conventional scanning, rapid scanning was performed for a total of 4 min (a 3-min emission and a 1-min transmission). PET images were anatomically standardized using NEUROSTAT, with pixel values normalized to the individual global value. Two database sets, from the 2 protocols, were compared by regional values and pixel-by-pixel analysis. A receiver-operating-characteristic analysis was performed for comparison of diagnostic accuracy between the 2 protocols. A kinetic simulation study was also performed to examine the possible difference due to the time lag between the protocols.
Results: Although small differences in normalized activity were found in several regions in the healthy subjects between the 2 protocols, no significant difference was found in any region in the patient group. The coefficients of variation of the normalized activity were 20%-30% larger in the rapidly scanned images, but the mean z images and their coefficient-of-variation images did not differ. The kinetic simulation study suggested that the differences were caused by the time lag between the 2 protocols. No significant differences were found in area under the receiver-operating-characteristic curves, and the diagnostic accuracies for the detection of AD were virtually equal between the 2 protocols.
Conclusion: The rapid scanning protocol used in the present study could provide results nearly equivalent to data from the conventional protocol. Thus, it is feasible to use this rapid protocol to detect AD, without losing diagnostic accuracy.