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Abstract
To evaluate the clinical and imaging characteristics of patients with visually equivocal amyloid PET images, patients from the Alzheimer's Disease Neuroimaging Initiative cohort who had fluorine-18-florbetapir PET scans both at baseline and 24 months were selected. Five nuclear medicine physicians visually assessed the PET images and classified them as either positive or negative. Images not reaching a majority agreement were classified as equivocal. Among a total of 379 patients, the number of patients in each fluorine-18-florbetapir PET negative/equivocal/positive categories was 218 (57.5%), 32 (8.4%), and 129 (34.0%). Eight to 9% of patients with normal cognition (N=12/141), mild cognitive impairment (N=20/214), and no Alzheimer's disease (N=0/24) showed equivocal PET finding for each. In negative/equivocal/positive groups, positive cerebrospinal fluid Aβ1-42 was observed in 25.7, 81.5, and 98.3%, respectively. Baseline standardized uptake value ratios of fluorine-18-florbetapir PET were 0.75±0.05, 0.86±0.09, and 1.01±0.09, respectively [F(2, 376)=603.547; P<0.001]. After 24 months of follow-up, the standardized uptake value ratios increased by 0.81±2.62, 2.81±2.90, and 2.17±3.66%, respectively [F(2, 376)=7.905, P<0.05 vs. the negative group]. Among mild cognitive impairment patients, the equivocal group showed a more rapid decline in glucose metabolism than the negative group [5.52±5.36 vs. 0.67±4.45; F(2, 122)=9.028, P<0.01]. 8.4% of the patients in this study showed a visually equivocal result of amyloid PET. These patients showed a moderate amount of amyloid accumulation and a rapid rate of accumulation.

Author information

Oh M1, Seo M2, Oh SY3, Kim H4, Choi BW5, Oh JS1, Kim JS1; Alzheimer’s Disease Neuroimaging Initiative.
1
Department of Nuclear Medicine, Asan Medical Center, University of Ulsan College of Medicine.
2
Department of Nuclear Medicine, Ulsan University Hospital, University of Ulsan College of Medicine, Ulsan.
3
Department of Nuclear Medicine, National Police Hospital, Seoul.
4
Department of Nuclear Medicine, Kosin University Gospel Hospital, Kosin University College of Medicine, Busan.
5
Department of Nuclear Medicine, Daegu Catholic University Medical Center, School of Medicine, Catholic University of Daegu, Daegu, Korea.