Background: To compare visual and semi-quantitative analysis of brain [18F]Florbetaben
PET images in Mild Cognitive Impairment (MCI) patients and relate this finding to the degree
of ß-amyloid burden.
Methods: A sample of 71 amnestic MCI patients (age 74 ± 7.3 years, Mini Mental State Examination
24.2 ± 5.3) underwent cerebral [18F]Florbetaben PET/CT. Images were visually scored as positive
or negative independently by three certified readers blinded to clinical and neuropsychological
assessment. Amyloid positivity was also assessed by semiquantitative approach by means of a previously
published threshold (SUVr ≥ 1.3). Fleiss kappa coefficient was used to compare visual analysis
(after consensus among readers) and semi-quantitative analysis. Statistical significance was
taken at P<0.05.
Results: After the consensus reading, 43/71 (60.6%) patients were considered positive. Cases that
were interpreted as visually positive had higher SUVr than visually negative patients (1.48 ± 0.19
vs 1.11 ± 0.09) (P<0.05). Agreement between visual analysis and semi-quantitative analysis was excellent
(k=0.86, P<0.05). Disagreement occurred in 7/71 patients (9.9%) (6 false positives and 1
false negative). Agreement between the two analyses was 90.0% (18/20) for SUVr < 1.1, 83%
(24/29) for SUVr between 1.1 and 1.5, and 100% (22/22) for SUVr > 1.5 indicating lowest agreement
for the group with intermediate amyloid burden.
Conclusion: Inter-rater agreement of visual analysis of amyloid PET images is high. Agreement between
visual analysis and SUVr semi-quantitative analysis decreases in the range of 1.1< SUVr
<=1.5, where the clinical scenario is more challenging.