The image quality, amyloid- detectability, and acquisition time of clinical florbetapir positron emission tomography in Alzheimer's disease and healthy adults

Background: Florbetapir positron emission tomography (AV45 PET) is a widely employed modality for detecting cerebral amyloid-beta (A beta) deposition. However, in clinical settings, patients with cognitive impairment are frequently unable to sustain adequate stillness during the scanning procedure. Therefore, we aimed to investigate the effects of a short acquisition time on the image quality and A beta detectability of AV45 PET.Methods: In this cross-sectional study, 29 patients with Alzheimer's disease (AD) and 13 healthy participants underwent 15-minute AV45 PET/magnetic resonance imaging scanning. The PET data were subsequently reconstructed into 15-, 10-, 8-, 6-, 4-, 2-, and 1-minute duration groups (G15, G10, G8, G6, G4, G2, and G1). Subjective PET image quality was scored based on a 5-point Likert scale (poor-excellent: 1-5,), and objective image quality was evaluated by the signal-to-noise ratio (SNR) of the 1 cm3 region of interest (ROI) inside the cerebellum. A beta detectability was assessed by the calculation of regional standardized uptake value ratio (SUVR) values in all groups. The Kruskal-Wallis rank sum test and paired t-test were performed to compare the subjective scores, SNR, and SUVR values. The visual inspection was also performed by 2 nuclear physicians to give a binary diagnosis to each case.Results: The subjective scores were decreased in the groups with shortened scanning time relative to the G15 group (4.67 +/- 0.48, all P<0.05). Notably, a good image quality score was also given to the G10 group (4.40 +/- 0.63), and sufficient image quality could be achieved with the G8 (3.86 +/- 0.68) and G6 (3.14 +/- 0.52) groups. The SNR values were decreased by 10.33%, 17.74%, and 23.26% in the G10, G8, and G6 group, respectively (all P<0.05). Compared with the G15 group (1.48 +/- 0.16), the composite SUVR values were increased in the G10 (1.50 +/- 0.16), G8 (1.50 +/- 0.17), and G6 groups (1.51 +/- 0.18, all P<0.05). By visual inspection, the diagnoses of each case in the G10, G8, and G6 group were identical with those in the G15 group.Conclusions: The acquisition time of AV45 PET is required to reach at least 6 minutes to achieve acceptable image quality and maintained A beta detectability.