Short-Duration [ 18 F]florbetapir PET Reconstructions: Centiloid Agreement and Temporal-Window Analysis

BACKGROUND AND PURPOSE: Shorter [18F]florbetapir PET acquisitions could improve workflow, but the effects of reconstruction duration and temporal-window position on Centiloid values are not well characterized. We evaluated quantitative agreement across short-duration reconstructions, temporal-window effects, and visual agreement. MATERIALS AND METHODS: This retrospective study included a primary cohort of 32 patients with early 1-, 2-, and 5-min reconstructions and a 10-min reference. A temporal-window cohort of 22 patients underwent early and late 5-min analysis. A validation cohort of 37 examinations underwent early, centered, and late 1- and 5-min reconstructions and a 10-min reference. Two readers independently classified early 1-min, early 5-min, and 10-min images across three separate reading sessions. Centiloid agreement was assessed using paired differences, Bland–Altman limits of agreement, and categorical agreement. RESULTS: In the primary cohort, mean differences from the 10-min reference were −3.70, −2.97, and −1.65 CL for early 1-, 2-, and 5-min reconstructions, respectively. In the temporal-window cohort, late 5-min values averaged 2.86 CL higher than early values. The validation cohort reproduced both findings: early-to-late shifts were +5.53 CL at 1 min and +3.07 CL at 5 min. In the reader study, agreement with 10 min was 70.3%–86.5% at 1 min and 94.6%–100% at 5 min; interreader κ was 0.49, 0.77, and 0.89 at 1, 5, and 10 min, respectively. CONCLUSIONS: Early short-duration reconstructions yielded systematically lower Centiloid values, while later temporal windows yielded higher values at fixed duration. Visual agreement with 10 min was high at 5 min but lower at 1 min. Reconstruction duration and frame timing should be standardized before abbreviated protocols are considered substitutes for standard 10-min imaging.