29 Shortening the scan duration SUVr using the interval 80–100 min (SUVr(80−100 min)) was also evaluated. Regional SUVr values obtained from this time interval were compared with the respective quantitative parameters (DVR, SRTM BPND and RPM BPND) estimated using the original scan duration (0–60/80–130 min). Test-Retest Repeatability Analysis For the test-retest repeatability (TRT) analysis, the test-retest cohort was used. The TRT of RPM BPND and R1 values derived from the optimal shortened scan duration were compared to the test-retest repeatability of RPM BPND obtained using the original scan duration (0–60/80–130 min). In addition, TRT for SUVr(80–100) was also assessed. The TRT was calculated using Eq. 1. Statistical Analysis Linear regression fitting and correlation coefficients (r2) were used to compare BP ND and R1 for the shortened scan durations and SUVr(80−100 min) against corresponding parametric values for the original scan duration (0–60/80–130 min) derived from plasma input–based and reference tissue–based NLR and RPM. Furthermore, Bland-Altman plots were used to assess and illustrate TRT performance. RESULTS Shortening the Second Part of the Scan (80–130 Min P.I.) The RPM BPND values obtained from the three shortened scan durations (0–60/80– 120, 0–60/80–110 and 0–60/80–100 min) provided excellent correlations with plasma input DVR-1, SRTM BPND and RPM BPND obtained using the original acquisition time window (0–60/80–130) (Table 1; all r2 > 0.93). Reduction of the time interval of the second part to 100 min had negligible effects on the RPM BPND estimation: correspondence to DVR-1 (HC: r2 = 0.94, slope = 0.95; AD: r2 = 0.94, slope = 0.92), SRTM BP ND (HC: r2 = 0.98, slope = 1.05; AD: r2 = 0.96, slope = 0.85) and RPM BP ND (HC: r2 = 0.98, slope = 1.04; AD: r2 = 0.99, slope = 0.94). Comparison of regional SRTM BP ND values obtained using the shorter time interval (0–60/80–100) to plasma input DVR-1 and SRTM BPND obtained with the original scan duration (0–60/80–130) are presented in Supplementary Table 1. The RPM R1 values obtained from the three shortened scan durations (0–60/80– 120, 0–60/80–110 and 0–60/80–100) also provided excellent correlations with SRTM R1 and RPM R1 estimated using the original acquisition time window (0–60/80–130) (Supplementary Table 2). 2
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