31 Shortening the scan duration Figure 1. Interpolation of the gap in reference region TAC (30 to 80 min) with different interpolation methods. Shortening the First Part of the Scan (0–60 Min P.I.) In Figure 1, the different interpolations of a typical reference TAC for the shortest dual-time-window (0–30/80–100 min) assessed in this study are presented. For all shortened scan durations, SRTM BPND using the reference TACs interpolated with either POP-IP_2T4k_VB or cubic interpolation methods had the best correspondence with plasma input DVR-1 and SRTM BPND (r2 > 0.90, Table 2) obtained with the original scan duration. Reduction of the time interval of the first part of the scan to 30 min and using POPIP_2T4k_VB for reference region interpolation had negligible effects on the quantitative accuracy of the estimated kinetic parameters with respect to that estimated using the original scan duration: DVR-1 (HC: r2 = 0.93, slope = 0.94; AD: r2 = 0.92, slope = 0.97) and SRTM BP ND (HC: r2 = 0.96, slope = 1.02; AD: r2 = 0.98, slope = 0.89). SRTM BPND values obtained with 0–30/80–100 min data using cubic interpolation for reference region had similar agreement with DVR-1 (HC: r2 = 0.94, slope = 0.91; AD: r2 = 0.91, slope = 0.92) and SRTM BP ND (HC: r2 = 0.96, slope = 0.98; AD: r2 = 0.98, slope = 0.85) from the original scan duration. Good correlations were observed for linear and exponential interpolation methods (r2 > 0.90, Table 2). However, these interpolation methods resulted in higher underestimation (15–25 %) of the parametric values. 2
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