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In oncologic PET, the SUV and standardized uptake ratio (SUR) of a viable tumor generally increase during the postinjection period. In contrast, the net influx rate ( K i ), which is derived from dynamic PET data, should remain relatively constant. Uptake-time-corrected SUV (cSUV) and SUR (cSUR) have been proposed as uptake-time-independent, static alternatives to K i Our primary aim was to quantify the intrascan repeatability of K i , SUV, cSUV, SUR, and cSUR among malignant lesions on PET/CT. An exploratory aim was to assess the ability of cSUR to estimate K i Methods: This prospective, single-center study enrolled adults undergoing standard-of-care oncologic PET/CT. SUV and K i images were reconstructed from dynamic PET data obtained before (∼35-50 min after injection) and after (∼75-90 min after injection) standard-of-care imaging. Tumors were manually segmented. Quantitative metrics were extracted. cSUVs and cSURs were calculated for a 60-min postinjection reference uptake time. The magnitude of the intrascan test-retest percent change (test-retest |%Δ|) was calculated. Coefficients of determination ( R 2 ) and intraclass correlation coefficients (ICC) were also computed. Differences between metrics were assessed via the Wilcoxon signed-rank test (α, 0.05). Results: This study enrolled 78 subjects; 41 subjects (mean age, 63.8 y; 24 men) with 116 lesions were analyzed. For both tracers, SUV max and maximum SUR (SUR max ) had large early-to-late increases (i.e., poor intrascan repeatability). Among [ 18 F]FDG-avid lesions ( n = 93), there were no differences in intrascan repeatability (median test-retest |%Δ|; ICC) between the maximum K i ( K i ,max ) (13%; 0.97) and either the maximum cSUV (cSUV max ) (12%, P = 0.90; 0.96) or the maximum cSUR (cSUR max ) (13%, P = 0.67; 0.94). For DOTATATE-avid lesions ( n = 23), there were no differences in intrascan repeatability between the K i ,max (11%; 0.98) and either the cSUV max (13%, P = 0.41; 0.98) or the cSUR max (11%, P = 0.08; 0.94). The SUV max , cSUV max , SUR max , and cSUR max were all strongly correlated with the K i ,max for both [ 18 F]FDG ( R 2 , 0.81-0.92) and DOTATATE ( R 2 , 0.88-0.96), but the cSUR max provided the best agreement with the K i ,max across early-to-late time points for [ 18 F]FDG (ICC, 0.69-0.75) and DOTATATE (ICC, 0.90-0.91). Conclusion: K i ,max , cSUV max , and cSUR max had low uptake time dependence compared with SUV max and SUR max The K i ,max can be predicted from cSUR max ., (© 2024 by the Society of Nuclear Medicine and Molecular Imaging.)