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 |%|) was calculated. Coefficients of determination (R²) 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 [¹⁸F]FDG-avid lesions (n = 93), there were no differences in intrascan repeatability (median test–retest |%|; 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 [¹⁸F]FDG (R², 0.81–0.92) and DOTATATE (R², 0.88–0.96), but the cSUR_max provided the best agreement with the K_i,max across early-to-late time points for [¹⁸F]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.

在肿瘤学 PET 中，活肿瘤的 SUV 和标准化摄取比 (SUR) 通常在注射后期间增加。相反，从动态 PET 数据得出的净流入率 ( K _i ) 应保持相对恒定。摄取时间校正 SUV (cSUV) 和 SUR (cSUR) 已被提议作为K _{i 的}与摄取时间无关的静态替代方案。我们的主要目的是量化 PET/CT 恶性病变中K _i 、SUV、cSUV、SUR 和 cSUR 的扫描内重复性。探索性目的是评估 cSUR 估计K _i的能力。方法：这项前瞻性、单中心研究招募了接受标准护理肿瘤学 PET/CT 的成年人。 SUV 和K _i图像是根据标准护理成像之前（注射后约 35-50 分钟）和之后（注射后约 75-90 分钟）获得的动态 PET 数据重建的。手动分割肿瘤。提取了定量指标。根据注射后 60 分钟参考摄取时间计算 cSUV 和 cSUR。计算扫描内测试-再测试百分比变化的大小（测试-再测试 |%|）。还计算了决定系数 ( R ² ) 和组内相关系数 (ICC)。通过 Wilcoxon 符号秩检验（α，0.05）评估指标之间的差异。结果：本研究纳入了 78 名受试者；对具有 116 个病变的 41 名受试者（平均年龄 63.8 岁；24 名男性）进行了分析。对于两种示踪剂，SUV _max和最大 SUR (SUR _max ) 从早期到晚期都有较大的增加（即扫描内重复性差）。 在 [ ¹⁸ F]FDG 强烈病变 ( n = 93) 中，最大K _i ( K _{i ,max} ) (13%; 0.97) 之间的扫描内重复性（中位测试-重测 |%|; ICC）没有差异以及最大 cSUV (cSUV _max ) (12%, P = 0.90; 0.96) 或最大 cSUR (cSUR _max ) (13%, P = 0.67; 0.94)。对于 DOTATATE 强烈病变 ( n = 23)， K _{i ,max} (11%; 0.98) 与 cSUV _max (13%, P = 0.41; 0.98) 或 cSUR _max ( 11%， P =0.08； [ ¹⁸ F]FDG ( R ² , 0.81–0.92) 和 DOTATATE ( R ² , 0.88–0.96) 的 SUV _max 、 cSUV _max 、 SUR _max和 cSUR _max均与K _{i ,max}强相关，但是对于 [ ¹⁸ F]FDG (ICC, 0.69–0.75) 和 DOTATATE (ICC, 0.90–0.91)，cSUR _max与K _{i ,max}在早到晚时间点上提供了最佳一致性。结论：与 SUV _max和 SUR _max相比， K _{i ,max} 、cSUV _max和 cSUR _max的摄取时间依赖性较低。 K _{i ,max}可以根据 cSUR _max进行预测。