Test-Retest Variability of Various Quantitative Measures to Characterize Tracer Uptake and/or Tracer Uptake Heterogeneity in Metastasized Liver for Patients with Colorectal Carcinoma

The aim of this study was to assess test-retest variability of various quantitative measures to characterize tracer uptake and/or tracer uptake heterogeneity. Two baseline whole-body 2-deoxy-2-[F-18]fluoro-d-glucose positron emission tomography/computed tomography (CT) scans were acquired in 29 subjects with colorectal carcinoma. Whole liver volumes of interest (VOI) were defined manually on CT. For each VOI, various quantitative measures were determined, e.g., skewness, kurtosis, and the area under a cumulative standardized uptake value-volume histogram (AUC). AUC showed a good reliability (intraclass correlation coefficients (ICC): 0.97) and low test-retest variability (10 %). Most other quantitative parameters showed excellent agreement between test and retest values (ICC: 0.78-0.97) and low test-retest variability (< 12 %), except for kurtosis. Skewness also showed a higher test-retest variability (19 %), but good ICC (0.96) and it correlated well with AUC (R (2): 0.90, all others: < 0.76). This high reproducibility and reliability of AUC warrant further investigation of its use for quantification of tracer uptake heterogeneity.