The assessment of apparent diffusion coefficient (ADC) repeatability is important to body diffusion weighted imaging (DWI). However, data onto evaluating the repeatability of ADC values for normal pancreas are limited. The aim of this study was to evaluate the ADC test-retest repeatability of the normal pancreas.Methods
Twenty-six healthy volunteers (mean 47.6 years; 13 men) were included and scanned twice with reposition using a DWI sequence at 3.0-T. ADCs of the pancreatic head, body and tail for two DWIs were measured by two readers. The mean ADCs of the pancreatic head, body and tail were calculated as the global pancreatic ADC. Test-retest repeatability and agreement of ADC measurement were evaluated by the Bland-Altman analysis, intra-class correlation coefficient (ICC) and coefficient of variation (CV).Results
The global pancreatic ADC showed the best test-retest repeatability (mean difference ± limits of agreement were 0.05 ± 0.25×10 -3 mm 2 /s; ICC, 0.79; CV, 6%). Test-retest repeatabilities for ADC of pancreatic head, body or tail were scattered, with mean difference ± limits of agreement between two tests were 0.03 ± 0.47, 0.05 ± 0.42 and 0.06 ± 0.31 (×10 -3 mm 2 /s), respectively (ICCs, 0.81, 0.52 and 0.68; CVs, 9%, 8% and 8%). Both intra-observer repeatability and inter-observer reproducibility were acceptable for whole pancreas between ADC measurements of the two DWIs.Conclusions
ADC values of the pancreas are technically challenging and repeatability is variable. Cautions should be taken when interpreting longitudinal clinical changes in ADC values of the normal pancreas because the measurements do have an inherent variability by locations.