Reproducibility of normalized apparent diffusion coefficient measurements on 3.0-T diffusion-weighted imaging of normal pancreas in a healthy population

To prospectively compare the reproducibility of normal pancreas-normalized apparent diffusion coefficient (ADC) measurements for the normal pancreas and mean normalized ADCs at different pancreas anatomic locations. In total, 22 healthy volunteers underwent pancreatic 3.0-T magnetic resonance (MR) imaging, including axial diffusion-weighted (DW) imaging with 3 b values used (0, 400, and 800s/mm(2)) and with the respiratory-triggered (RT) technique. The mean ADCs from 3 regions of interest (ROIs) in 5 anatomic locations (head [H], body [B], and tail [T] of pancreas and spleen [S] and erector spinae muscles [M]) were calculated. The pancreas-normalized ADC was defined as the ratio of the ADC for the pancreas to the ADC for the spleen or erector spinae muscle. Reproducibility of ADCs and normalized ADCs was assessed by the Bland-Altman method. The ADC and normalized ADC data were analyzed by repeated-measures ANOVA. Mean ADC and normalized ADC values did not differ (P >. 05) with repeated measurements at the different pancreas anatomic locations. Reproducibility of pancreas-normalized ADC measurements in each of the 3 pancreatic anatomic locations was better with the erector spinae muscle rather than the spleen used as a reference. Mean ADC and normalized ADC values significantly differed between the 3 pancreatic segments (H: 1.36 x 10(-3) mm(2)/s, B: 1.38 x 10(-3) mm(2)/s, T: 1.25 x 10(-3) mm(2)/s, P=.022; H/S: 1.75, B/S: 1.78, T/S: 1.59, P=.009; H/M: 0.91, B/M: 0.95, T/M: 0.85, P=.008). Mean ADC values and normalized ADC values showed a trend to decrease from the pancreatic head to tail. Our preliminary results suggest that normalized ADC measurements for the pancreas show good intra-and interobserver reproducibility, the erector spinae muscle is a better choice than the spleen for calculating normalized ADC values for the pancreas, and the normalized ADC values are lower for the pancreatic tail than other pancreatic segments.