Diffusion-weighted MR imaging of upper abdominal organs at different time points: Apparent diffusion coefficient normalization using a reference organ.

Purpose To compare the apparent diffusion coefficient (ADC) of upper abdominal organs acquired at different time points, and to investigate the usefulness of normalization. Materials and Methods We retrospectively evaluated 58 patients who underwent three rounds of magnetic resonance (MR) imaging including diffusion-weighted imaging of the upper abdomen. MR examinations were performed using three different 3.0 Tesla (T) and one 1.5T systems, with variable b value combinations and respiratory motion compensation techniques. The ADC values of the upper abdominal organs from three different time points were analyzed, using the ADC values of the paraspinal muscle (ADCpsm) and spleen (ADCspleen) for normalization. Intraclass correlation coefficients (ICC) and comparison of dependent ICCs were used for statistical analysis. Results The ICCs of the original ADC and ADCpsm showed fair to substantial agreement, while ADCspleen showed substantial to almost perfect agreement. The ICC of ADCspleen of all anatomical regions showed less variability compared with that of the original ADC (P < 0.005). Conclusion Normalized ADC using the spleen as a reference organ significantly decreased variability in measurement of the upper abdominal organs in different MR systems at different time points and could be regarded as an imaging biomarker for future multicenter, longitudinal studies. Level of Evidence: 5 J. MAGN. RESON. IMAGING 2017;45:1494–1501