A–B Pair of axial ADC maps generated from back-to-back DW-MR images for a single patient (55 years, prostatic adenocarcinoma, PSA 12.7) with cancerous ROI outlined in blue, C absolute difference in ADC between scan a and scan b for area within light blue box, and D relative percentage difference in ADC between scan a and scan b for area within light blue box. High areas of variability are common outside of the prostate, particularly in the rectum, and relative variation is high outside of the prostate where the signal intensity is very low. Although the variability in ADC is low within the prostate there are foci of 25% to 30% visible, demonstrating how variability within DW-MRI may affect not only quantitative imaging results, but also results of a qualitative, clinical assessment.