Diffusion-Weighted Magnetic Resonance Imaging in Pelvic Cancer

Diffusion-weighted MRI exploits intrinsic tissue contrast generated by movement of water within tissues over distances of around 1-20 microns. These distances are travelled by water within microcapillaries or in the extracellular space as a result of thermally driven random motion, where movement is limited by structural interfaces such as cell membranes. Diffusion-weighted imaging thus reflects microcapillary perfusion and tissue cellularity. In soft tissue pelvic neoplasms, the quantitative ADC maps generated can be used in conjunction with conventional T2-W images to improve tumour detection and staging, and are increasingly being explored as quantitative functional biomarkers of prognosis and response. This review summarizes the current clinical utility and future potential of diffusion-weighted MRI in prostate, rectal, gynaecological and bladder cancers.