Functional MRI for tumor delineation in prostate radiation therapy

A unique property of radiation therapy is the capacity for a differential treatment, in which a high dose can be delivered to tissue with a high tumor load, whereas a lower dose is applied to treat microscopic disease around the primary tumor. This approach is termed ‘dose painting’ and is currently tested in the radiation therapy of prostate cancer. Functional MRI techniques, such as dynamic contrast-enhanced MRI and diffusion-weighted MRI, are well established for tumor localization and staging. However, application for target delineation in radiotherapy raises some specific issues: at what spatial resolution can these techniques be used reliably? What is the detection limit of the techniques? Do different techniques identify the same regions as suspicious or do they provide complimentary information? In this article we address these issues and explore how functional MRI techniques can be used for radiotherapy dose painting.