Tumor response assessments with diffusion and perfusion MRI.

There is an increasing awareness that the evaluation of tumor response to oncologic treatments based solely on anatomic imaging assessments face many limitations, particularly in this era of novel biologic targeted therapies. Functional imaging techniques such as diffusion-weighted (DW) and dynamic contrast-enhanced (DCE) magnetic resonance imaging (MRI) have the ability to depict important tumor biologic features and are able to predict therapy response based on assessments of cellularity and tumor vascularity, which often precede morphologic alterations. In this article we focus on DW-MRI and DCE-MRI as response parameters addressing the technologies involved, quantification methods, and validation for each technique and their current role in imaging response to conventional and novel therapies. We also discuss the challenges that lie ahead in the deployment of these imaging methods into the clinical environment.