Diffusion weighted magnetic resonance imaging (DW-MRI) holds great potential for monitoring treatment response in cancer patients shortly after initiation of radiotherapy. It is hypothesized that a decrease in cellular density of irradiated cancerous tissue will lead to an increase in quantitative apparent diffusion coefficient (ADC) values. | Diffusion weighted magnetic resonance imaging DW-MRI as a non-invasive tissue cellularity marker to monitor cancer treatment response