Incorporating MR Imaging Into Prostate Radiotherapy Treatment Planning

In this research study, the investigators want to determine if prostate radiotherapy treatment planning can be improved by using an MRI scan to help doctors more accurately target the prostate with radiation and decrease radiation dose to the rectum, which is just behind the prostate. To do this, the investigators will create a treatment plan based on the MRI scan and compare it to the standard treatment, which currently uses a CT scan rather than an MRI. The results of this study will help inform doctors whether it is beneficial to routinely use an MRI scan for prostate radiotherapy treatment planning.