Primarily, this is a single arm phase I study of prostate motion for prostate cancer to primarily compare prostate motion between different treatment duration for IMRT and VMAT. The radiation therapy is to be delivered using intensity modulated radiotherapy (IMRT) or Volumetric Modulated Arc therapy (VMAT) with the aid of volumetric image guidance to ensure accuracy and real-time 3D ultrasound images as observational record of the prostate motion. All the recruited patients are prescribed and treated with either VMAT or IMRT treatment. In order to simulate the behaviour of prostate motion in an IMRT scenario, the group of VMAT patients will be required to remain in treatment position for an additional 7 minutes depending on techniques used (once a week).