For some decades, radiation therapy has been proved successful in cancer treatment. The major task of radiation therapy is to impose a maximum dose of radiation to the tumor cells. The IMRT technology makes it possible to deliver radiation more precisely by dividing the accelerator head into smaller units called "beamlets" that can be manipulated independently. This treatment planning requires a time consuming iterative work between a physician and an IMRT technician. The state of the art current technique is to determine the IMRT treatment plan at the beginning and use it without changing it in the course of the treatment. However, the assumption of fixed 'target volume' throughout the IMRT treatment, is very limiting given that the tumor shrinks in response to the radiation therapy. In this research, we apply time-varying volume rendering technique to the IMRT treatment and develop a proof-of-concept prototype system that enables capturing and relating the time dependent changes of the irradiated volume throughout the course of treatment. This prototype system will enable the researchers to explore different what-if scenarios, such as determining the 'Target Treatment Volume' depending on the delivered dose of radiation.