Adaptive RT (ART) – re-optimizing the radiation distribution based on the patient's daily anatomy in order to maintain the plan quality – has been proposed as a means to deliver more radiation with reduced normal tissue damage; increasing the chance of a cure, with fewer side effects. However, the implementation of ART is severely limited by the lack of a real-time device that can accurately measure the delivered radiation distribution within the patient. Currently no system exists which is capable of measuring the radiation dose distribution within the patient. Unlike imaging modalities, which use contrast agents such as gadolinium (MRI), iodine (kilo Voltage X-Rays/CT) or microbubbles (ultrasound), to enhance visibility, there is no contrast agent available to visualize the megavoltage (MV) X-rays used in radiation therapy. By combining two novel physics mechanisms, my current research aims to develop the first Radiation Therapy Contrast Agent, allowing us to see what we treat in real time, enabling Adaptive-RT.