Grant: Project Grant

Cancer is the leading cause of death in Canada and nearly half of the patients receive radiotherapy (RT). RT uses strong radiation to kill tumour cells, and the radiation is typically delivered by a device called linear accelerator (linac). If a tumour is static during irradiation, e.g. brain tumour, modern RT can deliver highly accurate radiation to the tumour without much damage to the adjacent normal cells. Unfortunately, most tumours are mobile and can deform due to respiratory and cardiac motions (e.g. lung tumour), and such accurate RT is difficult due to the lack of sufficient soft-tissue imaging. Most tumours reside in soft-tissue, and soft-tissue is best seen in MRI. However, current imaging devices on linacs are typically X-ray based, which provide poor soft-tissue imaging. Thus, small metal markers that can be seen in X-ray image must be surgically implanted near the tumour to estimate its shape and location during RT. Our laboratory built the first radiotherapy-MRI hybrid device (linac-MR) in 2008, and a human whole-body system in 2014. This MRI on-board linac allows continuous MR imaging during irradiation, providing clear image of moving tumours. Using linac-MR, our objective is to enhance the geometric accuracy of RT treating mobile tumours without the need of invasive surgery. To achieve the objective, we have established a framework of novel RT method, non-invasive intra-fractional tumour-tracked RadioTherapy (nifteRT). The feasibility of nifteRT was verified in 2013 using our prototype linac-MR system. We were able to deliver accurate radiation to a moving target reproducing 1D lung tumour motion in linac-MR. In this proposal, we aim to further improve our nifteRT research to the level of clinically usable technology. We expect < 3 mm error in radiation delivery to mobile tumours in nifteRT. This will allow the escalation of radiation dose only to the tumours without excessive damage to the adjacent normal cells, which is the ultimate goal of RT.