Devices and methods to directly measure absolute absorbed dose to water in non-standard complex beams in a radiotherapy clinical setting

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The goal of radiation therapy is to use radiation to damage tumor cells to an extent that they are either dead (necrotic), or not viable to reproduce (sterile). The treatment outcome is directly correlated with the accuracy of radiation dose delivery which itself is comprised of several steps starting from radiation delivery system calibration all the way to dose delivery. Current dosimetry protocols require a so-called `reference' conditions for calibration which traditionally has been a good reflection of radiotherapy delivery setup. However, with more recent novel developments in radiotherapy delivery technology (e.g. MR-linac, Tomotherapy, CyberKnife, Volumetric Modulated Arc Therapy (VMAT), scanned proton beams, etc.), there has been a general shift from low dose / low dose rate radiation fractions delivered using large static field sizes, to delivery of high dose fractions using small, highly modulated, complex fields dynamically delivered at relatively high dose rates. As such, the patient treatment conditions (and RT delivery units) are becoming far removed from reference calibration conditions. This has led to added uncertainties, or worst errors in dosimetry. The goal of our NSERC discovery grant is to reduce radiation dosimetry uncertainty and drastically decrease possibility of user error by innovating and developing new generation of detectors in radiation therapy or modification of current detectors and detection techniques for dose measurement in highly complex radiation delivery modalities. To that end, the main objectives of the research are: 1) To develop a new 3-D printed, portable and fully image-able water calorimeter appropriate for everyday clinical use; 2) to use the proposed absolute dosimeter in (1) to not only show feasibility of absolute dose measurement in a safe and accurate way in clinic, but to also determine correction factors for traditional detectors that will be essential to future dosimetry protocols in many of these new and complex delivery technologies. Building on our previous practice-changing dosimetry success of bringing new dosimeter technologies to market and contributing to the development of new protocols in modern RT, our research program will have strong positive impact on overall improvement of radiation dose uncertainty and reducing operator error in small and non-standard radiation dosimetry.