Advanced Accurate Dosimetry in Radiation Therapy using Calorimetric and Cherenkov Techniques

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In radiation therapy the accuracy of radiation dose delivery to the tumour volume and the level to which critical structures can be spared is directly correlated to treatment outcomes. The uncertainty of the absorbed dose to the patient is determined by uncertainties resulting from several steps in the treatment devices' calibration and the dose delivery. This starts with the determination of absorbed dose in water in clinical reference calibration conditions (reference dosimetry). Clinical application of modern radiation therapy delivery technology, such as TomoTherapy, Cyberknife, magnetic resonance image-guided radiation generators (i.e., MR-Linacs), volumetric modulated arc therapy, scanned proton beam radiation therapy, etc deliver radiation using small fields in high-dose fractions. Hence, the patient treatment conditions are physically and dosimetrically far removed from the standard reference calibration conditions. This has led to uncertainties in radiation delivery. Our NSERC discovery grant program aims to reduce these uncertainties by creating and developing new-generation clinically viable detector technologies, by defining new methodologies and by providing data for clinical dosimetry protocols. Two main detector methodologies are pursued, calorimetry and Cherenkov radiation detection in three main research objectives: (1) to develop a miniature `Aerrow' graphite probe calorimeter to address calibration of clinical small photon beams and proton beams; (2) to address inconsistencies in the reference dosimetry of kV intraoperative radiation beams using the Aerrow; (3) to develop a Cherenkov-radiation dosimeter technique suitable for in-situ clinical dosimetry. The impact of this program is to bring overall better consistency, conceptual clarity and improved accuracy to the dosimetry of small and nonstandard beams. Improved accuracy in the long term will lead to better outcomes. Our program builds on a track record of practice-changing dosimetry successes with some of our technologies to become available to end-users for testing and implementation.