As well as being a therapy-focused seminar (to contrast with the imaging one from last month) this is a special event as we are hearing from two of the residents at the cancer centre. This is particularly relevant for graduate students, as it provides another view into what an oncology physics residency is about. For the rest of us, it’s a chance to learn more about practical developments in radiation therapy!
Victoria Howard (Carleton University)
Development of a robust thermal calibration methodology for pyroelectric calorimeters
In radiation therapy treatments, ultra-high dose rate (UHDR) beams can produce what is known as the FLASH effect, where healthy tissue is spared while maintaining equivalent tumour control. However, accurate dose measurements for UHDR beams are challenging. Ionization chambers exhibit response saturation at high dose-per-pulse, requiring exorbitantly large correction factors for UHDR beams. While calorimeters have a dose rate independent response, their use has been restricted to standards laboratories due to the specialized equipment and expertise needed for operation. We propose the use of pyroelectric materials to make a calorimeter compatible with electrometer readout. Pyroelectric materials generate an electrical current when subject to a temperature change. If the temperature change is due to irradiation, the current is directly proportional to the absorbed dose to the medium.
Reproducible thermal calibrations are extremely important, as they can be used to determine the pyroelectric coefficient of the material, which is required to determine the dose to medium. In this talk I will present the development of a robust thermal calibration methodology for a pyroelectric calorimeter and the resulting pyroelectric coefficients for various materials.
John Lincoln (TOHCC)
Synchronous and Asynchronous Gap Tests to Standardize Transmission Modelling of Tilted Multi-Leaf Collimator Dynamics
Therapeutic radiation beams delivered by medical linear accelerators can be shaped using multi-leaf collimators (MLC). Complex beam apertures from increasingly more modulated treatments make it difficult to model dynamic MLC transmission. Furthermore, vendor-specific MLC types are different, which leads to a lack of standardization. Recent literature has proposed synchronous and asynchronous gap tests delivered to a farmer chamber, to standardize MLC transmission modeling. This research presents synchronous and asynchronous gap tests on 10 beam-matched tilted MLC including flattening filter free beam qualities.
Devin Van Elburg (TOHCC)
Clinical implementation of 3D printed cylindrical templates for interstitial gynecologic high-dose-rate brachytherapy
Interstitial gynecologic high-dose-rate brachytherapy is a complex procedure that requires considerable expertise, cost, and resources, and the quality of treatment is highly dependent on the implant quality. 3D printed cylindrical templates greatly simplify the implant process while reducing patient trauma and cost. Recently at TOH we have implemented 3D printed cylinders and treated our first two patients. This talk will summarize the procedural and dosimetric benefits of 3D printed cylinders versus standard interstitial techniques.