Prostate deformation analysis during ultrasound-guided radiotherapy procedures with transformative models

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With its high incidence rate (1 in 7 men), prostate cancer is the second leading cause of cancer death in men inNorth America. Towards this end, high-dose-rate (HDR) brachytherapy offers the ability to treat prostatecancer with a dose-modulated approach for optimized clinical performance, while avoiding sensitive zones thatmight interfere with the patient's well-being. The industrial partner, Elekta Ltd, is specialized in radiotherapyand radioactive brachytherapy systems used for focal treatments in patients with breast, lung, liver or prostatecancer. A key advantage of the technology developed by Elekta is the integration of pre-operative imaging tocreate a dose-plan and treat the tumor based on the patient's MRI, adapting the dose modulation during thetreatment phase. However a major limitation in the widespread use of HDR brachytherapy resides in theinvoluntary movement or local deformation of the prostate gland during the intervention. Indeed, theseradiotherapy systems depend on accurate tracking of the tumor during radiation treatment, which can be highlyinfluenced bu the deformation of the prostate. This can cause possible toxicity of local therapy to surroundingtissue and increase the risk of local persistence or recurrence. The goal of this project is to develop acomputerized tool which will measure the deformation induced in the prostate based on computer vision andmachine learning approaches, ultimately compensating the deformation during image-guided treatments. Thisproject will have the following objectives: (1) Create an interface to load the pre-operative (MRI) andintra-operative acquisitions (3D ultrasound or MRI); (2) Implement a 3D shape modelling tool of the prostate;(3) Compute a 4D deformation field, by developing a prostate registration algorithm using a non-parametricdiffeomorphic approach; (4) Clinical validation to verify prostate deformation between pre-operative andintra-operative acquisitions. A major impact of this work will be to enable tissue deformation analysis in aninterventional environment for precise dose-painting in combination with multiparametric MR imaging,potentially reducing recurrence and minimizing the risk that normal prostate is excessively irradiated.