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Zhang, Claire

University of British Columbia

Permanent breast seed implant (PBSI) brachytherapy is a single-session partial breast irradiation technique for early-stage breast cancer patients who have previously undergone lumpectomy. Despite excellent clinical outcomes and high patient satisfaction rates, this technique has not been widely adopted in clinical practice due to challenges in standardizing and optimizing the planning and delivery of the technique. The goal of this thesis is to quantitatively investigate the uncertainties in PBSI and develop methods and technologies to improve the accuracy and robustness of this technique. I investigated the uncertainties arising from varying lumpectomy surgical margins in our PBSI patient cohort. I compared the currently used safety margin in PBSI planning to Groupe Européen de Curiethérapie-European Society for Therapeutic Radiation and Oncology (GEC ESTRO) recommended margin. Our results showed that the current PBSI clinical safety margin provides satisfactory coverage on the GEC ESTRO recommended target. However, implementing GEC ESTRO recommendations in PBSI planning has dosimetric advantages in reducing dose of organs at risk. I also quantified PBSI seed displacement, as well as seed stability in breast tissue during the first month post implantation. We evaluated the dosimetric impact of seed displacement and movement and demonstrated that PBSI post-implant dosimetry remains within clinical goals even with local seed displacement and movement. Furthermore, we developed a simulation framework to evaluate PBSI plan robustness to seed displacement, which will be a useful tool for evaluating and improving planning methods. To address the challenges in target visualization and implant imaging guidance in PBSI mentioned in previous studies, I continued the development and implementation of 3D ultrasound technologies in PBSI. I characterized an encoded 3D ultrasound systems developed for PBSI, and further developed a new system with improved clinical usability. Our commissioning and testing results showed good feasibility to implement 3D ultrasound in PBSI and great potential to improve visualization and guidance of PBSI. In conclusion, our quantitative evaluation of some of the current uncertainties in the PBSI technique and the development of tools to improve its accuracy and user-dependence will facilitate the standardization and optimization of PBSI and promote the clinical adoption of this technique.

Text

2023-07-13

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/85238

Medical Physics

University of British Columbia

UBCO

http://creativecommons.org/licenses/by-nc-nd/4.0/