Towards a System for Micro-Ultrasound Guided Focal Brachytherapy Boost Delivery
Abstract
Purpose
We previously developed a system capable of acquiring accurate transrectal 3D micro-ultrasound (mUS) images to allow for visualization and focal treatment of intra-prostatic lesions during prostate brachytherapy. This system made use of a mUS probe with non-standard geometry, necessitating the creation of a custom workflow to interface with clinical intra-operative planning software. The purpose of this work is to test the system’s accuracy and guidance capabilities by delivering a mock focal boost brachytherapy procedure.
Methods
To compensate for the tilt of the crystal array relative to the rotation axis of the probe, the live 2D mUS images were first rotated before being passed into the intra-operative planning software, Vitesse v4.0 (Varian Medical Systems). In addition, a custom DLL was created to allow our stepper to communicate with Vitesse. 3D mUS images captured with this workflow were tested to ensure geometric and volumetric accuracy. To validate the system’s treatment guidance capability, a custom prostate phantom was developed containing an artificial tumour, rectum, and urethra. A mock focal high-dose-rate brachytherapy boost procedure was then performed by a radiation oncologist using this system. A medical physicist then created a treatment plan attempting to adhere to clinical dose constraints.
Results
The custom workflow was successfully developed and executed. Geometric and volumetric testing revealed an average distance and volume error of 0.01 ± 0.13mm and 0.27 ± 0.79cm3, respectively. A mock treatment was successfully planned, administering a prescription dose of 13.5Gy to the CTV, with a V100 > 91%, while maintaining acceptable doses to the urethra and rectum.
Conclusion
We demonstrated clinical readiness of our system by interfacing our system with clinical treatment planning software and successfully guiding a mock procedure. This work marks a crucial advancement toward our goal of developing a low-cost method to visualize and treat intra-prostatic lesions.