An Ultrasound-Guided Mechatronics-Assisted System for Semi-Automated Seed Implantation and Tracking in Prostate Brachytherapy

Prostate brachytherapy using radioactive seeds has emerged as an efficacious treatment option for men with prostate cancer. Due to the currently limited accuracy of delivering seeds, its scope has been restricted to primarily treating the entire prostate gland. In this paper we present a semi-automated seed delivery and tracking scheme for precise seed placement, to allow for more conformal treatment of localized prostate cancer. Standard seed-carrying needles are connected to a hand-held apparatus that the surgeon holds to steer the needle automatically as the surgeon manually inserts it. The apparatus is equipped with force sensors that are used to estimate the tissue properties during insertion. A needle steering controller employs ultrasound images of the needle in tissue to calculate the optimal steering manoeuvres online. A method is derived to track the position of the implanted seeds after the needle is withdrawn, allowing the surgeon to monitor the implant quality online. Experimental results over 90 seed implants indicate an average targeting accuracy of 0.46 mm.