A Hand-Held Assistant for Semiautomated Percutaneous Needle Steering

Objective: Permanent prostate brachytherapy is an effective and popular treatment modality for prostate cancer in which long needles are inserted into the prostate. Challenges associated with manual needle insertion such as needle deflection limit this procedure to primarily treat the entire prostate gland even for patients with localized cancer. In this paper, we present a new semiautomated hand-held needle steering assistant designed to help surgeons improve needle placement accuracy. Methods: Regular clinical brachytherapy needles are connected to a compact device that the surgeon holds. As the surgeon inserts the needle, the device rotates the needle base on a measured and calculated basis in order to produce a desired trajectory of the needle tip. A novel needle-tissue interaction model and a steering algorithm calculate such control actions based on ultrasound images of the needle in tissue. The assistant can also apply controlled longitudinal microvibrations to the needle that reduce needle-tissue friction. Results: Experimental validation of the proposed system in phantom and ex-vivo biological tissue report an average needle targeting accuracy of 0.33 mm over 72 needle insertions in 12 different experimental scenarios. Conclusion: We introduce a new framework for needle steering in prostate brachytherapy in which the surgeon remains in charge of the needle insertion. The device weighs 160 g, making it easy to incorporate with current insertion techniques. Significance: Expected benefits of the proposed system include more precise needle targeting accuracy, which can result in improved focal treatment of prostate cancer.