Three-dimensional needle steering towards a localized target in a prostate phantom

Prostate biopsy and brachytherapy are commonly used for surgical interventions. In this paper, we present a three-dimensional (3D) pre-operative target localization algorithm and a real-time closed-loop control algorithm to robotically steer flexible needles with an asymmetric tip towards a real target in a prostate phantom. The phantom is composed of different tissues including rectal wall, bladder and prostate. The elasticities of these tissues are obtained using an ultrasound-based (acoustic radiation force impulse imaging) technique, and their geometry are obtained using magnetic resonance images. Six experimental cases are performed to evaluate the steering system while inserting the needle into a prostate phantom with different skin thicknesses, insertion angles and surface inclinations. The experimental results show that the target is reached by the needle in all trials. The mean targeting errors between the needle tip and the center of the target embedded in phantoms with 0 mm, 1.5 mm and 2.5 mm skin thicknesses are 1.12 mm, 0.93 mm and 0.49 mm, respectively. The variation of the insertion angle does not have an appreciable affect on the targeting accuracy. The mean targeting error during insertion into a phantom with an inclined surface is 0.85 mm. The results demonstrate the capability of proposed system to robotically steer needles towards a target for interventions in the prostate.