Sensorless Motion Planning for Medical Needle Insertion in Deformable Tissue

Minimally invasive medical procedures such as biopsies, anesthesia drug injections, and brachytherapy cancer treatments require inserting a needle to a specific target inside soft tissue. This is difficult because needle insertion displaces and deforms the surrounding soft tissue causing the target to move during the procedure. To facilitate physician training and pre-operative planning for these procedures, we develop a needle insertion motion planning system based on an interactive simulation of needle insertion in deformable tissue and numerical optimization to reduce placement error. We describe a 2D physically-based, dynamic simulation of needle insertion that uses a finite element model of deformable soft tissue and models needle cutting and frictional forces along the needle shaft. The simulation offers guarantees on simulation stability for mesh modifications and achieves interactive, real-time performance on a standard PC. Using texture-mapping, the simulation provides visualization comparable to ultrasound images that the physician would see during the procedure. We use the simulation as a component of a sensorless planning algorithm that uses numerical optimization to compute needle insertion offsets that compensate for tissue deformations. We apply the method to radioactive seed implantation during permanent seed prostate brachytherapy to minimize seed placement error.