The University of British Columbia

This paper presents a new method of optimizing the needle insertion point, heading and depth for needle insertion into deformable tissue. The goal is to minimize the distance between a number of specified targets and the needle. Assuming a rigid needle and a deformable tissue described by a finite element model, an iterative optimization method is proposed that uses the needle insertion simulation. At each iteration, the best fitted 3D line to the targets in the simulated deformed configuration is used as a candidate for the new insertion line in the next iteration. This method has been implemented in a prostate brachytherapy simulator to minimize seed misplacement errors. The targets are designed to lie on a straight line in the undeformed configuration inside the prostate. To increase the accuracy while simulating the prostate rotation, a non-linear model is used. The neo-Hookean material model is exploited to determine the effects of geometric and mechanical nonlinearities and compressibility effects. It is shown that the optimization algorithm converges in few iterations and decreases the targeting error effectively.