3D simulation of needle insertion into the prostate for brachytherapy cancer treatment.
Medical procedures such as brachytherapy seed implantation, biopsies, and treatment injections require inserting a needle tip to a specific target location inside the human body. This is difficult because inserting needles into soft tissues causes the surrounding soft tissues to deform. Ignoring these deformations can result in substantial placement error, resulting in failure of the procedure or increased side effects.
To facilitate physician training and planning for medical procedures such as prostate brachytherapy, we are developing an interactive simulation of needle insertion and radioactive seed implantation in soft tissues. We are developing 2D and 3D simulations of needle insertion procedures by modeling tissue deformations using a finite element method, modeling needle frictional and cutting forces, and using novel re-meshing to ensure conformity of the mesh to the curvilinear needle path. Achieving a computationally efficient simulation is challenging; we parallelize the FEM computation over multiple cores and and used novel needle/tissue coupling algorithms to achieve a 25 Hz frame rate for a 3D prostate mesh composed of 13,375 tetrahedra on an 8-core 3.0 GHz PC.
Video of our interactive 3D simulator of needle insertion in the prostate for brachytherapy cancer treatment.
We are also developing a sensorless planning system for radioactive seed implantation that combines our simulation of needle insertion with numerical optimization to compute needle insertion offsets that compensate for tissue deformations. We applied the method using 2D simulation to seed implantation during permanent seed prostate brachytherapy to minimize seed placement error in simulation without relying on real-time imaging.
Without
planning
With
sensorless
planning
Simulation of needle insertion based on a 2D ultrasound image of a human prostate (green) to a target (cross). After needle retraction, the placement error, the distance between the target and implanted seed location, is 26% of the diameter of the prostate when no planning is used. Preoperative planning can anticipate and correct for the effects of tissue deformations, significantly reducing placement error, which improves treatment quality and reduces side effects.
Automatically guiding a traditional straight needle to a target by externally manipulating tissues to enable obstacle avoidance.