Needle Insertion Simulation for Image-Guided Brachytherapy of Prostate Cancer

Brachytherapy is an effective treatment for prostate cancer. Preciously implant of seeds with planned radioactive dose irradiate surrounding tissue over several months will minimize healthy tissue damage while maximize the destruction of cancerous cells. However, force load on the tip of insertion needle will cause the tissue deformation during the process and result in the misplaced seeds. This will lead to underdosed regions and complications, such as impotence or urinary incontinence. Apparently, improved implant accuracy can improve the local control and can improve global control of the disease and also reduce global toxicity. In this paper, a 3D model of needle insertion soft tissue based on large deformation non linear dynamic FEM (Finite Element Method) numerical algorithm combined with Mooney-Rivlin material model is described. Mechanical behavior of the non-linear material property can be simulated as well as the interaction between needle and soft tissue. Therefore, implant error can be calculated with the seeds implant position and planned seeds location. In this research, this model is used to test the sensitivity of seed placement error with insertion point, needle orientation, and insertion distance. As results shown, the shorter distance between the insertion point and target location, the smaller placement error occurred This method can be used as complementarities instruction for robot assistant prostate brachytherapy without template.