Biomechanical Modeling of the Prostate for Procedure Guidance and Simulation

Biomechanical models of the prostate have a number of potential applications in the diagnosis and management of prostate cancer. Most importantly, it has been shown in several studies that cancerous prostate tissue has different viscoelastic properties than normal prostate tissue: it is typically stiffer (higher storage modulus) and more viscous (higher loss modulus). If a strong correlation can be obtained between malignant tissue and its viscoelastic properties, then all commonly practiced prostate cancer procedures—biopsies, surgery and radiation treatment—can be improved by elasticity imaging. The elastic properties of the prostate and peri-prostatic tissue can also be used in procedure planning, even if such elastic properties do not show strong correlation to cancer. This chapter starts with an introduction to the prostate anatomy, prostate cancer, and a description of the most common procedures and their clinical needs. It continues by presenting the potential impact of elasticity imaging on these procedures. A brief survey of elastography techniques is presented next, with a sampling of some prostate elastography results to date. We describe two of the systems that we developed for the acquisition of prostate ultrasound and magnetic resonance elastography images and summarize our results to date. We show that these elasticity images can be used for prostate segmentation and cross-modality image registration. Furthermore, we show how prostate region deformation models can be used in the development of a prostate brachytherapy simulator which can also be used in the planning of needle insertions that account for deformation.