A three-dimensional deformable model for segmentation of human prostate from ultrasound images

Segmentation of human prostate from ultrasound (US) images is a crucial ste p in radiation therapy, especially in real-time planning for US image-guide d prostate seed implant. This step is critical to determine the radioactive seed placement and to ensure the adequate dose coverage of prostate. Howev er, due to the low contrast of prostate and very low signal-to-noise ratio in US images, this task remains as an obstacle. The manual segmentation of this object is time consuming and highly subjective. In this work, we have proposed a three-dimensional (3D) deformable surface model for automatic se gmentation of prostate. The model has a discrete structure made from a set of vertices in the 3D space that form triangle facets. The model converges from an initial shape to its equilibrium iteratively, by a weighted sum of the internal and external forces. Internal forces are based on the local cu rvature of the surface and external forces are extracted from the volumetri c image data by applying an appropriate edge filter. We have also developed a method for initialization of the model from a few initial contours that are drawn on different slices. During the deformation, a resampling procedu re is used to maintain the resolution of the model. The entire model is app lied in a multiscale scheme, which increases the robustness and speed, and guarantees a better convergence. The model is tested on real clinical data and initial results are very promising. (C) 2001 American Association of Ph ysicists in Medicine.