A graphics-based simulation has been proved as a powerful tool in surgical and therapeutic applications. In a computer aided surgical simulation system, it must provide real-time rendering performance as well as flexible 3D object manipulation. In this paper, we propose a new volume rendering scheme, namely SSB (Scan-line Based Semi-Boundary). The time complexity of SSB is O(MN) plus a 2-Dimensional image rotation, and the SSB is theoretically faster than the original Semi-Boundary algorithm that will take O(LMN) time, where L,M,N are the Semi-Boundary nodes in X,Y,Z axes, respectively. We experimentally evaluate SSB rendering performance using large pelvis volume data. Our preliminary results show that SSB can achieve an interactive rendering performance for large volume pelvis data set with size of 512 by 512 by 245.