Voon, for his persistent encouragement and guidance during the entire course of my PhD study. Without his support, the successful completion of my thesis is a mission impossible. I also want to express my deepest thankfulness and condolence to Associate Professor Ng Wan Sing, who just left us recently. As the founder and head of the Computer Integrated Medical Intervention Laboratory (CIMIL), he had influenced and supported me extensively in my research, career and life. His knowledgeable comments and suggestions in past days helped me a lot. His persistence and optimism shown in his fight against cancer has inspired me during my own hard days and this inspiration will last for my life. I would like to acknowledge Nanyang Technological University for providing the financial support and the research facilities. Thanks to Dr. Thng Choon Hua from National Cancer Centre of Singapore who has generously helped in my research work. Same gratitude to Dr. Henry Ho and Dr. Christopher Cheng from Singapore General Hospital who cooperated with us on this project and provided the medical support for my work.