1. Department of Electrical Engineering, Stanford University, Stanford, California 94305‐9505 and Department of Radiation Oncology, Stanford University, Stanford, California 94305‐5847
2. Department of Radiation Oncology, Stanford University, Stanford, California 94305‐5847
3. Department of Radiation Oncology, Ehwa University, Seoul 158‐710, Republic of Korea
4. Department of Electrical Engineering, Stanford University, Stanford, California 94305‐9505
5. Department of Statistics, Stanford University, Stanford, California 94305‐4065
6. Department of Radiation Oncology, Stanford University, Stanford, California 94305‐5304