1. Department of Radiation Oncology, Korea Institute of Radiological and Medical Science, Seoul, Korea.
2. Department of Nuclear Engineering, Hanyang University, Seoul, Korea.
3. Department of Radiation Oncology, Ilsan Paik Hospital, Goyang, Korea.
4. Department of Radiation Oncology, Kyung Hee University Hospital at Gandong, Seoul, Korea.
5. Department of Radiation Oncology, Kyung Hee University Hospital, Seoul, Korea.