1. Yale-New Haven Hospital; New Haven CT 06510-3202 USA
2. Department of Radiation Oncology; University of California San Diego; Rebecca and John Moores Comprehensive Cancer Center; La Jolla CA 92093-0843 USA
3. University of Florida Proton Therapy Institute; Jacksonville FL 32206 USA
4. Juntendo University Grduate School of Medicine; Bunkyo-ku Tokyo 113-8421 Japan
5. Department of Radiation Oncology; University of Florida, Davis Cancer Center; Gainesville FL 32610-0385 USA