Arthur J. Olch is Professor of Radiation Oncology and Clinical Pediatrics at the Keck School of Medicine at the University of Southern California in Los Angeles, California. He is also Chief of Physics for the Children’s Hospital of Los Angeles Radiation Oncology Program, one of only a few radiotherapy centers in the US that treat exclusively children. Dr. Olch received his BS degree in Engineering and his PhD in Medical Physics from the University of California, Los Angeles. He is a Fellow of the American Association of Physics in Medicine (AAPM). Dr. Olch has served as the Chair of the Physics Subcommittee of the Children’s Oncology Group Radiation Oncology Committee and of the AAPM Subcommittee on Quality Assurance and Outcome Improvement as well as serving as chair or member of various AAPM Task Groups. He has been a radiation therapy physicist for over 30 years and has authored or co-authored 50 journal articles and book chapters and written the book on pediatric radiotherapy treatment planning.