1. Stephenson School of Biomedical Engineering, University of Oklahoma, Norman, OK, USA
2. Department of Oncology, University of Oxford, Oxford, U.K
3. Department of Radiation Oncology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
4. Advanced Development, Mevion Medical Systems, Littleton, MA, USA
5. Department of Biomedical Engineering and Radiology, the Department of Radiological Sciences, and the Beckman Laser Institute and Medical Clinic, University of California Irvine, Irvine, CA, USA