1. Department of Human Oncology University of Wisconsin—Madison Madison WI 53792 USA
2. Department of Radiation Oncology Medical College of Wisconsin Milwaukee WI 53226 USA
3. Department of Diagnostic Radiology Mayo Clinic Rochester MN 55905 USA
4. Medical Physics Department Memorial Sloan‐Kettering Cancer Center New York NY 10065 USA
5. Department of Radiation Oncology Mayo Clinic Phoenix Arizona 85054 USA
6. Department of Radiation Oncology University of Michigan Ann Arbor MI 48109 USA