1. Medical Physics Graduate Program, Duke University Medical Center, Durham, North Carolina 27705 and Duke Radiation Dosimetry Laboratory, Duke University Medical Center, Durham, North Carolina 27710
2. Department of Chemistry, Duke University, 124 Science Drive, Durham, North Carolina 27708
3. Department of Physics and Astronomy, University of North Carolina, Chapel Hill, North Carolina 27599
4. Department of Physics and Astronomy, University of North Carolina, Chapel Hill, North Carolina 27599 and UNC Lineberger Comprehensive Cancer Center, Chapel Hill, North Carolina 27599
5. Department of Physics and Astronomy, University of North Carolina, Chapel Hill, North Carolina 27599; Department of Radiation Oncology, University of North Carolina, Chapel Hill, North Carolina 27599; and UNC Lineberger Comprehensive Cancer Center, Chapel Hill, North Carolina 27599
6. Medical Physics Graduate Program, Duke University Medical Center, Durham, North Carolina 27705;Duke Radiation Dosimetry Laboratory, Duke University Medical Center, Durham, North Carolina 27710; and Department of Radiology, Duke University Medical Center, Durham, North Carolina 27710