Parham Alaei is a Professor and the Director of Medical Physics at the Department of Radiation Oncology at the University of Minnesota. He has practiced and taught medical physics for over 20 years and has served on many AAPM committees. His recent research interest has been on image guidance in radiation therapy, including quantification of its dose, with a focus on kilovoltage imaging. George Ding is a Professor of Radiation Oncology at Vanderbilt University. A professed nature lover, he feels very fortunate to have learned from the scientists on the cutting edge of research while doing his Ph.D. He helped develop the Monte Carlo user code, BEAM, at the National Research Council of Canada. His main research interests include dosimetry in radiotherapy and imaging dose to patients from imaging guidance procedures.