is an Associate Professor in the Department of Radiology and Radiological Sciences at Vanderbilt University, with appointments in the Departments of Physics and Astronomy and Civil and Environmental Engineering. He heads the Vanderbilt Health Physics Graduate Program, teaching several courses in the area and orienting graduate students in their studies. He is the author of two textbooks (one on Health Physics) and over 250 journal articles, technical reports, book chapters, and textbooks, principally in the area of radiation dosimetry. He is an active member of the Health Physics Society, having served as chair of both Part I and Part II Panels for certification in Health Physics and numerous internal working committees. He is also a member of several working groups of the Society of Nuclear Medicine, American Association of Physicists in Medicine, International Commission on Radiological Protection, NCRP, United Nations Scientific Committee on the Effects of Atomic Radiation, and is regularly called as an expert to the International Atomic Energy Agency.