Lawrence E. Williams, Ph.D., is a professor of radiology and an imaging physicistat City of Hope National Medical Center in Duarte, California. In addition, he is anadjunct professor of radiology at University of California–Los Angeles (UCLA).While in high school, he was one of 40 national winners of the Westinghouse (nowIntel) Science Talent Search. Dr. Williams obtained his B.S. from Carnegie MellonUniversity and his M.S. and Ph.D. degrees (both in physics) from the University ofMinnesota, where he was a National Science Foundation (NSF) fellow. His initialgraduate training was in nuclear reactions at Minnesota, where he demonstratedexcited states of the mass-4 system (4He*). He later extended this work by findingexcited levels of mass-3 nuclides while working at the Rutherford High EnergyLaboratory in England. Since obtaining the National Institutes of Health (NIH) supportto become a medical physicist, Dr. Williams has devoted most of his research totumor detection and treatment and has written approximately 250 total publicationsas well as a number of patents in nuclear imaging and radionuclide therapy. He is acoauthor of Biophysical Science (Prentice Hall, 1979) and editor of Nuclear MedicinePhysics (CRC Press, 1987). He has been a grant and site reviewer for NIH since themid-1990s. Dr. Williams is associate editor of Medical Physics and a reviewer forseveral other journals. He is a member of the American Association of Physicistsin Medicine (AAPM), the Society of Nuclear Medicine, the New York Academy ofSciences, Sigma Xi, Society of Imaging Informatics in Medicine (SIIM), and theSociety of Breast Imaging. Dr. Williams has received a lifetime service award fromthe American Board of Radiology.Among Dr. Williams’ most significant biophysical discoveries is the mass-lawfor tumor uptake as a function of tumor size. He was also codiscoverer (with RichardProffitt) of tumor targeting with liposomes. This work involved one of the first applications of normal organ blockage by use of an unlabeled agent—that is, a two-stepprocess. Dr. Williams has developed a pair of indices for quantifying the ability of aradiopharmaceutical to permit imaging or therapy of lesions in animals or patients. Hehas also demonstrated that radioactive decay must be considered inherently as one possible exit route in modeling analysis of radioactive drugs. With his colleagues at City of Hope, Dr. Williams measured and calculated the brake radiation dose result for a source of 90Y in a humanoid phantom. This study remains as one of the few examples of a comparison of dose estimates and measurement in the nuclear medicine literature.