Ernesto Tomei, MD, is Professor of Radiology in the Department of Radiological Sciences, Oncology, and Pathological Anatomy at the ""Sapienza"" University of Rome in Rome, Italy. He was a visiting lecturer in 1988-89 in the Department of Radiology at the University of California San Francisco (USA), as well as in the Department of Radiology at the University of Berlin (Klinikum Charlottenburg). He is an international leader in the emerging use of MRI for bone age assessment, and is currently engaged in a major project on this topic, which is co-financed by the European Union and the Italian Ministry of the Interior. He is also heavily involved in teaching residents specializing in Internal Medicine and Radiology and is an associate editor or reviewer for several European radiology and internal medicine journals. Richard C. Semelka, MD, is one of the foremost authorities on MRI of the abdomen and pelvis, with six MRI text-books and over 200 peer-reviewed papers to his credit. Dr. Semelka has also authored numerous chapters and review articles on MRI of the body, and has presented his work at meetings around the world. Dr. Semelka is the Director of MR Services, Professor and Vice Chair for Research, Department of Radiology, University of North Carolina at Chapel Hill. Daniel Nissman, MD, is an Assistant Professor of Radiology at the University of North Carolina at Chapel Hill, USA. He is primarily a musculoskeletal radiologist with experience in bone age assessment using both ionizing and non-ionizing radiologic modalities.