Nuclear magnetic resonance: Beyond physical imaging: A powerful new diagnostic tool that uses magnetic fields and radio waves creates pictures of the body's internal chemistry

Since the discovery of X-rays by Wilhelm Roentgen in 1895, various types of radiation have been used in medical diagnosis and treatment to probe the human body noninvasively: X-rays, computerized axial tomography (CAT), positron emission tomography (PET), and ultrasound. The latest imaging scheme to emerge is nuclear magnetic resonance (NMR). Its image bears closest resemblance to CAT scans: both yield high-resolution anatomic information from the body and share similar computer-image reconstruction methods. NMR, however, has a number of advantages.