Fundamentals of magnetic resonance imaging

Medical imaging methods traditionally have depicted variations in one or two simple physical variables in tissues, e.g., physical density, atomic number, acoustic velocity, and radioactivity concentration. Magnetic resonance images reveal differences in several variables, with the prominent variables reflecting complex energy transfer mechanisms that occur at the atomic and nuclear levels. Furthermore, the relative contributions of these variables to the image are readily altered by changing the pulse sequence and the pulsing times within the sequence. These changes dramatically affect the image and its characterization of normal anatomy. Hence, magnetic resonance images and their contributions to diagnostic medicine can be properly appreciated only if one has some understanding of the procedures by which they are produced