The best known of the new 3-D imaging modalities is X-ray computed tomography, but exciting progress has been made and practical systems developed in 3-D imaging with radioisotopes, ultrasound, and nuclear magnetic resonance (NMR). These volumes will feature up-to-date reviews by leading scientists in each of these imaging areas, providing a timely and informative comparison of the intrinsic capabilities, complementary attributes, advantages and limitations, and medical significance among the different three-dimensional medical imaging modalities.