Apoptosis progresses through a series of energy-requiring and tightly regulated steps that conclude with the engulfment of dying cells by neighboring phagocytic cells, in a process that avoids the inflammatory reaction caused by cellular necrosis. Dysregulation of apoptosis is associated with a number of pathological states. The low-steady-state levels of apoptosis are partially explained by the fact that apoptotic cells are rapidly removed by surrounding cells, which means that the imaging target is only temporarily available before the surrounding tissue removes it. The use of MR to detect therapy response, apoptosis has been the subject of several recent reviews. The latter method is based on blood deoxyhemoglobin concentration, has shown promise to detect alterations in energy metabolism in both normal and pathological states. Finally, there is the issue of distinguishing between different forms of cell death, although given the interrelationship between necrosis and apoptosis, and the fact that just detecting cell death may be sufficient, this need be a problem.