Advances in the science and technology of medical imaging and
radiation therapy are more profound and rapid than ever before,
since their inception over a century ago. Furthermore, the disci￾plines are increasingly cross-linked as imaging methods become
more widely used to plan, guide, monitor, and assess treatments
in radiation therapy. Today, the technologies of medical imaging
and radiation therapy are so complex and so computer-driven
that it is difficult for the persons (physicians and technologists)
responsible for their clinical use to know exactly what is hap￾pening at the point of care, when a patient is being examined
or treated. The persons best equipped to understand the tech￾nologies and their applications are medical physicists, and these
individuals are assuming greater responsibilities in the clinical
arena to ensure that what is intended for the patient is actually
delivered in a safe and effective manner.