This book provides an account of the perspective, methodology, and experience in the physical and medical aspects of IMRT at Memorial Sloan-Kettering Cancer Center (MSKCC). The clinicians and scientists at MSKCC were fortunate to be involved in the development and implementation of this advanced form of radiotherapy. MSKCC was also at the forefront of using IMRT treatment with the use of dynamic multileaf collimation (DMLC) in 1995. Since then, MSKCC has amassed a vast body of technical and clinical experience in the use of this modality.