Fig 3.

Average daily patient throughput relative to cobalt-60 performance in year 1 of operation for four linear accelerator (linac) treatment techniques and for cobalt-60 units operated over 8 years with multileaf collimators (MLCs), one block change, or three block changes per patient per fraction. Intersections represent the average daily duration of power outages for which the corresponding treatment machines and techniques are expected to have equal patient throughput. Linac downtime is sampled from the 8% average distribution. IMRT, intensity-modulated radiotherapy; VMAT, volumetric-modulated arc therapy.