Fig. 1
From: Applications of various range shifters for proton pencil beam scanning radiotherapy
a Patient-related range shifters: U-shaped bolus (UB) indexed on couch top (two tracks on the couch top to let the UB slide in and index its position along the cranial-caudal direction), anterior-lateral bridge bolus (ALB) on a movable cart with indexed height (can move up and down), couch top bolus (CTB). The UB is applied in the clinic to treat brain, head, and neck targets. It allows anterior and left lateral beam in a and the ALB on the left side can be manually moved to the right side when it is needed (d). ALB is used across the patient body when anterior and lateral fields are planned. CTB is used for all treatments whenever posterior fields are used. b MRS mounted on the nozzle on a fixed beam nozzle. c An example of a head and neck patient planned with UB, ALB, and CTB in the planning images, but only UB and ALB were in the beam paths. d the same setup to a but the left ALB is moved to the right side. e ALB and CTB. f UB only