title: New compensator design options for charged-particle radiotherapy.
abstract: The purpose of this investigation is to propose new compensator design strategies for protons and heavier particles which are based on pencil-beam (PB) dose calculations and which significantly reduce the dose to tissues downstream from the target, yet provide acceptable target coverage under conditions of patient motion. Averaging and expansion operations are provided to improve the target coverage if the patient moves slightly during treatment, and a structure-sparing option is provided to protect critical structures lying downstream from the target. The new compensator design options were evaluated for two patients who had skull-base tumours. When the patient and compensator were perfectly aligned, the new PB compensator designs provided target coverage comparable to, if not better than, standard compensator designs for both patients. Furthermore, the volume of normal tissue distal to the target which received in excess of 95% of the prescription dose was roughly a factor of two lower for the averaged PB compensators than for the expanded standard compensators. In the event of patient motion, on average, the volume of the target receiving 95% or more of the prescribed dose was 3% less for the averaged PB compensators than for the expanded standard compensators. In conclusion, the new compensator design options evaluated in this investigation provide better protection for normal tissues distal to the target volume than standard compensator designs, with only a modest decrease in target volume coverage in the event of patient motion.
authors.affiliation: Department of Radiation Onocology, University of California, San Francisco 942143, USA.
authors.forename: P L
authors.initials: PL
authors.lastname: Petti
mesh_terms: D004867:Equipment Design; D006801:Humans; D009068:Movement; D011522:Protons; D011878:Radiotherapy / Q000379:methods*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D014057:Tomography, X-Ray Computed / Q000295:instrumentation / Q000379:methods*
chemical_list: D011522:Protons