title: Efficiency of respiratory-gated delivery of synchrotron-based pulsed proton irradiation.
abstract: Significant differences exist in respiratory-gated proton beam delivery with a synchrotron-based accelerator system when compared to photon therapy with a conventional linear accelerator. Delivery of protons with a synchrotron accelerator is governed by a magnet excitation cycle pattern. Optimal synchronization of the magnet excitation cycle pattern with the respiratory motion pattern is critical to the efficiency of respiratory-gated proton delivery. There has been little systematic analysis to optimize the accelerator's operational parameters to improve gated treatment efficiency. The goal of this study was to estimate the overall efficiency of respiratory-gated synchrotron-based proton irradiation through realistic simulation. Using 62 respiratory motion traces from 38 patients, we simulated respiratory gating for duty cycles of 30%, 20% and 10% around peak exhalation for various fixed and variable magnet excitation patterns. In each case, the time required to deliver 100 monitor units in both non-gated and gated irradiation scenarios was determined. Based on results from this study, the minimum time required to deliver 100 MU was 1.1 min for non-gated irradiation. For respiratory-gated delivery at a 30% duty cycle around peak exhalation, corresponding average delivery times were typically three times longer with a fixed magnet excitation cycle pattern. However, when a variable excitation cycle was allowed in synchrony with the patient's respiratory cycle, the treatment time only doubled. Thus, respiratory-gated delivery of synchrotron-based pulsed proton irradiation is feasible and more efficient when a variable magnet excitation cycle pattern is used.
authors: Department of Radiation Physics, The University of Texas M D Anderson Cancer Center, 1515 Holcombe Blvd., Unit 94, Houston, TX 77030, USA.
authors: Yoshikazu
authors: Y
authors: Tsunashima
authors: Sastry
authors: S
authors: Vedam
authors: Lei
authors: L
authors: Dong
authors: Masumi
authors: M
authors: Umezawa
authors: Takeji
authors: T
authors: Sakae
authors: Martin
authors: M
authors: Bues
authors: Peter
authors: P
authors: Balter
authors: Alfred
authors: A
authors: Smith
authors: Radhe
authors: R
authors: Mohan
mesh_terms: D000465:Algorithms; D003198:Computer Simulation; D003201:Computers; D004867:Equipment Design; D006801:Humans; D010315:Particle Accelerators; D019047:Phantoms, Imaging; D011522:Protons; D011880:Radiotherapy Planning, Computer-Assisted; D012119:Respiration; D012984:Software; D017356:Synchrotrons; D013997:Time Factors; D014584:User-Computer Interface
chemical_list: D011522:Protons