title: Optimization of X-ray microplanar beam radiation therapy for deep-seated tumors by a simulation study.
abstract: A Monte Carlo simulation was applied to study the energy dependence on the transverse dose distribution of microplanar beam radiation therapy (MRT) for deep-seated tumors. The distribution was found to be the peak (in-beam) dose and the decay from the edge of the beam down to the valley. The area below the same valley dose level (valley region) was decreased with the increase in the energy of X-rays at the same beam separation. To optimize the MRT, we made the following two assumptions: the therapeutic gain may be attributed to the efficient recovery of normal tissue caused by the beam separation; and a key factor for the efficient recovery of normal tissue depends on the area size of the valley region. Based on these assumptions and the results of the simulated dose distribution, we concluded that the optimum X-ray energy was in the range of 100-300 keV depending on the effective peak dose to the target tumors and/or tolerable surface dose. In addition, we proposed parameters to be studied for the optimization of MRT to deep-seated tumors.
authors.affiliation: Research Institute for Science and Engineering, Waseda University, Shinjuku-ku, Tokyo, Japan.
authors.forename: Kunio
authors.initials: K
authors.lastname: Shinohara
authors.affiliation: Department of Neurosurgery, Kobe University Graduate School of Medicine, Kobe-shi, Hyogo, Japan Shinsuma General Hospital, Kobe-shi, Hyogo, Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Kondoh
authors.affiliation: Japan Synchrotron Radiation Research Institute, Sayo-gun, Hyogo, Japan.
authors.forename: Nobuteru
authors.initials: N
authors.lastname: Nariyama
authors.affiliation: Research Institute for Science and Engineering, Waseda University, Shinjuku-ku, Tokyo, Japan.
authors.forename: Hajime
authors.initials: H
authors.lastname: Fujita
authors.affiliation: Research Institute for Science and Engineering, Waseda University, Shinjuku-ku, Tokyo, Japan.
authors.forename: Masakazu
authors.initials: M
authors.lastname: Washio
authors.affiliation: Medical Corporation YUKOUKAI Clinic, Funabashi-shi, Chiba, Japan.
authors.forename: Yukimasa
authors.initials: Y
authors.lastname: Aoki
mesh_terms: D003198:Computer Simulation; D008954:Models, Biological; D009369:Neoplasms / Q000532:radiotherapy*; D019047:Phantoms, Imaging; D011879:Radiotherapy Dosage; D011881:Radiotherapy, Computer-Assisted / Q000295:instrumentation / Q000379:methods*
keywords: Microbeam radiation therapy; Monte Carlo simulation; X-rays; energy dependence; transverse dose distribution