title: [Optimal parameter decision method in VMAT for lung tumors with respiratory motions].
abstract: When performing lung cancer treatments using volumetric modulated arc therapy (VMAT) technique, dose error related to respiratory motion of tumors and multi leaf collimator (MLC) movement may occur. The dose error causes daily dose variation in multiple fractionations irradiation. The purpose of this study is to verify the influence of the respiratory motion and the MLC movement on the daily dose variation, and to confirm the feasibility of deciding robust planning parameter against the dose variation. We prepared 5 VMAT plans for imitating lung tumor in thorax dynamic phantom. Dose calculations of these plans were done taking into account the respiratory motions. We examined the relation between dose variation and two parameters that were number of respiration in an arc and MLC gap width. We presented the relationship between the dose variation and each parameters using regression analysis, and we could derive the approximation formula for estimating the dose variation using these parameters. We could estimate dose variation in another VMAT plans using the approximation formula and another plans parameters. By confirming dose variation in planning procedure using this estimation method, we may decide planning parameter taking the dose variation into account. So, we could establish the estimation method to decide adequate planning parameters in VMAT.
authors.affiliation: Department of Radiation Therapy, Cancer Institute Hospital.
authors.forename: Fumiyasu
authors.initials: F
authors.lastname: Matsubayashi
authors.forename: Masatoshi
authors.initials: M
authors.lastname: Hashimoto
authors.forename: Ryuzo
authors.initials: R
authors.lastname: Uehara
authors.forename: Ryo
authors.initials: R
authors.lastname: Takahashi
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Ito
authors.forename: Satoko
authors.initials: S
authors.lastname: Saotome
authors.forename: Yuko
authors.initials: Y
authors.lastname: Sekiya
authors.forename: Masaru
authors.initials: M
authors.lastname: Nakajima
authors.forename: Nozomi
authors.initials: N
authors.lastname: Kitamura
authors.forename: Tomoharu
authors.initials: T
authors.lastname: Sato
authors.forename: Takuyo
authors.initials: T
authors.lastname: Kozuka
authors.forename: Masahiko
authors.initials: M
authors.lastname: Oguchi
mesh_terms: D006801:Humans; D008175:Lung Neoplasms / Q000503:physiopathology / Q000532:radiotherapy*; D009038:Motion; D011880:Radiotherapy Planning, Computer-Assisted; D050397:Radiotherapy, Intensity-Modulated / Q000295:instrumentation / Q000379:methods*; D012119:Respiration