title: Intrafractional respiratory motion for charged particle lung therapy with immobilization assessed by four-dimensional computed tomography.
abstract: The aim of this study was to quantify the magnitude of intrafractional lung tumor motion under free-breathing conditions with an immobilization device using four-dimensional computed tomography (4DCT). 4DCT data sets were acquired for 17 patients with lung tumors receiving carbon ion beam therapy. A single respiratory cycle was subdivided into 10 phases, and intrafractional tumor motion was calculated by identifying the gross tumor volume (GTV) center of mass (COM) in two scenarios; respiratory-ungated and -gated treatments, which were based on a whole respiratory cycle and a 30% duty cycle around peak exhalation, respectively. For the respiratory-ungated case, the mean (± standard deviation) GTV-COM displacements from the peak exhalation position over the 17 patients were 0.6 (± 0.8) / 0.9 (± 1.2) mm, 2.0 (± 1.4) / 0.4 (± 0.7) mm, and 0.2 (± 0.5) / 7.8 (± 6.9) mm in left/right, anterior/posterior and superior/inferior directions, respectively, while these were reduced for the respiratory-gated case to 0.3 (± 0.4) / 0.4 (± 0.6) mm (left/right), 0.8 (± 0.7) / 0.3 (± 0.5) mm (anterior/posterior), and 0.1 (± 0.2) / 2.8 (± 2.9) mm (superior/inferior). Quantitative analysis of tumor motion with immobilization is valuable not only for particle beam therapy but also for photon beam therapy.
authors.affiliation: Research Center for Particle Therapy, National Institute of Radiological Sciences, Inage, Chiba, Japan.
authors.forename: Suguru
authors.initials: S
authors.lastname: Dobashi
authors.forename: Toshio
authors.initials: T
authors.lastname: Sugane
authors.forename: Shinichiro
authors.initials: S
authors.lastname: Mori
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Asakura
authors.forename: Naoyoshi
authors.initials: N
authors.lastname: Yamamoto
authors.forename: Motoki
authors.initials: M
authors.lastname: Kumagai
authors.forename: Susumu
authors.initials: S
authors.lastname: Kandatsu
authors.forename: Masayuki
authors.initials: M
authors.lastname: Baba
mesh_terms: D000368:Aged; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods*; D007103:Immobilization / Q000379:methods*; D008175:Lung Neoplasms / Q000000981:diagnostic imaging / Q000503:physiopathology* / Q000532:radiotherapy*; D008297:Male; D009068:Movement; D015203:Reproducibility of Results; D015656:Respiratory Mechanics; D055425:Respiratory-Gated Imaging Techniques / Q000379:methods*; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000379:methods*