title: Evaluation of a combined respiratory-gating system comprising the TrueBeam linear accelerator and a new real-time tumor-tracking radiotherapy system: a preliminary study.
abstract: A combined system comprising the TrueBeam linear accelerator and a new real-time, tumor-tracking radiotherapy system, SyncTraX, was installed in our institution. The goals of this study were to assess the capability of SyncTraX in measuring the position of a fiducial marker using color fluoroscopic images, and to evaluate the dosimetric and geometric accuracy of respiratory-gated radiotherapy using this combined system for the simple geometry. For the fundamental evaluation of respiratory-gated radiotherapy using SyncTraX, the following were performed:1) determination of dosimetric and positional characteristics of sinusoidal patterns using a motor-driven base for several gating windows; 2) measurement of time delay using an oscilloscope; 3) positional verification of sinusoidal patterns and the pattern in the case of a lung cancer patient; 4) measurement of the half-value layer (HVL in mm AL), effective kVp, and air kerma, using a solid-state detector for each fluoroscopic condition, to determine the patient dose. The dose profile in a moving phantom with gated radiotherapy having a gating window ≤ 4 mm was in good agreement with that under static conditions for each photon beam. The total time delay between TrueBeam and SyncTraX was < 227 ms for each photon beam. The mean of the positional tracking error was < 0.4 mm for sinusoidal patterns and for the pattern in the case of a lung cancer patient. The air-kerma rates from one fluoroscopy direction were 1.93 ± 0.01, 2.86 ± 0.01, 3.92 ± 0.04, 5.28 ± 0.03, and 6.60 ± 0.05 mGy/min for 70, 80, 90, 100, and 110 kV X-ray beams at 80 mA, respectively. The combined system comprising TrueBeam and SyncTraX could track the motion of the fiducial marker and control radiation delivery with reasonable accuracy; therefore, this system provides significant dosimetric improvement. However, patient exposure dose from fluoroscopy was not clinically negligible.
authors.affiliation: Graduate School of Medicine, Yamaguchi University. shiinoki@yamaguchi-u.ac.jp.
authors.forename: Takehiro
authors.initials: T
authors.lastname: Shiinoki
authors.forename: Shinji
authors.initials: S
authors.lastname: Kawamura
authors.forename: Takuya
authors.initials: T
authors.lastname: Uehara
authors.forename: Yuki
authors.initials: Y
authors.lastname: Yuasa
authors.forename: Koya
authors.initials: K
authors.lastname: Fujimoto
authors.forename: Masahiro
authors.initials: M
authors.lastname: Koike
authors.forename: Tatsuhiro
authors.initials: T
authors.lastname: Sera
authors.forename: Yuki
authors.initials: Y
authors.lastname: Emoto
authors.forename: Hideki
authors.initials: H
authors.lastname: Hanazawa
authors.forename: Keiko
authors.initials: K
authors.lastname: Shibuya
mesh_terms: D003199:Computer Systems; D057918:Fiducial Markers; D005471:Fluoroscopy / Q000295:instrumentation*; D006801:Humans; D008175:Lung Neoplasms / Q000532:radiotherapy*; D009068:Movement; D010315:Particle Accelerators / Q000295:instrumentation*; D019047:Phantoms, Imaging; D017785:Photons; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D011881:Radiotherapy, Computer-Assisted / Q000379:methods; D012119:Respiration