title: Dose verification of volumetric modulated arc therapy (VMAT) by use of in-treatment linac parameters.
abstract: Linac parameters such as the multi-leaf collimator (MLC) position and jaw position, cumulative monitor units (MUs), and the corresponding gantry angle were recorded during the clinical delivery of volumetric modulated arc therapy for prostate, lung, and head/neck cancer patients. Then, linac parameters were converted into the beam-data format used in the treatment planning system, and the dose distribution was reconstructed. The dose-volume histogram and the dose difference (DD) were compared with the corresponding values in the treatment plan. A reproducible error of in-treatment linac parameters was observed when a sudden change of beam intensity or MLC/jaw speed occurred. The maximum cumulative MU error was more than 4 MU for lung cancer cases, and the maximum MLC position exceeded 5 mm for prostate and head/neck cancer patients. However, these errors were quickly compensated for at the next control point. All treatments analyzed in the present study were delivered within 0.4% accuracy at the planning target volume. The cumulative dose agreed with that of the plan within 3% of the prescribed dose. The 1% DD was 93.9, 99.9, and 93.4% of the prescription dose for prostate, lung, and head/neck cancer patients, respectively.
authors.affiliation: Department of Radiology, The University of Tokyo Hospital, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8655, Japan. haga@rcnp.osaka-u.ac.jp
authors.forename: Akihiro
authors.initials: A
authors.lastname: Haga
authors.forename: Akira
authors.initials: A
authors.lastname: Sakumi
authors.forename: Yukari
authors.initials: Y
authors.lastname: Okano
authors.forename: Saori
authors.initials: S
authors.lastname: Itoh
authors.forename: Naoya
authors.initials: N
authors.lastname: Saotome
authors.forename: Satoshi
authors.initials: S
authors.lastname: Kida
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Igaki
authors.forename: Kenshiro
authors.initials: K
authors.lastname: Shiraishi
authors.forename: Hideomi
authors.initials: H
authors.lastname: Yamashita
authors.forename: Kuni
authors.initials: K
authors.lastname: Ohtomo
authors.forename: Keiichi
authors.initials: K
authors.lastname: Nakagawa
mesh_terms: D003198:Computer Simulation; D006258:Head and Neck Neoplasms / Q000532:radiotherapy*; D006801:Humans; D008175:Lung Neoplasms / Q000532:radiotherapy*; D008297:Male; D011471:Prostatic Neoplasms / Q000532:radiotherapy*; D011785:Quality Assurance, Health Care; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D050397:Radiotherapy, Intensity-Modulated; D012984:Software