title: First clinical experience in carbon ion scanning beam therapy: retrospective analysis of patient positional accuracy.
abstract: Our institute has constructed a new treatment facility for carbon ion scanning beam therapy. The first clinical trials were successfully completed at the end of November 2011. To evaluate patient setup accuracy, positional errors between the reference Computed Tomography (CT) scan and final patient setup images were calculated using 2D-3D registration software. Eleven patients with tumors of the head and neck, prostate and pelvis receiving carbon ion scanning beam treatment participated. The patient setup process takes orthogonal X-ray flat panel detector (FPD) images and the therapists adjust the patient table position in six degrees of freedom to register the reference position by manual or auto- (or both) registration functions. We calculated residual positional errors with the 2D-3D auto-registration function using the final patient setup orthogonal FPD images and treatment planning CT data. Residual error averaged over all patients in each fraction decreased from the initial to the last treatment fraction [1.09 mm/0.76° (averaged in the 1st and 2nd fractions) to 0.77 mm/0.61° (averaged in the 15th and 16th fractions)]. 2D-3D registration calculation time was 8.0 s on average throughout the treatment course. Residual errors in translation and rotation averaged over all patients as a function of date decreased with the passage of time (1.6 mm/1.2° in May 2011 to 0.4 mm/0.2° in December 2011). This retrospective residual positional error analysis shows that the accuracy of patient setup during the first clinical trials of carbon ion beam scanning therapy was good and improved with increasing therapist experience.
authors.affiliation: Research Center for Charged Particle Therapy, National Institute of Radiological Sciences, Inage-ku, Chiba 263-8555, Japan.
authors.forename: Shinichiro
authors.initials: S
authors.lastname: Mori
authors.forename: Kouichi
authors.initials: K
authors.lastname: Shibayama
authors.forename: Katsuyuki
authors.initials: K
authors.lastname: Tanimoto
authors.forename: Motoki
authors.initials: M
authors.lastname: Kumagai
authors.forename: Yuka
authors.initials: Y
authors.lastname: Matsuzaki
authors.forename: Takuji
authors.initials: T
authors.lastname: Furukawa
authors.forename: Taku
authors.initials: T
authors.lastname: Inaniwa
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Shirai
authors.forename: Koji
authors.initials: K
authors.lastname: Noda
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Tsuji
authors.forename: Tadashi
authors.initials: T
authors.lastname: Kamada
mesh_terms: D005260:Female; D006258:Head and Neck Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy; D063193:Heavy Ion Radiotherapy / Q000295:instrumentation / Q000706:statistics & numerical data; D006801:Humans; D008297:Male; D056888:Patient Positioning / Q000706:statistics & numerical data; D010386:Pelvic Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy; D011471:Prostatic Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy; D011880:Radiotherapy Planning, Computer-Assisted; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed