Journal Article Carbon-Ion Pencil Beam Scanning Treatment With Gated Markerless Tumor Tracking: An Analysis of Positional Accuracy

森, 慎一郎  ,  軽部, 雅崇  ,  白井, 敏之  ,  田尻, 稔  ,  竹腰, 琢朗  ,  三木, 健太朗  ,  白石, ゆりか  ,  谷本, 克之  ,  柴山, 晃一  ,  安田, 茂雄  ,  山本, 直敬  ,  山田, 滋  ,  辻, 比呂志  ,  野田, 耕司  ,  鎌田, 正

95 ( 1 )  , pp.258 - 266 , 2016-04 , Tarrytown Ny : Elsevier Science Inc
Purpose:Having implemented amplitude-based respiratory gating for scanned carbon-ion beam therapy, we sought to evaluate its effect on positional accuracy and throughput.Methods and Materials: A total of 10 patients with tumors of the lung and liver partic- ipated in the first clinical trials at our center. Treatment planning was conducted with 4- dimensional computed tomography (4DCT) under free-breathing conditions. The plan- ning target volume (PTV) was calculated by adding a 2- to 3-mm setup margin outside the clinical target volume (CTV) within the gating window. The treatment beam was on when the CTV was within the PTV. Tumor position was detected in real time with a markerless tumor tracking system using paired x-ray fluoroscopic imaging units. Results: The patient setup error (mean ` SD) was 1.1 ` 1.2 mm/0.6 ` 0.4 . The mean internal gating accuracy (95% confidence interval [CI]) was 0.5 mm. If external gating had been applied to this treatment, the mean gating accuracy (95% CI) would have been 4.1 mm. The fluoroscopic radiation doses (mean ` SD) were 23.7 ` 21.8 mGy per beam and less than 487.5 mGy total throughout the treatment course. The setup, prep- aration, and irradiation times (mean ` SD) were 8.9 ` 8.2 min, 9.5 ` 4.6 min, and 4.0 ` 2.4 min, respectively. The treatment room occupation time was 36.7 ` 67.5 min.

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