Journal Article

Amplitude-based gated phase-controlled rescanning in carbon-ion scanning beam treatment planning under irregular breathing conditions using lung and liver 4DCTs

Shinichiro Mori, Taku Inaniwa, Takuji Furukawa, Wataru Takahashi, Mio Nakajima, Toshiyuki Shirai, Koji Noda, Shigeo Yasuda and Naoyoshi Yamamoto

in Journal of Radiation Research

Volume 55, issue 5, pages 948-958
Published in print September 2014 | ISSN: 0449-3060
Published online May 2014 | e-ISSN: 1349-9157 | DOI: https://dx.doi.org/10.1093/jrr/rru032

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  • Clinical Genetics
  • Molecular Biology and Genetics
  • Epidemiology
  • Radiology
  • Nuclear Chemistry, Photochemistry, and Radiation

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Amplitude-based gating aids treatment planning in scanned particle therapy because it gives better control of uncertainty with the gate window. We have installed an X-ray fluoroscopic imaging system in our treatment room for clinical use with an amplitude-based gating strategy. We evaluated the effects of this gating under realistic organ motion conditions using 4DCT data of lung and liver tumors. 4DCT imaging was done for 24 lung and liver patients using the area-detector CT. We calculated the field-specific target volume (FTV) for the gating window, which was defined for a single respiratory cycle. Prescribed doses of 48 Gy relative biological effectiveness (RBE)/fraction/four fields and 45 Gy RBE/two fractions/two fields were delivered to the FTVs for lung and liver treatments, respectively. Dose distributions were calculated for the repeated first respiratory cycle (= planning dose) and the whole respiratory data (= treatment dose). We applied eight phase-controlled rescannings with the amplitude-based gating. For the lung cases, D95 of the treatment dose (= 96.0 ± 1.0%) was almost the same as that of the planning dose (= 96.6 ± 0.9%). Dmax/Dmin of the treatment dose (= 104.5 ± 2.2%/89.4 ± 2.6%) was slightly increased over that of the planning dose (= 102.1 ± 1.0%/89.8 ± 2.5%) due to hot spots. For the liver cases, D95 of the treatment dose (= 97.6 ± 0.5%) was decreased by ∼ 1% when compared with the planning dose (= 98.5 ± 0.4%). Dmax/Dmin of the treatment dose was degraded by 3.0%/0.4% compared with the planning dose. Average treatment times were extended by 46.5 s and 65.9 s from those of the planning dose for lung and liver cases, respectively. As with regular respiratory patterns, amplitude-based gated multiple phase-controlled rescanning preserves target coverage to a moving target under irregular respiratory patterns.

Keywords: carbon ion beam; 4DCT; irregular breathing; lung; liver; scanning beam; treatment planning

Journal Article.  4805 words.  Illustrated.

Subjects: Clinical Genetics ; Molecular Biology and Genetics ; Epidemiology ; Radiology ; Nuclear Chemistry, Photochemistry, and Radiation

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