@article{oai:repo.qst.go.jp:00047003,
 author = {Tajiri, Minoru and Maeda, Takamasa and Isobe, Yosiharu and Tanimoto, Katsuyuki and Shibayama, Kouichi and 田尻 稔 and 前田 貴雅 and 磯部 喜治 and 谷本 克之 and 柴山 晃一},
 issue = {8},
 journal = {Physica Medica},
 month = {Jul},
 note = {Purpose: We previously proposed a calculation method using Clarkson integration to obtain the physical dose at the center of the spread-out Bragg peak (SOBP) for a treatment beam, the measurement point of which agrees with the isocenter [Tajiri et al. Med. Phys. 2013; 40: 071733−1−5]. However, at the measurement point which does not agree with the isocenter, the physical dose calculated by this method might have a large error. For this error, we propose a correction method.
Materials and methods: To confirm whether the error can be corrected using in-air off axis ratio (OAR), we measured the physical dose at the center of an asymmetric square field and a symmetric square field and in-air OAR. For beams of which the measurement point does not agree with the isocenter, as applied to prostate cancer patients, the physical dose calculated using Clarkson integration was corrected with in-air OAR.
Results: The maximum difference between the physical dose measured at the center of an asymmetric square field and the product of in-air OAR and the physical dose at the center of a symmetric square field was – 0.12 %. For beams as applied to prostate cancer patients, the differences between the measured physical doses and the physical doses corrected using in-air OAR were –0.17 ± 0.23%.
Conclusions: The physical dose at the measurement point which does not agree with the isocenter, can be obtained from in-air OAR at the isocenter plane and the physical dose at the center of the SOBP on the beam axis.},
 pages = {985--988},
 title = {Correction method for the physical dose calculated using Clarkson integration at the center of the spread-out Bragg peak for asymmetric field in carbon-ion radiotherapy},
 volume = {30},
 year = {2014}
}