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Simplified estimation method for dose distributions around field junctions in proton craniospinal irradiation

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Abstract

In radiotherapy involving craniospinal irradiation (CSI), field junctions of therapeutic beams are necessary, because a CSI target is generally several times larger than the maximum field size of the beams. The purpose of this study was to develop a simplified method for estimating dose uniformity around the field junctions in proton CSI. We estimated the dose profiles around the field junctions of proton beams using a simplified field-junction model, in which partial lateral dose distributions around the field edge were assumed to be approximated using the error function. We measured the lateral dose distributions of the proton beams planned for the CSI treatment using a two-dimensional (2D) ionization chamber array. Although dose hot spots and cold spots tend to be underestimated by a chamber array because of the partial volume effect of the sensitive volume and discrete chamber positions, the model estimation results were fairly consistent with the measurements obtained using a 2D chamber array subjected to CSI-simulated serial irradiation. The simplified junction model enabled us to estimate the dose distributions and dependence of the setup position gap on the dose uniformity around the field junctions on the basis of the field-by-field dose profiles measured using the 2D chamber array.

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Acknowledgments

We thank all the staff of the Radiation and Proton Therapy Center in the Shizuoka Cancer Center, and we thank the Mitsubishi Electric Corporation for their expert support with the proton beam irradiation.

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Authors and Affiliations

  1. Proton Therapy Division, Shizuoka Cancer Center Hospital, 1007 Shimonagakubo, Nagaizumi-cho, Shizuoka, 411-8777, Japan

    Haruo Yamashita, Yuki Kase & Shigeyuki Murayama

  2. Proton Therapy Division, Shizuoka Cancer Center Research Institute, 1007 Shimonagakubo, Nagaizumi-cho, Shizuoka, 411-8777, Japan

    Haruo Yamashita, Yuki Kase & Shigeyuki Murayama

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  1. Haruo Yamashita
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  2. Yuki Kase
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  3. Shigeyuki Murayama
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Correspondence to Haruo Yamashita.

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The authors declare that they have no conflicts of interest.

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Yamashita, H., Kase, Y. & Murayama, S. Simplified estimation method for dose distributions around field junctions in proton craniospinal irradiation. Radiol Phys Technol 10, 95–105 (2017). https://doi.org/10.1007/s12194-016-0373-2

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  • DOI: https://doi.org/10.1007/s12194-016-0373-2

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