Development of techniques for increasing the accuracy of dose calculation in a convolution method used for body stereotactic radiotherapy

开发提高身体立体定向放射治疗用卷积法剂量计算精度的技术

• 批准号: 18591375
• 负责人: IWASAKI Akira
• 金额: $ 2.37万
• 依托单位: Hirosaki University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 2006
• 资助国家: 日本
• 起止时间: 2006 至 2007
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-18591375/
• 关键词: Covolution method; High-energy X-rays; Stereotactic radiotherapy; X-ray spectrum; Kernel; Error function; Multileaf collimator; Radiation therapy physics; 線源軸外線量比; 軸外コリメータ散乱係数; リーフ照射野出力差分法; 高エネルギーX線スペクトル

The following studies have been performed:・High-energy x-ray spectra sets from six linear accelerators were reconstructed using about ten energy bins. Each set can be applied accurately to attenuators from low Z materials like water to high Z materials like lead. It was analyzed how each set varies with the off-axis distance.・A pair of primary and scatter dose kernels in water was constructed for monochromatic radiation at each energy bin using Monte Carlo simulations on the basis of the differential method. The primary dose kernel indicates relatively smaller values around the photon interaction point, when compared with a primary dose kernel yielded with a photon interaction point at the center of a large water phantom. This fact may leads to the increase of dose calculation accuracy around the jaw and MLC field borders when using primary dose kernels based on the differential method.・The in-water doses, calculated using a convolution method with sets of primary and scatter dose kernels yielded for respective energy bins, are generally within ±1% when compared with measurements. Namely, it can be understood that when the convolution is performed for monochromatic radiation at each energy bin, the beam hardening effect does not need to be taken into account.・With respect to the calculation of in-air x-ray intensity at a point, a method of using error functions on the x-ray target and flattening filter planes has been developed. For an open jaw field, the error functions are used in the area visual via the jaw collimators from the point. For an MLC field, a leaf-field output subtraction method is introduced using the error functions in the area visual via the jaw collimators from the point and using the error functions in the are a visual via each MLC leaf from the point.

已进行以下研究： ・使用约 10 个能量仓重建了来自 6 个直线加速器的高能 X 射线光谱集。每组都可以准确地应用于从低 Z 材料（如水）到高 Z 材料（如铅）的衰减器。分析了每组随离轴距离的变化情况。 ・使用基于微分法的蒙特卡罗模拟，构建了水中的一对初级剂量核和散射剂量核，用于每个能量仓的单色辐射。当与利用位于大水体模中心的光子相互作用点产生的初级剂量核相比时，初级剂量核指示在光子相互作用点周围相对较小的值。这一事实可能会导致在使用基于微分法的初级剂量核时，下颌和 MLC 场边界周围的剂量计算精度提高。 ・使用卷积方法计算出的水中剂量，以及为各个能量仓生成的初级和散射剂量核组，与测量值相比，通常在 ±1% 以内。也就是说，可以理解，当在每个能量仓对单色辐射进行卷积时，不需要考虑射束硬化效应。 ・针对空气中某点的 X 射线强度的计算，开发了一种在 X 射线目标上使用误差函数并平坦化滤波器平面的方法。对于开放的钳口视野，误差函数用于通过来自该点的钳口准直器进行视觉的区域。对于 MLC 场，引入了叶场输出减法，该方法使用通过来自该点的颚式准直器的视觉区域中的误差函数以及使用通过来自该点的每个 MLC 叶片的视觉区域中的误差函数。

项目成果

New Development of High-Energy X-Ray Primary and Scatter Dose Kernels by Monte Carlo Simulation

蒙特卡罗模拟高能 X 射线初级和散射剂量核的新发展

• 发表时间: 2006
• 期刊: Proceedings of the Thirteenth EGS Users' Meeting in Japan (KEK, Tsukuba, Japan)
• 作者: Makoto Sasamori;Akira Iwasaki;Hidetoshi Saitoh;Shigenobu Kimura;Morio Seino;Fumio Komai
• 通讯作者: Fumio Komai

Introduction of an off-axis collimator scatter factor(S_C)and a source off-center ratio(OCR_<source>)for calculation of off-axis in-air outputs

引入离轴准直器散射因子（S_C）和源偏心比（OCR_<源>）来计算离轴空中输出

• 发表时间: 2007
• 作者: Fumio Komai;Akira Iwasaki;Shigenobu Kimura;Morio Seino;Makoto Sasamori
• 通讯作者: Makoto Sasamori

X線スペクトルに基づいてモンテカルロシミュレーションで構築した高エネルギーX線一次及び散乱ドーズカーネルの開発

基于X射线谱的蒙特卡罗模拟构建的高能X射线初级和散射剂量核的开发

• 发表时间: 2007
• 期刊: 弘前大学医学部保健学科紀要 6巻
• 作者: 笹森真実;岩崎晃;齋藤秀敏;木村重伸;清野守央;駒井史雄
• 通讯作者: 駒井史雄

Characteristic features of a high-energy x-ray spectra estimation method based on the Waggener iterative perturbation principle

基于瓦格纳迭代摄动原理的高能X射线能谱估计方法的特征

• 发表时间: 2006
• 期刊: Medical Physics 33 ・ 11
• 作者: Akira Iwasaki;Mamoru Kubota;Junichi Hirota;Akira Fujimori;Katsumasa Suzaki;Masahiko Aoki;Yoshinao Abe
• 通讯作者: Yoshinao Abe

Proposals to improve the accuracy of convolution-based dose calculation

提高基于卷积的剂量计算准确性的建议

• 发表时间: 2007
• 作者: Akira Iwasaki;Shigenobu Kimura;Morio Seino;Fumio Komai;Makoto Sasamori
• 通讯作者: Makoto Sasamori