DOSE MEASUREMENTS AND CALCULATIONS OF SMALL RADIATION-FIELDS FOR 9-MV X-RAYS
DOSE MEASUREMENTS AND CALCULATIONS OF SMALL RADIATION-FIELDS FOR 9-MV X-RAYS
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DOI：
10.1118/1.595664
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发表时间：
1985-01-01
期刊：
影响因子：
3.8
通讯作者：
BASSI, FA
中科院分区：
文献类型：
--
作者：
ARCOVITO, G;PIERMATTEI, A;BASSI, FA
尺寸范围为 1 倍的方形视野的剂量分布测量。 1至30次据报道，来自 CGR 制造的 Neptune 10 直线加速器的 9-MV X 射线束的射程为 30 厘米。特别注意小于 4 倍的字段大小。 4厘米，用于放射外科技术。为了表达剂量-监测单位关系，通过实验测量获得了总散射校正因子、准直器校正因子和体模散射校正因子。显示出这些因素对最小射野尺寸（< 4 × 4 cm）的强烈依赖性。最大深度剂量 dmax 的测量（绘制为射野尺寸的函数）显示出最大值在约 5 倍处。 5 cm，与之前的结果非常一致，还测量了最小场的 dmax，这表明 X 射线束的污染电子成分并不是造成 dmax 偏移的原因。对交叉剂量分布的半影宽度（作为射野大小的函数）的分析使我们能够假设 dmax 偏移可能是由于幻影散射光子造成的，而幻影散射光子又是由准直器散射光子产生的。新导出的组织最大比和散射最大比数据用于2倍的剂量分布计算。 2、4 次。 4、和10次。 10 厘米视野尺寸。发现实验数据和计算数据之间的一致性为.+-。 2% 在场的几何边缘内和.+-。其中 6% 除外。来自 2 倍等角点的剂量分布。 2 厘米见方的区域在 360 度范围内移动。获得了旋转弧，并与 Ling 测量的 125I 屏蔽源中心的旋转弧进行了比较。讨论了与在放射外科中使用来自直线加速器的 X 射线束有关的优点和问题。
Measurements of dose distribution for square fields with sizes ranges from 1 .times. 1 to 30 .times. 30 cm for a 9-MV x-ray beam from a Neptune 10 linear accelerator, manufactured by CGR, are reported. Special attention was paid to field sizes smaller than 4 .times. 4 cm, used in radiosurgery techniques. To express the dose-monitor units relationship, total, collimator, and phantom scatter correction factors were obtained by experimental measurements. A strong dependence of these factors on the smallest field sizes (< 4 .times. 4 cm) was shown. Measurements of the maximum depth dose dmax, plotted as a function of field size, showed a maximum at about 5 .times. 5 cm, in good agreement with previous results, dmax was also measured for the smallest fields, demonstrating that the contaminating electron component of the x-ray beam was not responsible for the dmax shift. Analysis of the penumbra width of cross dose distributions, as a function of field sizes, allowed us to postulate that the dmax shift could be due to the phantom scattered photons, which in turn were generated by the collimator scattered photons. Newly derived tissue-maximum ratio and scatter-maximum ratio data were used for dose profile calculations of 2 .times. 2, 4 .times. 4, and 10 .times. 10 cm field sizes. The agreement between experimental and calculated data was found to be .+-. 2% within the geometrical edges of the fields and .+-. 6% outside of them. A dose profile from the isocenter of a 2 .times. 2 cm square field moving through a 360.degree. rotation arc was obtained and compared with that from the center of a 125I shielded source, as measured by Ling. Advantages and problems relating to the use of x-ray beams from linear accelerators in radiosurgery are discussed.