Company F Z
School of Engineering, University of Western Sydney, Kingswood, Australia.
Australas Phys Eng Sci Med. 2007 Mar;30(1):33-41. doi: 10.1007/BF03178407.
Synchrotron x-ray beams with high fluence rate and highly collimated may be used in stereotactic radiotherapy of lung tumours. A bundle of converging monochromatic x-ray beams having uniform microscopic thickness i.e. (microplanar beams) are directed to the center of the tumour, delivering lethal dose to the target volume while sparing normal cells. The proposed technique takes advantage of the hypothesised repair mechanism of capillary cells between alternate microbeam zones, which regenerate the lethally irradiated endothelial cells. The sharply dropping lateral dose of a microbeam provides low scattered dose to the off-target interbeam volume. In the target volume the converging bundle of beams are closely spaced, and relatively high primary and secondary electron doses overlap and produce a high dose region between the beams. This higher and lower dose margins in the target volume allows precise targeting. The advantages of stereotactic microbeam radiotherapy will be lost as the dose between microbeams exceeds the tolerance dose of the dose limiting tissues. Therefore, it is essential to optimize the interbeam doses in off-target volume. The lateral and depth doses of 100 keV microplanar beams are investigated for a single beam and an array of converging microplanar beams in a tissue, lung and tissue-lung phantoms. The EGS5 Monte Carlo code is used to calculate dose profiles at different depths and bundles of beams. The maximum dose on the beam axis (peak) and the minimum interbeam dose (valley) are compared at different energies, depths, bundle sizes, heights, widths and beam spacings. The interbeam dose is calculated at different depths and an isodose map of the phantom is obtained. An acceptable energy region is found for tissue and lung microbeam radiotherapy and a stereotactic microbeam radiotherapy model is proposed for a 4 cm diameter and 1 cm thick tumour on the lung phantom.
具有高注量率和高度准直的同步加速器X射线束可用于肺部肿瘤的立体定向放射治疗。一束具有均匀微观厚度的会聚单色X射线束（即微平面束）被导向肿瘤中心，在 sparing正常细胞的同时，向靶体积传递致死剂量。所提出的技术利用了交替微束区域之间毛细血管细胞的假设修复机制，该机制可使受到致死性照射的内皮细胞再生。微束的侧向剂量急剧下降，为靶外束间体积提供低散射剂量。在靶体积中，会聚束紧密排列，相对较高的初级和次级电子剂量重叠，在束之间产生高剂量区域。靶体积中这种较高和较低的剂量边缘允许精确靶向。当微束之间的剂量超过剂量限制组织的耐受剂量时，立体定向微束放射治疗的优势将丧失。因此，优化靶外体积中的束间剂量至关重要。研究了在组织、肺和组织-肺体模中，单束和会聚微平面束阵列的100 keV微平面束的侧向和深度剂量。使用EGS5蒙特卡罗代码计算不同深度和束束的剂量分布。比较了不同能量、深度、束尺寸、高度、宽度和束间距下束轴上的最大剂量（峰值）和束间最小剂量（谷值）。计算了不同深度的束间剂量，并获得了体模的等剂量图。找到了适用于组织和肺微束放射治疗的可接受能量区域，并针对肺体模上直径4 cm、厚1 cm的肿瘤提出了立体定向微束放射治疗模型。
