BLOOD VESSELS AND NEUTRONS: QUANTITATIVE STUDIES

临床高LET辐射面临的问题之一是晚期组织 与血管系统损伤相关的变化-特别是 毛细血管-与严重纤维化相关的晚期效应。 体内 在Sandison Clark耳室内测量微血管变化， 新西兰兔和体外实验使用器官培养物 兔血管细胞用于提供临床前信息 关于这种组织在体内和体外的反应。 分级单次中子剂量对在体微血管的影响 （12.5-500拉德）、分次中子照射、分级剂量的X射线和 这两种方式的相互作用和可能的加强将是 评估。 单次或多次手术后的早期和中期血管变化 联合治疗方案将通过测量 在毛细血管、小动脉和小静脉上的以下体内参数： 微血管长度、表面积和管壁厚度。 这些参数 将单独确定毛细血管（小于或等于10 Mu 直径）较大的血管（直径大于10 μ m），对于总数 微脉管系统 从这些测量的参数，微血管体积， 微血管密度/mm 2和随时间的扩张因子将是 计算了 平行进行的体外研究将使用可比较的 血管内皮细胞和平滑肌细胞培养物在体内辐照 为了进一步阐明这两种最具反应性的细胞群的作用， 辐射后的早期和中期效应。 因此，我们将确定a）中子剂量响应（Do，Dq，LD-50）， B）在体内的微脉管系统和在体外的其细胞组分， 早期和中期损伤和修复的程度，以及c） 通过使用分次给药方案对毛细血管进行差异性保护。 中子辐射剂量和剂量分馏与这种方式将 与在这两个系统中已经建立的观察结果进行比较 用千伏X射线 RBE随剂量和时间的动态变化 将建立与这两种临床使用模式的关系。 这些定量的实验将为发展 临床策略，以尽量减少后期血管变化的使用 人类癌症管理中的高L辐射。

One of the problems facing clinical High-LET radiation is the late tissue changes associated with injury to the vascular system - in particular the capillaries - late effects associated with severe fibrosis. In vivo measurements of microvascular changes in the Sandison Clark ear chamber in the New Zealand rabbit and in vitro experiments using organ cultures of rabbit vascular cells are directed to provide pre-clinical information concerning the response of this tissue in vivo and in vitro. The effects on the microvasculature in vivo of graded single neutron doses (12.5-500 rads), fractionated neutron exposures, graded doses of x-rays and the interaction and possible potentiation of these two modalities will be evaluated. Early and intermediate vascular changes following single or combined treatment regimens will be scored and correlated by measuring the following parameters in vivo on capillaries, arterioles and venules: microvascular length, surface area and wall thickness. These parameters will be determined separately for capillaries, (less than or equal to 10Mu in diameter) larger vessels (greater than 10Mu dia.), and for the total microvasculature. From these measured parameters, microvascular volume, microvascular density/mm2 and a dilatation factor over time will be calculated. In vitro studies carried out in parallel will use comparable cultures of vascular endothelial and smooth muscle cells irradiated in vivo to further elucidate the role of these two most reactive cell populations in early and intermediate effects following radiation. Thus we will determine a) the neutron dose response (Do, Dq, LD-50) for microvasculature in vivo and its cellular components in vitro, b) the extent of early and intermediate injury and repair and c) the extent of differential sparing of capillaries by the use of fractionated regimens. Doses of neutron radiation and dose fractionation with this modality will be compared with already established observations made in these two systems with kilovoltage x-rays. The dynamics of RBE over dose and time in relation to these two clinically used modalities will be established. These quantitative experiments will provide valuable information to develop clinical strategies to minimize the late vascular changes in the use of High-L radiation in human cancer management.