Volume effects in the irradiated canine spinal cord: do they exist when the probability of injury is low?
Volume effects in the irradiated canine spinal cord: do they exist when the probability of injury is low?
复制标题
DOI：
10.1016/s0167-8140(97)00213-2
复制
发表时间：
1998-03-01
影响因子：
5.7
通讯作者：
Gillette, EL
中科院分区：
文献类型：
--
作者：
Powers, BE;Thames, HD;Gillette, EL
目的：本研究的目的是研究辐照后犬脊髓的体积效应。材料与方法：89只beagle犬在4或20 cm的胸脊髓上以4 Gy的分量给予44-84 Gy的光子。作为对照，36只狗接受60-84 Gy的剂量，每次剂量为2 Gy，长度为20 cm， 6只狗未接受辐射。评估狗的临床症状，以及安乐死后的大体病变，严重的大出血，白质坏死和/或实质萎缩，轻度的局灶性纤维丢失。量化白质空泡、脑膜厚度和背根神经节病变。对数据进行分析，以检验体积对剂量-反应曲线的影响。结果：在4 ~ 20 cm长度的辐照脊髓中，一般病变、严重病变和轻度病变的体积效应显著（ED50水平差异8.3 ~ 15.0 Gy）。严重病变的4 Gy分数的ED50为56.9 Gy (95% CI 53.1-60.6)， 20 cm和4cm的ED50为68.8 Gy （95% CI 64.5-75.1）。当使用平行或非平行曲线模型时，数据与剂量-反应曲线的拟合显著改善，但在低损伤概率下，两种曲线之间都存在明显差异。脑膜厚度存在体积效应，剂量-反应曲线斜率不同。临床症状与20厘米（ED50 = 54.0 Gy）的严重病变相关，但与4厘米（ED50 = 77.6 Gy）的病变无关。结论：犬脊髓辐照后病理病变的发生存在体积效应。病理病变的临床代偿发生在很小的辐照量，而不是很大的辐照量。没有足够的数据支持剂量-反应曲线的斜率随着体积的减小而减小。在脊髓损伤的50%水平上估计的体积效应也可以在临床特征的低概率损伤中保持。(C) 1998爱思唯尔科学爱尔兰有限公司
Purpose: The purpose of this study was to investigate volume effects in the irradiated canine spinal cord.Materials and methods: Eighty-nine beagle dogs were given 44-84 Gy photons in 4 Gy fractions to 4 or 20 cm lengths of thoracic spinal cord. As controls, 36 dogs were given 60-84 Gy in 2 Gy fractions to a 20 cm length of spinal cord and six dogs were unirradiated. Dogs were evaluated for clinical signs, and after euthanasia, for occurrence of gross lesions, severe lesions of massive hemorrhage, white matter necrosis and/or parenchymal atrophy and mild lesions of focal fiber loss. White matter vacuoles, meningeal thickness and dorsal root ganglia lesions were quantified. Data were analyzed to test for an effect of volume on dose-response curves.Results: Significant volume effects were found between 4 and 20 cm lengths of irradiated spinal cord for gross lesions, severe lesions and mild lesions (8.3-15.0 Gy difference at the ED50 level). The ED50 in 4 Gy fractions for severe lesions was 56.9 Gy (95% CI 53.1-60.6) for 20 cm and 68.8 Gy (95% CI 64.5-75.1) for 4 cm fields. Significant improvements in the fit of data to dose-response curves resulted when using models with either parallel or non-parallel curves, but in either case an appreciable difference existed between curves at low probabilities of injury. Volume effects were present for meningeal thickness and slopes of dose-response curves were different. Clinical signs correlated well with severe lesions for 20 cm (ED5O = 54.0 Gy), but not for 4 cm fields (ED50 = 77.6 Gy).Conclusions: Volume effects exist for the occurrence of pathologic lesions in irradiated canine spinal cord. Clinical compensation for pathologic lesions occur at small, but not large irradiated volumes. There is insufficient data to support a decreased slope of dose-response curves with decreased volume. Volume effects estimated at the 50% level of spinal cord injury could also hold at low probabilities of injury characteristic of the clinic. (C) 1998 Elsevier Science Ireland Ltd.