Courdi A
Centre A Lacassagne, Biomedical Cyclotron, Nice, France.
Bull Cancer Radiother. 1996;83 Suppl:64s-7s. doi: 10.1016/0924-4212(96)84887-0.
Dose-response relationships of most tumours and normal tissues after neutron irradiation are characterized by relatively high alpha/beta ratios. Late reacting tissues are not as protected by low doses per fraction as they are after low linear energy transfer (LET) irradiation. Using the linear-quadratic (LQ) model with the time factor (when needed), we have calculated the therapeutic ratio (TR) as the ratio of the effect on a tumour (or an acutely responding tissue) over that on late reacting tissue. Hypothetical cases are given as well as a case derived from LQ parameters obtained experimentally in animals. It is shown that X-ray fractionation schemes that lead to a high TR will lead to a low neutron TR. For epithelial tumours, a neutron gain factor, GF (ratio of TR) is possible if neutron fractionation is compared to hypofractionated X-irradiation. Neutron treatment over conventional overall times of rapidly proliferating tumours carries a low TR and offers no GF. Neutron therapy for tumours with low alpha/beta ratios offer a potential advantage compared to tumours with high alpha/beta ratios.
大多数肿瘤和正常组织在中子照射后的剂量反应关系具有相对较高的α/β比值。与低线性能量传递（LET）照射后相比，晚期反应组织在低分次剂量照射下受到的保护较少。使用带有时间因素（必要时）的线性二次（LQ）模型，我们计算了治疗比（TR），即对肿瘤（或急性反应组织）的效应与对晚期反应组织的效应之比。给出了假设病例以及一个源自动物实验获得的LQ参数的病例。结果表明，导致高TR的X射线分次照射方案会导致低中子TR。对于上皮肿瘤，如果将中子分次照射与低分割X射线照射进行比较，可能存在中子增益因子GF（TR的比值）。在快速增殖肿瘤的常规总治疗时间内进行中子治疗，TR较低且无增益因子。与高α/β比值的肿瘤相比，低α/β比值肿瘤的中子治疗具有潜在优势。
