Coggle J E
Department of Radiation Biology, Medical College of St. Bartholomew's Hospital, London.
Int J Radiat Biol Relat Stud Phys Chem Med. 1988 Apr;53(4):585-97. doi: 10.1080/09553008814550911.
Dose-response curves were determined for pulmonary adenomas and adenocarcinomas in mice after single acute doses of 200 kVp X-rays and cyclotron neutrons (E = 7.5 MeV). A serial-killing experiment established that the radiation induces the tumours and does not merely accelerate the appearance of spontanoeus cancers [corrected]. The dose versus incidence (I) of tumours in male and female mice for X-ray doses between 0.25 and 7.5 Gy is 'bell-shaped' and best fitted with a purely quadratic induction and exponential inactivation terms, i.e. I = A + BD2e-alpha D. In contrast, the tumour dose-response after 0.1-4.0 Gy of neutrons is best fitted by I = A + BDe-alpha D and is steeply linear less than or equal to 1 Gy, peaks between 1 and 3 Gy and sharply declines at 4.0 Gy. The data for the female mice less than or equal to 1 Gy neutrons are best fitted to the square root of the dose. A major objective of the experiments was to derive neutron RBE values. Because of the differences between the X-ray (quadratic) and neutron (linear) curves, the RBEn will vary inversely with decreasing X-ray dose. The RBE values at 1 Gy of X-rays derived from the B coefficients in the above equations are 7.4 +/- 3.2 (male and female); 8.6 +/- 3.6 (female) and 4.7 +/- 1.8 (male). These are high values and imply even higher values at the doses of interest to radiation protection. If, however, one restricts the analysis to the initial, induction side of the response (less than or equal to 1 Gy neutrons, less than or equal to 3 Gy X-rays) then good linear fits are obtainable for both radiations and indicate neutron RBE values of 7.4 +/- 2.3 for female mice and 4.5 +/- 1.8 for males, and these are independent of dose level.
在给小鼠单次急性给予200 kVp X射线和回旋加速器中子（E = 7.5 MeV）后，测定了肺腺瘤和腺癌的剂量反应曲线。一项连续处死实验证实，辐射可诱发肿瘤，而不仅仅是加速自发癌症的出现[已修正]。对于0.25至7.5 Gy的X射线剂量，雄性和雌性小鼠肿瘤的剂量与发生率（I）呈“钟形”，最适合用纯二次诱导和指数失活项来拟合，即I = A + BD2e-αD。相比之下，0.1至4.0 Gy中子照射后的肿瘤剂量反应最适合用I = A + BDe-αD来拟合，在小于或等于1 Gy时呈陡峭线性，在1至3 Gy之间达到峰值，在4.0 Gy时急剧下降。小于或等于1 Gy中子照射的雌性小鼠的数据最适合用剂量的平方根来拟合。实验的一个主要目标是得出中子的相对生物效应（RBE）值。由于X射线（二次曲线）和中子（线性曲线）曲线之间的差异，中子RBE将随着X射线剂量的降低而呈反比变化。从上述方程中的B系数得出的1 Gy X射线时的RBE值为7.4±3.2（雄性和雌性）；8.6±3.6（雌性）和4.7±1.8（雄性）。这些值较高，意味着在辐射防护感兴趣的剂量下值更高。然而，如果将分析限制在反应的初始诱导阶段（小于或等于1 Gy中子，小于或等于3 Gy X射线），那么两种辐射都可获得良好的线性拟合，表明雌性小鼠的中子RBE值为7.4±2.3，雄性为4.5±1.8，且这些值与剂量水平无关。
