Slabbert J P, Theron T, Zolzer F, Streffer C, Bohm L
National Accelerator Centre, Faure, South Africa.
Int J Radiat Oncol Biol Phys. 2000 Jul 1;47(4):1059-65. doi: 10.1016/s0360-3016(00)00508-3.
To determine the relationship between photon sensitivity and neutron sensitivity and between neutron RBE and photon resistance for two neutron modalities (with mean energies of 6 and 29 MeV) using human tumor cell lines spanning a wide range of radiosensitivities, the principal objective being whether or not a neutron advantage can be demonstrated.
Eleven human tumor cell lines with mean photon inactivation doses of 1.65-4. 35 Gy were irradiated with 0-5.0 Gy of p(66)/Be neutrons (mean energy of 29 MeV) at Faure, S.A. and the same plating was irradiated on the same day with 0-10.0 Gy of Cobalt-gamma-rays. Twelve human tumor cell lines, many of which were identical with the above selection, and spanning mean photon inactivation doses of 1.75-4.08 Gy, were irradiated with 0-4 Gy of d(14)/Be neutrons (mean energy of 6 MeV) and with 0-10 Gy of 240 kVp X-rays at the Essen Klinikum. Cell survival was determined by the clonogenic assay, and data were fitted to the linear quadratic equation.
Radiobiological differences between high-energy and low-energy neutrons are particularly apparent in the dependence of the neutron RBE on photon sensitivity. The increase of RBE with photon resistance is more pronounced in the low-energy Essen neutrons than in the high-energy Faure neutrons. An RBE advantage is indicated for photon-resistant cell lines and this is particularly apparent in the low-dose range using alpha-coefficients as compared to the mean inactivation dose. The clinical application of low-energy neutrons may be more restricted because of poor penetration and lack of skin sparing. However, these neutrons discriminate better between photon-sensitive and photon-resistant cells giving an RBE range of 2-6 and a mean RBE of 4.1, than high-energy neutrons where the RBE range is 1.6-3.5 and the mean RBE is 2.4. From the radiobiological point of view it, therefore, appears that the clinical potential of low-energy neutrons is considerably underrated.
使用一系列辐射敏感性广泛的人类肿瘤细胞系，确定两种中子模态（平均能量分别为6和29 MeV）的光子敏感性与中子敏感性之间以及中子相对生物效应（RBE）与光子抗性之间的关系，主要目的是能否证明中子的优势。
在法尔（Faure, S.A.），用0 - 5.0 Gy的p(66)/Be中子（平均能量29 MeV）照射11种平均光子失活剂量为1.65 - 4.35 Gy的人类肿瘤细胞系，同一天用0 - 10.0 Gy的钴 - γ射线照射相同的接种物。在埃森临床医院（Essen Klinikum），用0 - 4 Gy的d(14)/Be中子（平均能量6 MeV）和0 - 10 Gy的240 kVp X射线照射12种人类肿瘤细胞系，其中许多与上述选择相同，平均光子失活剂量范围为1.75 - 4.08 Gy。通过克隆形成试验确定细胞存活情况，并将数据拟合到线性二次方程。
高能和低能中子之间的放射生物学差异在中子RBE对光子敏感性的依赖性方面尤为明显。低能埃森中子的RBE随光子抗性的增加比高能法尔中子更显著。对于抗光子细胞系显示出RBE优势，与平均失活剂量相比，在低剂量范围内使用α系数时这种优势尤为明显。由于穿透性差和缺乏皮肤保护，低能中子的临床应用可能更受限制。然而，与高能中子相比，这些中子在区分光子敏感和抗光子细胞方面表现更好，高能中子的RBE范围为1.6 - 3.5，平均RBE为2.4，而低能中子的RBE范围为2 - 6，平均RBE为4.1。因此，从放射生物学角度来看，低能中子的临床潜力似乎被大大低估了。
