Rivard Mark J, Melhus Christopher S, Zinkin Heather D, Stapleford Liza J, Evans Krista E, Wazer David E, Odlozilíková Anna
Department of Radiation Oncology, Tufts-New England Medical Center, Boston, MA 02111, USA.
Radiat Res. 2005 Sep;164(3):319-23. doi: 10.1667/rr3416.1.
While there is significant clinical experience using both low- and high-dose-rate 252Cf brachytherapy, there are minimal data regarding values for the neutron relative biological effectiveness (RBE) with both modalities. The aim of this research was to derive a radiobiological model for 252Cf neutron RBE and to compare these results with neutron RBE values used clinically in Russia. The linear-quadratic (LQ) model was used as the basis to characterize cell survival after irradiation, with identical cell killing rates (S(N) = S(gamma)) between 252Cf neutrons and photons used for derivation of RBE. Using this equality, a relationship among neutron dose and LQ radiobiological parameter (i.e., alpha(N), beta(N), alpha(gamma), beta(gamma)) was obtained without the need to specify the photon dose. These results were used to derive the 252Cf neutron RBE, which was then compared with Russian neutron RBE values. The 252Cf neutron RBE was determined after incorporating the LQ radiobiological parameters obtained from cell survival studies with fast neutrons and teletherapy photons. For single-fraction high-dose-rate neutron doses of 0.5, 1.0, 1.5 and 2.0 Gy, the total biologically equivalent doses were 1.8, 3.4, 4.7 and 6.0 RBE Gy with 252Cf neutron RBE values of 3.2, 2.9, 2.7 and 2.5, respectively. Using clinical data for late-responding reactions from 252Cf, Russian investigators created an empirical model that predicted high-dose-rate 252Cf neutron RBE values ranging from 3.6 to 2.9 for similar doses and fractionation schemes and observed that 252Cf neutron RBE increases with the number of treatment fractions. Using these relationships, our results were in general concordance with high-dose-rate 252Cf RBE values obtained from Russian clinical experience.
虽然在使用低剂量率和高剂量率的²⁵²Cf近距离放射治疗方面有大量临床经验，但关于这两种方式下中子相对生物效应（RBE）值的数据却很少。本研究的目的是推导²⁵²Cf中子RBE的放射生物学模型，并将这些结果与俄罗斯临床使用的中子RBE值进行比较。线性二次（LQ）模型被用作表征辐照后细胞存活的基础，在用于推导RBE的²⁵²Cf中子和光子之间具有相同的细胞杀伤率（S(N) = S(γ)）。利用这种相等关系，无需指定光子剂量就获得了中子剂量与LQ放射生物学参数（即α(N)、β(N)、α(γ)、β(γ)）之间的关系。这些结果被用于推导²⁵²Cf中子RBE，然后与俄罗斯的中子RBE值进行比较。在纳入从快中子和远距离治疗光子的细胞存活研究中获得的LQ放射生物学参数后，确定了²⁵²Cf中子RBE。对于单次高剂量率中子剂量分别为0.5、1.0、1.5和2.0 Gy的情况，总生物等效剂量分别为1.8、3.4、4.7和6.0 RBE Gy，²⁵²Cf中子RBE值分别为3.2、2.9、2.7和2.5。俄罗斯研究人员利用²⁵²Cf晚期反应的临床数据创建了一个经验模型，该模型预测对于相似的剂量和分割方案，高剂量率²⁵²Cf中子RBE值在3.6至2.9之间，并观察到²⁵²Cf中子RBE随治疗分割次数增加。利用这些关系，我们的结果与从俄罗斯临床经验获得的高剂量率²⁵²Cf RBE值总体一致。
