Pöller F, Sauerwein W, Rassow J
Department of Medical Radiation Physics, University of Essen, Federal Republic of Germany.
Phys Med Biol. 1993 Mar;38(3):397-410. doi: 10.1088/0031-9155/38/3/007.
Since 1978 the Essen Medical Cyclotron Facility has been used for fast neutron therapy. The treatment of deep-seated tumours by d(14) + Be neutron beam therapy (mean energy = 5.8 MeV) is still limited because of the steep decrease in depth-dose distribution. The interactions of fast neutrons in tissue leads to a thermal neutron distribution. These partially thermalized neutrons can be used to produce neutron capture reactions with 10B. Thus incorporation of 10B in tumours treated with fast neutrons will increase the relative local tumour dose due to the reaction 10B (n, alpha) 7Li. The magnitude of dose enhancement by 10B depends on the distribution of the thermal neutron fluence, 10B concentration, field size of the neutron beam, beam energy and the specific phantom geometry. The slowing down of the fast neutrons, resulting in a thermal neutron distribution in a phantom, has been computed using a Monte Carlo model. This model, which includes a deep-seated tumour, was experimentally verified by measurements of the thermal neutron fluence rate in a phantom using neutron activation of gold foil. When non-boronated water phantoms were irradiated with a total dose of 1 Gy at a depth of 6 cm, the thermal fluencies at this depth were found to be 2 x 10(10) cm-2. The absorbed dose in a tumour with 100 ppm 10B, at the same depth, was enhanced by 15%.
自1978年以来，埃森医学回旋加速器设施一直用于快中子治疗。由于深度剂量分布急剧下降，用d（14）+铍中子束疗法（平均能量 = 5.8兆电子伏）治疗深部肿瘤仍然受到限制。快中子在组织中的相互作用导致热中子分布。这些部分热化的中子可用于与10B产生中子俘获反应。因此，在用快中子治疗的肿瘤中掺入10B将因10B（n，α）7Li反应而增加相对局部肿瘤剂量。10B增强剂量的幅度取决于热中子注量分布、10B浓度、中子束场大小、束能量和特定的体模几何形状。使用蒙特卡罗模型计算了快中子的慢化，从而在体模中产生热中子分布。该模型包括一个深部肿瘤，通过使用金箔中子活化测量体模中的热中子注量率进行了实验验证。当在6厘米深度用1戈瑞的总剂量照射非硼化水体模时，发现该深度处的热注量为2×10（10）厘米-2。在相同深度处含有100 ppm 10B的肿瘤中的吸收剂量提高了15%。
