Beach J L, Watts R J, Milavickas L R
Med Phys. 1981 May-Jun;8(3):347-52. doi: 10.1118/1.594837.
We have devised a transit dose technique for fast neutron therapy treatment planning based on the 16O(n, p)16N reaction in recirculating water, and have determined the effect of simulated bone and lung inhomogeneities in phantom. An effective threshold of 10.2 MeV in the 16O(n, p) reaction is exploited to detect transmitted neutrons without the need detector collimation. This system has been demonstrated with 14 MeV (d, T) neutrons and with cyclotron produced p(42) + Be neutrons. 16N decays to the 6.13 MeV excited states of 16O in 7.14 s, allowing for easy identification by NaI(T1) and for rapid recirculation. The transmission of fast neutrons can thus be related to an effective thickness of soft tissue, providing a rapid and direct measure of the effects of inhomogeneities under actual treatment conditions, with the 10 MeV threshold providing a useful degree of insensitivity to multiply scattered neutrons. Equivalent thickness of compact bone and lung relative to water were found to be 1.4 and 0.34 respectively, closely resembling the effective thicknesses for Cobalt-60 gamma rays.
我们基于循环水中的(^{16}O(n,p)^{16}N)反应，设计了一种用于快中子治疗计划的透射剂量技术，并确定了模拟的骨骼和肺部不均匀性在体模中的影响。利用(^{16}O(n,p))反应中(10.2)兆电子伏的有效阈值来检测透射中子，无需探测器准直。该系统已通过(14)兆电子伏((d,T))中子和回旋加速器产生的(p(42)+Be)中子得到验证。(^{16}N)在(7.14)秒内衰变为(^{16}O)的(6.13)兆电子伏激发态，便于用碘化钠((Tl))进行识别并实现快速循环。因此，快中子的透射可以与软组织的有效厚度相关联，从而在实际治疗条件下快速直接地测量不均匀性的影响，(10)兆电子伏的阈值对多次散射中子具有有用程度的不敏感性。发现致密骨和肺相对于水的等效厚度分别为(1.4)和(0.34)，与钴 - 60伽马射线的有效厚度非常相似。
