Carlsson A K, Ahnesjö A
Department of Medical Radiation Physics, Karolinska Institute and Stockholm University, Sweden.
Med Phys. 2000 Oct;27(10):2320-32. doi: 10.1118/1.1290485.
Methods for scatter dose calculations in brachytherapy have been developed based on the collapsed cone superposition algorithm. The methods account for effects on the scatter dose caused by the three-dimensional distribution of heterogeneities in the irradiated volume and are considerably faster than methods based on straightforward superposition of kernels or direct Monte Carlo simulations. Use of a successive-scattering approach, in which the dose contribution from once- and multiply scattered photons are calculated separately, was found superior to conventional superposition using a single point kernel for all scatter generations. Use of the successive-scattering approach significantly reduces artifacts stemming from steep fluence gradients, typical of the brachytherapy geometry and critical for the collapsed cone approximation. The algorithm is tested versus Monte Carlo simulations for point sources of energies 28.4, 100, 350, and 662 keV. Results agree well for both a homogeneous water phantom and an air-water half-phantom.
近距离放射治疗中散射剂量计算方法已基于坍缩圆锥叠加算法得以开发。这些方法考虑了受照体积中不均匀性的三维分布对散射剂量的影响，并且比基于核的直接叠加或直接蒙特卡罗模拟的方法快得多。采用逐次散射方法（其中单次和多次散射光子的剂量贡献分别计算）被发现优于对所有散射世代使用单点核的传统叠加方法。逐次散射方法的使用显著减少了由陡峭注量梯度产生的伪影，这是近距离放射治疗几何结构的典型特征，且对坍缩圆锥近似至关重要。该算法针对能量为28.4、100、350和662 keV的点源与蒙特卡罗模拟进行了测试。对于均匀水模体和空气 - 水半模体，结果吻合良好。
