O'Meara J M, Chettle D R, McNeill F E, Prestwich W V, Svensson C E
Department of Physics and Astronomy, McMaster University, Hamilton, On, Canada.
Phys Med Biol. 1998 Jun;43(6):1413-28. doi: 10.1088/0031-9155/43/6/003.
This paper reports on the Monte Carlo simulation of in vivo x-ray fluorescence (XRF) measurements. Our model is an improvement on previously reported simulations in that it relies on a theoretical basis for modelling Compton momentum broadening as well as detector efficiency. Furthermore, this model is an accurate simulation of experimentally detected spectra when comparisons are made in absolute counts; preceding models have generally only achieved agreement with spectra normalized to unit area. Our code is sufficiently flexible to be applied to the investigation of numerous source-excited in vivo XRF systems. Thus far the simulation has been applied to the modelling of two different systems. The first application was the investigation of various aspects of a new in vivo XRF system, the measurement of uranium in bone with 57Co in a backscatter (approximately 180 degrees) geometry. The Monte Carlo simulation was critical in assessing the potential of applying XRF to the measurement of uranium in bone. Currently the Monte Carlo code is being used to evaluate a potential means of simplifying an established in vivo XRF system, the measurement of lead in bone with 57Co in a 90 degrees geometry. The results from these simulations may demonstrate that calibration procedures can be significantly simplified and subject dose may be reduced. As well as providing an excellent tool for optimizing designs of new systems and improving existing techniques, this model can be used in the investigation of the dosimetry of various XRF systems. Our simulation allows a detailed understanding of the numerous processes involved when heavy metal concentrations are measured in vivo with XRF.
本文报道了体内X射线荧光(XRF)测量的蒙特卡罗模拟。我们的模型是对先前报道的模拟的改进,因为它在模拟康普顿动量展宽以及探测器效率方面有理论基础。此外,当在绝对计数上进行比较时,该模型能准确模拟实验检测到的光谱;之前的模型通常仅在归一化为单位面积的光谱上达成一致。我们的代码足够灵活,可应用于众多源激发的体内XRF系统的研究。到目前为止,该模拟已应用于两种不同系统的建模。第一个应用是对一种新型体内XRF系统的各个方面进行研究,即采用57Co在背散射(约180度)几何构型下测量骨骼中的铀。蒙特卡罗模拟对于评估将XRF应用于骨骼中铀测量的潜力至关重要。目前,蒙特卡罗代码正用于评估一种简化已有的体内XRF系统的潜在方法,即采用57Co在90度几何构型下测量骨骼中的铅。这些模拟结果可能表明校准程序可显著简化,且受检者剂量可能降低。该模型不仅为优化新系统设计和改进现有技术提供了一个出色的工具,还可用于研究各种XRF系统的剂量学。我们的模拟能够详细了解在体内用XRF测量重金属浓度时所涉及的众多过程。