Nie Huiling, Chettle David R, McNeill Fiona E, O'Meara Joanne M
Medical Physics and Applied Radiation Sciences Unit, McMaster University, Hamilton, ON, L8S 4K1, Canada.
Phys Med Biol. 2004 Oct 7;49(19):N325-34. doi: 10.1088/0031-9155/49/19/n02.
Two sets of phantoms have been used to calibrate a 109Cd y-ray induced K-XRF bone-lead measurement system. Both sets of phantoms are made of plaster of Paris, but the calibration lines are significantly different. This results in a significant difference for the derived concentrations of bone lead for the same person using these two sets of phantoms. This study shows that the different calibration lines are due to the different compositions of the phantoms, which can then be accounted for by adjusting the parameters related to the phantom composition in spectral analysis. Bone-lead concentrations for ten lead-exposed smelter workers were computed before and after analysis modification, and the results show that the bone-lead concentrations for the same person calculated from two sets of phantoms are not significantly different, only after the modifications are incorporated. Through these investigations, it was discovered that a common practice of setting the ratio of the calcium edge amplitude to the coherent scatter amplitude as a constant is only valid when all spectra are acquired at the same system resolution. When there is a change in the resolution between spectra, it has been determined that the ratio of the calcium edge amplitude to the coherent area should instead be used as the constant factor in the analysis program.
使用了两组体模来校准一个由¹⁰⁹Cdγ射线诱导的K-XRF骨铅测量系统。两组体模均由熟石膏制成，但校准曲线存在显著差异。这导致使用这两组体模对同一个人得出的骨铅浓度存在显著差异。本研究表明，不同的校准曲线是由于体模成分不同所致，在光谱分析中可通过调整与体模成分相关的参数来解释这一现象。在分析修正前后计算了10名铅暴露冶炼工人的骨铅浓度，结果表明，只有在纳入修正后，由两组体模计算出的同一个人的骨铅浓度才没有显著差异。通过这些研究发现，将钙边缘幅度与相干散射幅度之比设为常数的常见做法仅在所有光谱都在相同系统分辨率下采集时才有效。当光谱之间的分辨率发生变化时，已确定应将钙边缘幅度与相干面积之比用作分析程序中的常数因子。
