肺部计数器虚拟校准结果的影响因素

Influence Factor on Virtual Calibration Result of Lung Counter

内照射活体测量中,肺部计数器通常忽略肺以外其他器官中沉积的放射性核素对探测器计数的贡献,且校准使用的参考体模和被监测人之间会有身体形态的差异。本文利用中国成年男性体模库,采用蒙特卡罗程序模拟计算了^(65)Zn和^(60)Co核素的器官源探测效率,并计算了总探测效率,研究了这两个因素对虚拟校准的影响。结果表明,对于类似65Zn的核素不能忽略肺部以外其他器官源的计数贡献;同一身高下,肺部计数器对^(65)Zn和^(60)Co核素的总探测效率随体重增加而降低,且对于65Zn核素的降低比例会随摄入时间而变化;对于同一体模的总探测效率会随时间而降低。由此证明,核素生物动力学分布和体模形态的差异对肺部计数器总探测效率均有较大影响,且对不同核素影响会有不同。

In the in vivo measurement for internal contamination, the detector count from the radionuclides deposited in organs other than the lung is neglected for lung counter. Besides, the monitored people have morphological deviation with the reference phantom in calibration. The organ-specific detection efficiency for 62 Zn and 60 Co nuclides was simulated with Monte Carlo code by using the Chinese adult male phantom library, and the total detection efficiency was calculated. The effect of organ-specific detectionefficiency and total detection efficiency on virtual calibration was studied. The results show that the contribution of nuclides like 65 Zn in the organs other than the lung can not be neglected in the virtual calibration. The total detection efficiency of the lung counter for 65 Zn and 60 Co nuclides decreases with the increase of weight at the same height, and the decreased proportion for 65 Zn varies with the time after intaking. For each phantom, the total detection efficiency decreases with the increase of time. The results prove that the radionuclide biokinetic distribution and morphological variation have a great influ- ence on the total detection efficiency of the lung counter, which varies with nuclides.