荧光CT是一种可无损重建元素空间分布的发射型断层成像技术, 对生物医学研究具有重要意义。 同步辐射的高通量、 高准直和能量可调等特性使荧光CT的生物医学应用成为可能。 文章通过优化设计, 在上海同步辐射光源建立了一套用于生物医学样品微量元素分析的荧光CT成像系统。 通过对实验装置的优化, 提高了系统的数据采集速度和空间分辨率。 将极大似然-期望最大化重建算法引入到荧光CT, 显著提高了图像重建精度。 最后采用测试样品和医学样品对系统进行了测试。 实验结果表明该系统能正确探测感兴趣元素在样品内的分布, 空间分辨率达150 μm。 可以认为, 该系统在图像重建精度、 空间分辨率和数据采集速度等方面均可满足大尺度生物医学样品研究的需要。

X-ray fluorescence computed tomography is a stimulated emission tomography that allows nondestructive reconstruction of the elements distribution in the sample, which is important for biomedical investigations. Owing to the high flux density and easy energy tunability of highly collimated synchrotron X-rays, it is possible to apply X-ray fluorescence CT to biomedical samples. Reported in the present paper, an X-ray fluorescence CT system was established at Shanghai Synchrotron Radiation Facility for the investigations of trace elements distribution inside biomedical samples. By optimizing the experiment setup, the spatial resolution was improved and the data acquisition process was obviously speeded up. The maximum-likelihood expectation-maximization algorithm was introduced for the image reconstruction, which remarkably improved the imaging accuracy of element distributions. The developed system was verified by the test sample and medical sample respectively. The results showed that the distribution of interested elements could be imaged correctly, and the spatial resolution of 150 m was achieved. In conclusion, the developed system could be applied to the research on large-size biomedical samples, concerning imaging accuracy, spatial resolution and data collection time.