Feasibility study of Compton cameras for x-ray fluorescence computed tomography with humans.
Feasibility study of Compton cameras for x-ray fluorescence computed tomography with humans.
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DOI：
10.1088/0031-9155/61/24/8521
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发表时间：
2016-12-21
影响因子：
3.5
通讯作者：
Xing L
中科院分区：
文献类型：
--
作者：
Vernekohl D;Ahmad M;Chinn G;Xing L
x射线荧光成像是一种很有前途的成像技术，能够描绘体内小剂量分子药物的空间分布。目前，该技术在临床前和临床应用中的转化受到长扫描时间的阻碍，因为物体是用限制通量的窄铅笔光束扫描的。提出了一种x射线荧光成像与康普顿成像相结合的新型成像方法。康普顿相机利用XFCT的成像性能，并取消了铅笔束激发的需要。该研究在蒙特卡罗模拟的基础上探讨了这种新的成像方法的潜力。在这项工作中，首次提出了与传统的体积康普顿成像相比，切片/扇形束x射线激发的特定选择在处理时间和图像质量方面具有图像重建的优势。在第二个实验中，在模拟肺部扫描场景中，研究了该方法与由金纳米颗粒制成的示踪剂临床应用的可行性。来自金的特征x射线光子的高能量有利于深层组织穿透，并且在康普顿相机中具有较低的角度模糊。发现康普顿相机第一级探测器的多普勒展宽对角度模糊的贡献最大；物理上限制了空间分辨率。根据空间分辨率测试结果的分析，在肺中心入路可以实现一厘米左右的分辨率。康普顿成像的概念允许在一定程度上根据散射光子和x射线荧光光子发射位置的不同来区分它们。结果表明，对于直径为50 nm的金纳米颗粒，在15 mGy下，对于直径为5 mm的损伤，分子灵敏度可降至240 pM/l。与传统的铅笔束XFCT相比，数据采集速度提高了45倍，而灵敏度却降低了。
X-ray fluorescence imaging is a promising imaging technique able to depict the spatial distributions of low amounts of molecular agents in vivo. Currently, the translation of the technique to preclinical and clinical applications is hindered by long scanning times as objects are scanned with flux-limited narrow pencil beams. The study presents a novel imaging approach combining x-ray fluorescence imaging with Compton imaging. Compton cameras leverage the imaging performance of XFCT and abolish the need of pencil beam excitation. The study examines the potential of this new imaging approach on the base of Monte-Carlo simulations. In the work, it is first presented that the particular option of slice/fan-beam x-ray excitation has advantages in image reconstruction in regard of processing time and image quality compared to traditional volumetric Compton imaging. In a second experiment, the feasibility of the approach for clinical applications with tracer agents made from gold nano-particles is examined in a simulated lung scan scenario. The high energy of characteristic x-ray photons from gold is advantageous for deep tissue penetration and has lower angular blurring in the Compton camera. It is found that Doppler broadening in the first detector stage of the Compton camera adds the largest contribution on the angular blurring; physically limiting the spatial resolution. Following the analysis of the results from the spatial resolution test, resolutions in the order of one centimeter are achievable with the approach in the center of the lung. The concept of Compton imaging allows to distinguish to some extend between scattered photons and x-ray fluorescent photons based on their difference in emission position. The results predict that molecular sensitivities down to 240 pM/l for 5 mm diameter lesions at 15 mGy for 50 nm diameter gold nano-particles are achievable. A 45-fold speed up time for data acquisition compared to traditional pencil beam XFCT could be achieved for lung imaging on cost of a small sensitivity decrease.
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