技术说明：具有大功率 X 射线源和透射 CT 成像功能的台式锥形束 X 射线荧光计算机层析成像（XFCT）系统。
Technical Note: A benchtop cone-beam x-ray fluorescence computed tomography (XFCT) system with a high-power x-ray source and transmission CT imaging capability.
机构信息
Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, TX, 77030, USA.
Department of Imaging Physics, The University of Texas MD Anderson Cancer Center, Houston, TX, 77030, USA.
出版信息
Med Phys. 2018 Oct;45(10):4652-4659. doi: 10.1002/mp.13138. Epub 2018 Sep 14.
PURPOSE
This report describes upgrades and performance characterization of an experimental benchtop cone-beam x-ray fluorescence computed tomography (XFCT) system capable of determining the spatial distribution and concentration of metal probes such as gold nanoparticles (GNPs). Specifically, a high-power (~3 kW) industrial x-ray source and transmission CT capability were deployed in the same platform under the cone-beam geometry.
METHODS
All components of the system are described in detail, including the x-ray source, imaging stage, cadmium-telluride detector for XFCT, and flat-panel detector for transmission CT imaging. The general data acquisition scheme for XFCT and transmission CT is also explicated. The detection limit of the system was determined using calibration samples containing water and GNPs at various concentrations. Samples were then embedded in a small-animal-sized phantom and imaged with XFCT and CT. The reconstructed XFCT and CT images were compared and analyzed using the contrast-to-noise ratio for each GNP-containing region of interest. Also, measurements of the incident beam spectra used for XFCT and CT imaging were made and the corresponding x-ray dose rates were estimated, along with the imaging dose.
RESULTS
The present configuration produced a GNP detection limit of 0.03 wt. % with the delivery of an effective dose of 1.87 cGy per projection. XFCT scan of an animal-sized phantom containing low concentrations (down to 0.03 wt. %) of GNP-loaded inserts can be performed within an hour.
CONCLUSIONS
The high performance of the system combined with the ability to perform transmission CT in tandem with XFCT suggests that the currently developed benchtop cone-beam XFCT/CT system, in conjunction with GNPs, can be used for routine multimodal preclinical imaging tasks with less stringent dose constraints such as ex vivo imaging. With further effort to minimize XFCT imaging dose as discussed in this report, it may also be used for in vivo imaging.
目的
本报告介绍了一种实验性台式锥形束 X 射线荧光计算机断层扫描（XFCT）系统的升级和性能特征，该系统能够确定金属探针（如金纳米颗粒（GNPs））的空间分布和浓度。具体来说，在锥形束几何形状下，在同一平台上部署了高功率（约 3kW）工业 X 射线源和透射 CT 能力。
方法
详细描述了系统的所有组件，包括 X 射线源、成像台、用于 XFCT 的碲化镉探测器和用于透射 CT 成像的平板探测器。还说明了 XFCT 和透射 CT 的一般数据采集方案。使用含有不同浓度水和 GNPs 的校准样品确定了系统的检测极限。然后将样品嵌入小动物大小的体模中，并进行 XFCT 和 CT 成像。使用每个含 GNP 的感兴趣区域的对比度噪声比比较和分析重建的 XFCT 和 CT 图像。还测量了用于 XFCT 和 CT 成像的入射光束光谱，并估计了相应的 X 射线剂量率以及成像剂量。
结果
目前的配置在每投影有效剂量为 1.87cGy 的情况下，产生了 GNP 检测极限为 0.03wt.%。可以在一小时内完成包含低浓度（低至 0.03wt.%）GNP 负载插入物的动物大小体模的 XFCT 扫描。
结论
该系统的高性能与在 XFCT 与透射 CT 串联运行的能力相结合，表明目前开发的台式锥形束 XFCT/CT 系统，结合 GNPs，可以用于常规的多模态临床前成像任务，剂量限制不太严格，如离体成像。根据本报告中讨论的努力进一步降低 XFCT 成像剂量，也可用于体内成像。
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