Developing a dual energy x-ray source for low-cost spectral CT

摘要 与常规CT相比，双能量计算机断层扫描（DECT）提供了更多的信息。 CT.它越来越多地用于各种临床任务，包括组织分化，金属伪影减少， 自动去骨、对比增强和碘定量。虽然有几种技术 虽然已经为DECT开发了一个新的系统，但一个主要的限制是显著增加的设备成本，这阻碍了 更广泛的临床应用。 本项目的目标是开发一种新的X射线源技术，以降低成本并提高 DECT的性能。具体地说，我们提出了一种双能x射线源，它发射出两种不同的辐射， 与通过光谱过滤或快速分析获得的能量谱相比， kVp切换方法。这将通过利用两个阴极-阳极对和一个电压 在恒定的施加管电压下，分压器用于降低其中一个阳极的有效电压。的辐射 进一步优化以减少光谱重叠， 光谱滤波器对于DECT，通过选择性地激活两个阳极，从两个阳极交替地发射X射线辐射。 对应的阴极。碳纳米管（CNT）场发射阴极用于实现快速开关 以及以微秒精度对两个光束进行强度调制。 与现有技术相比，该源的优点是：1）显著降低 设备成本-无需快速kVp切换、能量敏感探测器或两套源/探测器; 2） 增加能量分离和减少重叠，这将导致增强的DECT性能; 3） 独立控制两个X射线束的曝光，以最大限度地减少图像噪声; 4）启用DE-CBCT 在一次机架旋转中成像;以及5）以微秒瞬时切换能谱 响应时间，从而提高了剂量分布的准确性和可靠性。 本可行性研究将重点关注用于双能量锥形束CT（DE-CBCT）的固定阳极X射线源， 颌面部和头部成像，开发的技术可应用于医学成像的其他领域 目前部署CBCT的领域，如图像引导放射治疗、介入放射学和肢体 显像该方法还可以扩展到多能量（3个或更多），用于高级光谱成像。它可以 用于空间分布的X射线源阵列，其发射具有2个或更多能量谱的光子， 固定机架双能量断层合成和CT。具体目的是：1）论证双 用于低成本DE-CBCT的能量X射线源;以及2）使用原型双 能量X射线源。

ABSTRACT Dual energy computed tomography (DECT) provides significantly more information compared to a regular CT. It is increasingly used for a variety of clinical tasks including tissue differentiation, metal artifact reduction, automatic bone removal, contrast enhancement, and iodine quantification. Although several technologies have been developed for DECT, a major limitation is a significantly increased equipment cost, which has hindered the more widespread clinical use. The goal of this project is to develop a new x-ray source technology to reduce the cost and to enhance the performances of DECT. Specifically, we propose a dual energy x-ray source that emits radiations with two distinct energy spectra with an increased energy separation compared to those obtained by spectral filtration or the rapid kVp switching method alone. This will be accomplished by utilizing two cathode-anode pairs and a voltage divider to reduce the effective voltage of one of the anodes, at a constant applied tube voltage. The radiations from the two anodes are further optimized to reduce the spectral overlap by incorporating two individualized spectral filters. For DECT, x-ray radiation is emitted alternately from the two anodes by selectively activating the corresponding cathode. The carbon nanotube (CNT) field emission cathodes are used to enable rapid switching and intensity modulation of the two beams with micro-second accuracy. The advantages of the proposed source compared the current technologies are: 1) Significantly reduced equipment cost – no rapid kVp switching, energy sensitive detector or two sets of source/detector is required; 2) Increased energy separation and reduced overlap which will lead to an enhanced DECT performance; 3) Independent control of the exposures of the two x-ray beams to minimize image noise; 4) Enabling DE-CBCT imaging in one gantry rotation; and 5) Instantaneous switching of the energy spectrum with micro-second response time resulting in improved accuracy and reliable in the dose profile. This feasibility study will focus on a fixed-anode x-ray source for dual-energy cone-beam CT (DE-CBCT) for maxillofacial and head imaging, the technology developed can be applied to other areas of medical imaging where CBCT is currently deployed such as image guided radiation therapy, interventional radiology and extremity imaging. The approach can also be extended to multi-energy (3 or more) for advanced spectral imaging. It can be used for spatially distributed x-ray source array that emits photons with 2 or more energy spectra from for fixed-gantry dual energy tomosynthesis and CT. The Specific Aims are: 1) Demonstrating the feasibility of a dual energy x-ray source for low-cost DE-CBCT; and 2) Demonstrating DE-CBCT imaging using a prototype dual energy x-ray source.