This study presents a practical alignment method for X-ray spectral measurement in a rotating gantry based micro-computed tomography (micro-CT) system using three-dimensional (3D) printing technology. In order to facilitate the spectrometer placement inside the gantry, supporting structures including a cover and a stand were dedicatedly designed and printed using a 3D printer. According to the relative position between the spectrometer and the stand, the upright projection of the spectrometer collimator onto the stand was determined and then marked by a tungsten pinhole. Thus, a visible alignment indicator of the X-ray central beam and the spectrometer collimator represented by the pinhole was established in the micro-CT live mode. Then, a rough alignment could be achieved through repeatedly adjusting and imaging the stand until the pinhole was located at the center of the acquired projection image. With the spectrometer being positioned back onto the stand, the precise alignment was completed by slightly translating the spectrometer-stand assembly around the rough location, until finding a "sweet spot" with the highest photon rate and proper distribution of the X-ray photons in the resultant spectrum. The spectra were acquired under precise alignment and misalignment of approximately 0.2, 0.5, and 1.0mm away from the precise alignment position, and then were compared in qualitative and quantitative analyses. Qualitative analysis results show that, with slight misalignment, the photon rate is reduced from 1302 to 1098, 1031, and 416 photons/second (p/s), respectively, and the characteristic peaks in the acquired spectra are gradually deteriorated. Quantitative analysis indicates that the energy resolutions for characteristic peak of Kα1 were calculated as 1.56% for precise alignment, while were 1.84% and 2.40% for slight misalignment of 0.2mm and 0.5mm. The mean energies were reduced from 43.93keV under precise alignment condition to 40.97, 39.63 and 37.78keV when misaligned. Accurate spectral measurements in micro-CT systems are significantly influenced by the alignment precision. This practical alignment method using 3D printing technology could be readily applied to other rotating gantry based micro-CT systems with modified design of the supporting structures and careful considerations of the spectrometer and gantry dimensions.

中文翻译：

---

基于3D打印技术的微CT系统X射线光谱测量实用对准方法

本研究提出了一种使用三维 (3D) 打印技术在基于旋转机架的微型计算机断层扫描 (micro-CT) 系统中进行 X 射线光谱测量的实用对准方法。为了方便光谱仪放置在机架内，使用3D打印机专门设计和打印了包括盖子和支架在内的支撑结构。根据光谱仪与支架的相对位置，确定光谱仪准直器在支架上的垂直投影，然后用钨针孔标记。因此，在微 CT 实时模式下建立了 X 射线中心束和以针孔为代表的光谱仪准直器的可见对准指示器。然后，通过反复调整和成像支架，直到针孔位于获取的投影图像的中心，可以实现粗略对齐。将光谱仪放回支架上，通过围绕粗糙位置稍微平移光谱仪支架组件来完成精确对准，直到找到具有最高光子速率和 X 射线光子在其中正确分布的“最佳点”得到的光谱。在距离精确对准位置大约 0.2、0.5 和 1.0 毫米的精确对准和未对准下获得光谱，然后在定性和定量分析中进行比较。定性分析结果表明，在轻微错位的情况下，光子速率分别从 1302 降低到 1098、1031 和 416 光子/秒 (p/s)，并且采集到的光谱中的特征峰逐渐变差。定量分析表明，Kα1特征峰的能量分辨率计算为精确对准为1.56%，而0.2mm和0.5mm的轻微错位为1.84%和2.40%。平均能量从精确对准条件下的 43.93keV 降低到未对准时的 40.97、39.63 和 37.78keV。微 CT 系统中的准确光谱测量受对准精度的显着影响。这种使用 3D 打印技术的实用对准方法可以很容易地应用于其他基于旋转机架的微 CT 系统，并修改了支撑结构的设计并仔细考虑了光谱仪和机架尺寸。定量分析表明，Kα1特征峰的能量分辨率计算为精确对准为1.56%，而0.2mm和0.5mm的轻微错位为1.84%和2.40%。平均能量从精确对准条件下的 43.93keV 降低到未对准时的 40.97、39.63 和 37.78keV。微 CT 系统中的准确光谱测量受对准精度的显着影响。这种使用 3D 打印技术的实用对准方法可以很容易地应用于其他基于旋转机架的微 CT 系统，并修改了支撑结构的设计并仔细考虑了光谱仪和机架尺寸。定量分析表明，Kα1特征峰的能量分辨率计算精确对准为1.56％，而0.2mm和0.5mm的轻微错位为1.84％和2.40％。平均能量从精确对准条件下的 43.93keV 降低到未对准时的 40.97、39.63 和 37.78keV。微 CT 系统中的准确光谱测量受对准精度的显着影响。这种使用 3D 打印技术的实用对准方法可以很容易地应用于其他基于旋转机架的微 CT 系统，并修改了支撑结构的设计并仔细考虑了光谱仪和机架尺寸。0.2mm 和 0.5mm 的轻微错位为 40%。平均能量从精确对准条件下的 43.93keV 降低到未对准时的 40.97、39.63 和 37.78keV。微 CT 系统中的准确光谱测量受对准精度的显着影响。这种使用 3D 打印技术的实用对准方法可以很容易地应用于其他基于旋转机架的微 CT 系统，并修改了支撑结构的设计并仔细考虑了光谱仪和机架尺寸。0.2mm 和 0.5mm 的轻微错位为 40%。平均能量从精确对准条件下的 43.93keV 降低到未对准时的 40.97、39.63 和 37.78keV。微 CT 系统中的准确光谱测量受对准精度的显着影响。这种使用 3D 打印技术的实用对准方法可以很容易地应用于其他基于旋转机架的微 CT 系统，并修改了支撑结构的设计并仔细考虑了光谱仪和机架尺寸。