Sato Kohei, Ohnishi Takashi, Sekine Masashi, Haneishi Hideaki
Graduate School of Engineering, Chiba University, Chiba, 263-8522, Japan.
Center for Frontier Medical Engineering, Chiba University, Chiba, 263-8522, Japan.
Int J Comput Assist Radiol Surg. 2017 May;12(5):707-717. doi: 10.1007/s11548-017-1557-x. Epub 2017 Mar 25.
Tomosynthesis is attracting attention as a low-dose tomography technology compared with X-ray CT. However, conventional tomosynthesis imaging devices are large and stationary. Furthermore, there is a limitation in the working range of the X-ray source during image acquisition. We have previously proposed the use of a portable X-ray device for tomosynthesis that can be used for ward rounds and emergency medicine. The weight of this device can be reduced by using a flat panel detector (FPD), and flexibility is realized by the free placement of the X-ray source and FPD. Tomosynthesis using a portable X-ray device requires calibration of the geometry between the X-ray source and detector at each image acquisition. We propose a method for geometry calibration and demonstrate tomosynthesis image reconstruction by this method.
An image processing-based calibration method using an asymmetric and multilayered calibration object (AMCO) is presented. Since the AMCO is always attached to the X-ray source housing for geometry calibration, the additional setting of a calibration object or marker around or on the patients is not required. The AMCO's multilayer structure improves the calibration accuracy, especially in the out-of-plane direction.
Two experiments were conducted. The first was performed to evaluate the calibration accuracy using an XY positioning stage and a gonio stage. As a result, an accuracy of approximately 1 mm was achieved both in the in-plane and out-of-plane directions. An angular accuracy of approximately [Formula: see text] was confirmed. The second experiment was conducted to evaluate the reconstructed image using a foot model phantom. Only the sagittal plane could be clearly observed with the proposed method.
We proposed a tomosynthesis imaging system using a portable X-ray device. From the experimental results, the proposed method could provide sufficient calibration accuracy and a clear sagittal plane of the reconstructed tomosynthesis image.
与X射线计算机断层扫描（CT）相比，断层合成作为一种低剂量断层扫描技术正受到关注。然而，传统的断层合成成像设备体积大且固定不动。此外，在图像采集过程中，X射线源的工作范围存在限制。我们之前提出使用一种用于断层合成的便携式X射线设备，可用于查房和急诊医学。通过使用平板探测器（FPD）可以减轻该设备的重量，并且通过X射线源和FPD的自由放置实现了灵活性。使用便携式X射线设备进行断层合成需要在每次图像采集时对X射线源和探测器之间的几何关系进行校准。我们提出了一种几何校准方法，并通过该方法演示了断层合成图像重建。
提出了一种基于图像处理的校准方法，使用不对称多层校准物体（AMCO）。由于AMCO始终附着在X射线源外壳上进行几何校准，因此不需要在患者周围或身上额外设置校准物体或标记。AMCO的多层结构提高了校准精度，特别是在平面外方向。
进行了两项实验。第一项实验使用XY定位台和测角台来评估校准精度。结果，在平面内和平面外方向均实现了约1毫米的精度。确认了约[公式：见原文]的角度精度。第二项实验使用足部模型体模来评估重建图像。使用所提出的方法只能清晰观察到矢状面。
我们提出了一种使用便携式X射线设备的断层合成成像系统。从实验结果来看，所提出的方法可以提供足够的校准精度，并在重建断层合成图像中得到清晰的矢状面。
