Development and clinical applications of digital tomosyuthesis system with the capabilities of dual energy subtraction and multi-directional tomography

我们已经开发了一个数字断层合成系统，该系统包含一个x射线荧光成像电视单元，具有进行多向断层扫描的能力，并能够在低能和高能之间快速切换kV暴露脉冲x射线，一个数字图像处理单元和显示单元，包括一个高分辨率CRT显示器和一个激光打印机。本文研究了利用单次多方位层析成像获得的图像数据重构多层数字层析成像的方法，以及利用多种数字图像处理技术提高多层层析成像质量的方法。我们的系统的基本处理技术是空间频率滤波，尽管双能量和模糊掩膜层减法是可选的技术，并在本研究中显示出明显的进步。这种方式的临床应用证明了以下优点：1)重建层析成像的纵向格式便于对层析成像进行解释，并有助于与传统x线片进行比较。2)从一组层析成像数据中进行多层析成像的数字重建，缩短了检查时间，降低了患者的辐射暴露。此外，当在CRT上显示多张断层扫描时，它有助于物体的三维识别。3)图像处理可以有效地提高断层成像的图像质量，增强与临床问题相关的某些特定图像信息。4)双能量减法数字断层合成可以有效地显示病变中的骨结构或小钙化，并可以区分钙化和致密纤维化数字血管断层合成技术可以对血管病变进行详细观察，并有望用于血管动态研究

We have developed a digital tomosynthesis system, which incorporates an x-ray fluororadiographic TV unit and has the capabilities to perform multi-directional tomography and to expose pulsed x-rays with rapid kV switching between low energy and high energy, a digital image processing unit and display unit, including a high-resolution CRT monitor and a lase printer. We have studied the methods of re-constructing digital tomographs of multilayrs, utilizing image data obtained from a single multi-directional tomographic movement, and of improving image quality of those reconstructed tomographs by means of several digital image processing techniques. The basic processing technique in our system was spatial frequency filtration, although dual energy and blurred mask layr-subtractions were the optional techniques and showed the distinct advancements shown in this study. Clinical applications of this modality has proved a number of advantages as listed below :1) Longitudinal format of the reconstructed tomographs facilitated an easy interpretation of the tomographs and helped comparison against conventional radiographs2) Digital reconstruction of multiple tomographs from a single set of tomographic image data shortened examination time and lowered patient radiation exposure. Moreover it helped three-dimensional recognition of the object when multiple tomographs were displayd on a CRT in cine mode3) Image processing was effective to improve image quality of the tomograph and enhanced some specific image informations pertinent to the clinical problem at hand4) Dual energy subtraction digital tomosynthesis was effective to clearly demonstrate bony structures or a small calcification in the lesion and permitted discrimination of calcifications from dense fibrotic lesions5) Digital angiotomosynthesis permitted a detailed observation of vascular disorders and was promising for dynamic vascular study