For a cone-beam three-dimensional computed tomography(3D-CT) scanning system, voxel size is an important indicator to guarantee the accuracy of data analysis and feature measurement based on 3D-CT images. Meanwhile, the voxel size changes with the movement of the rotary stage along X-ray direction. In order to realize the automatic calibration of the voxel size, a new and easily-implemented method is proposed. According to this method, several projections of a spherical phantom are captured at different imaging positions and the corresponding voxel size values are calculated by non-linear least-square fitting. Through these interpolation values, a linear equation is obtained that reflects the relationship between the voxel size and the rotary stage translation distance from its nominal zero position. Finally, the linear equation is imported into the calibration module of the 3D-CT scanning system. When the rotary stage is moving along X-ray direction, the accurate value of the voxel size is dynamically exported. The experimental results prove that this method meets the requirements of the actual CT scanning system, and has virtues of easy implementation and high accuracy.
目的:探讨能谱CT最佳单能量图像在30例婴幼儿肝移植供体术前影像评估中的应用价值。方法:对30例供者做术前能谱CT检查。对肝动脉、门静脉和肝静脉做单能CT和混合能量CT的CT血管造影(CTA)。测量供者的肝脏总体积及模拟切除体积,并与术中切除标本对照。结果:单能CT在50 ke V时的肝内血管CTA成像质量优于混合能量CT(P<0.001)。供者肝脏各血管变异情况均在CTA得以显示。结论:能谱CT单能CTA作为婴幼儿肝移植供体术前评估的一种方法,可以获得良好的血管与软组织对比,保证血管CT成像的质量和评估的准确性。
