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Evaluation of the spatial resolution of a dedicated breast CT system using computer simulation

机译:使用计算机仿真评估专用乳腺CT系统的空间分辨率

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摘要

Spatial resolution is one of the most crucial parameters for an imaging system. The modulation transfer function (MTF) was physically measured using wire images on a prototype breast CT scanner previously. In this study, the effects on MTF from different components in the imaging chain, including the x-ray focal spot distribution, detector lag, and x-ray detector MTF were physically measured. The contributions of these three factors and gantry motion affecting CT system resolution were studied using computer simulation. The CT system MTF was computed and the role of each factor was studied independently. The simulated MTF results demonstrated that the x-ray focal spot size and detector MTF have an effect on the system resolution, while the scanner motion degrades only the azimuthal MTF, with greater degradation occurring further from isocenter where greater rotational velocities occur. The azimuthal MTF of this system has a cutoff frequency of 2.0 cycles/mm at the isocenter but degrades to 1.0 cycles/mm at the periphery. The radial MTF has a cutoff frequency of 2.0 cycles/mm, at both the isocenter and periphery. The comparison between the computer simulated and physically measured MTF values demonstrates reasonable accuracy in the simulation process. The results from computer simulation also suggest ways in which the spatial resolution can be improved by system modification.
机译:空间分辨率是成像系统最关键的参数之一。调制传递函数(MTF)以前是在原型乳腺CT扫描仪上使用导线图像进行物理测量的。在这项研究中,从物理角度测量了成像链中不同组件对MTF的影响,包括X射线焦点分布,探测器滞后和X射线探测器MTF。使用计算机仿真研究了这三个因素和机架运动对CT系统分辨率的影响。计算了CT系统的MTF,并独立研究了每个因素的作用。模拟的MTF结果表明,X射线焦点的大小和检测器MTF对系统分辨率有影响,而扫描仪的运动只会使方位MTF降低,而距等中心点(旋转速度更大)会进一步降低质量。该系统的方位MTF在等中心点的截止频率为2.0个周期/毫米,但在外围下降到1.0个周期/毫米。径向MTF在等中心点和外围都具有2.0周期/ mm的截止频率。计算机模拟的MTF值和物理测量的MTF值之间的比较证明了模拟过程中的合理准确性。计算机仿真的结果还提出了通过系统修改可以改善空间分辨率的方法。

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