管球旋转时间对Volume Shuttle成像技术中成像质量及辐射剂量的影响

Influence of rotation time on radiation and imaging quality for volume shuttle technique

目的:GE公司推出的Lightspeed VCT机型配置有Volume Shuttle技术,可以在不增加现有探测器排数的前提下扩展Z轴扫描范围,提高灌注和血管CT成像大扫描区域的时间分辨率。但是由于不断的重复扫描,X射线辐射剂量较大。本文就是否可以通过调整管球旋转时间对Volume Shuttle技术成像质量及辐射剂量进行优化的角度进行研讨。方法:实验体模采用美国Salem公司生产的Catphan 500 CT质控体模测量物理成像参数,评价图像质量。剂量参数选取CT容积剂量指数(CTDIvol)进行定量分析。结果:对于不同的材料,管球旋转时间对CT值准确性的影响不具有同一性。较长的旋转时间可以降低噪声,提高图像对比度噪声比(CNR),但细节分辨力无变化。根据剂量归一化后图像CNR显示,较短的管球旋转时间更具有优势。结论:从单位辐射剂量对图像CNR的贡献角度而言,相对短的管球旋转时间的效率更高。有望寻求到管球旋转时间和图像质量的最佳匹配点,实现Volume Shuttle技术的辐射剂量优化。

Objective： Volume Shuttle technique, proposed on GE Lightspeed VCT, expends z-scanning area without the limitation of detector width. Therefore, this technique made CT perfusion and angiography for large area with good temporal resolution. However, non-stop shuttle increases radiation dose. The purpose of the present study was to verify whether it is possible to adjust rotation time to optimize radiation without deteriorating image quality.Methods： Catphan 500 CT quality control phantom was used to obtain physical metrics of CT imaging and to evaluate imaging. CTDIvol was selected to be radiation parameter. Results： For different materials, rotation time affected the accuracy of CT number in different ways. Longer rotation time decreased average noise and increased CNR, without changing detail resolution. However, according to the normalized CNR to radiation, shorter rotation time was more effective to the CNR of imaging. Conclusion： As for the contribution of normalized radiation to imaging CNR, shorter rotation time was more efficient. It was potential to adjust rotation time to match the golden combining of radiation and imaging quality in order to optimize volume shuttle techniques.