轴位容积扫描与螺旋扫描颅脑CT图像质量与辐射剂量对比观察

目的 通过步进式轴位容积扫描与常规螺旋扫描模式为对比，探讨颅脑CT最佳扫描方式。方法 回顾性分析389例相同扫描参数及重建参数的步进式轴位容积扫描和常规螺旋扫描模式影像学资料及辐射剂量报告，对图像质量分别进行主观评价及客观评价，主观图像评价：质量优秀的图像为3级；质量好的图像为2级；质量差但足以满足诊断的图像为1级。客观图像质量评价：根据手动定位获得图像四个感兴趣的区域分析评价信噪比（SNR），同时对剂量报告中的容积CT剂量指数（CTDI_vol）、剂量长度乘积（DLP）进行分析。结果 步进式轴位容积扫描和常规螺旋扫描图像主观评价和客观评价均无显著性差异（P>0.05）。步进式轴位容积扫描CTDI_vol略高于螺旋扫描模式，DLP明显低于螺旋扫描模式。结论 相同扫描及重建条件下，步进式轴位容积扫描辐射剂量低于常规螺旋扫描，颅脑CT推荐步进式轴位扫描模式。但日常工作中应根据特殊需要制定个体化扫描方案。

A comparative study of cranial CT image quality and radiation dose between stepped axial volume scan and spiral scan

Objective To investigate the best scan mode of cranial CT by comparing step to step axial volume scan mode with conventional spiral scan mode.Methods The imaging data and radiation dose reports of 389 cases with the same scanning parameters and reconstruction parameters were retrospectively analyzed. The image quality was evaluated subjectively and objectively.The method of subjective image evaluation as follow:the image with excellent quality is level 3, good quality image is level 2, the image quality is poor but enough to satisfy the diagnosis is level 1. Objective image quality evaluation as follow:Four regions of interest(ROI) are obtained by manual localization to evaluate signal-to-noise ratio (SNR), the volume CT dose index (CTDI_vol) and dose-length product (DLP) in dose reports were analyzed.Results There was no significant difference in subjective and objective evaluation between step to step axial volume scan mode and conventional spiral scan (P>0.05). CTDI_vol of step to step axial volume scan mode is slightly higher than that of spiral scanning mode, and DLP is significantly lower than that of spiral scanning mode.Conclusion With the same scanning and reconstruction parameters, the radiation dose of step to step axial volume scan mode was lower than that of conventional spiral scanning. step to step axial volume scan mode is recommended for cranial CT examination. However individualized scanning schemes should be formulated according to special needs in daily work.