宽体探测器CT颞骨成像扫描最优化方案研究

Study on the optimal scheme of wide detector CT in the imaging scan of temporal bone

目的:定量评估宽体探测器CT不同扫描条件下颞骨成像的剂量和图像质量,筛选最优化扫描参数组合,提高颞骨CT影像质量。方法:分别采用轴位扫描和螺旋扫描的不同扫描条件,对CT成像性能检测模体及仿真头模进行扫描,记录辐射剂量,并以噪声、低对比分辨力、高对比分辨力及信噪比等指标定量评估图像质量。结果:管电压≥120 kV、管电流时间乘积≥160 mAs的轴扫描方案,或管电压≥120 kV、管电流时间乘积≥130 mAs的螺旋扫描方案,均可得到稳定的具备高空间分辨力与高密度分辨力的图像;相同图像质量情况下,轴位扫描方案的有效剂量为0.29 mSv,螺旋扫描时的有效剂量0.94 mSv;两种扫描方式信噪比、低对比分辨力和高对比分辨力差异无统计学意义(t=1.679,t=-0.383,t=1.417;P>0.05);螺旋扫描的噪声稍低于轴位扫描,而轴位扫描图像的有效剂量比螺旋扫描下降了75%,差异有统计学意义(t=16.210,t=9.603;P<0.05)。结论:针对宽体探测器CT的颞骨成像,采用管电压≥120 kV、管电流时间乘积≥160 mAs的轴位扫描方案可获得高质量图像,并有效降低了辐射剂量。

Objective:To quantitatively assess the dose and image quality of temporal bone imaging of wide detector CT under different scanning conditions,and screen the optimal parameter combination of scan so as to improve CT image quality of temporal bone.Methods:The different scanning conditions of axial scanning and helical scanning were adopted to scan the detection model and artificial head model of CT imaging performance,and to record the radiation dose.And then,the noise,low contrast resolution,high contrast resolution and signal-to-noise ratio(SNR)were used to quantitatively assess the image quality.Results:Both the axial scanning scheme,which tube voltage was greater than or equal to 120kV and the product of tube current and time was greater than or equal to 160mAs,or the helical scanning scheme,which tube voltage was greater than or equal to 120kV and product of tube current and time was greater than or equal to 130mAs,could obtain stable images with high spatial resolution and high density resolution.Under the same image quality,the effective dose of axial scanning scheme was 0.29 mSv and that of helical scanning scheme was 0.94 mSv.There were no significant differences in SNR,low contrast resolution and high contrast resolution between the two scanning methods(t=1.679,t=-0.383,t=1.417,P>0.05).The noise of helical scanning was slightly lower than that of axial scanning,and the effective dose of axial scanning image decreased 75%by that of helical scanning,the differences of them between two groups were significant(t=16.210,t=9.603,P<0.05).Conclusion:Aimed at the temporal bone imaging of wide detector CT,the axial scanning scheme that adopts tube voltage which is greater than or equal to 120Kv,as well as the product of tube current and time which is greater than or equal to 160mAs,can obtain the images with high quality.It can effectively reduce the radiation dose.