宽体探测器CT不同扫描方式对胸部低剂量CT图像质量及辐射剂量的影响

Effect of Scan Method on Low Dose Chest CT Image Quality and Radiation Dose

目的探讨宽体探测器轴位扫描方式和螺旋扫描方式对胸部低剂量CT图像质量和辐射剂量的影响。方法将160例胸部CT检查的患者随机分为2组,A组采用螺旋扫描,B组采用轴位扫描。记录患者的扫描时间、容积CT剂量指数和剂量长度乘积。比较两组图像肺尖部、肺中部及肺底部区域的客观噪声及信噪比(Signal-to-Noise Ratio,SNR),由2名具有十年以上放射工作经验的医师采用双盲法对获得的CT图像进行图像质量评分。结果肺尖部及肺底部层面两种扫描方式的噪声值及SNR差异有统计学意义(P<0.05)。在肺中部层面两种扫描方式的噪声值及SNR差异无统计学意义(P>0.05)。螺旋扫描和轴位扫描的曝光时间分别为2.22±0.24、4.23±1.19s,具有显著统计学差异(P<0.05)。两组患者的有效剂量分别为0.51±0.12、0.46±0.10mSv,具有显著统计学差异(P<0.05)。两组患者间图像质量的主观评价指标差异无统计学意义(P>0.05)。结论对于胸部低剂量CT扫描,宽体探测器CT轴位扫描方式可在保证图像质量的前提下,提高射线利用率并减小辐射剂量。

Objective To evaluate the effect of scanning method on low-dose chest CT image quality and radiation dose.Methods A total of 160 patients who underwent chest CT examination were randomly divided into two groups.Group A underwent spiral scan and group B underwent axial scan.Scanning time,volume CT dose index(CTDIvol)and dose length product(DLP)were recorded.The noise and signal-to-noise ratio(SNR)of the apex,middle and bottom regions of the lung were compared between the two groups.Two doctors with more than ten years of radiation experience scored the quality of CT images by double-blind method.Results There were significant differences in noise value and SNR between the two scanning modes in apex and bottom of lung(P<0.05).There was no significant difference in noise value and SNR between the two scanning modes in the central lung region(P>0.05).The exposure time of spiral scan and axial scan were 2.22±0.24 s and 4.23±1.19 s,respectively,with significant difference(P<0.05).The effective doses of the two groups were 0.51±0.12 mSv and 0.46±0.10 mSv,respectively,with significant difference(P<0.05).There was no significant difference in subjective evaluation of image quality between the two groups(P>0.05).Conclusion For low-dose chest CT scanning,the axial scan mode of wide-body detector CT is able to improve the utilization rate of radiation and reduce radiation dose on the premise of ensuring image quality.