噪声指数指导自动管电流调制技术在肺结核CT复查中降低辐射剂量的应用价值

摘要

目的：探讨噪声指数指导自动管电流调制技术对肺结核患者CT复查中降低辐射剂量的应用价值。方法 CATPHAN500模体测试，采用噪声指数10~27，每次增加1进行图像采集，共采集18组，图像采集分别用肺和标准算法重建，获得噪声指数与高对比分辨率的关系。初诊患者采用常规剂量（噪声指数10）扫描，诊断为肺结核后复查时采用低剂量（噪声指数17）扫描，记录扫描中自动生成的受检者X线剂量参数，包括CT容积剂量指数（CTDIvol）、剂量长度乘积（DLP），采用5分制双盲法对图像作量化评价，测量升主动脉的SD值。结果模体测试，高对比分辨率在噪声指数<19时，7LP/cm线对数均能清晰显示。初诊和复查时的图像质量主观评价均符合临床诊断要求。初诊及复查图像升主动脉SD值分别为（8.52±1.30）Hu、（13.90±2.37）Hu，差异有统计学意义（P<0.05），复查时图像噪声大于初查睦。CTDIvol、DPL初诊时分别为（9.87±2.23）mGy、（333.79±73.24）mGy.cm，复查时分别为（4.15±1.96）mGy、（139.91±63.86）mGy.cm，二者差异均有统计学意义（P<0.05）。结论噪声指数指导自动管电流调制技术用于肺结核CT复查，图像质量符合要求，且可降低对患者的辐射剂量。%Objective Application value and significance of noise index guiding automatic tube current modulation technique in pulmonary tuberculosis review by CT scanning. Methods CATPHAN500 model test,between the noise index of 10~27,each 1 increase in image acquisition,which were collected in 18 groups,respectively with lung and standard reconstruction algorithm,to obtain the relationship of noise figure and high contrast resolution. Patients were randomly selected in our hospital during January 2012 year to January 2013 year,and they were diagnosed if pulmonary tuberculosis with conventional dose(noise index 10)CT scan of the chest,55 cases of the patients needed to review the diagnosis,using low dose in the review(noise index 17)of chest CT scan, record CT scanning their X-ray dose parameters of automatic generation in detail,including CT volume dose index(CTDIvol)and dose length product(DLP). By 2 radiologists using 5 points double blind method for quantitative evaluation of images,measured SD value of the ascending aorta,and all the data for statistical analysis using SPSS13.0 software. Results In the model test,the high contrast resolution was used when the noise figure was less than 19,7LP/cm pairs can clearly display. Subjective assessment of image quality in newly diagnosed group and review diagnosed group were consistent with the clinical diagnostic requirements. In newly diagnosed group and review group photos ascending aortic SD values were(8.52±1.30)Hu and(13.90±2.37)Hu, both two groups had statistics significant difference(P<0.05),and review diagnosed group photos noise were more than the newly diagnosed group. The average CTDIvol,DPL in newly diagnosed group were(9.87±2.23)mGy,(333.79±73.24)mGy. cm,and the average CTDIvol,DPL in review diagnosed group were(4.15±1.96)mGy,(139.91±63.86)mGy.cm,which the two groups’ difference had statistics significance respectively(P≤0.05). Conclusion Noise index guiding automatic tube current modulation technique in pulmonary tuberculosis review by CT scanning can significantly reduce the patient radiation dose, meanwhile images quality meet the clinical diagnostic requirements.