摘要
目的:初步探讨迭代重建算法(iDose4)在胸部低剂量扫描中的临床应用价值。方法:将120例拟行全胸部CT增强扫描的患者随机分为3组(每组40例)。3组在平扫及肺动脉期时扫描参数相同(120kV,管电流自动调控),在主动脉期时3组管电流分别为40、30和20mAs。平扫以及肺动脉期扫描采用滤波反投影算法(FBP)重建图像,主动脉期采用FBP和迭代重建算法(iDose4等级为1、2、3、4、5、6级)。比较肺动脉期与主动脉期有效辐射剂量的变化及气管腔内空气CT值和其标准差(SD)及信噪比(SNR)的差异。在肺窗图像上观察肺内小结构(胸膜下2cm内小血管)的显示情况并对其评分(3分评价法),记录各mAs-iDose4组的平均分,平均分>2分为临床阅片能够接受的图像质量。结果:有效辐射剂量:肺动脉期常规剂量组为(5.84±1.41)mSv;主动脉期40mAs组为(1.49±0.70)mSv,30mAs组为(1.04±0.19)mSv,20mAs组为(0.71±0.05)mSv。气管腔CT值在不同管电流及不同重建算法各组间差异无统计学意义(P>0.05)。不同管电流组间及不同重建方法的图像平均SD值、平均SNR差异有统计学意义(P<0.05)。对肺内小结构的评分:肺动脉期图像为3分;主动脉期40mAs组内iDose4-4、5、6重建图像的平均分大于2分;30mAs组iDose4-5、6重建图像的平均分大于2分;20mAs组的iDose4-6重建图像的平均分大于2分。结论:迭代重建算法(iDose4)在胸部螺旋CT扫描的应用能显著降低辐射剂量且保证图像质量,40mAs采用iDose4-4重建、30mAs采用iDose4-5重建以及20mAs采用iDose4-6重建图像质量均能达到临床要求。
Objective：To study the value of iterative reconstruction （iDose 4） in radiation dose reduction in chest CT scan. Methods：One hundred and twenty patients planning to have contrast-enhanced chest CT examination were randomly assigned to 3 groups, with 40 patients in each group. The scanning parameters in plain scan and pulmonary artery phase were similar （120Kv, automatic tube current regulation）. In the aortic phase, the tube current was 40mAs, 30mAs and 20mAs respectively in these 3 groups. Filtered back projection （FBP） was used in plain and pulmonary artery phase for im- age reconstruction. Both filtered back proiection （FBP） and iDose 4 were used in aortic phase,the ilDose 4 grade le,Tels were 1 to 6. The effective radiation exposure was compared between pulmonary arterial phase and aorta phase. The differences of CT value of the air within tracheal lumen,the standard deviation （SD value） and signal-to-noise ratios （SNR） were com- pared and analyzed. Image quality was evaluated subjectively and using a 3-grade scale according to the pulmonary mini- structure （subpleural small vessels within the area 2cm from the pleura） on pulmonary window. Taking the mean score 〉2 as the acceptable image quality for clinical application, the mean score in different mAs-iDose 4 groups were evaluated. Results：The effective radiation exposure in routine dosage group for pulmonary arterial phase was （5.84± 1.41）mSv. For a- orta phase,the 40mAs group was （1.49±0.70）mSv;the 30 mAs group was （1.04±0.19）mSv and the 20mAs group was （0.71±0.05）mSv. The CT value of the intra tracheal air revealed no significant difference between groups with different e lectric current and with different image reconstruction method （P〉0.05）. The average SD value and SNR showed signifi- cant differences between groups with different electric current and with different reconstruction methods （P〈0.05）. For the grading of intra-pulmonary mini-structure,the mean score for each group in pulmonary arterial phase was 3. The mean score deviation of aorta phase was more than 2 for the group of 40mAs under reconstruction of iDose4-4.5.6, the group of 30mAs under reconstruction of iDose4-5.6 and the group of 20 mAs under reconstruction of iDose4-6. Conclusion： The ap- plication of iterative reconstruction （iDose 4） was valuable in radiation dose reduction with image quality guarantee in Chest CT. Acceptable image quality can be obtained for chest CT images acquired at 40mAs by using iDose4-4,30mAs by using iDose4-5 and 20mAs by using iDose4-6.
出处
《放射学实践》
2013年第12期1262-1266,共5页
Radiologic Practice
