多层螺旋CT扫描降低仟伏值对婴幼儿胸部图像质量的影响  

Evaluation of Low-kilovoltage MSCT Chest Imaging in Children

作　　者：徐小普[1] 孔秋雁[2] 许崇永[2] 陈宇[2] 陈廷港[2] 

机构地区：[1]温州医学院附属第二医院临床工程科,浙江325027 [2]温州医学院附属第二医院放射科,浙江325027

出　　处：《放射学实践》2008年第12期1373-1375,共3页Radiologic Practice

摘　　要：目的:比较婴幼儿胸部低仟伏值CT扫描与常规扫描的图像质量,探讨降低仟伏值低剂量扫描应用于婴幼儿胸部检查的可行性。方法:体模测试:用120和90kV条件扫描体模的空间分辨力插件,选择相同位置的4帧图像测量平均空间分辨力;再用相同的方法扫描体模的水层,测量每组4帧图像的平均CT值标准差,作2组的噪声水平比较。病例扫描:选择胸部检查的患儿80例,随机分成2组,每组40例。2组分别用常规剂量(120kV,80mAs)和低剂量(90kV,80mAs)扫描,层厚5mm。比较不同剂量的CT权重剂量指数(CTDIvol)及剂量长度乘积(DLP);测量、比较2组图像降主动脉处的噪声值;并由2位医师按优、合格、不合格的等级盲法评价2组图像质量。结果:90kV扫描的CTDIvol为2.3mGy,DLP为26.4mGy·cm,与常规剂量的比值为43.4%和43.1%。低剂量图像的噪声水平(H=0.66%)较常规组(H=0.44%)高,两者差异有统计学意义(t=11.86,P<0.001)。虽然低剂量组的优质图像所占比率有所降低,但不存在不合格图像,所有低剂量图像都符合临床诊断要求。结论:90kV可以作为多层螺旋CT婴幼儿日常胸部检查的扫描条件。Objective：To compare the image qualities of the low-kilovoltage with the conventional-kV in the pediatric chest MSCT examination and to evaluate its application in routine pediatric chest study. Methods：Phantom measurement： The phantom scans were performed on the same location of the multi-pin layer using tube voltage 120 and 90kV, and the spatial resolution of images with different kVs were measured. Then the noise level of images with different protocols were appraised after same scans had been performed on the water layer. Patients scans：80 children requiring chest CT were randomly assigned to one of two protocol groups （n=40 in each group）. The MSCT scans were performed in one group with parameter 90kV and 80 mAs and the standard protocol （120kV and 80mAs） was used in another group. The weighted CT close index （CTDIvol） and dose length product （DLP） of two groups were compared. The noise of images of each group was also measured in the thoracic aorta. At last the image quality was graded as excellent, acceptable and unacceptable by two experienced radiologists. Results：The phantom measurement suggested that the lower the tube voltage,the higher the noise level was. The CTDIvol of low-dosage protocol was 2.3mGy and its DLP was 26.4mGy · cm, and they were 43.4% and 43.1 %of those in conventional dosage group respectively. The noise of images with low-dosage protocol （0. 665） was significantly higher than that with standard protocol （0. 445） （t= 11.86, P〈0. 001）, and no image in low-dosage group was unacceptable although the image quality of low-dosage group was inferior to that of conventional-dosage group. Conclusion： It was recommended that the tube voltage 90kV is applicable for routine pediatric chest examination.

关 键 词：体层摄影术 X线计算机 放射摄影术 胸部 辐射剂量 

分 类 号：R816.92[医药卫生—放射医学]