64排CT胸部低剂量扫描极限的探讨

Search of the lowest limit about 64 row in chest low-dose CT scanning

目的探讨64排CT结合迭代重建算法在肺部疾病检查中辐射剂量降低的极限。方法前瞻性选取150例2014年6～7月在山东省聊城市东昌府人民医院接受64排128层肺癌筛查者及慢性病复查者，所有受检者身高在165-175啪，18k酢午≤BMI≤26kg／m^2，平均44岁。将受检者随机分为3组，每组50例。扫描参数：A组：管电压100kV，管电流50mAs；B组：管电压80kV，管电流30mAs；C组：管电压80kV，管电流15mAs。扫描完成后采用迭代重建算法idose4-4对各组图像进行重建，从客观噪声、CT值及主观图像质量三方面进行评估。主观图像质量主要评估肺窗质量，采用3段式，第三胸椎棘突以上层面为上段，双肺下叶底段支气管分叉以下层面为下段，上段与下段之间的部分为中段。从每段图像里面选出一帧存在肺纹理或病理改变的图像进行评估，评价每帧图像纹理或病变的边缘清晰度。由2名具有10年以上诊断经验的医师采用3分制方法评价。纵隔窗比较其客观噪声及CT值。结果上段及下段图像中，各组图像质量评分差异均有统计学意义（均P〈0．05），中段图像中，各组图像质量评分差异均无统计学意义（均P〉0．05）。与A组相比，B组、C组分别增加噪声约38．57％、103．58％，3组图像之问噪声差异有统计学意义（P〈0．05），CT值差异无统计学意义（P〉O．05），B组、C组有效辐射剂量分别降低了69．77％、84．88％。结论结合idose。迭代重建算法，根据扫描位置不同设置不同扫描条件能把有效辐射剂量降到最低。

Objective To search the lowest limit about 64 row in chest low-dose CT scanning. Methods From June to July 2014 150 persons in Dongchangfu District People＇s Hospital of Liaocheng were selected in advance. All the subjects were 165-175 cm tall, 18 kg/m2≤BMI≤26 kg/m^2, the average age was 44. The subjects were randomly divided into 3 groups, 50 cases in each group. Scan parameters： group A： tube voltage was 100 kV, tube current was 50 mAs; group B： tube voltage was 80 kV, tube current was 30 mAs; and group C： tube voltage was 80 kV, tube current was 15 mAs. The iterative reconstruction algorithm idose4-4 was used for each image after scanning completed. The assessment was done from the objective noise and CT value and subjective image quality. The pulmonary window quality was evaluated using three stages. Chose one piece of image from each stages for evaluation. Two doctors who had 10 years experience in diagnosis assessed subjective image quality using three-point method. Mediastinal window was used to compare its noise and CT value objectively. Results The difference of image quality score of the image in the upper and lower segment had all statistical significance （P〈0.05）. All of the image quality score of middle image had no statistical significance （P〉0.05）. Compared with group A, the noises of group B and group C increased by about 38.57%, 103.58%, respectively. The difference of image noise between the three groups was statistically significant （P〈0.05）, and there were no statistical significance about CT values （P〉0.05）. Group B, group C effective radiation dose was reduced by 69.77% and 84.88%, respectively. Conclusion Combining idose4 iterative reconstruction, algorithm, and according to the scanning position setting different scan conditions can keep effective radiation dose to a minimum.