间质性肺疾病患者BMI与有效剂量、图像质量间关系

目的采用128层MSCT自动曝光控制（automated exposurecontrol，AEC）技术进行胸部扫描，分析间质性肺疾病患者体重指数（BMI）与有效剂量（ED）、体厚及图像质量的关系。方法对102例结缔组织疾病患者采用MSCT自动曝光控制技术进行胸部扫描，记录全肺扫描ED（mSv），根据BMI将研究对象分为体重过轻、正常、超重三组，并测量每一位患者体厚，采用双盲法对图像质量进行主观评价，以图像诊断接受率评分法和噪声评分法进行评分，采用5分制；用Kappa检验评价两名观察者的一致性。结果①两名医师在诊断接受率和图像噪声评估分值方面有很好的一致性（Kappa值分别为0．623和0．687）；②随着体重指数增加，体厚增厚、患者接受的有效剂量增大、噪声也越大，患者接受的ED、体厚及噪声的组间差异有统计学意义（P〈0．01）；而年龄分布、诊断接受率和病程三组间无统计学差异（P〉0．05）；同时，体重过轻者年龄相对较低，超重者年龄相对较大；随BMI增加，图像质量略有下降，诊断接受率评分也逐渐下降；③多因素变量间线性关系分析显示ED与BMI、体厚有明显正相关，并得出多元线性回归方程Y=-2．438＋（O．182×BMI）＋（O．162×体厚），Y即患者接受剂量的预测值。结论在获得稳定图像质量的前提下，随着BMI增加、体厚增大，ED相应增加、图像质量相应略下降。

Relationship between BMI,effective dose and image quality in patients with interstitial lung disease

Objective To investigate the relationship between BMI, effective dose, body thickness and image quality in patients with interstitial lung disease using 128-slice MSCT automated exposure control （AEC） technique. Methods Chest MSCT scans of 102 patients with connective tissue disease were examined using AEC technique and effective dose （ED） was recorded （mSv）. Patients were divided into three groups according to BMI, including underweight, normal and overweight. Patient＇s body thickness was measured. Image quality was evaluated with double-blind method. And image di- agnosis accepted rate score and image noise score were recorded using five-point scale. The consistency of two observers was evaluated with Kappa test. Results The consistency of two observers was good in diagnosis accepted rate score and image noise score （Kappa value was 0. 623 and 0. 687 respectively）. ED and image noise increased with the increase of BMI and body thickness. The difference of ED, body thickness and image noise between groups was statistically significant （ P d0.01）. The difference of age, diagnosis accepted rate and course of disease between three groups was no statistically sig- nificant （ P ~0.05）. The age of underweight group was relatively younger and that of overweight older. Image quality and diagnosis accepted rate score decreased with increase of BMI. Results of multiple regression analysis revealed that ED positively was correlated with BMI and body thickness. Multiple linear regression equation was Y=-2. 438＋0. 182 × BMI ＋ 0. 162 × body thickness and Y was predictive value of patienfs accepted dose. Conclusion When image quality is accept- able, ED increases and image quality decreases with the increase of BMI and body thickness.