超短回波时间(UTE)肺部MR成像对慢性阻塞性肺疾病的初步应用

The Preliminary Application of Ultra-Short Echo Time(UTE) MR Pulmonary Imaging in COPD

目的探讨MR超短回波时间（UTE）成像对慢性阻塞性肺疾病（COPD）的不同CT表现型及临床分级的评估能力,并与肺功能检查（PFT）及量化CT比较。方法 16例COPD患者同天内分别进行PFT、CT及3T UTE MR检查。UTE MR成像自动产生T_2~＊图,定义经升主动脉中间的冠状层面为测量的第一层（A1）;由此层向背侧每隔5 cm设定一个测量层面,分别为A2、A3,感兴趣区分别在不同层面的上、中、下肺野选取,计算其平均值。通过软件（Lung Density,Philips）自动获得阈值〈-950 HU的肺气肿指数（EI_（-950））。图像分别由具有4年及12年胸部诊断经验的放射影像医生评价。Spearman相关分析评价UTE MRI的T_2~＊值与CT容积参数及PFT的相关性。对于COPD患者的不同临床分级及CT亚型比较,近似正态分布数据组间比较用单因素方差分析,两两组间比较采用Bonferroni法;非正态分布数据多组间比较用Kruskal-Wallis检验,两两组间比较用Mann-whitney U testing法进行分析。结果 UTE MRI的T_2~＊值与用力呼气第1秒量实测值与预测值的百分比（%FEV1）,第1秒用力呼气容积占用力肺活量百分比（FEV1/FVC）及CT的容积参数具有强、中度相关性（︱r︱=0.503~0.668,P〈0.05）。轻、中度COPD组T_2~＊值明显高于极重度组（P〈0.05）,不同CT表现型的PFT-%FEV1、UTE-T_2~＊及CT-EI_（-950）值具有明显的差异（P〈0.05）。结论 UTE成像的T_2~＊值与PFT的变化、CT容积参数存在明显负相关性,且其在COPD患者的不同临床分级及CT亚型中存在差异。肺内T_2~＊的测量具有评估COPD的潜力。

Objective To evaluate the transverse relaxation time star（ T_2~＊） values measured using ultra-short echo time（ UTE） MR pulmonary imaging in different CT phenotypes and stages of COPD,and to correlate them with PFT values and CT volumetric parameters. Methods Sixteen COPD patients underwent PFT,CT and MR perfusion imaging on the same day. The T_2~＊maps were generated automatically from UTE-MRI. The anterior coronal slice（ A1） was the first appearance of aortic arch. On this basis,the corresponding A2 and A3 coronal slices were determined with an interval of 5 cm and10 cm posterior to A1,respectively. Then,three ROIs were encircled from upper,middle and lower lung fields at each coronal slices. The mean T_2~＊value of the 3 coronal slices was calculated. Emphysema indexes（ EI_（-950）） were evaluated from CT post processed images called by＂lung density＂software. All the images were interpreted by two thoracic radiologists with 4 and 12 years of experience. Correlations between PFT,T_2~＊and CT parameters were assessed using Spearman correlation analysis. The differences in T_2~＊,PFT and CT parameters were compared between different COPD phenotypes and stages. Results Moderate to strong correlations were found between T_2~＊,EI_（-950） and PFTs parameters（ ︱r︱ = 0. 503 ~ 0. 668,P 0. 05）. There were significant differences in T_2~＊between ＂mild and moderate COPD＂and ＂very severe COPD＂（ P 0. 05）. Significant differences were found in % FEV1,T_2~＊and EI_（-950） among three CT phenotypes（ P 0. 05）. Conclusion T_2~＊was different in different CT phenotypes and stages of COPD,and correlated with PFT and CT volumetric parameters,indicating measurement of T_2~＊in the lungs has great potential in assessment of COPD.