压缩感知联合并行采集技术的屏气3D LAVA FLEX序列在肝脏磁共振快速成像中的应用

Application of compressed sensing combined with parallel acqusition technique of breath-holding 3D LAVA FLEX sequence in rapid magnetic resonance imaging of liver

目的探讨压缩感知(compressed sensing,CS)不同加速因子(acceleration factor,AF)联合并行采集技术(parallel acquisition technique,PAT)基于区域增长和相位校正水脂分离技术的三维肝脏容积加速采集(three-dimensional liver acqusition with volume acceleration flexible,3D LAVA FLEX)屏气序列在肝脏MR快速成像中的应用。材料与方法招募28名健康受试者,采用GE Architect 3.0 T MR仪行结合PAT AF 2以及不同CS AF的屏气3D LAVA FLEX序列的肝脏扫描。扫描序列分为五组,分别为PAT 2组和基于PAT 2的CS 1.2、CS 1.5、CS 2、CS 2.4组。由两位观察者分别对肝脏的水相、同相位(in-phase,IP)、反相位(opposed-phase,OP)图像质量进行5分制主观评分。取肝门水平的同一层面,放置感兴趣区域(region of interest,ROI)于肝右叶前、后段和肝左叶内、外段及其同一相位方向的右侧竖脊肌。记录各个ROI的平均信号强度(signal intensity,SI)及竖脊肌的噪声强度(standarddeviationg,SD)值,分别计算图像信噪比(signal-to-noiseratio,SNR)以及对比噪声比(contrast-to-noise ratio,CNR)。用组内相关系数(intra-class correlation cofficient,ICC)分析两位观察者主观评分和测量数据一致性;用Kruskal-Wallis H检验分析主观评分间差异;使用单因素方差分析(analysis of variance,ANOVA)对比不同组间SNR、CNR的差异。结果两位观察者对图像质量的主观评分及测量数据均为一致性良好(ICC>0.75)。五组水相、IP和OP图的主观评分组间差异有统计学意义(P<0.001,P<0.001,P<0.001)。五组图像肝右叶前、后段和肝左叶内、外段SNR的组间差异有统计学意义(P<0.001,P=0.004,P=0.002,P<0.001),CNR的组间差异无统计学意义(P=0.802,P=0.979,P=0.772,P=0.910)。当CS AF=2.4时,水相、IP、OP图像的主观评分与常规PAT 2组差异有统计学意义(P=0.009,P<0.001,P<0.001),肝右叶前、后段和肝左叶内、外段SNR与常规PAT 2组差异有统计学意义(P=0.010,P=0.002,P<0.001,P<0.001)。结论随着CS AF的增加,扫描时间逐渐缩短,在保证图像质量的前提下,基于PAT AF 2的屏气3D LAVA FLEX序列临床推荐CS AF 2作为肝脏动态增强和IP、OP成像的扫描参数,并且比常规PAT AF 2的方案扫描时间下降44%,成像效率大幅提高。

Objective:To investigate the application of compressed sensing(CS)with different acceleration factors(AF)and combined with parallel acqusition technique(PAT)of three-dimensional liver acqusition with volume acceleration flexible(3D LAVA FLEX)breath-holding sequence in rapid magnetic resonance imaging of liver.Materials and Methods:A total of 28 healthy subjects were recruited for liver MRI scan using breath-holding 3D LAVA FLEX sequence combined with PAT AF 2 and CS with different AF at GE Architect 3.0 T MR scancer.The scanning sequences were divided into PAT 2 group and CS 1.2,CS 1.5,CS 2,CS 2.4 group based on PAT 2.Two observers were subjectively rated a 5-point scale on the image quality of water phase,in-phase(IP)and opposed-phase(OP)of liver.In the same slice of porta hepatis,the regions of interest(ROI)were placed on the anterior and posterior segments of the right hepatic lobe,the inner and outer segments of the left hepatic lobe,and the right erector spinae.The signal intensity(SI)value of each ROI and the standard deviationg(SD)value of erector spinae were recorded,and calculated the signal-to-noise ratio(SNR)and contrast-to-noise ratio(CNR).Inter-class correlation cofficient(ICC)was used to analyze the consistency of subjective scores and measurement data of the two observers.Kruskal-Wallis H test was used to analyze the differences among subjective scores.One-way analysis of variance(ANOVA)was used to compare the differences of SNR and CNR among different groups.Results:There was good agreement between the two observers on the subjective score of image quality and the measured data(ICC>0.75).There was significant difference in subjective evaluation among the five groups of water phase,IP and OP images(P<0.001,P<0.001,P<0.001).There was significant difference in the SNR of the right anterior and posterior lobe and the inner and outer segments of the left lobe among the five groups(P<0.001,P=0.004,P=0.002,P<0.001),but there was no significant difference in the CNR among the five groups(P=0.802,P=0.979,P=0.772,P=0.910).When CS AF=2.4,the subjective scores of water phase,IP and OP images were significantly different from those in the regular PAT 2 group(P=0.009,P<0.001,P<0.001),and the SNR in the anterior and posterior segments of the right hepatic lobe,the inner and outer segments of the left hepatic lobe were significantly different from those in the conventional PAT 2 group(P=0.010,P=0.002,P<0.001,P<0.001).Conclusions:With the increase of CS AF,the scanning time was gradually shortened.Under the premise of ensuring image quality,CS AF 2 was clinically recommended as the scanning parameter of liver dynamic enhancement and IP,OP imaging for breath-holding 3D LAVA FLEX sequence based on PAT AF 2,and the scanning time was reduced by 44%compared with the regular scanning scheme of PAT AF 2,and the imaging efficiency was greatly improved.