同时多层成像技术在大腿肌肉磁共振应用价值研究

Simultaneous multi-slice accelerated turbo spin echo imaging for the thigh muscle--an image quality analysis

目的与采用并行采集(parallel acquisition technique,PAT)技术的压脂T2加权自旋回波(T2 weighted turbo spin echo imaging,T2WI TSE)序列进行比较,评价同时多层成像(simultaneous multi-slice,SMS)技术用于大腿肌肉磁共振压脂T2WI TSE序列的图像质量。材料与方法研究共纳入正常志愿者19例及因病情需要行大腿肌肉磁共振检查的患者8例,共27例受试者。采用3.0 T磁共振进行检查。在同一次检查中,分别采用使用SMS采集技术的压脂T2WI TSE序列及采用PAT采集技术的压脂T2WI TSE序列对受试者的大腿进行轴位扫描。采集时间分别为:使用SMS采集技术的压脂T2WI TSE序列:1 min 20 s,采用PAT采集技术的压脂T2WI TSE序列:2 min 28 s。获得的图像在工作站上进行测量。在两组图像中相同的层面测量大腿肌肉的信号强度(signal intensity,SI)及噪声(standard deviation,SD),测量位置为右侧股内侧肌,ROI面积1 cm^(2)。分别计算两组图像的信噪比(signal to noise ratio,SNR),SNR=SI/SD。同时由2名有经验的放射科医生独立对图像质量进行主观评价,评价采用5分法。采用配对t检验,对两组图像的SD及SNR进行比较,P<0.05时,认为两组数据有统计学差异。采用Wilcoxon符号秩检验对两组图像的主观图像质量评分进行比较,P<0.05时,认为两组图像主观图像质量评分有统计学差异,同时评价不同观察者判断的一致性,组内相关系数(intraclass correlation coefficient,ICC)>0.6时,认为不同观察者间一致性好。结果采用SMS采集技术的压脂T2WI TSE序列,其噪声明显低于采用PAT采集技术的压脂T2WI TSE序列(1.37±0.25 vs.1.57±0.33,P=0.032);两组图像SNR无显著差异(41.50±15.75 vs.46.23±10.89,P=0.085)。2名观察者对两组图像给出的主观图像质量评分均无显著差异(观察者1,P=0.317,观察者2,P=0.527),两组图像的观察者间一致性均较好(采用SMS采集技术的压脂T2WI TSE序列:ICC=0.75,采用PAT采集技术的压脂T2WI TSE序列,ICC=0.782)。结论采用SMS采集技术对腿部肌肉进行压脂TSE扫描,与采用PAT采集技术的压脂TSE序列比较,在缩短扫描时间的同时,不降低SNR,可获得类似的图像质量。

Objective:To investigate the image quality of simultaneous multi-slice(SMS)accelerated fat-saturated(FS)T2WI turbo spin echo(TSE)magnetic resonance imaging protocol on the thigh muscle in comparison with parallel acquisition technique(PAT)accelerated FS T2WI TSE protocol.Materials and Methods:Twenty-seven subjects(19 healthy volunteers and 8 patients indicated for MRI examination for thigh muscle)were included in the research in total.All subjects were scanned using a 3.0 tesla MRI.Axial SMS accelerated FS T2WI TSE images and PAT accelerated FS T2WI TSE images of the thigh muscle were acquired for all the subjects.The scan time was 1 minute 20 seconds for SMS accelerated FS T2WI TSE image and 2 minutes 28 seconds for PAT accelerated FS T2WI TSE imaging respectively.Images were transferred to the workstation for further measurement.Signal intensity(SI)and noise(standard deviation,SD)of thigh muscle were measured on the same slice of two image sequences with SMS or PAT technique.The ROIs were located at the right medial vastus muscles,with an area of 1 cm^(2).Signal to noise ratio(SNR)was calculated accordingly.Subjective image quality was evaluated by 2 experienced radiologists independently using a 5-point scale.Paired student’s t-test was used to compare the SD and SNR for the two groups of images.Wilcoxon signed ranks test was used to compare the subjective scores between the two groups.Statistically difference was considered while P<0.05.The accordance between two different observers was investigated at the mean time.ICC values of more than 0.6 were considered good accordance between the two observers.Results:SMS accelerated FS T2WI TSE images showed significantly lower noises in comparison with PAT accelerated FS T2WI TSE images[(1.37±0.25)vs.(1.57±0.33);P=0.032].There was no significant difference in SNR between two groups[(41.50±15.75)vs.(46.23±10.89);P=0.085].The subjective image quality was of no significant difference by both of the two observers.Observer 1:[(3.81±0.68)vs.(3.93±0.50);P=0.317];Observer 2:[(3.85±0.53)vs.(3.78±0.64);P=0.527].Both groups of images showed good inter-observer accordance(SMS accelerated TSE images:ICC=0.75,conventional TSE images.ICC=0.782).Conclusions:By using a SMS accelerated FS T2WI TSE scan protocol in the imaging of the thigh muscle,compared with PAT accelerated FS T2WI TSE scan protocol,the acquisition time is reduced while the image quality remains similar.