合成磁共振成像不同带宽对T1、T2及PD测量值的影响-体膜研究

The effect of bandwidth on evaluation of T1,T2 relaxation times and proton density using synthetic MRI:A phantom study

目的观察多动态多回波序列(multi-dynamic multi-echo,MDME)不同带宽对T1、T2及质子密度(proton density,PD)测量值的影响。材料与方法3种具有不同T1、T2及PD的体膜[脑灰质(gray matter,GM),白质(white matter,WM),脑脊液(cerebrospinal fluid,CSF)]分别行7组不同带宽(19.23 kHz~100.00 kHz)的MDME序列扫描,每组序列扫描9次。使用MAGiC(magnetic resonance imaging compilation)软件分别测量GM、WM、CSF的T1、T2及PD值。组内之间的差异程度用组内变异系数(coefficient of variation,CV)表示,组间的差异程度用组间CV表示。每组GM、WM的T1差异性及T2差异性比较采用配对样本t检验,PD差异性比较采用Wilcoxon检验。结果测量所得T1、T2及PD值最大组内CV分别为2.09%,8.73%,10.61%;最大组间CV分别为1.36%,2.85%,3.72%。每组内GM与WM的T1值以及T2值之间的差异有统计学意义(P<0.01),PD值之间的差异无统计学意义(P>0.05)。结论当接收带宽在19.23 kHz~100.00 kHz变化时,T1、T2测量值不受带宽影响。当带宽低于50 kHz时,PD测量值可重复性减低。

Objective:To evaluate the effect of bandwidth on quantification of T1,T2 relaxation times and proton density using multi-dynamic multi-echo sequence.Materials and Methods:Phantoms consisting of 3 kinds of materials with different T1,T2 and PD[gray matter(GM),white matter(WM),cerebrospinal fluid(CSF)]were included in the study.The phantoms were scanned 9 times using MDME sequence with 7 sets of scan parameters with different bandwidths(19.23 kHz—100.00 kHz).T1,T2,and PD maps were acquired and processed using MAGiC(magnetic resonance imaging compilation)post-processing software,and T1,T2,PD values were acquired.Intragroup coefficient of variation(CV)was performed to evaluate the reproducibility of measured values.Intergroup CV was used to evaluate the discrepancy of measured values across all the groups.The T1,T2 values between GM and WM were compared with paired-samples t test.The PD values between GM and WM were compared with Wilcoxon singled Rank test.Statistical analysis was performed using SPSS software(SPSS for Windows,23.0.0.0,IBM).Results:The highest intragroup CVs of T1,T2 and PD were 2.09%,8.73%,10.61%,respectively.The highest intergroup CVs of T1,T2 and PD values were 1.36%,2.85%,3.72%,respectively.Significant differences were revealed when comparing T1 and T2 values between GM and WM(P<0.01)and no significant differences were found when comparing PD values between GM and WM(P>0.05).Conclusions:T1 and T2 measurements are not affected by bandwidth within range of 19.23 kHz—100.00 kHz.Repeatability of PD measurements is reduced when the bandwidth is below 50 kHz.