SE-EPI与IR-EPI序列在3.0 T胎儿颅脑磁共振扩散加权成像中的对比研究

Comparison of SE-EPI and IR-EPI sequences in diffusion-weighted imaging of fetal brain

目的研究自旋回波-平面回波成像(SE-EPI)与短时反转恢复-平面回波成像(IR-EPI)序列在3.0 T胎儿颅脑磁共振扩散加权成像(DWI)中图像质量及表观扩散系数(ADC)值差异。方法前瞻性分析47例因产前超声可疑胎儿颅脑异常行3.0 T磁共振检查资料。分别采集SE-EPI-DWI和IR-EPI-DWI序列图像,对两组图像质量进行主观及客观评估。主观评估由两名具有5年以上经验丰富副主任医师根据Likert 7分评分系统对图像磁敏感伪影、图像整体质量进行评分并分析,采用Wilcoxon符号秩和检验进行图像质量评分差异性分析,采用Spearman等级相关检验进行两名医师之间相关性分析。客观评估分别测量计算两组DWI图像的信噪比(SNR)、对比噪声比(CNR)、正常ADC值及特异吸收率(SAR)值差异,并进行统计学分析。结果47例胎儿成像主观评价一致性分析提示:阅者1和阅者2评分结果显示SE-EPI序列图像优于IR-EPI序列图像,SE-EPI有效降低图像伪影、提高图像整体质量(P均=0.000);两名阅者之间相关性评分图像伪影、图像整体质量呈高度正相关(r=0.939、0.925,P=0.000、0.000)。客观评价:IR-EPI-DWI序列组额叶白质区及侧脑室后角区SNR高于SE-EPI-DWI序列组(F=0.037、1.386,P=0.847、0.242),差异无统计学意义;SE-EPI-DWI序列组CNR高于IR-EPI-DWI序列组(F=0.550,P=0.460),差异无统计学意义;额叶白质区ADC值两组序列差异无统计学意义(F=2.386,P=0.126),侧脑室后角区ADC值两组序列差异无统计学意义(F=0.615,P=0.435);SAR值两组序列对比,差异具有显著统计学意义(P=0.000)。结论3.0 T胎儿颅脑磁共振SE-EPI-DWI序列采集速度快、图像伪影小、检查成功率高,可作为常规胎儿头颅磁共振检查首选序列,IR-EPI-DWI的SNR稍高于SE-EPI-DWI序列图像,可作为SE-EPI-DWI序列外的补充序列。

Objective To compare the image quality and apparent diffusion coefficient(ADC)values between spin-echo echo-planar imaging(SE-EPI)and inversion recovery EPI(IR-EPI)sequences in fetal brain diffusion-weighted magnetic resonance imaging(DWI).Methods 47 pregnant women with prenatal ultrasound suspicion of fetal brain abnormality underwent 3.0 T magnetic resonance examination including SE-EPI-DWI and IR-EPI-DWI.The image quality of the two sets of DWI was evaluated qualitatively by two radiologists with more than 5 years of experience using the 7-point Likert scale.Wilcoxon symbolic rank sum test was used to analyze the difference in image quality scores.Spearman rank correlation test was used to analyze the correlation between the two observers.The signal-to-noise ratios(SNR),contrast-to-noise ratios(CNR),ADC,and specific absorption rates(SAR)of the two sequences were measured and compared.Results The SE-EPI sequence was significantly(P=0.000)superior to IR-EPI sequence with reduced image artifacts and overall image quality for both observers.There was high positive correlation between the observers in both image artifacts(r=0.939,P=0.000)and overall image quality(r=0.925;P=0.000).The frontal white matter SNR(F=0.037,P=0.847)and posterior periventricular white matter SNR(F=1.386,P=0.242)on IR-EPI-DWI were not significantly higher than that on SE-EPI-DWI whereas the CNR of SE-EPI-DWI were not significantly higher than that of IR-EPI-DWI group(F=0.550,P=0.460).The ADC values in the frontal white matter(F=2.386,P=0.126)and posterior periventricular white matter(F=0.615,P=0.435)were also not significantly different between the two sequences whereas the SAR were significantly different(P=0.000).Conclusion The SE-EPI-DWI sequence has fast acquisition,mild image artifacts and high examination success rate,and is the preferred sequence for routine fetal cranial DWI.The SNR of IR-EPI-DWI is slightly higher than that of SE-EPI-DWI,and can be used as a supplemental sequence.