压缩感知技术在腰椎磁共振快速成像中的应用

Application of compressed sensing technology in rapid lumbar magnetic resonance imaging

目的探讨压缩感知(compressed sensing,CS)不同加速因子(acceleration factor,AF)对腰椎MRI图像质量的影响。材料与方法招募32例受检者(男12例,女20例),年龄(45.28±14.11)岁。行3.0 T MR结合敏感度编码(sensitivity encoding,SENSE)以及CS的腰椎矢状位T1WI、T2WI和轴位T2WI序列扫描,采用的AF分别为无加速、SENSE AF=2、CS AF=2、3、4、5。两观察者在矢状位T1WI、T2WI和轴位T2WI划定感兴趣区测量信号强度(signal intensity,SI)和噪声强度(standard deviation,SD),并计算信噪比(signal to noise ratio,SNR)和对比噪声比(contrast to noise ratio,CNR)。对图像质量进行五分法主观评分。组内相关系数(intra-class correlation coefficient,ICC)、Kappa检验分析两观察者测量数据和主观评分的一致性。对各序列不同组间图像的SNR、CNR和主观评分采用单因素ANOVA分析。结果两观察者测量数据和主观评分一致性良好(ICC:0.878~0.997,Kappa:0.763~0.948)。单因素ANOVA检验矢状位T1WI、T2WI、轴位T2WI不同AF间SNR、CNR及评分差异有统计学意义(P<0.01)。两两比较结果:当CS=4时,矢状位T1WI椎体和间盘的SNR、矢状位T2WI椎体和间盘的SNR、CNR和主观评分较常规序列差异有统计学意义(P<0.05);当CS=3时,轴位T2WI椎体SNR较常规序列差异有统计学意义(P<0.05)。结论腰椎MRI扫描时间随着AF的增加逐渐降低,在保证图像质量的前提下,临床推荐AF分别以3、3、2行腰椎矢状位T1WI、T2WI和轴位T2WI序列扫描。

Objective:To explore the influence of different acceleration factors(AF)of compressed sensing(CS)on the quality of lumbar MRI images.Materials and Methods:Thirty-two subjects(twelve males)were recruited with an average age of(45.28±14.11)years.The sagittal T1WI,T2WI,and axial T2WI sequences of the lumbar spine were scanned with 3.0 T MR equipment through the sensitivity encoding(SENSE),and CS technology for AF=0,SENSE AF=2,CS AF=2,3,4,and 5,respectively.Two radiologists delineated the region of interest(ROI)on the sagittal T1WI,T2WI and transverse T2WI to measure the signal intensity(SI)and standard deviation(SD).Then we calculated the signal to noise ratio(SNR)and contrast to noise ratio(CNR).Finally,subjective score of image quality was assessed by five points method.The intra-class correlation coefficient(ICC)and Kappa test was adopted to evaluate the consistency of the scores from the two radiologists.In the following analysis,the ANOVA test was used to assess the difference of SNR,CNR and score between groups.Results:The measured datas and the subjective score of the two radiologists were in good agreement(ICC:0.878-0.997,Kappa:0.763-0.948).It was shown that there were statistically significant differences in SNR,CNR and subjective score of sagittal T1WI,T2WI and transverse T2WI sequences.If the CS equaled 4,the SNR,CNR and subjective score of sagittal T1WI and T2WI were significantly different from those of conventional sequences(P<0.05).If the CS equaled 3,the SNR,CNR and subjective score of axial T2WI were significantly different from conventional sequences(P<0.05).Conclusions:Scan time for the lumbar spine decreased gradually with increase of the CS AF.CS factor of 3 was recommended for clinical sagittal T1WI and T2WI,and CS factor of 2 was best for clinical transverse T2WI to achieve an optimal balance between scan time and image quality.