矢状位全视野及小视野体素内不相干运动脊柱骨髓成像的对比研究

目的比较矢状位全视野(full field of vision,f FOV)与小视野(reduced field of vision,r FOV)脊柱骨髓体素内不相干运动(intravoxel incoherent motion,IVIM)成像质量及参数值的差异。材料与方法纳入健康志愿者26名,其中男12名,女14名,年龄(41.12±14.96)岁。行腰椎常规MRI扫描及FOV(cm)分别为32×12.8及32×32的矢状位r FOV及f FOV-IVIM扫描,b值为0 s/mm~2、15 s/mm~2、30 s/mm~2、50 s/mm~2、70 s/mm~2、100 s/mm~2、300 s/mm~2、500 s/mm~2、800 s/mm~2,于GE AW4.6工作站的Functool软件进行后处理,每个椎体用一个感兴趣区覆盖,记录r FOV及f FOV-IVIM腰椎椎体骨髓的表观扩散系数(apparent diffusion coefficient,ADC)_(slow)、ADC_(fast)及f值。用五分量表法对r FOV及f FOV-IVIM图像质量进行主观评价。然后测量T2WI、r FOV及f FOV-IVIM图像上L_3椎体面积、上下径、前后径,并计算其形变率。整个测量及评价过程由两位放射科诊断医师实施,并隐藏临床及序列信息,对两位观察者测值及评分进行一致性分析,然后取均值。根据正态分布与否,选择配对t检验或配对秩和检验对两组IVIM参数值、图像质量评分及形变率进行对比。结果结果显示,两名放射诊断医师测得的腰椎骨髓r FOV及f FOV IVIM参数(ADC_(fast)、ADC_(slow)、f)、形变率及取得的图像质量评分的一致性良好。脊柱骨髓的r FOV及f FOV IVIM间ADC_(fast)(t=-9.92,P0.01)、ADC_(slow)(Z=-2.20,P0.05)、f值(t=-17.86,P0.01)、图像质量评分(Z=-12.76,P0.01)、面积(Z=-4.27,P0.01)及前后径形变率(Z=-6.20,P0.01)差异有统计学意义,而上下径形变率(t=-0.50,P=0.62)差异则无统计学意义。结论与全视野IVIM相比,脊柱骨髓小视野IVIM图像质量更高、形变伪影小,有助于获得相对准确的IVIM脊柱骨髓参数值。

The comparison of sagittal full field-of-view and reduced field-of-view intravoxel incoherent motion imaging of spinal bone marrow

Objective: The purpose of this study is to compare image quality and the intravoxel incoherent motion (IVIM) parameters obtained with full FOV or reduced FOV IVIM imaging. Materials and Methods: Twenty-six healthy volunteers (12 male, 14 female) with age of 41.12±14.96 years (Mean±SD) were enrolled in this retrospective study. The lumbar imaging protocol included routine imaging, rFOV IVIM DWI (FOV 32 cm×12.8 cm, b=0 s/mm2, 15 s/mm2, 30 s/mm2, 50 s/mm2, 70 s/mm2, 100 s/mm2, 300 s/mm2, 500 s/mm2, 800 s/mm2 ) and fFOV IVIM DWI ( FOV 32 cm×32 cm, b=0 s/mm2, 15 s/mm2, 30 s/mm2, 50 s/mm2, 70 s/mm2, 100 s/mm2, 300 s/mm2, 500 s/mm2, 800 s/mm2). Raw rFOV and fFOV IVIM DWI data were post-processed by Functool provided in Advantage Workstation (version 4.6, GE), and each vertebral body was selected as a region of interest (ROI). Image quality of rFOV and fFOV IVIM DW images were qualitatively evaluated by using a 5-point likert scale. IVIM DWI distortion was quantitatively evaluated by calculating the distortion rate of L3 vertebral body. The quantitative measurements and qualitative scores of IVIM DW images were performed by two radiologists who were blinded to the clinical and sequences information, and the consistency of the two readers was evaluated, and the mean IVIM parameters, qualitative scores, and distortion ratios of the two readers were calculated. The IVIM parameters (ADCfast, ADCslow, f), qualitative scores, and distortion ratios of the two IVIM DWI were compared with paired t-test or Wilcoxon's test according to the Kolmogorov-Smirnov test. Results: In this study, there was good inter reader agreement in IVIM parameters, qualitative scores and distortion rate of rFOV-IVIM DWI and fFOV IVIM DWI. Statistically significant differences in ADCfast (t=-9.92, P<0.01) , ADCslow (Z=-2.20, P<0.05), f (t=-17.86, P<0.01), image quality scores (Z=-12.76, P<0.01), area distortion rate (Z=-4.27, P<0.01), and anteroposterior distances distortion rate (Z=-6.20, P<0.01) between rFOV and fFOV IVIM DWI was observed, while no significant difference in craniocaudal distances distortion rate (t=-0.50, P=0.62) between rFOV and fFOV IVIM DWI was observed. Conclusions: Compared with fFOV IVIM, rFOV IVIM DW images of spine bone marrow show improved image quality, and rFOV IVIM technique of spine may help to obtain relatively accurate IVIM parameters.