颈动脉狭窄患者扩散加权成像的b值优化

Optimization of b-value in Cerebral Diffusion-Weighted 1.5T MR Imaging of Carotid Stenosis

目的:探讨颈动脉狭窄患者在1.5T MR扩散加权成像合理b值的取值范围。方法:对27例经磁共振血管成像证实为颈动脉中度以上狭窄患者行DWI检查,b值分别采用0、50、100、150、200、400、600、800、1000、1600、2000、2400、3000 s/mm^2。测量不同b值下的同侧不同脑区ADC值和图像的SNR、CNR、SIR,采用Pearson相关检验分析不同b值时各参数变化规律,采用配对t检验分析不同脑区ADC值变化规律。结果:b值与感兴趣区的SNR、CNR、SIR、ADC值呈负相关。狭窄侧侧脑室旁前部与同侧额叶白质区、狭窄侧与健侧侧脑室旁前部白质区ADC值比较,差异均有统计学意义(P<0.05)。结论:b值的选择对于SNR、CNR、SIR、ADC值的测量均有显著影响,b值为800~1000 s/mm2时低灌注脑白质的图像质量、ADC值测量稳定性较好,可能提供更加准确的信息。

Objective： To optimize the b-value of cerebral diffusion-weighted MRI at 1.5T on DWI. Method： 27 patients were examined using EPI-DWI with different b values on a 1.5T MR scanner. The b-value of EPI-DWI was 0, 50, 100, 150, 200, 400, 600, 800, 1000, 1600, 2000, 2400, 3000 s/mm2, respectively. The SNR, CNR, SIR, and ADC value of periventricular anterior and the frontal lobe were measured. The correlation between the b-value and SNR, CNR, SIR, ADC was analyzed by Pearson correlation analysis. The differences were compared among the ADC value of the narrow side and the healthy side, periventricular anterior and the frontal lobe with Paired T test. Result： The SNR, CNR, SIR of DWI and ADC value of periventricular anterior decreased as the b-value increased, showed inverse correlations separately. The differences among the ADC value of the narrow side and the healthy side, periventricular anterior and the frontal lobe were significant. Conclusion： The selections of b values affected SNR, CNR, SIR and ADC values significantly. The optimized b-values of DWI for cerebral hypoperfusion at 1.5T is between 800 s/mm2 and 1000 s/ram2, when measuring stability of SNR, CNR, SIR and ADC value are better than others.