MR扩散加权成像在眼眶肿块中b值选择

Determination of b value in diffusion weighted imaging of orbital masses

目的:探讨不同扩散敏感因子(b值)MR扩散加权成像对眼眶肿块图像质量及ADC值影响。方法:对81例眶内肿块术前行DWI检查和MRI常规扫描。每次取2个扩散敏感因子即b=0和/或400、700、1000s/mm2,利用固定参数组合的自旋回波-平面回波(SE-EPI)序列进行DWI检查。计算不同b值(400、700、1000s/mm2)下病灶信号-噪声比(SNR)、病灶-对侧颞叶脑白质对比噪声比(CNR)、病灶的ADC值、病灶与对侧颞叶白质ADC的比值(ADCR)。结果:眼眶肿块在DWI400、DWI700、DWI1000的SNR分别为(85.10±48.90)、(61.46±37.00)、(42.92±25.53),差异有统计学意义(χ2=125.654,P=0.000);CNR分别为(28.36±26.67)、(20.11±17.19)、(16.59±15.29),差异有统计学意义(χ2=14.519,P=0.000);ADC值分别为(1.42±0.44)×10-3、(1.25±0.43)×10-3和(1.16±0.40)×10-3 mm2/s,差异有统计学意义(F=7.932,P=0.000);ADCR值分别为(1.47±0.45)、(1.39±0.46)、(1.37±0.46),差异无统计学意义(F=1.199,P=0.303)。结论:b=700s/mm2是眼眶肿块扩散加权成像的较佳b值,可以得到良好显示眼眶肿块DWI图像。

Objective：To study the influences of different b values on the image quality of DWI and ADC value of or bital mass. Methods： Routine MRI and DWI were performed in 81 subjects with intra-orbital mass before surgery with the b value-0 and/or 400,700,1000s/mm^2. SE-EPI sequence with fixed parameters combination was used for DWI. The signal noise ratio （SNR） of lesion, contrast-to noise ratio （CNR） of lesion/white matter of eontra-lateral temporal lobe, ADC value of lesion, ADC ratio （ADCR） of lesion/white matter of contra-lateral temporal lobe were calculated with different b values （400,700,1000s/mm^2 ）. Results： The SNR of intra-orbital tumor on DWI （b= 400s/mm^2 , 700s/mm^2 , 1000s/mm^2 ） was 85.10±48.90,61.46±37.00,42.92±25.53 respectively （Х^2= 125. 654,P=0. 000）,with significant statistic differences. The CNR between the mass and white matter of contra-lateral temporal lobe with different b values was 28.36 ± 26.67, 20.11± 17.19,16.69±15.29 respectively （Х^2= 14. 519,P=0. 000） ,with significant statistic differences. The ADC values were （1.42±0.44）×10^-3mm^2/s,（1.25±0.43）×10^-3mm^2/sand （1.16±0.40））×10^-3mm^2/swith b=400s/mm^2,700s/mm^2 and 1000s/mm^2,respectively （F=7.932,P 0.000）,with significant statistic differences. The ADCR was （1.47±0.45）, （1.39±0.46） and （1.37±0.46） withb=400s/mm^2,700s/mm^2 and 1000s/mm^2,respectively（F=1.199,P=0.303）,with no statistic difference. Conclusion：The optimal b value in demonstrating orbital mass on DWI was 700s/mm^2.