改良敏感编码技术在肝脏MR扩散加权成像中对肝细胞癌小病灶的影响

The comparative study of diffusion-weighted MR imaging with modified sensitivity encoding technique for small hepatocellular carcinoma lesions

目的评价在肝脏 MR 扩散加权成像(DWI)中应用改良敏感编码(mSENSE)技术是否有助于提高图像质量及对肝细胞癌(HCC)小病灶的表观扩散系数(ADC)值测量有无影响。方法分别用常规 DWI 和 mSENSE-DWI 对32例47个 HCC 小病灶行单次屏气自旋回波-平面回波(sE-EPI)DWI,扩散梯度因子(b)值为300、500、800 s/mm^2。对图像质量、对比噪声比(CNR)、病灶的ADC 值进行观测和比较,运用配对 Wilcoxon signed rank 和 Friedman 检验进行统计学分析。结果图像质量 DWI 组 b=300 s/mm^2时图像评分2级5例、3级24例、4级3例,b=500 s/mm^2时2级9例、3级22例、4级1例,b=800 s/mm^2时1级2例、2级24例、3级6例;mSENSE-DWI 组 b=300 s/mm^2时3级4例、4级25例、5级3例,b=500 s/mm^2时3级10例、4级20例、5级2例,b=800 s/mm^2时2级7例、3级23例、4级2例。同一 b 值条件下,mSENSE-DWI 组的图像质量均优于常规 DWI 组(3个不同 b 值组的 Z 分别为-5.578、-5.488、-4.796,P 值均<0.01)。DWI 组病灶的中位 ADC 值在 b=300、500、800 s/mm^2时分别为(1.578×10^(-3))、(1.390×10^(-3))、(1.173×10^(-3))mm^2/s,mSENSE-DWI 组病灶的中位 ADC 值在3个 b 值下分别为(1.381×10^(-3))、(1.242×10^(-3))、(1.136×10^(-3))mm^2/s,在大 b 值条件下(500、800 s/mm^2),2组所测得的病灶 ADC 值差异无统计学意义(Z 值分别为-0.873、-0.862,P 值分别为0.383、0.388)。结论在肝脏 DWI 中应用 mSENSE 技术可获得高质量的图像,同时对 HCC 小病灶的 ADC 值测量没有影响。

Objective To prospectively evaluate whether DWI with mSENSE （mSENSE-DWI） can help to improve image quality and affect the calculation of lesion＇s ADC, compared with DWI with conventional phase encoding （ conventional DWI） in patients with small HCC lesions. Methods Thirty-two patients with 47 small HCC lesions underwent single-shot spin-echo echo-planar （SE-EPI） DWI with conventional phase encoding and mSENSE. Three b values of 300, 500 and 800 s/mm^2 were used. Image quality and CNR between conventional DWI and mSENSE-DWI group were compared with different b value. Lesion＇s ADC were also calculated and compared. Matched-pairs Wilcoxon signed rank test and Friedman test were used to test statistical significance. Results The image quality was assessed with a five-point scale. For conventional DWI group, image quality score of 2 was assigned in 5 cases, score of 3 in 24 cases, score of 4 in remaining 3 cases with b = 300 s/mm^2, score of 2 in 9 cases, score of 3 in 22 cases, score of 4 in remaining 1 cases with b = 500 s/mm^2, score of 1 in 2 cases, score of 2 in 24 cases, score of 3 in remaining 6 cases with b = 800 s/mm^2. For mSENSE-DWI group, image quality score of 3 was assigned in 4 cases,score of 4 in 25 cases,score of 5 in 3 cases with b =300 s/mm^2 ,score of 3 in 10 cases,score of 4 in 20 cases, score of 5 in remaining 2 cases with b = 500 s/mm^2, score of 2 in 7 cases, score of 3 in 23 cases, score of 4 in remaining 2 cases with b = 800 s/mm^2. Higher image quality scores were achieved at mSENSE- DWI group than conventional DWI group（ Z = - 5. 578, - 5. 488, - 4. 796 respectively, P 〈 0. 01 ） with the same b value. The lesion＇s median ADC value was respectively （1. 578 ×10^-3）, （1. 390 ×10^-3）, （1. 173 ×10^-3）mm^2/s for b =300,500,800 s/mm^2 in conventional DWI group and （ 1. 381 ×10^-3 ） , （ 1. 242 ×10^-3 ）, （ 1. 136 × 10^-3 ） mm^2/s in mSENSE-DWI group. There was no significant difference in the lesion＇s ADC between mSENSE-DWI group and conventional DWI group with high b value （500 and 800 s/mm^2, Z = - 0. 873, - 0. 862 ; P = 0. 383, 0. 388, respectively）. Conclusion Higher quality images can be achieved in liver DWI with mSENSE without compromising small HCC lesion＇s ADC calculation.