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

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/mm² 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/mm², score of 2 in 9 cases, score of 3 in 22 cases, score of 4 in remaining 1 cases with b=500 s/mm², score of 1 in 2 cases, score of 2 in 24 cases, score of 3 in remaining 6 cases with b=800 s/mm². 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/mm², score of 3 in 10 cases, score of 4 in 20 cases, score of 5 in remaining 2 cases with b = 500 s/mm² , score of 2 in 7 cases, score of 3 in 23 cases, score of 4 in remaining 2 cases with b = 800 s/mm². 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 x 10^-3), (1.390 x 10^-3), (1.173 x 10^-3)mm²/s for b =300,500,800 s/mm² in conventional DWI group and (1.381 x 10^-3), (1.242 x 10^-3), (1.136 x 10^-3) mm²/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/mm², 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. (authors)