Diffusion-weighted MR neurography of the tibial nerve and the common peroneal nerve with different motion probing gradients / 中华放射学杂志

ABSTRACT

Objective To compare the image quality of diffusion-weighted MR neurography (DW-MRN) of the tibial nerve and the common peroneal nerve prospectively using different motion probing gradients (MPGs).Methods A total of 21 healthy volunteers underwent DW-MRN at the knee (unilateral imaging) on a 3.0 T magnetic resonance system with unidirectional MPGs.The protocol included anteriorposterior unidirectional,right-left unidirectional,three-directional and six-directional MPGs.The apparent SNR and CNR of tibial nerve and common peroneal nerve were calculated.Three-dimensional MIP images of the nerves were evaluated blindly by two radiologists using a four-point grading scale on basis of entirety depiction and the signal intensity.Significance was determined by using Friedman and paired Wilcoxon tests.Results The SNR of tibial nerves on DW-MRN with anterior-posterior,right-left,three directional and six directional MPGs were 4.17 (2.70-5.65),4.35 (0.47-4.69),3.46 (2.27-4.62) and 3.30 (2.06-4.43),respectively.CNR were 0.61 (0.46-0.70),0.63 (0.36-0.73),0.55 (0.39-0.64) and 0.53(0.35-0.63),respectively.The scores of tibial nerve image quality were 4.0 (2.0-4.0),4.0 (3.0-4.0),2.5 (2.0-3.5),2.0 (1.0-2.5),respectively.Interobserver agreement was good and the Kappa value was 0.69 (P ＜ 0.05).The SNR of the common peroneal nerves on DW-MRN with anteriorposterior,right-left,three directional and six directional MPGs were 3.05 (2.30-4.20),3.05 (2.26-4.34),2.72 (1.84-13.80) and 2.68 (1.87-3.67),respectively.CNR were 0.51 (0.39-0.62),0.51 (0.39-0.63),0.46(0.30-0.86) and 0.46(0.30-0.57),respectively.The scores of the common peroneal nerve image quality were 3.5 (2.0-4.0),4.0 (2.0-4.0),2.0 (1.0-3.0) and 2.0 (1.0-2.5),respectively.Interobserver agreement was good and the Kappa value was 0.70(P ＜0.05).For SNR,CNR and nerve image quality of the tibial nerves and the common peroneal nerves,there were significant differences among different MPGs (x2 =215.01,215.01,60.49 and 182.82,182.82,60.22,respectively,P ＜ 0.05).SNR,CNR and nerve image quality of the tibial nerves and the common peroneal nerves on DW-MRN with unidirectional MPGs were better than those with three-directional and sixdirectional MPGs (Z =-6.90-4.03,P ＜ 0.05).The SNR and CNR of the tibial nerves on DW-MRN with right-left direction were better than those with anterior-posterior unidirectional MPGs (Z =-3.53,-3.41,P ＜ 0.05),but there was no significant difference of image quality between right-left and anteriorposterior directional MPGs (Z =-0.58,P ＞ 0.05).DW-MRN of the tibial nerves with three-directional MPGs was better than that with six-directional MPGs (Z =-3.00,-2.80,-3.92,P ＜ 0.05).There were no significant differences between right-left and anterior-posterior unidirectional MPGs,or between three-directional and six-directional MPGs of common peroneal nerves (Z =-1.94--0.31,P ＞ 0.05).Conclusions DW-MRN has capability to provide three-dimensional visualization of the tibial and common peroneal nerves,and the image quality with unidirectional MPGs is better than that with three or six directional MPGs.