Application of diffusion weighted imaging based on intravoxel incoherent motion model in diagnosis of compressed lumbosacral nerve roots

Objective To explore the feasibility of diffusion weighted imaging(DWI) based on intravoxel incoherent motion(IVIM) in the diagnosis of compressed lumbosacral nerve roots. Methods The prospective study was conducted. A total of 60 images were collected and analyzed in this study, 30 of which were from the observation group. Routine lumbar MR sequences, 3D-fiesta sequences and IVIM-DWI sequences of patients with lumbar disc herniation caused nerve root compression in Affiliated Hospital of Taishan Medical College from April 2017 to October 2017. Thirty healthy volunteers were selected as the control group, their ages and sexes matched with those of observation group. At GE ADW 4.6 workstation, MADC software package was used to measure the slow diffusion coefficient(D), fast diffusion coefficient(D*), apparent diffusion coefficient(ADC), fraction of fast ADC(f) values of bilateral L4, L5 and S1 ganglia of control group, and the D, D*, f and ADC values of compressed side and opposite nerve roots of observation group were measured. The measured values of left and right ganglion and different ganglion of the same segment in control group were compared. The measured values of the compressed side nerve roots in the observation group were compared with the measured values of the normal nerve roots in the opposite side, to see whether the differences between the values were statistically significant. Results The D values of nerve roots of L4, L5 and S1 in control group were (0.603±0.064)×10-3 mm2/s, (0.624±0.079)×10-3 mm2/s, (0.628±0.088) ×10-3 mm2/s, respectively. The D* values were (3.815±0.541) ×10-3, (3.862±0.414) ×10-3, (3.915±0.611) ×10-3, respectively, in mm2/s. The f values were 0.454%±0.076%, 0.484%±0.101% and 0.445%±0.094%, respectively. The ADC values were (0.934±0.085) ×10-3, (0.945±0.051) ×10-3, (0.953±0.064) ×10-3, respectively, in mm2/s.The values of D, D*, f and ADC on the compression side of nerve root in observation group were (0.669±0.081) ×10-3 mm2/s, (3.852±0.776)×10-3 mm2/s, 0.528%±0.115%, (1.096±0.087) ×10-3 mm2/s, and the values of D, D*, f and ADC on the healthy side were (0.617±0.080) ×10-3 mm2/s, (3.961±0.684) ×10-3 mm2/s, 0.479%±0.083%, (0.938±0.074)×10-3 mm2/s, respectively. The values of D, D*, f and ADC measured by the left and right ganglion of the same segment and the ganglion of different segments were not statistically significant(all P values>0.05). Compared with the normal nerve roots on the opposite side, the values of D and ADC were both increased, the difference was statistically significant(all P values 0.05). ROC curve was drawn and analyzed, and D value was highly effective in diagnosing nerve root compression, followed by ADC value, The AUC of D value was 0.923(95%CI 0.803-0.987), and the AUC of ADC value was 0.895 (95%CI 0.865-0.999). Conclusions The diffusion-weighted imaging technique of IVIM model can be used for lumbosacral nerve root examination.Compared with the diffusion-weighted imaging technique of single exponential model, it can reflect the pathological changes after nerve root compression in more details and accurately. Key words: Magnetic resonance imaging; Radiculopathy; Lumbosacral nerve root; Intravoxel incoherent motion; Diffusion weighted imaging