Intravoxel incoherent motion diffusion-weighted imaging in evaluating preoperative staging of esophageal squamous cell carcinoma : Evaluation of preoperative stage of primary tumour and prediction of lymph node metastases from esophageal cancer using IVIM: a prospective study.

Background: The aim of this research is to prospectively investigate the diagnostic performance of intravoxel incoherent motion (IVIM) using the integrated slice-specific dynamic shimming (iShim) technique in staging primary esophageal squamous cell carcinoma (ESCC) and predicting presence of lymph node metastases from ESCC.

Methods: Sixty-three patients with ESCC were prospectively enrolled from April 2016 to April 2019. MR and IVIM using iShim technique (b = 0, 25, 50, 75, 100, 200, 400, 600, 800 s/mm²) were performed on 3.0T MRI system before operation. Primary tumour apparent diffusion coefficient (ADC) and IVIM parameters, including true diffusion coefficient (D), pseudodiffusion coefficient (D^*), pseudodiffusion fraction (f) were measured by two independent radiologists. The differences in D, D^*, f and ADC values of different T and N stages were assessed. Intraclass correlation coefficients (ICCs) were calculated to evaluate the interobserver agreement between two readers. The diagnostic performances of D, D^*, f and ADC values in primary tumour staging and prediction of lymph node metastasis of ESCC were determined using receiver operating characteristic (ROC) curve analysis.

Results: The inter-observer consensus was excellent for IVIM parameters and ADC (D: ICC = 0.922; D^*: ICC = 0.892; f: ICC = 0.948; ADC: ICC = 0.958). The ADC, D, D^* and f values of group T1 + T2 were significantly higher than those of group T3 + T4a [ADC: (2.55 ± 0.43) ×10^- 3 mm²/s vs. (2.27 ± 0.40) ×10^- 3 mm²/s, t = 2.670, P = 0.010; D: (1.82 ± 0.39) ×10^- 3 mm²/s vs. (1.53 ± 0.33) ×10^- 3 mm²/s, t = 3.189, P = 0.002; D^*: 46.45 (30.30,55.53) ×10^- 3 mm²/s vs. 32.30 (18.60,40.95) ×10^- 3 mm²/s, z=-2.408, P = 0.016; f: 0.45 ± 0.12 vs. 0.37 ± 0.12, t = 2.538, P = 0.014]. The ADC, D and f values of the lymph nodes-positive (N+) group were significantly lower than those of lymph nodes-negative (N0) group [ADC: (2.10 ± 0.33) ×10^- 3 mm²/s vs. (2.55 ± 0.40) ×10^- 3 mm²/s, t=-4.564, P < 0.001; D: (1.44 ± 0.30) ×10^- 3 mm²/s vs. (1.78 ± 0.37) ×10^- 3 mm²/s, t=-3.726, P < 0.001; f: 0.32 ± 0.10 vs. 0.45 ± 0.11, t=-4.524, P < 0.001]. The combination of D, D^* and f yielded the highest area under the curve (AUC) (0.814) in distinguishing group T1 + T2 from group T3 + T4a. D combined with f provided the highest diagnostic performance (AUC = 0.849) in identifying group N + and group N0 of ESCC.

Conclusions: IVIM may be used as an effective functional imaging technique to evaluate preoperative stage of primary tumour and predict presence of lymph node metastases from ESCC.