Differentiation of parotid gland tumors using intravoxel incoherent motion magnetic resonance imaging integrated with susceptibility-weighted imaging

Purpose To evaluate the value of combining susceptibility-weighted imaging (SWI) with intravoxel incoherent motion (IVIM) magnetic resonance (MR) imaging in the characterisation of parotid gland tumors. Materials and Methods Seventy parotid gland tumors of 66 patients who had undergone SWI and IVIM were retrospectively reviewed. The true diffusion coefficient (D), pseudo-diffusion coefficient (D*), and fraction of perfusion (f) values calculated from IVIM imaging and the intra-tumoural susceptibility signal (ITSS) obtained from SWI were assessed and compared using independent Student’s t , Mann–Whitney U , Chi-square, or Fisher’s exact tests. Receiver operating characteristic (ROC) curve analysis was conducted to evaluate the diagnostic performance for the classification of parotid gland tumors. Results The D values of malignant parotid gland tumors (MT) were significantly lower than those of benign parotid gland tumors (BT) ( P <0.001). The ITSS of MT was significantly higher than that of BT ( P= 0.009). Subgroup analyses revealed that the D values of MT and Warthin tumors (WT) were significantly lower than those of pleomorphic adenoma (PA) ( P =0.001 and P =0.014, respectively) and basal cell adenoma (BCA) ( P =0.002 and P =0.005, respectively); however, the f values of MT and WT were significantly higher than those of BCA ( P =0.028 and P =0.04, respectively). The ITSS of MT was significantly higher than those of WT and PA ( P =0.038 and P =0.011, respectively). Integration with ITSS enhanced the diagnostic performance of D in differentiating MT from BT (area under the curve [AUC]0.858 vs 0.828) and PA (AUC 0.893 vs 0.852). Compared with the application of a single parameter (D or f), the application of the combination model enhanced the diagnostic performance for differentiating MT from BCA (AUC 0.950 vs 0.911 vs 0.790). The D* values exhibited no significant difference in terms of discriminating between the parotid gland tumors. Conclusions IVIM plays a critical role in discriminating MT from benign parotid tumors and characterizing the subgroups of benign parotid tumors. SWI offers additional diagnostic differentiation information for IVIM and servers a supplementary imaging marker for the characterization of parotid gland tumors.