The value of diffusion kurtosis imaging and dynamic contrastenhanced magnetic resonance imaging in the differential diagnosis of parotid gland tumors

Background: Parotid gland tumors (PGTs) are the most common benign tumors of salivary gland tumors. However, the diagnostic value of relative values of dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) and diffusion kurtosis imaging (DKI) parameters for PGTs has not been extensively studied. Therefore, this study aimed to evaluate the diagnostic performance of combined DKI and DCE-MRI for differentiating PGTs by introducing the concept of relative value. Methods: The DCE-MRI and DKI imaging data of 142 patients with PGTs between June 2018 and August 2022 were collected. Patients were divided into four groups by histopathology: malignant tumors (MTs), pleomorphic adenomas (PAs), Warthin tumors (WTs), and basal cell adenomas (BCAs). All MRI examinations were conducted using a 3 T MRI scanner with a 20-channel head and neck coil. Quantitative parameters of DCE-MRI and DKI and their relative values were determined. Kruskal-Wallis H test, posthoc test with Bonferroni correction, one-way analysis of variance (ANOVA) and post-hoc test with least significant difference (LSD) method, and the receiver operating characteristic (ROC) curve were used for statistical analysis. Statistical significance was set at P<0.05. Results: Only the combination of DKI and DCE-MRI parameters could reliably distinguish BCAs from other PGTs. PAs demonstrated the lowest transfer constant from plasma to extravascular extracellular space (K-trans) value [0.09 (0.06, 0.20) min(-1)], relative K-trans (rK(trans)) [-0.24 (-0.64, 1.00)], rate constant from extravascular extracellular space to plasma (Kep) ep ) value [0.32 (0.22, 0.53) min(-1)], relative K-ep (rK(ep)) [0.32 (0.22, 0.53) min(-1)], and initial area under curve (iAUC) value [0.15 (0.09, 0.26) mmol<middle dot>s/kg] compared with WTs, BCAs, and MTs (all P<0.05). The K trans values for MTs were substantially lower [0.17 (0.10, 0.31) min(-1)] than those for WTs (P=0.01). The K-ep values for MTs [0.71 (0.52, 1.28) min(-1)] were substantially lower (all P<0.05) than those for WTs and BCAs. PAs and BCAs had higher diffusion coefficient (D) values and lower diffusion kurtosis (K) values and relative K (rK) values than MTs and WTs. However, the D and K values did not differ significantly even in their relative values of PAs and BCAs (all P>0.05). By using logistic regression, the combination of K value and rKep ep value further enhanced their discriminatory power between PAs and WTs [area under the ROC curve (AUC), 0.986], the combination of K and rKep ep value further enhanced their discriminatory power between PAs and MTs (AUC, 0.915), and the combination of D and K ep value further enhanced their discriminatory power between BCAs and MTs (AUC, 0.909). Conclusions: DKI and DCE-MRI can be used to differentiate PGTs quantitatively and can complement each other. The combined use of DKI and DCE-MRI parameters can improve the diagnostic accuracy of distinguishing PGTs.