Magnetic resonance elastography for noninvasive evaluation of parotid tumors: a feasibility study.

PURPOSE: Fine-needle aspiration cytology (FNAC), the current standard for parotid tumor evaluation, is minimally invasive and has limited sensitivity. Magnetic resonance elastography (MRE) is a noninvasive technique that quantifies tissue biomechanics and may provide complementary quantitative information for tumor characterization. This study evaluated the feasibility of parotid MRE using a custom driver.

METHODS

In this exploratory feasibility study, fourteen patients (7F, 7 M; mean age 59.1 ± 13.1 years) with parotid tumors underwent preoperative 80-Hz MRE on a 1.5 T scanner. Vibrations were applied via a custom bilateral facial driver, and wave propagation was acquired with a motion-sensitive 2D GRE sequence. Stiffness maps were reconstructed using multimodel direct inversion. Tumor stiffness was measured from ROIs; contralateral healthy gland stiffness was assessed in nine patients (in the remaining five patients, both parotids showed pathology). Postoperative histopathology confirmed pleomorphic adenomas (n = 6), Warthin tumors (n = 6), lymphoepithelial lesions (n = 2), and one mucoepidermoid carcinoma. Tumor-healthy gland stiffness was compared with the Wilcoxon signed-rank test; correlations with size were assessed using Spearman's rho.

RESULTS

MRE succeeded in all cases, providing interpretable stiffness maps.Pleomorphic adenomas (3.72 ± 1.42 kPa) and mucoepidermoid carcinoma (3.41 kPa) were stiffer than Warthin tumors (2.54 ± 0.70 kPa) and lymphoepithelial lesions (2.78 ± 0.33 kPa). Tumor stiffness exceeded healthy gland values (1.96 ± 0.44 kPa; p = 0.02),though overlap was observed. No correlation with tumor size was found(ρ = 0.20, p = 0.47).

CONCLUSIONS

Parotid MRE with a custom driver is feasible and provides quantitative stiffness maps. While stiffness varied across tumor types, overlap with healthy tissue and between tumors limits standalone diagnostic accuracy. Larger studies and advanced MRE approaches are warranted to refine its role as a source of complementary quantitative information in the preoperative evaluation of parotid tumors.