3 T MR 3D fast imaging employing steady state acquisition demonstrating branches of intraparotid facial nerve, parotid duct, and relation with parotid tumors

Abstract

Objective To investigate the usefulness of 3 T MRI 3D-FIESTA in the evaluation of the intraparotid components of the facial nerve and parotid duct, and compare them with surgical findings. Methods Twenty-two cases with parotid benign tumors were scanned with conventional and 3D-FIESTA sequences on 3 T MRI scanner. Postprocessed multiplanar images were obtained with the workstation. Parotid ducts and facial nerves and tumors were identified on these images. The relationship of the tumors to the facial nerves and Parotid ducts was confirmed at surgery. Results Various types of parotid benign tumors had their characteristics on 3 T MR imaging. Parotid benign tumors mainly showed hypo-intensity on T_1WI in 21 cases, and hyper-intensity on T_2WI in 22 cases. But on 3D-FIESTA images, they appeared hypo-intensity (10 cases) or high intensity (12 cases) due to different types. Facial nerves in parotid appeared as linear structures with hypo-inteusity. The indication of the main trunks were 16 and 18 cases for T_1WI and T_2WI images, while on 3D-FIESTA images, the main trunks and cervicofacial and temporofacial divisions of the facial nerves were found in 22, 21,22 cases. Parotid ducts appeared as structures with hypo-intensity on T_1WI and hyper-intensity on multiplanar images (14, 20, 22 cases). Compared with surgical results, the main trunks of the facial nerve were correctly showed by 3D-FIESTA images in 20 cases. However, in 2 cases they were not located in the operation because of shifting. Conclusion 3 T MR 3D-FIESTA imaging could depict the extracranial facial nerve and the parotid duct in the parotid gland, which is useful for preoperative evaluation of parotid gland tumors. Key words: Parotid neoplasms; Facial nerves; Magnetic resonance imaging