Three-Dimensional Sheath Inked Rapid Acquisition with Refocused Echoes Imaging (SHINKEI) MRI for Delineating the Intraparotid Facial Nerve Branches and Their Anatomical Relationship with Parotid Tumors

Abstract

Background: Accurate imaging of the anatomical relationship between the intraparotid facial nerve branches and parotid tumor can be helpful for surgical planning and effective protection of the facial nerve during surgery. Three-dimensional sheath inked rapid acquisition with refocused echoes imaging (3D-SHINKEI) is a new MRI sequence with a high tissue contrast resolution, which has been used for imaging the peripheral nerves in several organs. Objectives: To evaluate the value of 3D-SHINKEI sequence in representing the intraparotid facial nerve branches and their anatomical relationship with neoplasms of the parotid gland. Patients and Methods: Thirty-six patients with parotid tumors underwent MRI with 3D-SHINKEI and 3D-T2-fast field echo (3D-T2-FFE) sequences in the coronal plane. The contrast-to-noise ratios (CNRs) and signal intensity ratios (SIRs) of the facial nerves in the two sequences were compared. The relationship between the intraparotid facial nerve branches and parotid tumor was also analyzed in 36 patients, and the results were compared with the intraoperative anatomy and postoperative pathological findings. Results: The image quality score of the 3D-SHINKEI sequence for anatomical representation of the intraparotid facial nerve branches was significantly higher than that of the 3D-T2-FFE sequence (Z = −6.197, P < 0.01). The SIRs and CNRs of the facial nerves were significantly higher in the SHINKEI images as compared to the 3D-T2-FFE images (t = 10.772, P < 0.01 and t = 11.586, P < 0.01, respectively). The delineation accuracy of the anatomy of the main trunk of the facial nerve and its first-level branches and their relationship with tumors was significantly higher with the 3D-SHINKEI sequence than with the 3D-T2-FFE sequence (P < 0.01). Besides, the relationship between parotid tumors and the main trunk of the facial nerve and its first-level branches was classified into six types. Conclusion: A high-resolution 3D-SHINKEI sequence could accurately represent the relationship between the intraparotid facial nerve branches and parotid gland neoplasms. It was also found to be more accurate than the 3D-T2-FFE sequence.