Three-dimensional T2-weighted fast field echo imaging in the determination of the relationship between the intraparotid facial nerve and parotid tumors.

BACKGROUND

To assess the performance of three-dimensional T2-weighted fast field echo imaging (3D-T2-FFE) in the visualization of the intraparotid facial nerve (IFN) and localization of tumors.

METHODS

Magnetic resonance imaging data from sixty-four patients who underwent 3D-T2-FFE (Time of repetition 8.30 ms, Time of echo 4.10 ms, Voxel 0.65 × 0.65 × 1.00 mm, Field of view 220 × 220 × 65 mm, Matrix 340 × 339 × 130, Number of signal average 2, Flip angle 30°) were retrospectively enrolled. Finally, 64 cases of tumors were included (including 55 benign tumors and 9 malignant tumors). The identification certainty of IFN on 3D-T2-FFE was scored with an arbitrary scale of 0-3. The parotid gland was divided into superior and inferior parts, with the level of the earlobe (approximately at the level of the external auditory canal). The tumor location was categorized as deep or superficial directly on 3D-T2-FFE images and indirectly by the facial nerve line (FNL) and the retromandibular vein line (RMVL). Surgical localization was considered the reference standard. The accuracy, sensitivity, and specificity of each method for localizing parotid lesions were compared using the McNemar test.

RESULTS

The accuracy, sensitivity, specificity, positive predictive value, and negative predictive value for deep lobe lesions in the superior part of the parotid gland using the direct method were 97.8%, 92.3%, 100.0%, 100.0%, and 96.9%, respectively. The 3D-T2-FFE method showed significantly higher sensitivity and specificity than those of FNL (p < 0.05) in the superior part of the parotid gland, and there was no significant difference in sensitivity, specificity, and accuracy between 3D-T2-FFE and RMVL (p > 0.05). The relationship between the tumor and the main trunk of the IFN was correctly predicted in 93.3% and 100% of 3D-T2-FFE images in the superior and inferior parts of the parotid glands, respectively.

CONCLUSIONS

3D-T2-FFE can provide detailed morphological information on the nerve in relation to adjacent parotid gland structures and tumors before surgery.