Curved planar reformation of the facial nerve canal with multislice spiral CT / 中华放射学杂志

ABSTRACT

Objective To study the methods of delineating the whole length of bilateral facial nerve canals in one image. Methods High resolution computed tomography of the temporal bone was performed in 60 cases (120 ears) by Philips Mx8000 multislice spiral CT. Parameters 120 kV, 200～250 mAs, Collimation 0.5 mm, Pitch 0.875, Scan time 0.75 s/ring, Matrix 512?512, Reformation interval 0 1～0.2 mm, Reformation matrix 1 024?1 024. Curved planar reformation(CPR)images were prepared along the facial nerve canal in the axial plane, and in the coronal and sagittal plane of multiplanar reconstruction(MPR). In the axial plane, a reference line was traced following the facial nerve canal from the internal auditory meatus, through the labyrinthine segment, the tympanic segment up to the second genu and mastoid segment. Another two protocols of curved reformatting were adopted (a) a curved line was delineated along the facial nerve canal on the coronal reformatted image; (b) a curved line was drawn along the facial nerve canal on the sagittal reformatted image. The reference lines were carefully revised and moved exactly to the center of each segment of the facial nerve canal. For displaying bilateral facial nerve canals in one image, one reference line should be drawn along bilateral facial nerve canals. Results In 56 cases of 60 CPR, images in the axial plane, and coronal plane of MPR could show the unilateral or bilateral facial nerve canals clearly. The result of CPR of bilateral facial nerve canals in sagittal plane of MPR was unsatisfactory. The image on one side was often clear, but just part of it could be showed on the other. So the left and right facial nerve canals should be reformed separately. In 4 cases, CPR was unsatisfactory. In 1 of them the labyrinthine and tympanic segment had breaks because the patient′s head shook during the scanning. In 3 of them the facial nerve canals were showed unsatisfactorily because of the inexact position of head during the scanning. Conclusion The unilateral or bilateral facial nerve canals could be showed in one image by CPR. Combining the images of the high resolution CT in axial scan and MPR of the temporal bone, it would be helpful in the diagnosis of the lesions of facial nerve canal.