Abstract: To study the action of multiplanar reconstruction by high resolution CT (HRCT) in showing the full length of semicircular canal. Methods： HRCT was performed in 86 patients (79 normal ears and 93 ears with disease) with chronic otitis media (COM). The imagings of the full canal at axial, cranial and sMPR level were taken before treatment. Result： Of normal ears, 86.7% of the full lateral semicircular canal could be shown at the axial level, and the superior and posterior semicircular canal could not be fully displayed; the lateral, superior and posterior semicircular canal could not be completely displayed at the cranial level; 92.45％ of the superior， all the lateral， 97.58％ of the posterior semicircular canal could be fully displayed at sMPR level. Of the ears with disease, labyrinthine fistula of lateral semicircular canal was found in 5 ears at the axial and 4 ears at the cranial level； labyrinthine fistula of superior semicircular canal was found in 1 ears at both the axial and the cranial level; labyrinthine fistula of lateral and superior semicircular canal were respectively found in 6 and 2 ears at the sMPR level, which corresponded with the operation findings. Conclusions： sMPR can completely display the semicircular canal and definitely justify the position of labyrinthine fistula.

Key words: Semicircular canals, Tomography, Xray computed, Otitis media, labyrinthine fistula