Guidance Of Temporal Bone Thin Slice Scanning By 256-ranked Spiral CT In Tympanoplasty

Objective:Through carrying on the temporal bone axis high resolution CT (HRCT) and coronal multiplanar reformation (MPR) for patients with otitis media with cholesteatom by 256-slice spiral CT, compare the preoperative imaging analysis with actual situation of operation, to assess their coincidence, and then discuss the guidance of temporal bone thin slice scanning by 256-slice spiral CT in selecting surgical procedures and route of mastoidectomy and tympanoplasty type.Methods:We observed 60 patients (60 ears) with otitis media with cholesteatoma, who were treated with mastoidectomy with tympanoplasty and diagnosed by otology examination in our department from October 2008 to December 2010. All patients were carried on the temporal bone axis HRCT by 256-slice spiral CT. And the coronal images were obtained by MPR. We read the axial images of temporal bone HRCT and coronal images of MPR, and observed middle ear lesions carefully before the surery, focusing on not only scutum tympanicum, antrotympanic roof, facial nerve canal, ductus semicirculares, sigmoid sinus bone wall and posterior wall of external acoustic meatus, but also integrity of ossicular chain, joints of auditory ossicles and relationship with the surrounding lesions. We instituted surgical procedures and route of mastoidectomy and tympanoplasty type according to imaging diagnosis. And then we compared the analysis of axial images of temporal bone HRCT and coronal images of MPR with the actual situation of operation, with the gold standard—the operative findings, using Kappa consistency test, to assess the accordance between temporal bone HRCT combined with MPR diagnosis and intraoperative findings.Results:1. Comparing the accordance of the middle ear bone destruction by temporal bone HRCT combined with MPR: Compared with the actual situation of operation, the temporal bone HRCT combined with MPR had high conformity level in diagnosising the distruction of sigmoid sinus bone wall, scutum tympanicum, posterior wall of external acoustic meatus, ductus semicirculares, antrotympanic roof and facial nerve canal. The coincidence rate separately was 100%, 96.4%, 93.8%, 87.5%, 86.7% and 86.7%. Kappa values were greater than 0.75 by Kappa consistency test, indicating that temporal bone HRCT combined with MPR have higher accordance compared with intraoperative findings in diagonosising middle ear bone destruction.2. Comparing the accordance of ossicular chain display by temporal bone HRCT combined with MPR: The temporal bone HRCT combined with MPR can clearly show the destruction of incus short legs, incudomalleolar joint, head of malleus, corpus incudis and handle of malleus. Compared with the intraoperative findings, the coincidence rate separately was 96.9%, 96.4%, 95%, 92.9% and 90.9%. Kappa values were greater than 0.75. It showed that temporal bone HRCT combined with MPR and intraoperative findings have higher accordance to diagnosing the structures above. The coincidence rate of incus long legs, stapes and incudostapedial joint separately was 97.7%, 95.2% and 89.4%. Kappa values were in the 0.4-0.75, showing that temporal bone HRCT combined with MPR has accordance compared with intraoperative findings in diagnosising the three structures.3. Comparing the accordance of judging surgical procedures and route of mastoidectomy and tympanoplasty type by temporal bone HRCT combined with MPR: From reading temporal bone HRCT combined with MPR, the coincidence rate of selecting surgical route (epitympanic route and cribriform area route) separately was 95.2% and 97.5%. Kappa values were greater than 0.75, indicating that temporal bone HRCT combined with MPR can judge surgical surgical route very accurately. The coincidence rate of selecting surgical procedures of mastoidectomy (open mastoidectomy and intact canal wall mastoidectomy) separately was 92% and 71.4%, the coincidence rate of selecting tympanoplasty type (typeⅢa and typeⅢb) separately was 97.6% and 95%. Kappa values were in the 0.4-0.75, which indicate that temporal bone HRCT combined with MPR can accurately judge surgical procedures of mastoidectomy and tympanoplasty type.Conclusions:1. Combining temporal bone axial images of HRCT and coronal images of MPR by 256-slice spiral CT, can clearly show middle ear bone (including sigmoid sinus bone wall, scutum tympanicum, posterior wall of external acoustic meatus, ductus semicirculares, antrotympanic roof and facial nerve canal) destruction, the fine structure and connection of ossicular chain, the extent and scope of lesions.2. Combining temporal bone axial images of HRCT and coronal images of MPR by 256-slice spiral CT provides a reliable basis for the diagnosis of otitis media with cholesteatoma, as well as is significant to select surgical procedures and route of mastoidectomy and the type of tympanoplasty.