FP03-1. EVALUATION OF OTOSCLEROTIC LESIONS BY HIGH-RESOLUTION CT USING MULTIPLANAR RECONSTRUCTION

Nozomu Mori, Seiko Fujiwara, Takenori Miyashita, Hiroshi Hoshikawa, Yoshihiro Toyama (Kagawa University, Japan)

 

Objectives: To examine the value of multislice computed tomography (MSCT) using multiplanar reconstruction (MPR) in the detection of the otosclerotic lesions.

Materials and Methods:  Twenty-six ears of 13 patients (1 male and 12 females) ranging 36 to 70 years old with a mean age of 51.4 years underwent MSCT with MPR image. They were diagnosed clinically as the otosclerosis. Nine ears of 8 patients were operated on. MSCT imaging was performed by Aquilion^® (Toshiba Medical Systems, Tokyo, Japan).  The axial spiral scans were obtained in the following parameters: a helical pitch of 3.0, 0.5-mm slice thickness, 0.2-mm reconstruction interval, high-resolution reconstruction algorithm (FC 80), 512 ×512 matrix, 100-mm field of view, a tube current of 300 mA, a tube voltage of 120 kV, a window width of 4000 and a window level of 400. Dosimetric measurements using a head calibration phantom were performed for evaluating the radiation exposure of the lenses. The acquired high-resolution data were transferred to a workstation (ALATO VIEW, Toshiba). The MPR image was created at the planes parallel and vertical to the stapedial crus and analyzed on the monitor screen by the radiologist (Y.T.)

Results: The analysis of MPR images showed no abnormal findings in 5 of all 26 ears (19%) and abnormal findings in 21 ears (81%), 5 of which had a finding of demineralization located at the region anterior to the oval window corresponding to the fissula antefenestram. Sixteen ears (62%) showed the demineralization extending into the oval window from the region of the fissula antefenestram.  The demineralization around the cochlea was observed in 2 ears (8%). Two of 5 ears (40%) with an average air-bone gap of less than 10 dBHL at 500 Hz to 2000Hz had abnormal findings, whereas 13 of 15 ears (87%) with air-bone gap of more than 10 dBHL had abnormal findings (p<0.05).

Conclusion:  MSCT with MPR image is found to detect the lesions in otosclerosis more frequently than the conventional axial CT. Abnormal MPR findings were observed at a significantly higher rate in the ears with worse hearing loss.