Copyright @ 200 Otology & Neurotology, Inc. Unauthorized reproduction of this article is prohibited. 8 Rotating Computed Tomographic Movie for Evaluating Partially Ossified Cochlea Ken Ito, Rumi Ishida, Shotaro Karino, and Tatsuya Yamasoba Department of Otolaryngology, Faculty of Medicine, University of Tokyo, Tokyo, Japan Objective: To describe our newly devised method of viewing intracochlear ossification for the purpose of minimizing bone drilling during cochlear implantation for partially ossified cochleas and to evaluate its usefulness. Study Design: Descriptive study that compares 1) conven- tional computed tomographic (CT) films with the newly devised CT movie and 2) preoperative evaluation using the CT movie with the findings during surgery. Setting: University Hospital Patients: Four cochlear implantees with partial ossification of cochlea due to meningitis. Intervention: Diagnostic. Main Outcome Measures: Reconstruction of high-resolution CT images of the temporal bone was performed using a multi- planar reformat software. By rotating the cochlear cross plane from the round window niche in the direction of the inferior segment by 5 degrees, 72 images were obtained for 360-degree rotation, which were converted to a movie using QuickTime Pro software. The preoperative evaluation and intraoperative findings were compared. Results: The advantage of CT movie over sequential CT films was facility in understanding the 3-dimensional space in the cochlea. Evaluation of the extent of the ossified region on CT movie corresponded to the intraoperative find- ings in all 4 patients. In 1 patient, the CT movie corrected an erroneous evaluation based on conventional CT films. However, additional drilling over the extent of ossification was necessitated in another patient because of scar tissue development. Conclusion: Computed tomographic movie is considered an innovative new method for preoperative evaluation of ossified cochleas and is able to reduce human errors. However, additional drilling beyond ossified part can become necessary during sur- gery. Key Words: Cochlear implantationVCTVMeningitisV MovieVPartially ossified cochlea. Otol Neurotol 29:124Y130, 2008. Ossified cochlea in deaf patients remains a challenge to cochlear implantation, which is frequently encoun- tered in patients who become profoundly deaf because of meningitis (1Y4), although improvements in surgical technique (intact canal wall drill-out procedure) enabled placement of electrodes around the modiolus even in totally ossified cochlea (5Y8). Figure 1 demonstrates the difficulties encountered during this procedure. There have been not a few reports on cochlear ima- ging concerning cochlear implantation (9Y14), but few reports evaluated the accuracy of preoperative imaging studies. Further effort to develop more useful methods is important along with the accumulation of experience using such new methods. In our previous article, an efficient method for visua- lizing the intracochlear space using reconstructed images, 1 Bbasal turn plane[ perpendicular to modiolus and multiple Bcochlear cross planes,[ including modio- lus, was reported (15). However, this method did not escape certain disadvantages. Basal turn plane cannot discriminate between scala tympani and scala vestibuli and causes false-positive ossification findings because the basal turn cannot always be arranged in 1 plane. Therefore, evaluation using cochlear cross planes is inevitable for the final decision, but it is not always easy, as demonstrated in Figure 2. To cope with these drawbacks, the authors devised a rotating computed tomographic (CT) movie to promote easier understanding of the intracochlear spaces. This innovative, interactive new method of ours is presum- ably the first radiographic movie in the field of otolar- yngology that is not based on time series such as videofluorography. Furthermore, application of this method to evaluate intracochlear spaces in partially ossi- fied cochleas from meningitis is presented. Evaluations Address correspondence and reprint requests to Ken Ito, M.D., Department of Otolaryngology, Faculty of Medicine, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8655, Japan; E-mail: itoken-tky@umin.ac.jp Supplemental digital content for this article is available on the journal’s Web site at www.otology-neurotology.com. Otology & Neurotology 29:124Y130 Ó 2008, Otology & Neurotology, Inc. 124