Analysis of Cochlear Morphology for Cochlear Implantation Using Three-Dimensional Reconstruction of Computed Tomography Images.

INTRODUCTION: Preoperative evaluation of cochlear morphology is important for successful cochlear implantation. This study analyzed the cochlear canal by three-dimensional reconstructions of temporal bones using computed tomography (CT). METHODS: Fifty temporal bones from 25 patients aged 42-74 years were evaluated. The inner spaces of the bony cochlea were reconstructed using a surface rendering technique on the CT images. Eight angular points (P0-P7) every 90° were selected from 0° to 630° from the center of the round window using the reconstructed cochlear canal images. The radius (R) and thickness (T) of the cochlear canal at each point were measured. The cochlear canal length (CoCL) was estimated using an equation based on the radius at each point. The cochlear width and height based on multiplanar CT images were also measured and compared with the length and volume of the cochlear canal. RESULTS: The mean CoCL from 0° to 630° was 31.5 mm, and the cochlear volume was 55.9 mm3. The CoCL to P7 was correlated with the cochlear volume (r = 0.77), coiling ratios (R4/R0, r = 0.47; R5/R1, r = 0.384), cochlear width (long) (r = 0.539), cochlear height (r = 0.385), and total thickness at each point (r = 0.475). The cochlear volume was correlated with CoCL (630°) (r = 0.77), coiling ratio (R4/R0, r = 0.367), cochlear width (long) (r = 0.616), cochlear height (r = 0.447), and total T (r = 0.566). CONCLUSION: Preoperative evaluation using three-dimensional reconstruction can elucidate the size and shape of the cochlear canal before cochlear implantation.

Surgical considerations during cochlear implantation: the utility of temporal bone computed tomography.

OBJECTIVE: This paper describes the construction of portals for electrode placement during cochlear implantation and emphasises the utility of pre-operative temporal bone three-dimensional computed tomography. METHODS: Temporal bone three-dimensional computed tomography was used to plan portal creation for electrode insertion. RESULTS: Pre-operative temporal bone three-dimensional computed tomography can be used to determine the orientation of temporal bone structures, which is important for mastoidectomy, posterior tympanotomy and cochleostomy, and when using the round window approach. CONCLUSION: It is essential to create appropriate portals (from the mastoid cortex to the cochlea) in a step-by-step manner, to ensure the safe insertion of electrodes into the scala tympani. Pre-operative three-dimensional temporal bone computed tomography is invaluable in this respect.

The analysis of maxillary sinus aeration according to aging process; volume assessment by 3-dimensional reconstruction by high-resolutional CT scanning.

OBJECTIVE: To evaluate change of the maxillary sinus volume according to patient age and gender by using a 3-dimensional (3-D) reconstruction of computed tomography images. STUDY DESIGN AND SETTING: One hundred seventy-three people (totaling 238 maxillary sinuses) who had undergone paranasal sinus CT scan between December 2000 and November 2003 and had no evidence of inflammation or hypoplasia in the CT finding and had no specific history of paranasal sinus surgery or maxillofacial trauma were retrospectively analyzed. The 3-D reconstruction images were obtained by using a surface-rendering technique (Vworks; CybeMed, Seoul, Korea) on a personal computer. The mean volume of maxillary sinus was evaluated according to patient chronologic age and gender. The ratio of the maximum horizontal and half-horizontal extension for the estimation of the morphological change of maxillary sinus and the degree of descent of the sinus below the nasal floor were evaluated in the 3-D image. RESULTS: The development of the maxillary sinus continued until the 3rd decade in males and until the 2nd decade in females. The mean maxillary sinus volume in early adults was 24,043 mm 3 (males) and 15,859.5 mm 3 (females). There was a significance difference in the sinus volume ( P < 0.05) according to gender, and there was a significant difference in the maxillary sinus volume according to age before it reached maximum. After its maximum growth period, however, there was no significant difference in the volume change of maxillary sinus and the descent below the nasal floor between two adjacent groups. CONCLUSIONS: The growth of the maxillary sinus continues until the 3rd decade in males and the 2nd decade in females. Therefore, a maxillary sinus operation affecting the bony structures before these ages might affect the development of the sinus and needs to be performed carefully.

Three-dimensional reconstruction based on images from spiral high-resolution computed tomography of the temporal bone: anatomy and clinical application.

The aim of this study was to investigate the usefulness of a three-dimensional (3D) reconstruction of computed tomography (CT) images in determining the anatomy and topographic relationship between various important structures. Using 40 ears from 20 patients with various otological diseases, a 3D reconstruction based on the image data from spiral high-resolution CT was performed by segmentation, volume-rendering and surface-rendering algorithms on a personal computer. The 3D display of the middle and inner ear structures was demonstrated in detail. Computer-assisted measurements, many of which could not be easily measured in vivo, of the reconstructed structures provided accurate anatomic details that improved the surgeon's understanding of spatial relationships. A 3D reconstruction of temporal bone CT might be useful for education and increasing understanding of the anatomical structures of the temporal bone. However, it will be necessary to confirm the correlation between the 3D reconstructed images and histological sections through a validation study.