Computed tomography virtual endoscopy imaging for spacial anatomy of the middle ear

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Abstract

BACKGROUND:

The middle ear is a little aerated cavity with a complex anatomy and a deep location. Computed tomagraphy virtual endoscopy (CTVE) can be used to reconstruct the stereoscopic images of internal surface of hollow organs using spiral CT volumetric data, providing findings similar to fiberendoscope.

OBJECTIVE:

To verify the ability to show the normal middle ear and the clinical application of virtual endoscopy based on 64-detector CT data.

DESIGN, TIME AND SETTING:

A confirmatory controlled observation was performed at Department of Radiology, First Affiliated Hospital of Sun Yat-sen University between October 2005 and March 2006.

PARTICIPANTS:

A total of 33 patients (66 ears) with suspected middle ear disease who underwent spiral CT examination were included in this study. Among included ears, 35 were normal, and 31 were impaired, including 24 ears presenting with chronic suppurative otitis media (10 simple otitis media, 5 granulomatous otitis media, and 9 middle ear cholesteatoma), 2 ears with post-operative recurred suppurative otitis media, 2 ears with carcinoma of middle ear, and 2 ears with temporal bone fracture, and 1ear with foreign body granuloma.

METHODS:

CT images of the temporal bone were obtained using 0.5 mm thick axis slices with a soft reconstruction kernel at 0.3 mm intervals. Virtual endoscopic images of middle ear on CT were generated from volumetric data using the Navigator software. CTVE images were observed from multiple directions using the Fly Through software, and compared with the axial and coronal images and surgery findings.

MAIN OUTCOME MEASURES:

The following structures were observed: auditory ossicle and joints, superior, middle, and inferior tympanum, sinus tympani, external acoustic meatus, tympanum, facial recess, tegmental wall, anterior and superior ligaments of malleus, posterior ligament of incus, and retrotympanum.

RESULTS:

A series of images were acquired as the virtual endoscope moved from the external auditory canal to the middle ear cavity. CTVE displayed the structures of normal middle ear with high details in 100%, except the anterior and posterior limbs of stapes in 68.6% (24/35) and 74.3 %(26/35), respectively. In the ears with supperative otitis media, the destruction of bone of handle, head of malleus, long and short limbs of incus, and limbs of stapes was found on CTVE in 91.7%(22/24), 95.8%(23/24), 95.8%(23/24), 100%(24/24), and 87.5%(21/24), respectively. CTVE clearly showed the destruction of promontory, tegmental wall and facial nerve tube in one ear with carcinoma. CTVE showed the dislocation of incudomallear joint in one ear with temporal bone fracture. It took about 10-15 minutes to perform CTVE.

CONCLUSION:

CTVE can be used as a noninvasive and reliable method in displaying normal and pathologic middle ears. In cases of suspected bony destruction and confirmed trauma, it is helpful for diagnosis and surgical planning. CTVE of the middle ear can currently be considered as a complementary technique to conventional CT, and it is time-saving and reserves clinical generalization.

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