Virtual endoscopy of the middle and inner ear with spiral computed tomography

OBJECTIVE: To evaluate the inner anatomy of the auditory apparatus by means of virtual endoscopy of spiral computed tomography (CT) data sets. BACKGROUND: Virtual endoscopy permits simulation of the fiberoptic endoscopy perspective by processing CT or magnetic resonance images. METHODS: Seven formalin-fixed specimens of human mastoid were scanned with spiral CT with the following protocol: beam collimation 1 mm, pitch ratio 1, reconstruction spacing 0.2 to 0.5 mm, field of view 90 mm. For the generation of endoscopic views of the auditory spaces, the axial images were processed with Navigator software 2.0 running on UltraSparc I workstation. RESULTS: Virtual endoscopy allowed the demonstration of the external auditory canal, the head and handle of the malleus, the stapes and incudostapedial articulation, the corpus, the long process of the incus with its lenticular process and the short limb, the malleoincudal articulation, the rounded promontory, the round and oval windows, and Prussak's space. From inside the basal turn of the cochlea, virtual endoscopy showed the orifices of the fenestrae cochlea and vestibuli, the origin of the lateral and the anterior semicircular canals, and the basal turn of cochlea. The optimal perspectives that allowed demonstration of the anatomical details of the middle and inner ear are described. CONCLUSION: Virtual endoscopy allows the generation of inner views of the auditory spaces. This new method of image processing can be proposed as an integrative tool of spiral CT imaging.