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 endoscop y 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 genera tion of endoscopic views of the auditory spaces, the axial images were proc essed with Navigator software 2.0 running on UltraSparc 1 workstation. Results: Virtual endoscopy allowed the demonstration of the external audito ry canal, the head and handle of the malleus, the stapes and incudostapedia l articulation, the corpus, the long process of the incus with its lenticul ar process and the short limb, the malleoincudal articulation, the rounded promontory, the round and oval windows, and Prussak's space. From inside th e basal turn of the cochlea, virtual endoscopy showed the orifices of the f enestrae cochlea and vestibuli, the origin of the Lateral and the anterior semicircular canals, and the basal turn of cochlea. The optimal perspective s that allowed demonstration of the anatomical details of the middle and in ner ear are described. Conclusion: Virtual endoscopy allows the generation of inner views of the a uditory spaces. This new method of image processing can be proposed as an i ntegrative tool of spiral CT imaging.