Computer-aided virtual surgery for congenital aural artresia

Hypothesis: Computer-enhanced three-dimensional (3D) computed tomography (C T) provides accurate spatial representation of the complex surgical anatomy of congenitally atretic ears, and is superior to conventional CT for surgi cal planning. Background: The surgical repair of congenital aural atresia is challenging. Conventional CT, routinely used for surgical planning, is limited in its a bility to represent spatial relationships between important structures. Bec ause of the lack of density differences between bony structures in the ear, 3D CT has thus far been useful for representing surface contour but not in ternal anatomy. Methods: A two-level segmentation scheme was developed to distinguish struc tures in the temporal bone. 3D CT reconstructions of congenital ears were p roduced with a high-resolution helical scanner. An interactive tool was use d to mark the ossicles and facial nerve. The segmentation scheme was used t o color-enhance the ossicles and otic capsule, and render the surrounding b one translucent. "Virtual surgery" was then performed by subtracting a cyli ndrical volume of bone lateral to the atresia plate. The enhanced 3D CT rec onstructions were correlated with intraoperative video recordings. Results: In four congenital ears, computer-enhanced 3D CT was highly predic tive of the actual anatomy. Surgery was avoided in two anatomically unfavor able cases. Conclusion: Computer-enhanced 3D CT is a major advance over conventional CT for demonstrating the complex spatial relationships in congenitally atreti c ears.