Computer-aided virtual surgery for congenital aural atresia.

HYPOTHESIS: Computer-enhanced three-dimensional (3D) computed tomography (CT) provides accurate spatial representation of the complex surgical anatomy of congenitally atretic ears, and is superior to conventional CT for surgical planning.

BACKGROUND

The surgical repair of congenital aural atresia is challenging. Conventional CT, routinely used for surgical planning, is limited in its ability to represent spatial relationships between important structures. Because 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 internal anatomy.

METHODS

A two-level segmentation scheme was developed to distinguish structures in the temporal bone. 3D CT reconstructions of congenital ears were produced with a high-resolution helical scanner. An interactive tool was used to mark the ossicles and facial nerve. The segmentation scheme was used to color-enhance the ossicles and otic capsule, and render the surrounding bone translucent. "Virtual surgery" was then performed by subtracting a cylindrical volume of bone lateral to the atresia plate. The enhanced 3D CT reconstructions were correlated with intraoperative video recordings.

RESULTS

In four congenital ears, computer-enhanced 3D CT was highly predictive of the actual anatomy. Surgery was avoided in two anatomically unfavorable cases.

CONCLUSION

Computer-enhanced 3D CT is a major advance over conventional CT for demonstrating the complex spatial relationships in congenitally atretic ears.