USE OF CRANIAL SURFACE ANATOMIC FIDUCIALS FOR INTERACTIVE IMAGE-GUIDED NAVIGATION IN THE TEMPORAL BONE - A CADAVERIC STUDY

OBJECTIVE: Because of the intricate anatomy of the temporal bone, we e xamined the feasibility and reliability of cranial surface anatomic fi ducials to register computed tomographic images of the temporal bone b y using a frameless image-guided system. METHODS: One-millimeter thick computed tomographic slices and the smallest possible field of view w ere used to register 10 dry and 10 fresh temporal bones from cadavers. The fiducials used for registration included the umbo of the tympanic membrane, emissary foramina, the asterion, various sutures, the tip o f the mastoid process, and Henle's spine. RESULTS: Mean initial fiduci al registration error ranged from 0.6 to 0.7 mm,, and was reduced to 0 .5 and 0.4 mm for the dry cranial and cadaveric studies, respectively, by eliminating or reregistering inexact fiducials. Mean target locali zation error ranged from 0.91 to 2.44 mm for superficial structures of the temporal bone in the dry cranial specimens and from 0.71 to -1.52 mm for deep structures such as the facial nerve, semicircular canals and ossicles in the cadaveric study. CONCLUSION: Interactive image-gui ded navigation in the temporal bone is possible with registration of c ranial surface anatomic fiducials. It may be useful to the neurosurgeo n and otologist in identifying critical anatomic structures of the tem poral bone encountered during the translabyrinthine, retrolabyrinthine presigmoid, and suboccipital approaches.