Virtual labyrinthoscopy: Visualization of the inner ear with interactive direct volume rendering

Computed tomography (CT) is the modality of choice for detailed imaging of the bony labyrinth. Usually, information about the complex three-dimensiona l anatomic structures of the inner ear is presented as two-dimensional sect ion images. Interactive direct volume rendering is a powerful method for vi sualization of the labyrinth. Unlike other visualization methods, direct vo lume rendering enables direct visualization of the bony labyrinth without e xplicit segmentation prior to the visualization process. Direct volume rend ering was applied to visualization of the structures of the temporal bone i n five patients without pathologic conditions and four patients with pathol ogic conditions. In all cases, clear representations of the bony labyrinth and the facial canal were provided. Because standard CT examinations combin ed with interactive visualization based on direct volume rendering are used , the method is fast and flexible. Therefore, this approach is applicable i n routine clinical work. Problems occur in patients with effusion in the te mporal bone because adjustment of imaging parameters for proper delineation of the target structures is difficult in this situation. However, direct v olume rendering can produce meaningful images of high quality even in these problematic cases. The term virtual labyrinthoscopy is suggested for visua lization of the labyrinth by using direct volume rendering.