Three Dimensional Imaging of the Nasal Cavity and Paranasal Sinuses S. BISDAS 1 , M. VERINK 1 , M. STIEVE 2 , A. LAZAKIDOU 3 , I. EVANGELOU 4 , H. BECKER 1 1 Dept. of Neuroradiology, Hannover Medical School, Hannover, GERMANY , 2 Dept. of Otorhinolaryngology, Hannover Medical School, Hannover, GERMANY 3 Health Informatics Laboratory, University of Piraeus, Piraeus, GREECE 4 Dept. of Radiology, University of Oxford, Oxford, UNITED KINGDOM Abstract: - The clinical application of 3D-Imaging of the head and neck offers the possibility to visualize the region of the nasal cavity and paranasal sinuses. In comparison to just looking at plain radiographs it allows otolaryngologists and radiologists to better understand the complex and varied osseous structures. This study intends to explore the possibilities, the applicability, and value of shaded surface display in the region of nasal fossae. Key-Words: - 3D Imaging, Nasal Cavity, Paranasal Sinuses, Endoscopy, Computed Tomography 1 Introduction Computed tomography (CT) has long been used to image organs and other volumes of the body. This was done initially by sequential scanning to obtain consecutive slices, but since 1989 has been possible by continuous volume scanning using Spiral-CT, which became shortly widely accepted. Nevertheless, the principal advantages of continuous scanning in short times met various compromises in everyday clinical applications. The introduction of multislice spiral scanning in 1998 was a breakthrough. The scanning principle remains essentially unaltered but the number of slices scanned simultaneously, dose efficiency, and image quality are remarkably improved [1]. Multislice Spiral-CT, offering the possibility to acquire volumetric data sets from different anatomical regions, demonstrates special benefits in imaging the head and neck. Because of its speed, motion artefacts are no longer a problem. Furthermore, images reconstructed from very thin increments yield superb anatomical detail [2]. 2 Materials & Methods Various 2D- and 3D-postprocessing methods allow visualization of the volumetric data sets in different ways. In addition to the axial (source) images multiplanar reformations (MPR), maximum intensity projections (MIP), shaded surface displays (SSD), and perspective volumetric rendering (PVR) are used routinely. Those methods process and thus display the coded properties of the scan material differently. Although the reconstructed two- and three-dimensional images contain no more information than do the corresponding series of axial single scans, it is generally admitted that the viewer can better appreciate spatial relationship in a three- dimensional display than in a series of “flat” two- dimensional images. The 3D-postprocessed (SSD, PVR) images have the advantage of visualizing the complete situs, including every pathological finding, eliminating the redundant details and number of the required multiplanar views. This may still be improved by interactive video presentation. The clinical application of 3D-imaging of the head and neck offers the possibility to visualize the region of the nasal cavity and paranasal sinuses. In comparison to just looking at plain radiographs it allows otolaryngologists and radiologists to better understand the complex and varied osseous structures. This study intends to explore the possibilities, the applicability, and value of shaded surface display in the region of nasal fossae. 50 patients, with the diagnose of an acute or chronic nasal obstructive disease, were referred to our institution for scanning of the sinuses, undergoing a multislice spiral CT (LightSpeed GE, High Resolution, 1.25 collimation, pitch 3, interval 1 mm, 40 mA, 120 kV). The source images were reconstructed with an increment of 0.5 mm and were transferred to workstation (Sun Microsystems Ultra