Radiologische Untersuchung des Os temporale mittels digitaler Volumentomographie und Computertomographie -Eine vergleichende Untersuchung an anatomischen Felsenbeinpräparaten

High resolution computed tomography (HR-CT) of the temporal bone in axial and coronal projections is an established standard examination technique. Digital volume tomography (DVT) is a relatively new technique. It is used in dental surgery for preoperative planning of dental implantation. The main advantage of DVT over HR-CT is a ten times smaller radiation dose with a higher resolution. The aim of this study was to evaluate the importance of digital volume tomography in temporal bone imaging. For this examination 38 temporal bone specimen were scanned using DVT and CT. The visibility of 43 important anatomic landmarks in coronal and axial projection was evaluated by two observers. In the second part of the study reconstructive operations like tympanoplasty type III b and c and stapesplasty were performed on some specimen. For the reconstructive procedures different prosthesis and different materials such as gold, titanium, ceramic and platinum were used. After the reconstruction of the middle ear, the specimens were scanned again to visualize the positioning of the implants and the anatomical landmarks near the prosthesis. 12 anatomical landmarks like the crura and the footplate of the stapes and the oval and round window niche could be significally better visualized by DVT. All macroscopically defined parts of the ossicular chain were demonstrated well. Due to the partial-volume effect the ossicular chain could often be demonstrated fragmentary by HR-CT. Even soft tissue like the tensor tympani muscle and the ligaments of the tympanic cavity were shown significally better by DVT. The lower soft-tissue contrast did not affect the imaging of these structures. The imaging of the prostheses highly depended on which material was used. Ceramic and titanium implants could be visualized much better than gold- and platinum prostheses. They caused strong metal artifacts which affected the quality of the images. However, in contrast to the CT, they were less pronounced on the DVT-images. This study shows some main advantages of temporal bone imaging by digital volume tomography. Some clinically relevant structures could be visualized significally better by DVT. Diagnosis and therapy of middle ear diseases and preoperative planning of middle ear reconstruction could be improved. Patients profit from a low radiation dose with high spatial resolution. Even postoperative analysis of middle ear implants could profit from a higher spatial resolution and less metal artifacts. Summing up it may be said that digital volume tomography adds useful additional information to established temporal bone imaging methods.