gms | German Medical Science

Virtual techniques combine the advantages of data flow from high-resolution cross-sectional imaging techniques with those of three-dimensional imaging. We describe clinical cases in which virtual middle ear visualization is compared with intraoperative findings for different middle ear pathologies. A so-called multislice spiral CT (MSCT) was used for CT-guided petrous bone imaging, performed exclusively in multislice technique with the following parameters: spiral mode, 120kW, 50mAs, 0.5mm slice thickness, 0.2mm reconstruction interval, examination area from the upper edge of the petrous bone to the stylomastoid foramen. The number of cross-sectional images is increased by the factor 4-5 for high-resolution CT of the petrous bone in MSCT technique compared to conventional incremental CT (1 mm slice thickness). With the surface- (SRT) or volume-rendering technique of three-dimensional imaging, also known as “virtual endoscopy”, virtual endoluminal views of hollow spaces examined by CT are generated using virtual light sources, surface shading, perspective viewing angles and color coding. The aim of this study is to report on the volume-rendering technique of virtual imaging in otological middle ear diagnostics and to compare virtual endoscopy with intraoperative findings. The following case examples selected from a patient population (n=12) were described: two patients with middle ear malformations and one patient with suspected prosthesis dislocation. The middle ear findings obtained by 3-dimensional reconstruction and virtual endoscopy coincided with the intraoperative clinical findings. In patients with middle ear malformations, it is possible to precisely demonstrate the type and localization of the malformation as well as its relation to anatomically important structures like the facial nerve, the oval and round window, and the basal spiral canal of the cochlea, etc. The localization of prostheses can likewise be reliably ascertained in cases of suspected dislocation. Summing up, it may be said that virtual endoscopy of the middle ear is a very helpful and dependable procedure, particularly for diagnosing malformations.