Biomedical subjects

Th Zahnert

Publications and source records attributed to Th Zahnert.

3 recordsLinked to original sources

PubMed2006

Rotational tomography of the normal and reconstructed middle ear in temporal bones: an experimental study.

Imaging is an essential diagnostic tool in reconstructive middle ear surgery, especially in pre-operative planning. Due to ongoing improvement of imaging quality and development of new imaging techniques like e.g. rotational tomography (RT) post-operative follow-up and immediate evaluation of surgical results may become more important. The aim of this experimental study was to evaluate RT as a new tool for postoperative determination of middle ear anatomy and implant position in temporal bones. RT was performed in ten temporal bone specimen after insertion of different middle ear prostheses concerning material, shape and length (PORP; TORP; Stapes piston). An implantable hearing device (Symphonix Soundbridge) was also implanted and visualized. For comparison some specimen additionally underwent conventional computed tomography (CT), including the newest technology. Characterization of anatomical structures of the temporal bone using RT was of comparable quality to conventional CT-scans in all investigated specimen while requiring approximately 30% of the CT's irradiation exposure. Unlike CT the RT showed almost no problems due to metallic artefacts of the implanted prostheses. Furthermore RT enabled a 3-dimensional view of the temporal bone and angle determination of inserted prostheses towards the tympanic membrane and/or the malleus handle. Detailed imaging of the prostheses allowed determination of shape, material and localization within the specimen's reconstructed middle ear. The new imaging technique of RT allows precise presentation of anatomical structures and middle ear implants in temporal bones. Following these experimental results it will be our future work to evaluate this method in clinical practise.

Ear, Middle↗

PubMed2004

Titanium clip prosthesis.

OBJECTIVE: Prostheses for the reconstruction of a defective ossicular chain should be stable and firmly anchored to the ossicular remnants. This will prevent a defective connection from causing diminished sound transmission efficiency and will keep the prosthesis from tilting or even losing contact, which would result in a sound transmission block. Through temporal bone experimentation, we have consequently developed a very lightweight titanium prosthesis, which is fastened onto the stapes head with a clip mechanism. METHODS: When temporal bone experiments using laser Doppler vibrometry confirmed that the prosthesis functioned well acoustically and when luxation experiments proved that it could be safely used without the risk of stapes dislocation, the prosthesis was used in a clinical application within an observational study. The University of Dresden Otorhinolaryngological Hospital as well as seven surgeons from five other hospitals participated in the study. RESULTS: The results of 133 operations showed that, in over 90% of the cases, the prosthesis could be implemented without problems and with good mechanical stability. The first acoustical results obtained during the first year from 49 patients showed a sound transmission improvement range from 12 dB to 14 dB. CONCLUSION: With the clip prosthesis, it seems possible to further improve defective middle ear function, which would allow the patient to regain social hearing after middle ear reconstruction. The reliability of the fastening is an innovation. Revision operations showed a stable prosthesis-stapes complex in the middle of a recurring cholesteatoma and the prosthesis could always be easily pulled from the stapedial suprastructure.

Auditory Threshold↗

PubMed2002

Movements of cochlear implant electrodes inside the cochlea during insertion: an x-ray microscopy study.

BACKGROUND: There are no satisfactory, noninvasive techniques currently available to visualize the cochlear implant (CI) electrode in a dynamic state as it is advanced inside the cochlea. OBJECTIVE: This study describes a radiologic technique that can be used in temporal bones to monitor the electrode position in real time and to visualize the basilar membrane. METHODS: A cochleostomy was performed in accordance with the normal procedure for cochlear implantation in seven fresh cadaveric temporal bones. A special x-ray tube (Microfocus; Focus, Wunstorf, Germany) with a spot size of 1 microm and fluoroscopy were used for continuous videotape imaging of the advancing electrode in the cochlea. Conventional electrodes (MED-EL 40+; MED-EL, Innsbruck, Austria) and prototypes of perimodiolar electrodes (MED-EL), with varying thicknesses and angles of insertion, were used for the study. Finally, contrast liquid (Ultravist; Berlex Imaging, Schering, Germany) was injected into the scala vestibuli through the stapes footplate. RESULTS: The advancing electrode carrier was clearly visible at x20 magnification. With the perimodiolar electrodes, deep insertion was impossible if the guiding wire was too rigid, and retraction occurred if the wire was soft. The intact nature of the basilar membrane could be confirmed by the sequential filling of scala vestibuli and the scala tympani. CONCLUSION: To our knowledge, this is the first noninvasive study demonstrating continuous visualization with high-resolution and x-ray magnification of CI electrode advancement inside the intact cochlea. Our technique can be used for the development of CI electrodes with optimal design characteristics, especially stiffness. Visualization of the basilar membrane will influence the insertion techniques when CIs are developed for patients with residual hearing.

Basilar Membrane↗