PubMed · 13802032
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de BOER, P D SIX. The cochlear difference tone.. https://doi.org/10.3109/00016486009124467
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Surface and bulk modification techniques of polydimethylsiloxane (PDMS) polymers were used to develop a new intracochlear electrode that can closely hug the inner wall of scala tympani. Laser-induced surface grafting of poly (2-hydroxyethyl methacrylate) (PHEMA) and sequential method for preparation of interpenetrating polymer networks (IPNs) of PDMS/PHEMA were, respectively, used for surface and bulk modifications. The hydrogel content and water-uptake capability of the modified samples were optimized by Taguchi method for experimental design. The modified PDMS samples were examined by performing attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy, water contact-angle measurement, and peel strength tests. The performances of actual-sized fabricated electrodes were assessed inside a transparent model of scala tympani, which was filled with saline. After a swelling process, the hydrophilic branch begins to elongate and detach from hydrophobic branch and pushes it toward the inner wall.
AIM OF THE STUDY: To compare high resolution MRI examinations of inner ear structures at 1.5 T and at 3 T. METHOD: Temporal bones were measured bilaterally in 3 healthy volunteers in a 1.5 T and in a 3 T MR-scanner using the respective one channel head coil (quadrature detection) of the manufacturer. The same steady-state gradient echo sequence (3D-CISS) was employed at a voxel size of 0.4 x 0.4 x 0.4 mm(3). The signal-to-noise ratio (SNR) was determined quantitatively. RESULTS: An SNR of 8 could be achieved for the measurements at 3 T in 7:37 min. The SNR at 3 T was, on average, a factor of 1.34 higher than that at 1.5 T despite the fact that the excitation angle had to be drastically reduced (alpha = 42 degrees instead of alpha = 70 degrees at 1.5 T) due to the limit of the specific absorption rate (SAR). DISCUSSION: The MR representation of the inner ear is clearly improved at 3 T. To obtain the same SNR at 1.5 T approximately the double measuring time would be required, connected with reduced patient comfort and an increased risk for a displacement of the head during the high resolution measurement.
Three methods of determining electrode insertion depth in cochlear implantees are studied: intraoperative counting of inserted electrodes, plain film radiography using Stenvers projection and postoperative electrode function testing. In 16 cases the number of electrodes inserted in the cochlea were counted both by the surgeon at surgery and by two independent observers on plain film radiographs using Stenvers projections. The electrode function was tested postoperatively. The differences between the three methods in estimation of the number of intracochlear electrodes were analyzed with t-tests, and 95% confidence intervals (95% CI) of the mean differences were calculated. The mean difference between the radiograph observers was 0.25 electrode (95% CI, -0.69 to 1.19 electrodes.) The mean difference between radiography observations and the surgical counts was 0.60 electrode (95% CI, -0.71 to 1.91 electrodes.) The mean difference between surgical counting and electrode function testing was 0.40 electrode (95% CI, -0.66 to 1.46 electrodes.) The mean difference between radiograph observations and electrode function testing was 0.50 electrode (95% CI, -0.51 to 1.51 electrodes.) No significant differences existed between the three methods. Our findings showed similar results in estimating electrode array insertion depth with the three methods. Plain film radiography using Stenvers projection is satisfactory if imaging is indicated for determining the number of inserted electrodes.