A TRANSPARENT MODEL OF THE HUMAN SCALA TYMPANI CAVITY

A dimensionally accurate clear model of the human scala tympani has be en produced to evaluate the insertion and position of clinically appli ed intracochlear electrodes for electrical stimulation. Replicates of the human scala tympani were made from low melting point metal alloy ( LMA) and from polymethylmeth-acrylate (PMMA) resin. The LMA metal cast s were embedded in blocks of epoxy and in clear silicone rubber. After removal of the metal alloy, a cavity was produced that accurately mod els the human scala tympani. Investment casting molds were made from t he PMMA scala tympani casts to enable production of multiple LMA casts from which identical models were fabricated. Total dimensional distor tion of the LMA casting process was less than 1% in length and 2% in d iameter. The models have been successfully integrated into the design process for the iterative development of advanced intracochlear electr ode arrays at UCSF. These fabrication techniques are applicable to a w ide range of biomedical design problems that require modelling of visu ally obscured cavities.