User Specific Cochlear Implant Stimulating Strategies and Speech Processor
CHOI CHARLES T. M.
聲調式語言 (tonal language) 特別是國語的辨識效果更是不足。而增加有效電子耳
個使用者專屬模型 (user specific model)。於是提出一個根據配戴者的電流生理資
料 (如生理阻抗或最低可聽到聲音的刺激電流強度(T level)與可接受最大刺激電
流強度(M level)) 來建立使用者專屬模型的方法。藉此可用來改善個別配戴者的四
Research shows that 6 ~ 9 effective channels are sufficient for cochlear implant (CI) users to listen and understand English in a completely quiet environment. However, it is not enough for listening to speech in noise, music and tonal language, particularly Mandarin Chinese, which are the last major frontiers in CI research. One accepted approach to improve the hearing performance is to increase the effective number of channel CI users can perceive. Unfortunately, there is no easy way to do that. In his previous NSC work, the principal investigator (PI) has focused on refining the cochlear implant computer model. He developed a four-electrode current steering scheme (FECSS), based on a generic computer model, which is much more complex than the two-electrode current steering scheme (TECSS) available commercially, and it led to a dramatic improvement in clinical performance. In unpublished clinical tests, a CI user was able to rank more than 300 different pitches in a pitch ranking test, which is almost three times the current best record by using commercial cochlear implants. Unfortunately, it is found that one generic computer model, no matter how accurate it is, it cannot be applied to all CI patients. A new computer model is needed for each CI patient, i.e. a patient specific computer model is needed. The PI is proposing a novel method to create a patient specific CI computer model based on electrophysiological measurement such as impedance, voltage, current, T level (threshold) and M level (most comfortable level). Once the CI user specific computer model is created, it can be used to develop a FECSS for that particular patient. With the patient specific computer model and FECSS, a patient specific FECSS will be created and tested on "static" pitch ranking test first. Simultaneously, we will develop this patient specific FECSS into a real time dynamic CI stimulating strategy. In order to implement and test this stimulating strategy in the clinical setting, access to the internal programming of the commercially available speech processor that is compatible with the patients’ headpiece is needed. Since commercial cochlear implants contain proprietary information, we need to develop a new CI research and clinical speech processor to implement and test this patient specific FECSS stimulating strategy. In order to test our user specific FECSS stimulating strategy on CI patients, the cochlear implant speech processor needs to be compatible with commercial implants, e.g. Advanced Bionics implant. We will develop a new research and clinical speech processor based on off the shelf digital signal processor (DSP) boards coupled with a custom designed transcutaneous transmission circuit to provide power and instructions to the implant electronics and CI electrodes inside the patient bodies. A new mapping software will be developed to map the CI patients. The speech processor will be subjected to electromagnetic compatibility (EMC) and related tests to satisfy all the pre-clinical test requirements for medical devices. Lastly, we will test the new stimulating strategy in the new CI research and clinical speech processor in clinical experiments if time permits.