Study On Acquisition System Of Vestibular Evoked Potential

The detection of vestibular evoked myogenic potentials (VEMP) has become an important method for vestibular function test because of its high specificity. In this thesis, based on the VEMP inducing and testing researches, a reflex hammer is designed for inducing vestibular evoked extraocular myogenic potentials (OVEMP) by tapping on forehead, so that the function of vestibular organ connecting to extraocular muscle can be evaluated.Based on the method of inducing OVEMP by tapping on forehead, a vestibular evoked potential acquisition system is developed. By using low-noise amplifier design techniques, the weak and short latency OVEMP is extracted from strong noise background. Complex programmable logic device EPM240 is used to achieve the conversion between digital-analog chip and SPI interface, and the collected data will be transmitted to the FIFO of USB chip Cy7c68013A by using Slave FIFO mode. Cy7c68013A employs the USB2.0 high-speed mode to communicate with the host computer, so the signal real-time transmission is achieved. Multi-threading and buffer technology are adopted in host computer software to realize the signal real-time processing, display and storage.Specifications of vestibular evoked potential acquisition system:①Sampling rate: 150KHz(3 channels);②Amplifier input impedance≥200M? (double-ended input), CMRR≥100dB, dark noise:≤0.32μV (peak-peak), frequency response: 0.1 ~ 500Hz, input range: 1 ~ 100μV;③Power isolation: 6000VDC, signal isolation: 4000Vpeak;④Stimulus sampling synchronously with the system, adopting lag time 1ms±5μs.To verify the effectiveness of this system, OVEMP detection experiments are performed using this system on healthy subjects who have neither histories of vestibular disease nor symptoms of vestibular deficits. The results show that OVEMP can be induced by using reflex hammer tapping on forehead, with average latency of 6.8ms and average amplitude of 10.5μV.