Portable EEG Signal Acquisition System

The 21 st century is called “the century of the brain”. Brain science has attracted enough attention from all over the world. Currently, research on brain is still in the start stage in China. Most of domestic electro encephalogram(EEG)acquisition equipments are imported. These instruments are expensive and bulky,so they are only applied in large scale hospitals and academies. It limits research on brain science in many small scale institutions and is not good for popularization of EEG equipments. So it is significant for research on brain, and popularization of products related to EEG in home application and community hospitals to design portable EEG signal acquisition system.EEG is a kind of weak and low-frequency signal. It is easily interfered by other physiological and non-physiological signals. Based on these characteristics,a portable EEG signal acquisition system is built in this paper. The system is divided into two parts: one is the module to acquire signals and filter noise, and the other is the personnal computer(PC) based telemedicine system.First of all, it is guaranteed that clinic electrodes have close contact with scalp of patient by circuits for detecting connection status. Weak EEG signals are induced to the signal conditioning circuits with bipolar leads. Signals will undergo multi-level amplifying, filtering and suppressing common mode interference in the signal conditioning circuits. After that, EEG is acquired by TMS320VC5509 and these digitized signals are digitally filtered in it. The baseline drift from electrodes are removed with median filter. The power interference varied with power grid is removed by adaptive filtering algorithm.The ocular artifacts are filtered out with independent component analysis algorithm. The filtered EEG signals are displayed on liquid crystal display(LCD)and are saved in secure digital(SD) card.To improve the usability of the system, the telemedicine service software based on PC is developed under Visual Studio 2012. EEG data is uploaded to the server by network communication. Personal information of patients is managedby structured query language(SQL) Server database on the server, and patients' EEG data files are saved on the server. In order to ensure the accuracy of the data transport, buffers and hash map are used to realize of double confirm and retransmission timeout on the application layer. Doctors can download the EEG data files on doctor client. Doctors check and analyze EEG on the remote doctor client. As a return, Doctors can give diagnostic results to the server and patient.Experimental results show that the system can acquire weak EEG signals in real time, display and save processed data. The system can manage patients' information and EEG data files on the server to realize telemedicine. The portable acquisition system is easy to use and carry, and helpful to the popularity of community-based and family-based EEG diagnostic equipments. Not only does it meet quality requirement, but also economic request.