Compression Image Processing and Bio-signal Transmission

135 Figure 4.21 Continuation b moderate compression of 1:20; c compressed to 1:100 FONG et al 2011

4.2.4 Bio-potential Electrode Sensing

To measure the rate of heartbeat and the behaviors of other vital organs such as the brain or even sleeping patterns, the Electro- 136 cardiogram ECG, Electromyography EMG and Electroen- cephalography EEG graphic hypnograms are used. The devic- es measure the electrical activities associated with nerve stimulation and muscle contract of the related organs, which can be illustrated as the generation of waves with the plot of electric currents over time. To have a good idea of the procedure, only the mechanisms of ECG will be focused as other devices exhibit the similar properties. The mechanisms of the devices are shown in Figure 4.22. The most significant property that is similar in these plots is that asymmetrical amplitudes are emit- ted throughout the measuring period. The heartbeat is measured via the electric potentials generated by the heart and not by transferring electrical currents to the organs. The rhythms of the heart are plotted via impulse generation which is used to identi- fy a wide range of abnormalities associated with the vital organ. However, as with other devices, the measurement can be disrup- tion by noise waves and significantly impair the diagnosis pro- cess. Other causes of disruption include some diagnosis protocols. For example, patients are required to exercise on the treadmill to measure the shrinking of the artery using ECG. If patients are not able to perform the task, the measurement would nevertheless be useless. Movements and shocks that in- curred during the measurement process may also result in dis- crepancies of the result as electrical conductors are placed on the chest. The period of measurement varies based on the nature of the diagnosis. A brief diagnosis tends to be more advanta- geous as it is less likely to be disrupted by unwanted noises. The analysis of ECG diagrams is normally conducted manually by doctors. As with the storing of images, there is a possibility of data loss while transmitting or storing graphs. The graphs must be restored to its exact features to prevent any loss of cru- cial information. However, there is a certain difficulty as signals are required to be separated from its grid. Therefore, the use of colours is encouraged instead of black and white to help in ex- tracting the signals even though it is represented by mono- 137 chrome lines. In addition, pink grids in the plot can be eliminat- ed through the elimination of red components. Figure 4.22 Electrical activities. a Electrocardiogram ECG; b Electroencephalography EEG FONG et al 2011 138 Figure 4.22 Continuation c Electromyography EMG; d graphic hypnograms FONG et al 2011