Bipolar measuring depth

In addition, the relative contribution of the deeper layers will increase. Even so, the sensitivity is proportional to the current density squared, so a given volume of tissue proximal to the electrodes is more important for the result flian the same volume in the deeper layers. By varying the distance between the electrodes, it is therefore possible to control the measuring depth. Ollmar and Nicander (1995) varied the measurement depth by inserting a third active current carrying electrode between the two measuring electrodes. 

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The distance between two surface electrodes will influence measuring depth. Figure 6.18. If the bipolar electrodes are driven from a constant amphtude voltage source, the total current and in particular the current density will decrease with increasing distance. 

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