Magnetorheography; calculation of blood flow from surface induced potentials

This research is an attempt to measure blood flow without doing any hurt to the body. When the body is placed in a high magnetic field the blood-flow-induced electromotive force (EMF) can be detected with the surface electrodes using the same principle as an electromagnetic flow-meter. This blood flow measurement is named magnetorheography (its recording: MRG). A theoretical analysis of the potential in the tissue shows that blood flow can be calculated from the surface-induced EMF (MRG) without measuring the radius and the depth of the vessel from the skin surface, when the surface is fairly flat in the vicinity of the vessel. A model experiment verified the theory. In order to apply the theory to the measurement in an in situ situation, a structural coefficient was introduced which is related to the external shape, internal tissue compositions and their impedance of the body. Using such a coefficient the flow calculated from MRG, by an equation including the coefficient, agreed with the flow actually recorded. In experiments on the thighs of 8 dogs weighing 7 to 17 Kg, MRG proved to be proportional to arterial flow and the coefficients were approximately constant. These results indicate that blood flow may possibly be estimated by the calculation from MRG.