An Eddy Current System for the Study of the Cranial Rhythmic Impulse

The cranial rhythmic impulse (CRI) is an important osteopathic medicine concept that refers to the health of the individual. The technique of the eddy current (EC) sensors has the advantage to be directly sensitive to the CRI. In this paper, we present an EC system dedicated to the measurement of the CRI. To detect the CRI, a flexible aluminum foil covered with an adhesive layer is placed on the crane of the patient. The oscillations of the aluminum sheet induced by the CRI are detected by a dedicated EC sensor constituted of a printed coil. The sensing coil is put with an identical reference coil in an ac bridge. The bridge output voltage is analyzed with a lock-in amplifier. A spectral analysis is done on the output signal obtained after a 2 min long record on a patient. Different signals can be observed: 1) cardiac signal; 2) respiration signal; and 3) baroreflexe signal, showing the capability of the EC system in the analysis of the CRI.