1. A method of constructing a magnetocardiogram (MCG) image of a double-layer dipole, comprising: acquiring a magnetic image provided by a sensor unit including a plurality of electromagnetic sensors, each electromagnetic sensor contributing its output data to said magnetic image; providing a data processing device to implement the following steps: obtaining the magnetic image, said magnetic image being of an image of a magnetic field generated by a double-layer dipole, wherein said double-layer dipole is of an undefined shape, size, depth and orientation; submitting said magnetic image to a current dipole constructing system to determine a 3D position and momentum of an electric current in accord with the magnetic image; using the Biot-Savart Law to construct said MCG image based on the identified 3D position and moment of the electric current, including: assigning the 3D position of the electric current to the geometric center of a single double-layer 2D patch; and assigning the geometric center of the single double-layer 2D patch to the position of an equivalent dipole moment of said double-layer dipole, said equivalent dipole moment being characterized by the generation of an electric field substantially similar to that produced by said double-layer dipole; and displaying the constructed MCG image.