A method of measuring Bone Mineral Density (BMD) including providing a model of a plurality of constituents of at least a portion of a subject body, the model including at least one bone constituent, injecting electric current into the portion of the subject body using a current injection electrode, such that at least part of the current flows through the at least one bone constituent, measuring a value of electric potential at a surface of the subject body using a pickup electrode, using a value of the injected electric current as input to a model of the at least a portion of a subject body, and calculating a value of conductance of the bone constituent corresponding to a value of the injected electric current and the measured value of the electric potential. Related apparatus and methods are also described.