[en] A method is described which permits the measurement of layer thicknesses and in-depth localization of β-emitting isotopes in live and inert material. It is based upon the measurement of the energy loss ΔE due to the presence of an absorbing layer between the source and the detector. The Esub(max) value of an allowed continuous spectrum, eventually after passage through such a layer is found by extrapolating the Kurie-plot for a selected optimum energy region. For layers of known thickness, excellent agreement is observed between the energy losses determined experimentally using a semiconductor detector assembly, and the theoretical ΔE values calculated from the Landau equation. The method has been particularly applied to ⁴⁵Ca. In this instance localization in a range of depths from approximately 20 to approximately 400 μm is possible with an accuracy of about 10 μm