The invention relates to a device for determining positions of objects (1i) positioned in a measurement area, wherein the objects (1i) are capable of at least temporarily generating a magnetic field. The device comprises magnetometers (3i) arranged at a plurality of locations in a vicinity of the measurement area for locally measuring the magnetic field generated by the objects (1i), and an evaluation unit (5) coupled to the magnetometers (3i), the evaluation unit (5) being configured to determine the positions of the objects (1i) on the basis of the magnetic field measurements by the magnetometers (3i). The objects (1i) may be included in a human or animal body and may particularly be brachytherapy seeds.
