The present invention relates to a positioning marker intended to be inserted in tissue. The marker is an elongated object with a longitudinal axis A and with a diameter perpendicular to said longitudinal axis, wherein the diameter is at the most 1,2 mm. The marker further has a predetermined total length LTOT. The marker comprises a plurality of first segments 1 and a plurality of second segments 2, wherein the first and the second segments are arranged alternately after each others. The marker comprises a first material with a density of at least 10 g/cm3, and this material constitute at least 90% by volume of the marker, and a second material that is magnetic and that constitute at the most 10% by volume of the marker.
