A marker loading assembly for transferring an elongated positioning marker from a loader needle of said assembly into an insertion needle of a medical insertion device, the marker loading assembly comprises an elongated hollow housing having a manoeuvring end and a marker transfer end, and a loader needle mounted within said loading assembly along a longitudinal axis of said assembly, said loader needle being adapted to receive and hold said positioning marker until the positioning marker is transferred to said insertion needle, a transfer opening provided at the marker transfer end and being adapted to receive a distal end of the insertion needle, said transfer opening being provided with a shape gradually opening up in a direction away from said manoeuvring end, and said transfer opening at its narrow end leading to a transfer channel arranged along said longitudinal axis, and wherein the transfer channel has a circular cross-sectional shape having a diameter slightly larger than an outer diameter of the insertion needle or of an outer protective sleeve provided on the outside of the insertion needle, and wherein a loading end of the loader needle is concentrically arranged in the transfer channel such that an annular space having a predetermined length along the longitudinal axis is provided around the loading end, and wherein the outer diameter of the loader needle is slightly smaller than the inner diameter of the insertion needle, which enables the distal end of the insertion needle to be inserted into said annular space in the transfer channel and simultaneously the loading end of the loader needle to be inserted into the distal end of the insertion needle to set said assembly in a marker loading ready state, and wherein the loading assembly further comprises a transfer mandrel, said transfer mandrel being adapted to be arranged within said loading needle and being arranged to receive a force in the direction towards the insertion needle and thereby achieve t
