A medical device according to the invention for insertion into a human and/or animal body comprises an elongated tubular lead probe including a proximal end portion and a distal end portion, an opening which opens into a lumen extending in the axial direction being formed on the proximal end of the lead probe, and the distal end of the lead probe being closed. The medical device further comprises an elongated core which is constructed in such a manner that it can be inserted into the lead probe and removed again via the lumen, and the core is made from non-metallic filaments and a matrix material.