The invention is directed to a brachytherapy source assembly to a kit of parts to a method for preparing a brachytherapy source assembly to uses of a specific coating and to a brachytherapy treatment. The brachytherapy source assembly of the invention comprises a push/pull wire and at the distal end thereof a capsule suitable for brachytherapy wherein said capsule comprises a chamber for holding one or more radioactive sources said chamber being defined by a wall and wherein at least part of the exterior surface of the wall of the capsule comprises a coating the coating comprising one or more selected from TiN TiCN TiCrN CrN TiA1CrN DLC and M?S wherein said capsule is attached to the push/pull wire or wherein said capsule is comprised in the push/pull wire.
