Abstract: The invention relates to radioactive ruthenium sources with a dosage rate of at least 1.5 Gy/min at a distance (water) of 2 mm, consisting of an activity carrier and an encapsulation of the carrier made of a material compatible with the human body. A multilayer system made of metals and/or alloys is galvanically applied on the carrier. At least two layers in said system are made of ruthenium 106 and inactive intermediate layers made of other metals or alloys are provided between the radioactive ruthenium layers. The activity carrier is encapsulated with a material compatible with the human body, for instance a metal or a plastic material. Encapsulation can be carried out by filing a capsule and subsequently sealing or galvanically depositing a top layer made, for instance of hard gold.