Patent Number: 
Section: claims

1. A calibrated radioactive source, comprising a flexible sheath of a container material, and a labeled material labeled by at least one radionuclide, wherein:the labeled material is contained in the flexible sheath;at least part of the container material is transparent to radiation emitted by the at least one radionuclide; andat least part of the labeled material is a self-hardening polymer chemically inert relative to the container material. 2. The calibrated radioactive source according to claim 1, wherein the flexible sheath is a hollow cylinder of essentially constant diameter. 3. The calibrated radioactive source according to claim 1, wherein the container material is a polymer material. 4. The calibrated radioactive source according to claim 3, wherein the polymer material is a silicone elastomer. 5. The calibrated radioactive source according to claim 1, wherein the self-hardening polymer of the labelled material is an epoxy type resin. 6. The calibrated radioactive source according to claim 5, wherein the self-hardening polymer comprises 53±1% of epoxy resin, 32±1% of hardener, and 15±1% of liquefier. 7. The calibrated radioactive source according to claim 1, wherein the labelled material comprises cobalt 57. 8. An assembly comprising a brick of a tissue-equivalent phantom and at least one calibrated source according to claim 1, wherein:the brick is a polymer block, one face of which comprises a hole intended to receive the calibrated radioactive source;the calibrated radioactive source has at least one curvature along its length, whereby a distance between a highest part and a lowest part of the calibrated radioactive source along its width is equal to a largest internal diameter of the hole; andthe calibrated radioactive source is in contact with a wall of the hole in at least two contact points and exerts a force on the wall on level with the at least two contact points. 9. An assembly according to claim 8, wherein the hole is a cylindrical and rectilinear hole of essentially constant diameter. 10. A method for placing a calibrated radioactive source according to claim 1 in a hole on one face of a block, wherein the calibrated radioactive source has at least one curvature along its length, the method comprising:deforming the calibrated radioactive source until a distance between a highest part and a lowest part of the calibrated radioactive source along its width is less than a smallest diameter of the hole of the block;inserting the calibrated radioactive source into the hole; andblocking the calibrated radioactive source in the hole by returning the calibrated radioactive source to its non-deformed state, wherein the distance between the highest part and the lowest part of the source along its width in a non-deformed state is greater than the smallest diameter of the hole. 11. The method for placing a calibrated radioactive source in a hole of one face of a block according to claim 10, wherein the block is a brick of a tissue-equivalent phantom of polymer.