example by welding the outer diameter of the treating elements is preferably between approximately 0 3 and 0 8 mm being sized of course to slidably fit into the respective receiving bores of the carriages bodies and catheter lumens described above to permit maximum mobility through the loading devices and catheters the inner diameter of each of the bores or lumens the treating elements pass through should preferably be less than twice the outer diameter of the cylindrical treating elements this allows the treating elements to move quickly through the lumen minimizes unnecessary exposure of other tissue to the treating elements and in particular minimizes radiation exposure to other tissue each treating element as constructed above encapsulates a therapeutic agent such as radiation emitting substance radiation emitting substance is contained within interior chamber of the treating element and may be composed of any alpha beta or gamma particle emitting substance preferably however the radioactive source is a pure beta particle emitter or beta and gamma emitter examples of such substances include strontium 90 yttrium 90 ruthenium 106 thulium 170 tungstun 185 phosphorus 32 iridium 192 and or iodine 125 the amount and strength of the radioactive material contained in the combined number of treating elements should be sufficient to deliver a desired dosage of from 100 to about 10 000 rads preferably about 700 to 5000 rads in about 1 to 10 minutes radioactivity is generally measured in units of u201c curie u201d ci and the radioactivity of the material for the present invention is selected to provide the above dosage for the preferred dosage the radioactive material may have.