Patent Number: 059848537
Section: claims

1. The method of invasively delivering radiation to a therapy location in a living body, comprising: a) forming a miniaturized source of ionizing radiation on a support comprising at least one plate member, including a pair of electrodes in the form of an anode and a cathode on the support;  b) inserting the source into a living body and directing the source at the therapy location; and  c) activating the source of ionizing radiation by selectively energizing and deenergizing the source so as to direct a highly accelerated electron emission from the cathode to the anode in the vicinity of the therapy location. 2. The method of claim 1, wherein the high electron emission is created by applying a positive voltage on the anode to cause electrons to be emitted from the cathode. 3. The method of claim 2, wherein the voltage is in kV range. 4. The method of claim 1, wherein the high electron emission is created by heating the cathode to a high temperature, giving rise to thermal emission of electrons toward the anode. 5. The method of claim 1, including, retarding the electron emission by impact at the anode. 6. The method of claim 1, including forming the anode of a metal selected from a group consisting of tungsten, molybdenum, cobalt and aluminium. 7. The method of claim 1, including forming the anode of a metal having an atomic number higher than 50. 8. The method of claim 7, including depositing the anode metal in the form of a thin film on a first plate member. 9. The method of claim 8, including forming the cathode with a thin deposited film of a material having a low work function on a second plate member. 10. The method of claim 9, including forming a miniature platform formed by the plate members. 11. The method of claim 10, including connecting the anode and cathode to a voltage source by deposition of metallic strips. 12. The method of claim 1 wherein the support includes a first plate and a second plate. 13. The method of claim 12, including forming the first and second plates of a semiconductor material and doping leads therein, and connecting the anode and cathode to a voltage source by doping leads onto the semiconductor. 14. The method of claim 12, including forming a microcavity in one of the first and second plates, and forming at least the cathode in the microcavity and the anode on the other plate. 15. The method of claim 12, including forming the microcavity by etching off a sacrificial layer between the first and second plates. 16. The method of claim 12, including adhesively bonding adjoining surfaces of the first and second plates. 17. The method of claim 12, including forming at least one of the first and second plates of simple crystalline silicone. 18. The method of claim 1, including forming the anode at least partly of a metal having an atomic number greater than 20. 19. The method of claim 1, including forming a third electrode in the form of a gate within the microcavity, controlling the electronic current emitted toward the anode. 20. The method of claim 1, including isolating the electrodes to prevent short circuits and current leakage. 21. The method of claim 1, including forming a sharp tip in the microcavity and forming the cathode on the tip. 22. The method of claim 1, including determining a desired radiation level and duration of radiation, and energizing the source to achieve the desired level and duration. 23. The method of claim 22, including deenergizing the source and withdrawing the source from the location. 24. The method of claim 22, including repeating the steps of inserting the source, deenergizing the source and withdrawing the source at selected time intervals. 25. The method of claim 1, including encompassing the source within a cannula element comprising material transparent to emitted radiation, penetrating tissue of the living body and directing the source in the cannula to the therapy location. 26. The method of claim 25, including connecting electrical leads to the anode and the cathode, connecting insulated wires to the leads and extending the wires through the cannula to a power source. 27. The method of claim 1, including mounting the source near a distal end of a wire. 28. The method of claim 27, including inserting a catheter into body tissue, and directing the source and wire through the catheter to the therapy location.