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Radiation Protection in Radiotherapy

Radiation Protection in Radiotherapy. IAEA Training Material on Radiation Protection in Radiotherapy. Part 11 Medical Exposure: Brachytherapy Lecture 1 (cont.): Sources, implant techniques and equipment. 4. Brachytherapy equipment.

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Radiation Protection in Radiotherapy

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  1. Radiation Protection inRadiotherapy IAEA Training Material on Radiation Protection in Radiotherapy Part 11 Medical Exposure: Brachytherapy Lecture 1 (cont.): Sources, implant techniques and equipment

  2. 4. Brachytherapy equipment • Design considerations often similar to external beam therapy • Many points made in part 10 of the course are also relevant for brachytherapy Nucletron Part 11, lecture 1 (cont.): Equipment and rad. prot. issues

  3. Design Considerations (BSS appendix II.11) • “Equipment used in medical exposure shall be so designed that: • failure of a single component of the system be promptly detectable so that any unplanned medical exposure of patients is minimized • the incidence of human error in the delivery of unplanned medical exposure be minimized” Part 11, lecture 1 (cont.): Equipment and rad. prot. issues

  4. Why not verify the elapsed time using your watch? Defence in depth example: Timers • Need two completely independent timers • One should count time up, one down • Should be tested regularly Part 11, lecture 1 (cont.): Equipment and rad. prot. issues

  5. Defence in depth example • Retraction of sources: • Normal power • Backup battery (must be checked) • Manual system Part 11, lecture 1 (cont.): Equipment and rad. prot. issues

  6. Design Considerations BSS II.13 • “Registrants and licensees, in specific co-operation with suppliers (a) the equipment conform to applicable standards of the International Electrotechnical Commission (IEC) and the ISO or to equivalent national standards Part 11, lecture 1 (cont.): Equipment and rad. prot. issues

  7. BSS appendix II Design criteria specific to radiotherapy • II.15. “Registrants and licensees, in specific co-operation with suppliers, shall ensure that: ... (e) radioactive sources for either teletherapy or brachytherapy be so constructed that they conform to the definition of a sealed source; and (f) when appropriate, monitoring equipment be installed or be available to give warning of an unusual situation in the use of radiation generators and radionuclide therapy equipment.” Part 11, lecture 1 (cont.): Equipment and rad. prot. issues

  8. Remote Afterloading Equipment • The most complex pieces of equipment in brachytherapy • Low dose rate units • High dose rate units • Many important design consideration in IEC standard Part 11, lecture 1 (cont.): Equipment and rad. prot. issues

  9. Low dose rate brachytherapy • Selectron for gynecological brachytherapy • 137-Cs pellets pushed into the applicators using compressed air • Location of active and inactive pellets can be chosen by the operator to optimize the source loading for an individual patient • Shown are 6 channels - the red lights indicate the location of an active source Nucletron Part 11, lecture 1 (cont.): Equipment and rad. prot. issues

  10. Other features • No computer required • Two independent timers • Optical indication of source locations • Permanent record through printout • Key to avoid unauthorized use Part 11, lecture 1 (cont.): Equipment and rad. prot. issues

  11. HDR brachytherapy units • Must be located in a bunker • Have multiple channels to allow the same source to drive into many catheters/needles MDS Nordion Part 11, lecture 1 (cont.): Equipment and rad. prot. issues

  12. Nucletron HDR unit control Printout = permanent record Keypad Emergency off button Display Key Key for source out Memory card for transfer of the dwell positions for the treatment of a particular patient - labelled Part 11, lecture 1 (cont.): Equipment and rad. prot. issues

  13. Catheters are indexed to avoid mixing them up Transfer catheters are locked into place during treatment - green light indicates the catheters in use Part 11, lecture 1 (cont.): Equipment and rad. prot. issues

  14. Transfer of sources • Important design issue - connectors and transfer tubes must be well designed and checked • Should be labelled and easily identifiable The correct channel of the afterloader must be connected to the correct applicator/needle in the patient Part 11, lecture 1 (cont.): Equipment and rad. prot. issues

  15. Regular maintenance is required • Source drive must be working within specified accuracy (typically 1-2mm) • Emergency buttons must work • Manual retraction of the source in case of power failure must work Part 11, lecture 1 (cont.): Equipment and rad. prot. issues

  16. Regular maintenance is required • Maintenance work should follow manufacturers recommendations • All modifications MUST be documented • A physicist should be notified to perform appropriate tests Part 11, lecture 1 (cont.): Equipment and rad. prot. issues

  17. LDR and HDR units are not all... • Other brachytherapy equipment: • PDR (pulsed dose rate) units • Seed implant equipment • Endovascular brachytherapy Part 11, lecture 1 (cont.): Equipment and rad. prot. issues

  18. LDR and HDR units are not all... • Other brachytherapy equipment: • PDR units - similar to HDR • Seed implant equipment - discussed in more detail in the second lecture of part 6 • Endovascular brachytherapy Part 11, lecture 1 (cont.): Equipment and rad. prot. issues

  19. Endovascular brachytherapy • Details of function was discussed in part 6 • Some similarities to HDR units, however, different catheters and sources are in use Courtesy Guidant Part 11, lecture 1 (cont.): Equipment and rad. prot. issues

  20. Centering of the source in the catheter • May be important due to short range of many radiation sources • Improves dose distribution on all vessel walls Courtesy Guidant Part 11, lecture 1 (cont.): Equipment and rad. prot. issues

  21. For all equipment... • Operator must be familiar with the unit • Maintenance staff must be trained and aware of radiation protection issues • Present course can not replace manufacturer training Part 11, lecture 1 (cont.): Equipment and rad. prot. issues

  22. Auxiliary equipment for brachytherapy • Diagnostic equipment for localization of the applicators and/or sources • May be simulator (compare part 10) or other diagnostic units (more details in the course on diagnostics) Courtesy Siemens Part 11, lecture 1 (cont.): Equipment and rad. prot. issues

  23. Auxiliary equipment for brachytherapy • Other equipment may also be required with modifications for brachytherapy. • Prior to each implant its integrity must be checked as patient safety and appropriate treatment delivery can rely on it. Part 11, lecture 1 (cont.): Equipment and rad. prot. issues

  24. A note on intercom systems • Need to be able to see the patient - is he/she comfortable? Is she/he moving? • Need to be able to talk to the patient • Need to be able to hear if the patient is in distress Part 11, lecture 1 (cont.): Equipment and rad. prot. issues

  25. 5. Radiation protection issues in brachytherapy • Patients, a variety of staff and potentially visitors are involved • Use of sources with high activity • Preparation of sources • Insertion of sources • Removal of sources Part 11, lecture 1 (cont.): Equipment and rad. prot. issues

  26. Training and information: staff • Training of staff is essential • This applies to radiation workers and others, such as domestic or maintenance staff Part 11, lecture 1 (cont.): Equipment and rad. prot. issues

  27. Information for patients • Patients must be aware of the particulars of their treatment prior to it commencing (and consent to it) • It is often a shock for patients waking up after an operation with catheters and needles in place Part 11, lecture 1 (cont.): Equipment and rad. prot. issues

  28. Source change in High Dose Rate (HDR) Brachytherapy • Source change is required about every 3 to 4 months due to 192-Ir decay • Is also required if any variations of source movement from the planned treatment are noticed or if a source stuck in the patient... Part 11, lecture 1 (cont.): Equipment and rad. prot. issues

  29. HDR brachytherapy source change • Must be done by suitably qualified personal • Calibration of the new source is essential - it is NOT appropriate to trust the source certificate only • Different calibration methods are possible - more in the next lecture Part 11, lecture 1 (cont.): Equipment and rad. prot. issues

  30. HDR brachytherapy source change • Need to ensure source dimensions are unchanged (fits in all applicators) • Need to verify source movement e.g. using a suitable jig or a video camera for observation Part 11, lecture 1 (cont.): Equipment and rad. prot. issues

  31. A source stuck in the patient • Maybe due to kink in catheter or other problems • In the case of HDR, the source MUST be removed within < 1min • This requires a suitably trained person (RSO, medical physicist) to be present • Emergency procedures must be established • Relevant equipment must be present (e.g. radiation monitor, crank to rewind the source drive cable manually) Part 11, lecture 1 (cont.): Equipment and rad. prot. issues

  32. A source stuck in the patient • Maybe due to kink in catheter or other problems • In the case of HDR, the source MUST be removed within < 1min • This requires a suitably trained person (RSO, medical physicist) to be present • Emergency procedures must be established • Relevant equipment must be present (e.g. radiation monitor, crank to rewind the source drive cable manually) The procedure must be trained regularly Part 11, lecture 1 (cont.): Equipment and rad. prot. issues

  33. Transfer of sources to the patient in afterloading procedures • All source channels in the patient must be easily identifiable • Mix-up of channels is a serious accident • Transfer pathways should be kept as short as possible For HDR units the transfer time may need to be considered for the treatment plan Part 11, lecture 1 (cont.): Equipment and rad. prot. issues

  34. After a temporary implant is completed • One must ensure that ALL sources are removed from the patient • This requires: • accounting of sources • monitoring of the patient Part 11, lecture 1 (cont.): Equipment and rad. prot. issues

  35. One must ensure that ALL sources are stored safely This requires: accounting of sources monitoring of the patient monitoring of the room Room monitoring may include the bed. However, as only sealed sources are used in brachytherapy, contamination of linen and cloths is typically not a problem After a temporary implant is completed Part 11, lecture 1 (cont.): Equipment and rad. prot. issues

  36. Summary • Due to the use of radioactive sources in direct contact with the patient, brachytherapy has the potential of radiation protection problems • Written procedures, protocols and adherence to good design can eliminate many sources of safety issues Part 11, lecture 1 (cont.): Equipment and rad. prot. issues

  37. Typical Radiation Levels • Iodine-125 Prostate Implant • 100 seeds of 0.36 mCi/seed = 36 mCi • less than 0.25 mR/h at 1m  0.0025 mSv/h • 17 days for 1 mSv (Background) • Gold-198 seed lip implant • 8 seeds of 3 mCi/seed = 24 mCi • 6 mR/h at 1m  0.06 mSv/h • 17 hours for 1 mSv (Background) Part 11, lecture 1 (cont.): Equipment and rad. prot. issues

  38. Typical Radiation Levels • Selectron LDR (Cs-137) Cervix insertion • 10 pellets of 15 mCi/seed = 150 mCi • 20 mR/h at 1m  0.2 mSv/h • 5 days for 1 mSv (Background) • this is inside the room! • microSelectron HDR (Ir-192) turned ON! • 10 Ci source = 10 000 mCi • 4700 mR/h at 1m  47 mSv/h • 1.3 minutes for 1 mSv (Background) • door interlock ensures that no-one is in room Part 11, lecture 1 (cont.): Equipment and rad. prot. issues

  39. Brachytherapy • Additional points covering safety associated with brachytherapy equipment are made in the lectures on shielding (part 7) and on brachytherapy (part 6). Part 11, lecture 1 (cont.): Equipment and rad. prot. issues

  40. Any questions?

  41. Question: Please provide a list of equipment which you would expect to find in a hot lab used for preparation of sources for brachytherapy

  42. Issues and items for the Hot Lab • Good ventilation and lighting • Close to brachytherapy treatment area • Lockable • Shielding as required • Appropriate signs and documentation • Equipped with: • Telephone • Radiation Monitor • Well counter for calibration (or equivalent) • Shielded workbench • Safe for storage of sources • Safe for waste • Mobile storage safe Part 11, lecture 1 (cont.): Equipment and rad. prot. issues

  43. Acknowledgement • Mamoon Haque, Royal Prince Alfred Hospital, Sydney • Craig Lewis, LRCC, London, Ontario Part 11, lecture 1 (cont.): Equipment and rad. prot. issues

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