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Radiation Protection in Radiotherapy

Radiation Protection in Radiotherapy. IAEA Training Material on Radiation Protection in Radiotherapy. Part 11 Medical Exposure: Good Practice and Radiation Protection in Brachytherapy. Medical Exposure.

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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: Good Practice and Radiation Protection in Brachytherapy

  2. Medical Exposure • In brachytherapy the quality of the treatment depends mostly on the skills of the operator who places the applicators and/or sources in the patient - modern equipment allows the physicist/operator a certain degree of optimization after the actual implant has taken place. • Brachytherapy uses radioactive sources which cannot be turned off like X Ray equipment typically used for external beam radiotherapy - therefore radiation protection is more likely to be an issue in brachytherapy than in EBT Part 11, lecture 1: Sources, techniques and equipment

  3. Objectives • To be familiar with the brachytherapy process • To be able to discuss methods for brachytherapy planning and dosimetry • To understand the optimization of dose delivery to the target by choosing appropriate isotopes and delivery techniques • To understand the implications of the above for radiation safety Part 11, lecture 1: Sources, techniques and equipment

  4. Contents • Lecture 1: Sources, implant techniques and equipment - radiation protection aspects • Lecture 2: Dosimetry, planning and verification Lectures complement part 6 of the course and are complemented by parts 14 to 16 Part 11, lecture 1: Sources, techniques and equipment

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

  6. Brachytherapy • Brachytherapy installations cover • direct source loading • 137-Cs sources for gynaecological applications (radium should not be used) • permanent seed implants (gold or 125-I) • surface applicators (moulds, 125-I, strontium and ruthenium plaques) • manual afterloading (137-Cs, 192-Ir) • automatic afterloading (LDR, PDR and HDR) Part 11, lecture 1: Sources, techniques and equipment

  7. Brachytherapy • Highly customized treatment techniques - each patient is treated differently • Techniques depend on • Disease site and stage • Operator/clinician • Technology/equipment available • Many of the points covered for External Beam installations also apply to Brachytherapy installations, particularly for automatic afterloading systems Part 11, lecture 1: Sources, techniques and equipment

  8. Objectives of lecture 1 in part 11 • To be aware of radiation safety issues when handling radioactive sources used for brachytherapy • To be familiar with the brachytherapy process • To understand the function of remote afterloading brachytherapy equipment • To appreciate the scope for optimization in stepped source brachytherapy • To understand the implications of the above for radiation safety Part 11, lecture 1: Sources, techniques and equipment

  9. Contents 1. Source storage and handling 2. Preparation of sources for an implant 3. Implant techniques 4. Brachytherapy equipment 5. Radiation protection issues Part 11, lecture 1: Sources, techniques and equipment

  10. 1. Source storage and handling • Radioactive sources must be under the control of an appropriate person at all times… • Ordering • Receiving • Storage • Handling • Use • Disposal Part 11, lecture 1: Sources, techniques and equipment

  11. Tests for Brachytherapy Sources • The following should be done on receipt of the sources and documented • Physical/chemical form • Source encapsulation, wipe test • Radionuclide distribution and uniformity • Autoradiograph • Uniformity of activity amongst seeds • Visual inspection of seeds in ribbons Part 11, lecture 1: Sources, techniques and equipment

  12. Source Storage Source stores must: • provide protection against environmental conditions • be only for radioactive materials • provide sufficient shielding • be resistant to fire • be secure • be labelled Part 11, lecture 1: Sources, techniques and equipment

  13. Features of source storage • Secure (lock and key) • Labels • Different compartments • Shielding • Easy access • Well organized Part 11, lecture 1: Sources, techniques and equipment

  14. Transferring sources from and into a safe • Use of tweezers • Behind shielding • Short transport ways Part 11, lecture 1: Sources, techniques and equipment

  15. Safe for 137-Cs sources Numbered and easily identifiable source draws - color coding of sources Part 11, lecture 1: Sources, techniques and equipment

  16. Commercially available isotope safe Shielding of drawers lockable Part 11, lecture 1: Sources, techniques and equipment

  17. Storage and transport of 125-I seeds Courtesy of Mentor Part 11, lecture 1: Sources, techniques and equipment

  18. Storage room • Must be lockable • Check environmental conditions: good lighting and ventilation • Typically some source handling area should be available • Radiation monitor must be available • Regular (e.g. 6-monthly) checks of background exposure rate is recommended Part 11, lecture 1: Sources, techniques and equipment

  19. Accountability of Sources Source accountancy records should contain: • radionuclide and activity of sources • location and description of sources • disposal details The records should beupdated regularly, andthe location of thesources checked. Part 11, lecture 1: Sources, techniques and equipment

  20. Handling of sources • General: • avoid contamination • use gloves • no eating/drinking in room • use long forceps • Let someone know if you work with radioactivity Part 11, lecture 1: Sources, techniques and equipment

  21. Transport Courtesy Nucletron • More details in part 4 • Use a mobile safe - this can double up as emergency container Part 11, lecture 1: Sources, techniques and equipment

  22. Disposal of sources • More details in part 15 • Check activity prior to disposal • Must be to a licensed operator • Provide and keep appropriate records Part 11, lecture 1: Sources, techniques and equipment

  23. Check of sources • Frequency of tests depends on source type and isotope • Tests should include a measure of dose and a check of source integrity • Useful is a combination of auto-radiograph and X Ray of the source to assess integrity of the encapsulation and distribution of activity Part 11, lecture 1: Sources, techniques and equipment

  24. 2. Preparation of sources for brachytherapy • Choosing the correct sources is an important part of the implant optimization • This is applicable for situations when: • there are several different sources available (e.g. 137-Cs source with slightly different length and activity for gynecological implants) • sources are ordered and customized for an individual patient (e.g. 192-Ir wire) Part 11, lecture 1: Sources, techniques and equipment

  25. Require a pre-implant plan... Part 11, lecture 1: Sources, techniques and equipment

  26. Choosing the correct sources • Prepare a plan for a particular implant following the prescription • Select appropriate sources • If existing sources are to be used select sources from the safe and place in transport container • Document what is done safe source shielding Part 11, lecture 1: Sources, techniques and equipment

  27. Preparation of seeds • Ordering planned number of seeds + some (around 10%) spares • Checking seed activity • either all (one by one) • or a representative subset (>10%) Wellchamber courtesy of MedTec Part 11, lecture 1: Sources, techniques and equipment

  28. Preparation of seeds • Sorting seeds and inactive spacers into the desired pattern • Loading seeds into needles Seed alignment tray Part 11, lecture 1: Sources, techniques and equipment

  29. Seed handling tools (MedTec) Brass funnel to channel seeds into needles or containers Radiation monitor can locate lost seeds Part 11, lecture 1: Sources, techniques and equipment

  30. Implant needle loaded with seeds and spacers Part 11, lecture 1: Sources, techniques and equipment

  31. Interstitial implants • For LDR usually use 192-Ir wire (compare part 6) • Optimization is possible as the length of the wire can be adjusted for a particular implant Part 11, lecture 1: Sources, techniques and equipment

  32. 192-Ir wire for LDR implants • Purchase 50cm coils of Iridium wire • Sources are cut to length to suit a particular application Extra shielding Wire cutter Part 11, lecture 1: Sources, techniques and equipment

  33. Source form 192-Ir wires • Cut wire • Encapsulate in a thin plastic sheath • Seal ends (heat shrink) • Can all be done in a purpose built cutter or manually Length measurement Shielding Movement controls Nucletron wire cutter Part 11, lecture 1: Sources, techniques and equipment

  34. HDR sources • No preparation necessary • Ensure • source calibration • optimized plan Part 11, lecture 1: Sources, techniques and equipment

  35. Rules for working with sealed Radioisotopes • Never handle a source with your hands - use forceps. Long forceps are preferable to reduce dose rate • Stand behind a shield when possible Part 11, lecture 1: Sources, techniques and equipment

  36. Rules for working with sealed Radioisotopes • Work efficiently - it may pay to ‘rehearse’ a certain activity (e.g. putting active wire in a thin sheath) with inactive materials first • Always wear a personnel monitor • Always have an area monitor “ON” Part 11, lecture 1: Sources, techniques and equipment

  37. Rules for working with sealed Radioisotopes • Always survey the area after the sources are put away • Survey gloves and equipment used • Always log the activity Radiation monitor Part 11, lecture 1: Sources, techniques and equipment

  38. 3. Implant techniques • Compare part 6 of the course: • Permanent implants • patient discharged with implant in place • Temporary implants • implant removed before patient is discharged • Here particular emphasis on radiation protection issues in medical exposures Part 11, lecture 1: Sources, techniques and equipment

  39. Permanent Implants: Radiation protection issues Implant of activity in theatre: • Radiation protection of staff from a variety of professional backgrounds - radiation safety training is essential • RSO or physicist should be present • Source transport always necessary • Potential of lost sources Part 11, lecture 1: Sources, techniques and equipment

  40. The time to place the sources in the best possible locations is typically limited Work behind shields or with other protective equipment may prolong procedure and result in sub-optimal access to the patient Problems with handling activity in the operating theatre Part 11, lecture 1: Sources, techniques and equipment

  41. Working behind shields Part 11, lecture 1: Sources, techniques and equipment

  42. Permanent Implants: Radiation protection issues Patients are discharged with radioactive sources in place: • lost sources • exposure of others • issues with accidents to the patient, other medical procedures, death, autopsies and cremation - compare part 15 of the course Part 11, lecture 1: Sources, techniques and equipment

  43. Temporary implants • Mostly done in afterloading technique • Radiation safety issues for staff: • Source handling and preparation • Exposure of nursing staff in manual afterloading • Radiation safety issues for patients: • Source placement and removal Part 11, lecture 1: Sources, techniques and equipment

  44. Nursing issues • LDR brachytherapy patients are treated for up to one week in a ward requiring regular nursing • If sources cannot be removed, there will be exposure to nursing staff • Staff needs to be trained, informed and monitored • Shielding should be employed Part 11, lecture 1: Sources, techniques and equipment

  45. Manual The sources are placed manually usually by a physicist The sources are removed only at the end of treatment Remote The sources are driven from an intermediate safe into the implant using a machine (“afterloader”) The sources are withdrawn every time someone enters the room Afterloading Part 11, lecture 1: Sources, techniques and equipment

  46. Afterloading advantages • No rush to place the sources in theatre - more time to optimize the implant • Treatment is verified and planned prior to delivery • Significant advantage in terms of radiation safety (in particular if a remote afterloader is used) Part 11, lecture 1: Sources, techniques and equipment

  47. Some radiation safety aspects of afterloading • No exposure in theatre • Optimization of medical exposure possible • No transport of a radioactive patient necessary ‘Live’ implants should be avoided for temporary implants Part 11, lecture 1: Sources, techniques and equipment

  48. Design Considerations BSS appendix II.13 • “Registrants and licensees, in specific co-operation with suppliers ... (g) exposure rates outside the examination or treatment area due to radiation leakage or scattering be kept as low as reasonably achievable” This typically implies the use of shielding which is not straight forward in the case of brachytherapy where sources are in direct contact with a patient. Part 11, lecture 1: Sources, techniques and equipment

  49. Shielding example for a radioactive mould Treatment of superficial basal cell carcinoma of the upper chest and lower neck Part 11, lecture 1: Sources, techniques and equipment

  50. Use of lead shield reduces scatter to the patient

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