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Radiation Protection in Radiotherapy

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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 8 Occupational Exposure

  2. Occupational Exposure(Fundamentals, IAEA Safety Series N0 120, 1996) “All exposures of workers incurred in the course of their work” (some exceptions are listed in BSS)

  3. Overview • Radiotherapy is a multidisciplinary approach which involves a variety of staff from different backgrounds • Radiation sources, capable of producing intense radiation fields, may be handled and moved in a radiotherapy department • Employers are required to ensure safe working conditions for staff • Dose limits and the need for optimization apply Part 8: Occupational exposure

  4. IAEA guidanceSeveral publications exist - sometimes it is also useful to check the extensive literature on occupational health and safety, e.g. from the International Labour Organisation (ILO) Part 8: Occupational exposure

  5. Responsibilities for Occupational Exposure BSS Appendix I.1. “Registrants and licensees and employers of workers who are engaged in activities involving normal exposures or potential exposure shall be responsible for: • the protection of workers from occupational exposure; and • compliance with any other relevant requirements of the Standards.” Part 8: Occupational exposure

  6. Objectives of the lecture • To know the variety of professionals involved in radiotherapy • To be aware of different scenarios which could lead to staff exposure in radiotherapy • To understand mechanisms to avoid or reduce staff exposure • To be familiar with the legal requirements for employers and employees Part 8: Occupational exposure

  7. Contents of the lecture 1. Occupations involved in radiotherapy 2. Where can occupational exposure occur 3. Local rules and supervision 4. Protective measures, equipment and tools 5. Monitoring 6. Investigation and follow up Part 8: Occupational exposure

  8. 1. Occupations involved in radiotherapy • Radiation Oncologists • Other Clinicians • Radiation Therapy Technologists • Treatment Planning Staff/Dosimetrists • Radiation Physicists • Engineers, Technicians, Maintenance staff • Nursing Staff • Allied Health (dietician, social worker,…) • Domestic Staff (Cleaners, porters, …) Part 8: Occupational exposure

  9. Occupational exposure • The professions involved in the radiotherapy process may vary in different departments • The type and magnitude of occupational exposure depends on the profession • In radiotherapy the risk is not as much the exposure as a normal and inevitable part of the profession (such as in nuclear medicine) but the potentialexposure to very high doses as an accident. Part 8: Occupational exposure

  10. Typical exposure levels of staff in radiation oncology • Australia: More than 99% of staff has occupational exposure < 1mSv • Exemptions: physicists preparing brachytherapy sources and nursing staff in brachytherapy wards where manual afterloading is practiced. Part 8: Occupational exposure

  11. Typical exposure levels of staff in radiation oncology • Exemptions: physicists preparing brachytherapy sources and nursing staff in brachytherapy wards where manual afterloading is practiced. These incidences will become less frequent with the introduction of HDR brachytherapy and remote afterloading techniques Part 8: Occupational exposure

  12. Occupationally exposed professionals in radiotherapy • Radiation Oncologists • Other Clinicians • Radiation Therapy Technologists • Treatment Planning Staff/Dosimetrists • Radiation Physicists • Engineers, Technicians, Maintenance staff • Nursing Staff • Allied Health (dietician, social worker,…) • Domestic Staff (Cleaners, porters, …) Part 8: Occupational exposure

  13. Occupationally exposed staff • Staff who may be exposed to ionizing radiation as a direct result of their profession • Typically educated about radiation safety • Typically monitored for exposure • Other dose constraints apply (compare BSS section 2.26) Part 8: Occupational exposure

  14. …but keep in mind • BSS appendix I.5.: “Employers, registrants or licensees shall ensure that workers exposed to radiation from sources other than natural sources that are not directly related to their work or not required by their work receive the same level of protection as if they were members of the public.” Part 8: Occupational exposure

  15. Other staff potentially exposed due to radiotherapy • Domestic staff, technical staff (e.g. electricians, plumbers), allied health, other clinicians, nurses Require training and potentially personal monitoring !!! Part 8: Occupational exposure

  16. Radiation Protection Officer • Shall be appointed by the licensee for every radiotherapy department • First point of call for all staff concerned about radiation safety • Provides education and training • Determines the need for monitoring • Must have appropriate qualifications • More detail in part 18 of the course Part 8: Occupational exposure

  17. Practical issues 1 • RPO must ensure all staff who can potentially be exposed are educated about the risks • Some suggestions for education: Lectures, video tapes, site visits, practical demonstrations,... • Should be part of new staff orientation and then offered at least annually Part 8: Occupational exposure

  18. Practical issues 2 • BSS appendix I.34.: “For any worker who is regularly employed in a supervised area or who enters a controlled area only occasionally, individual monitoring shall not be required but the occupational exposure of the worker shall be assessed. This assessment shall be on the basis of the results of monitoring of the workplace or individual monitoring .” Part 8: Occupational exposure

  19. Practical issues 2 (cont.) • For staff who are not normally employed in a controlled area, but may be at risk occasionally, the method of monitoring depends on the magnitude of likely exposure (compare BSS I.33) • e.g. electronic pocket dosimeter Make sure to record readings if no permanent record is given Part 8: Occupational exposure

  20. Dose Limits (Schedule II, BSS) • Occupational exposure: • 20mSv/year averaged over 5 years • 50mSv in any single year • lens equivalent dose 150mSv in a year • extremities (hands and feet) equivalent dose 500mSv in a year Part 8: Occupational exposure

  21. Dose Limits (Schedule II, BSS) • Occupational exposure: • 20mSv/year averaged over 5 years • 50mSv in any single year • lens equivalent dose 150mSv in a year • extremities (hands and feet) equivalent dose 500mSv in a year Remember: The need for optimization still applies Part 8: Occupational exposure

  22. 2. Where can occupational exposure occur? • As part of normal operation • Machine malfunction - discussed in the relevant parts on equipment (5 and 6) • Operator mistake - discussed in parts on QA • Design problems (discussed in part 7 on facility design and shielding) Part 8: Occupational exposure

  23. BSS Glossary: Normal Exposure • “An exposure which is expected to be received under normal operating conditions of an installation or a source, including possible minor mishaps that can be kept under control.” Part 8: Occupational exposure

  24. Exposure as normal part of operation (BSS: “Normal Exposure”) • Not common in radiotherapy (unlike nuclear medicine) • Typical only in the context of use of radioactive substances • 60-Co teletherapy background in treatment room • Brachytherapy source preparation • Nursing of patients with implants Part 8: Occupational exposure

  25. Potential exposures • BSS 1996 glossary: “Exposure that is not expected to be delivered with certainty but that may result from an accident at a source or owing to an event or sequence of events of a probabilistic nature, including equipment failures and operating errors.” Part 8: Occupational exposure

  26. Potential exposures • Are in principle avoidable • Need to be considered and the risk minimized • Prevention • Education • Protective equipment • Mitigating the effects Part 8: Occupational exposure

  27. In general, the management of occupational exposures can be made more effective by the classification of areas (BSS I.21-25) • Controlled areas • Supervised areas • … both are in addition to public areas. Part 8: Occupational exposure

  28. Controlled Areas • BSS Appendix I.21. “Registrants and licensees shall designate as a controlled area any area in which specific protective measures or safety provisions are or could be required for: • controlling normal exposures or preventing the spread of contamination during normal working conditions; and • preventing or limiting the extent of potential exposures.” Part 8: Occupational exposure

  29. Controlled areas • BSS appendix I.22.: “In determining the boundaries of any controlled area, registrants and licensees shall take account of the magnitudes of the expected normal exposures, the likelihood and magnitude of potential exposures, and the nature and extent of the required protection and safety procedures.” Part 8: Occupational exposure

  30. Controlled areas in radiotherapy • All treatment rooms • Brachytherapy source preparation rooms • Source storage areas Part 8: Occupational exposure

  31. Controlled areas • Require access restrictions • Require interlocks where appropriate • Require signs • Protective equipment and monitoring • Require staff to follow written procedures Part 8: Occupational exposure

  32. …in the words of the BSS • I.23. “Registrants and licensees shall: (a) delineate controlled areas by physical means or, where this is not reasonably practicable, by some other suitable means; (b) where a source is brought into operation or energized only intermittently or is moved from place to place, delineate an appropriate controlled area by means that are appropriate under the prevailing circumstances and specify exposure times; (c) display a warning symbol, such as that recommended by the International Organization for Standardization (ISO) [12], and appropriate instructions at access points and other appropriate locations within controlled areas; Part 8: Occupational exposure

  33. BSS appendix I.23 (cont.) (d) establish occupational protection and safety measures, including local rules and procedures that are appropriate for controlled areas; (e) restrict access to controlled areas by means of administrative procedures, such as the use of work permits, and by physical barriers, which could include locks or interlocks; the degree of restriction being commensurate with the magnitude and likelihood of the expected exposures; (f) provide, as appropriate, at entrances to controlled areas: (i) protective clothing and equipment; (ii) monitoring equipment; and (iii) suitable storage for personal clothing; Part 8: Occupational exposure

  34. BSS appendix I.23 (cont.) (g) provide, as appropriate, at exits from controlled areas: (i) equipment for monitoring for contamination of skin and clothing; (ii) equipment for monitoring for contamination of any object or substance being removed from the area; (iii) washing or showering facilities; and (iv) suitable storage for contaminated protective clothing and equipment; and (h) periodically review conditions to determine the possible need to revise the protection measures or safety provisions, or the boundaries of controlled areas. Part 8: Occupational exposure

  35. Supervised Areas BSS Appendix I.24. “Registrants and licensees shall designate as a supervised area any area not already designated as a controlled area but where occupational exposure conditions need to be kept under review even though specific protection measures and safety provisions are not normally needed.” Part 8: Occupational exposure

  36. Supervised areas in radiotherapy • Operator consoles • Areas where calculated exposure rates through shielding barriers are likely to result in exposures of 1mSv per year (IAEA TECDOC 1040, 1998) Part 8: Occupational exposure

  37. 3. Local Rules and Supervision BSS Appendix I.26. “Employers, registrants and licensees shall, in consultation with workers, through their representatives if appropriate: establish in writing such local rules and procedures as are necessary to ensure adequate levels of protection and safety for workers and other persons” Part 8: Occupational exposure

  38. Establish • relevant investigation level or authorized level (in radiotherapy this can typically be set low as ‘normal exposure’ is small) • … and the procedure to be followed in the event that any such value is exceeded; Part 8: Occupational exposure

  39. Ensure • that any work involving occupational exposure be adequately supervised and take all reasonable steps to ensure that the rules, procedures, protective measures and safety provisions be observed • that a radiation protection officer is appointed (when required by the Regulatory Authority) Part 8: Occupational exposure

  40. 4. Protective measures • A safe environment for staff is provided by • Good building design • education • signage • shielding • of the equipment • room housing the equipment • interlocks • if triggered will cause the equipment to go into a safe mode Part 8: Occupational exposure

  41. Basic protective measures • Time, • Distance, • Shielding… Compare notes to part 4 of the course Part 8: Occupational exposure

  42. Time Dose proportional to Time Dose = Dose-rate x Time Part 8: Occupational exposure

  43. Time in practice • Important when handling radioactive sources in brachytherapy • ‘live’ implants • handling/nursing patients with implants • When holding patients during diagnostic procedures (e.g. simulator) • …otherwise not of great relevance. Part 8: Occupational exposure

  44. Distance Inverse square law : Dose-rate  1/(distance)2 dose-rate distance Part 8: Occupational exposure

  45. Distance in practice • Important when dealing with brachytherapy patients • Important when handling active sources in brachytherapy (long tweezers!) • … otherwise usually not something staff can influence. Part 8: Occupational exposure

  46. Shielding Tenth Value Thickness incident radiation transmitted radiation D Sv/h D/10 Sv/h Part 8: Occupational exposure

  47. Shielding in practice • Radiotherapy typically uses sources with highly penetrating radiation - need substantial shielding. • Design of appropriate shielded treatment rooms is essential (compare part 7 of the course) • Personal protective equipment (compare BSS Appendix I.28) such as lead aprons, lead gloves, thyroid shields are typically of not much use in radiotherapy... Part 8: Occupational exposure

  48. Source preparation area Part 8: Occupational exposure

  49. In practice, education and training are often the best protection BSS Appendix I.27. “Employers, in co-operation with registrants and licensees, shall: provide to all workers adequate information on the health risks due to their occupational exposure, whether normal exposure or potential exposure, adequate instruction and training on protection and safety, and adequate information on the significance for protection and safety of their actions” Part 8: Occupational exposure

  50. 5. Monitoring BSS Appendix I.32: “The employer of any worker, as well as self-employed individuals, and the registrants and licensees shall be responsible for arranging for the assessment of the Occupational exposure of workers, on the basis of individual monitoring where appropriate, and shall ensure that adequate arrangements be made with appropriate dosimetry services under an adequate quality assurance programme.” Part 8: Occupational exposure