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Radiation Protection in Radiotherapy

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 9 Medical Exposure

  2. IAEA Safety Fundamentals SS No 120: Medical Exposure • Exposure incurred by patients as part of their own medical or dental diagnosis and treatment • by persons, other than occupationally exposed, knowingly while voluntarily helping in support and comfort of patients • by volunteers in a program of biomedical research involving their exposure Part 9: Medical exposure

  3. Objectives • To understand the concept of “medical exposure” as set out by the BSS in the context of radiotherapy • To appreciate the importance of justification and optimization for medical exposures • To understand strategies for optimization of dose to patients, relatives and volunteers Part 9: Medical exposure

  4. Contents 1. Medical Exposure and the BSS 2. Who is affected? 3. Justification and optimization 4. Dose constraints for volunteers 5. The role of different professions Part 9: Medical exposure

  5. Contents 1. Medical Exposure and the BSS 2. Who is affected? 3. Justification and optimization 4. Dose constraints for volunteers 5. The role of different professions Will be complemented and expanded on in parts 10 to 13 of the course Part 9: Medical exposure

  6. Medical Exposure • Detailed information in BSS appendix II • Additional and more recent information in IAEA Safety Guide RS-G-1.5 Part 9: Medical exposure

  7. Structure of Appendix II: BSS • Responsibilities • Justification of Medical Exposures • Optimization of Protection for Medical Exposures • Guidance Levels • Dose Constraints for volunteers • Investigation of Accidental Medical Exposures and Incidents • Records Part 9: Medical exposure

  8. Let’s have a closer look... “BSS quotes”

  9. Responsibilities: “Registrants and licensees shall ensure that: • No patient be administered a diagnostic or therapeutic medical exposure unless the exposure is prescribed by a medical practitioner • Medical practitioners be assigned the primary task and obligation of ensuring overall patient protection and safety in the prescription of, and during the delivery of, medical exposure” BSS appendix II.1 Part 9: Medical exposure

  10. In radiotherapy practice: • The medical practitioner has the ultimate responsibility for the patient - this includes safety • The prescription is a legal document • The prescription must be in writing • The prescription must be detailed enough to describe the treatment adequately § Part 9: Medical exposure

  11. “Medical and paramedical personnel be available as needed, and either be health professionals or have appropriate training adequately to discharge assigned tasks in the conduct of the diagnostic or therapeutic procedure that the medical practitioner prescribes • For therapeutic uses of radiation, the calibration, dosimetry and QA requirements of the Standards be conducted by or under the supervision of a qualified expert in radiotherapy physics” BSS appendix II.1 Part 9: Medical exposure

  12. In radiotherapy practice: • Radiotherapy is a multidisciplinary approach - a variety of other professionals are also involved • This includes radiation professionals such as physicists, radiotherapy technicians, dosimetrists and engineers specialized in radiotherapy equipment as well as oncology and patient support staff such as oncology nurses, dieticians, social workers and other allied health professionals. • In regards to all physical aspects of the radiation delivery the medical physicist (BSS: “qualified expert in radiotherapy physics”) carries the ultimate responsibility More in section 5 of the lecture... Part 9: Medical exposure

  13. “The exposure of individuals incurred knowingly while voluntarily helping (other than in their occupation) in the care, support or comfort of patients undergoing medical diagnosis or treatment be constrained” • In radiotherapy practice this extends the concept of medical exposure to persons other than the patient. These ‘others’ do not benefit directly from the irradiation like the patient, however, it is assumed that they are undergoing the irradiation voluntarily and fully informed of the risks. BSS appendix II.1 Part 9: Medical exposure

  14. “Training criteria be specified or be subject to approval, as appropriate, by the Regulatory Authority in consultation with relevant professional bodies” • In radiotherapy practice this places additional responsibilities on the licensee - not only do they have to make sure staff is adequately trained, they also must involve professional organizations in the decision making process BSS appendix II.1 Part 9: Medical exposure

  15. … and finally • “Medical practitioners shall promptly inform the registrant or licensee of any deficiencies or needs regarding compliance with the Standards with respect to protection and safety of patients and shall take such actions as may be appropriate to ensure the protection and safety of patients” BSS appendix II.3 Part 9: Medical exposure

  16. 2. Who is affected by medical exposures? • Patients • Persons supporting the patient (other than occupationally exposed persons) • Volunteers for research Part 9: Medical exposure

  17. Exposure incurred by patients by persons helping in support and comfort of patients by volunteers in a programme of biomedical research Who is affected in radiotherapy? Cancer patients - external beam and brachytherapy; Small number of other patients (chelates, endovascular brachytherapy) Parents helping children; Relatives of patients with permanent implants Volunteers; Patients treated but also evaluated as part of clinical research Part 9: Medical exposure

  18. Exposure incurred by patients by persons helping in support and comfort of patients by volunteers in a programme of biomedical research In numbers in practice ... Cancer patients - external beam and brachytherapy; Small number of other patients (chelates, endovascular brachytherapy) Parents helping children; Relatives of patients with permanent implants Volunteers; Patients treated but also evaluated as part of clinical research Part 9: Medical exposure

  19. Medical Exposure in radiotherapy: Patients • Exposure incurred by patients • part of their medical treatment • diagnostic exposures (diagnostic X Rays, nuclear medicine scans, diagnostic CT scans,…) - not covered in this course • planning exposures • therapeutic exposures • verification exposures Part 9: Medical exposure

  20. Patient exposure specific for radiotherapy • Planning CTs, simulator films • Radiotherapy • External Beam RT - part 10 • Brachytherapy - part 11 • Portal images, verification CTs Planning Delivery of Therapy Verification Part 9: Medical exposure

  21. 3. Justification and optimization • Two important principles for radiation protection • Part of the ‘system of radiation protection’ promoted in ICRP report 60 (1991) and expanded on in the BSS Part 9: Medical exposure

  22. Justification of Medical Exposures BSS, appendix II: “Medical exposures should be justified by weighing the diagnostic or therapeutic benefits they produce against the radiation detriment they might cause, taking into account the benefits and risks of available alternative techniques that do not involve medical exposure.” Part 9: Medical exposure

  23. Justification in practice for radiotherapy patients • A clinical decision for the benefit of the patient. • It takes into consideration the disease, the patient and the resources available. • It must be documented. Part 9: Medical exposure

  24. Radiation is the therapeutic agent If the medical practitioner in consultation with the patient has decided that radiotherapy is indicated, radiation protection is usually a secondary concern

  25. …but even as a ‘secondary’ concern it is important: • Radiation protection is part of good practice and helps to a) limit side effects b) reduce the probability of complications - or at least their severity c) reduce the probability of accidents • Wherever there are potential choices in approach, protection must be considered as one factor Part 9: Medical exposure

  26. It is also worth considering that • Radiotherapy has been shown to be capable of increasing the risk of secondary cancers in lymphoma patients (large fields, young patients) and breast cancer patients (long survivors, radiosensitive structures). Part 9: Medical exposure

  27. …and • Radiotherapy may cause short and long term deterministic side effects and complications - examples are skin damage,lung fibrosis, risk of spinal cord injury • Like in most medical procedures there is the potential of an accident • Therefore it is important to evaluate risk benefit for individual patients and consider this in the justification. Part 9: Medical exposure

  28. Increased tumor control probability also increases risk of intolerable complications Window of opportunity Part 9: Medical exposure

  29. Optimization - BSS • Design Considerations • Operational • Calibration • Clinical Dosimetry • Quality Assurance • Minimize dose to healthy tissue outside the study volume or treatment volume Part 9: Medical exposure

  30. Optimization • The major task in radiotherapy • Through optimization one may be able to separate the curves of tumor control and complication probability further • Subject of part 10 and 11 of the course Part 9: Medical exposure

  31. Another aspect of optimization • Optimization of radiotherapy includes the ‘minimization’ of the likelihood of accidents. In this context optimization includes: • accident prevention • mitigation • planning to allow appropriate response • This is discussed in more detail in part 13 of the present course Part 9: Medical exposure

  32. Dose limits are not applicable to patients in radiotherapy Provided there is a prescription by a medical practitioner.

  33. Medical Exposure: Support persons during irradiation • Typically no one is in the treatment room during external beam irradiation • Children are to be sedated or anesthetized during irradiation • Relatives or supporting persons may be affected in prolonged treatments such as in-patient brachytherapy or permanent implants Part 9: Medical exposure

  34. Supporting persons • An issue in brachytherapy • Affects visitors of patients in in-patient low dose rate brachytherapy • Affects carers, relatives and friends of patient with permanent implants • Written guidelines should be established - and must be given to the patient (and/or his/her relatives) Part 9: Medical exposure

  35. A note on pregnant patients • Effects of radiation after conception in animal studies: • Increased incidence of spontaneous abortion a few days after conception. • Malformations especially if irradiated during organogenisis. • Growth disturbances. • Neonatal death. Part 9: Medical exposure

  36. E.J. Hall “Radiobiology for the Radiologist” 4th edition (1994) Part 9: Medical exposure

  37. BSS appendix II.18. “Registrants and licensees shall ensure that: (b) radiotherapeutic procedures causing exposure of the abdomen or pelvis of women who are pregnant or likely to be pregnant be avoided unless there are strong clinical indications; ... (d) any therapeutic procedure for pregnant women be planned to deliver the minimum dose to any embryo or foetus; and (e) the patient be informed of possible risks.” Part 9: Medical exposure

  38. In radiotherapy practice: • Find out if patient is (or could be) pregnant • In most cases radiotherapy to a pregnant person is contraindicated • The patient must be informed of risks and involved in the decision making process • Shielding the fetus of a radiation therapy patient may be possible - internal scatter will remain • Dose to the fetus MUST be estimated (phantom measurements are a good way to do this) • Therapeutic abortions should be considered after 10 cGy due to the possibility of mental retardation • This decision depends on the circumstances Part 9: Medical exposure

  39. 4. Dose Constraints for persons assisting patients • “Registrants and licensees shall constrain any dose to individuals incurred knowingly while voluntarily helping (other than in their occupation) in the care, support or comfort of patients undergoing medical diagnosis or treatment, and to visitors to patients who have received therapeutic amounts of radionuclides or who are being treated with brachytherapy sources, to a level not exceeding that specified in Schedule II, para.II-9 of BSS” BSS appendix II.27 Part 9: Medical exposure

  40. Dose Constraints for persons assisting patients According to BSS • Adults: should be unlikely to exceed 5mSv • Children: should be unlikely to exceed 1mSv Part 9: Medical exposure

  41. External beam radiotherapy • Volunteers:not possible in the conventional way, however considered must be • participants in clinical trials • patients who undergo radiotherapy and are at the same time included in radiobiological evaluations • patients who undergo radiotherapy and have their treatment modified to answer research questions. Part 9: Medical exposure

  42. Volunteers: Justification of Medical Exposures • The exposure of humans for medical research is deemed to be not justified unless it is • in accordance with the provisions of the Helsinki Declaration and follows the guidelines for its application prepared by Council for International Organizations of Medical Sciences (CIOMS) and WHO (see references in BSS no 115) • subject to the advice of an Ethical Review Committee (or any other body assigned similar functions by national authorities) and to applicable national and local regulations. Part 9: Medical exposure

  43. Dose Constraints to Volunteers in Medical Research • “The Ethical Review Committee or other institutional body assigned similar functions on the subject by national authorities shall specify dose constraints to be applied on a case by case basis in the optimization of protection for persons exposed for medical research purposes if such medical exposure does not produce direct benefit to the exposed individual.” BSS appendix II.26 Part 9: Medical exposure

  44. 5. The role of professionals • Radiation Oncologists • Medical Physicists • Radiation Therapy Technologists • Others Part 9: Medical exposure

  45. Radiation Oncologist is the ‘medical practitioner’ in radiotherapy • Medical Practitioner (BSS glossary): “An individual who: (a) has been accredited through appropriate national procedures as a health professional; (b) fulfills the national requirements on training and experience for prescribing procedures involving medical exposure; and (c) is a registrant or a licensee, or a worker who has been designated by a registered or licensed employer for the purpose of prescribing procedures involving medical exposure. Part 9: Medical exposure

  46. Radiation Oncologist • Is the medical practitioner • BSS II.1. Registrants and licensees shall ensure that: ... (b) medical practitioners be assigned the primary task and obligation of ensuring overall patient protection and safety in the prescription of, and during the delivery of, medical exposure; Part 9: Medical exposure

  47. Radiation Oncologists • Ultimately responsible for the justification of exposure • In the best position to evaluate the results of the optimization • does the treatment plan maximize the probability of “Complication Free Tumor Control”? Part 9: Medical exposure

  48. Justification - the role of the radiation oncologist • Based on clinical assessment • May include the consultation of other health professionals • Based on clinical evidence • Has to be discussed with the patient • Is reflected in the prescription - which shall be complete and in writing Part 9: Medical exposure

  49. Clinical Evidence • Practice of Evidence Based Medicine • Radiation Oncology has good track record of prospective clinical trials • The oncologist must be aware of the literature • Access to internet may be necessary Part 9: Medical exposure

  50. Prescription • Must be understandable by others... • Should follow accepted guidelines • Guidance by the ICRU • International Commission on Radiation Units and Measurements ICRU 50, Bethesda. Prescribing, recording, and reporting photon beam therapy. 1993. • International Commission on Radiation Units and Measurements ICRU 55, Bethesda. Prescribing, recording, and reporting interstitial brachytherapy. 1998. • International Commission on Radiation Units and Measurements ICRU 62, Bethesda. Prescribing, recording, and reporting photon beam therapy. 2000. Part 9: Medical exposure