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Postgraduate Educational Course in Radiation Protection and the Safety of Radiation Sources VIII.2. Medical Exposures in Nuclear Medicine. 1. Justification System of radiological protection for medical exposure VIII.2.1. Justification 2 System of radiological protection for medical exposure The system of radiological protection for medical exposure has basically to do with the general ethical principles of the health care system Ethics is the science of morality; the principles of proper professional conduct concerning the rights and duties of the health care professional, his patients, and his colleagues.* *Webster’s New World, Medical Dictionary VIII.2.1. Justification 3 Principles Commonly Addressed in any Ethical Theory AUTONOMY BENEFICIENCE CONFIDENTIALITY JUSTICE TRUTH TELLING INFORMED CONSENT VIII.2.1. Justification 4 Principles Commonly Addressed in any Ethical Theory AUTONOMY: The right of the individual patient to make decisions regarding personal medical care The patient is to be given adequate information about the alternatives so an intelligent decision can be made The health care worker is to respect the decision of the patient. VIII.2.1. Justification 5 Principles Commonly Addressed in any Ethical Theory BENEFICIENCE The duty of the health care worker to perform those acts or administer care that will be of benefit to the patient ALARA Responsibility of the staff to monitor the patient. VIII.2.1. Justification 6 Principles Commonly Addressed in any Ethical Theory CONFIDENTIALITY The legal right of privacy All patient records are confidential material The “need to know” VIII.2.1. Justification 7 Principles Commonly Addressed in any Ethical Theory JUSTICE All people are created equal and, therefore, should be treated as equals The right to receive medical care Treat patients with the same level of courtesy and respect VIII.2.1. Justification 8 Principles Commonly Addressed in any Ethical Theory TRUTH TELLING The patient’s right to a truthful diagnosis and prognosis It is the responsibility of the physician, not the health care worker, to discuss the patient's diagnosis and prognosis with the patient VIII.2.1. Justification 9 Principles Commonly Addressed in any Ethical Theory INFORMED CONSENT The patient must have adequate information about the procedure in order to be able to make an informed decision Truth telling must be practiced in the discussion of procedures with the patient The patient must be allowed autonomy VIII.2.1. Justification 10 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.” VIII.2.1. Justification 11 JUSTIFICATION OF MEDICAL EXPOSURE Objective of treatment/examination Medical exposure Radiation risks VIII.2.1. Justification 12 RADIATION RISKS IN NUCLEAR MEDICINE EXAMINATIONS Examination Radiopharmaceutical Myocardium Tl-201 chloride Bone Tc-99m MDP Thyroid Tc-99m pertechnetate Lungs Tc-99m MAA Kidney clearance Cr-51 EDTA VIII.2.1. Justification Effective dose (mSv) 23 3.6 1.1 0.9 0.01 Risk (%) 0.12 0.018 0.006 0.005 0.00005 13 Risk of stochastic effects(%/ Sv) 20 Male 15 Embryo and fetus Female 10 5 0 0 10 20 30 40 50 60 70 80 (age at exposure) VIII.2.1. Justification 14 Absorbed dose to the fetus Examination Bone (Tc99m) Brain (CBF) Lung (Tc99m-MAA) Kidneys (MAG3) Tumour or abscess (Ga-67 citrate) Heart (Tc99m-MIBI) Heart (Tl-201) Thyroid (Tc99m) Thyroid (I-131) Kidney clearance (Cr-51-EDTA) Activity (MBq) Dose to fetus (mSv) 600 500 160 100 300 300 100 100 100 4 4 0.4 2 28 5 10 1 7 4 0.02 (Data from Russell, Stabin et al Radiation dose to the embryo/fetus from radiopharmaceuticals Draft, 1997 VIII.2.1. Justification 15 Absorbed dose to the fetus 0,3 I-131 iodide Tc-99m-MAG3 mGy/MBq 0,2 0,1 0,0 Early 3 months 6 months 9 months Pregnancy month (Data from Russell, Stabin et al Radiation dose to the embryo/fetus from radiopharmaceuticals Draft, 1997 VIII.2.1. Justification 16 Risk of stochastic effects(%/ Sv) 20 The higher Male risk for young people as well as for the fetus must be Female considered in the justification of an examination. Special concern should be given to: •Children •Pregnant women 15 10 5 0 0 10 20 30 40 50 60 70 80 (age at exposure) VIII.2.1. Justification 17 The justification of a practice The decision to adopt or continue any human activity involves a review of the benefits and disadvantages of the possible options E.g.: choosing between the use of nuclear medicine or ultrasound or MR Often, the radiation detriment will be only a small part of the total detriment Most of the assessments needed for the justification of a practice are made on the basis of experience, professional judgement, and common sense VIII.2.1. Justification 18 Three levels of justification General level: The use of radiation in medicine is accepted as doing more good than harm Generic justification (specific procedure with a specific objective: bone scan for patients with ca prostate showing relevant symptoms) Third level: the application of the procedure to an individual patient VIII.2.1. Justification 19 Generic justification (I) It is a matter for national professional bodies, sometimes in conjunction with national regulatory authorities The exposures to staff (occupational) and to members of the public should be taken into account The possibility of accidental or unintended exposures (potential exposure) should also be considered The decisions should be reviewed from time to time as new information becomes available VIII.2.1. Justification 20 Generic justification (II) The resources in a country or region should be considered (single detectors in renography instead of gammacamera for economical reasons) The justification of diagnostic examinations for which the benefit to the patient is not the primary objective needs special consideration (e.g. examinations for insurance purposes or medical research) VIII.2.1. Justification 21 Justification for an individual patient To check that the required information is not yet available Once the procedure is generically justified, no additional justification is needed for simple diagnostic examinations e.g. determination of kidney clearance or other laboratory methods. For complex procedures and therapy individual justification by the nuclear medicine specialist and the referring physician should be done VIII.2.1. Justification 22 When radiation is the therapeutic agent If the medical practitioner in consultation with the patient has decided that radionuclide therapy is indicated, patient protection is usually a secondary concern VIII.2.1. Justification 23 JUSTIFICATION (BSS) ”II.6. Any radiological examination for occupational, legal or health insurance purposes undertaken without reference to clinical indications is deemed to be not justified unless it is expected to provide useful information on the health of the individual examined or unless the specific type of examination is justified by those requesting it in consultation with relevant professional bodies.” VIII.2.1. Justification 24 Children (BSS II.17) (e) administration of radionuclides to children for diagnostic procedures be carried out only if there is a strong clinical indication, and the amount of activity administered be reduced according to body weight, body surface area or other appropriate criteria. VIII.2.1. Justification 25 BREASTFEEDING Breastfeeding a baby should be considered in the justification of a nuclear medicine procedure of the mother. Normally, breastfeeding should not exclude the mother from a justified examination. The problem should be solved by restrictions on the continuing feeding (optimization) VIII.2.1. Justification 26 Nuclear Medicine (BSS II.17) (c) administration of radionuclides for diagnostic or radiotherapeutic procedures to women pregnant or likely to be pregnant be avoided unless there are strong clinical indications; VIII.2.1. Justification 27 Therapeutic Procedures (BSS II.18) (c) administration of radionuclides for therapeutic procedures to women who are pregnant or likely to be pregnant or who are nursing 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 …. VIII.2.1. Justification 28 JUSTIFICATION & PREGNANCY In some circumstances, the unborn child may be at increased risk, which should be considered in justification. Prenatal doses from most properly done diagnostic procedures present no measurably increased risk of prenatal death, malformation, mental impairment. Higher doses such as those from therapeutic procedures can result in significant fetal harm. VIII.2.1. Justification 29 Radio-iodine therapy As a rule, a pregnant woman should not be treated with a radioactive substance unless the therapy is required to save her life: in that extremely rare event, the potential absorbed dose and risk to the fetus should be estimated and conveyed to the patient and the referring physician. Considerations may include terminating the pregnancy. VIII.2.1. Justification 30 Becoming pregnant after irradiation • ICRP has recommended that a woman not become pregnant until the potential fetal dose from remaining radionuclides is less than 1 mGy. • This is not usually a consideration except for radiopharmaceuticals labelled with 59Fe (for metabolism studies) or 75Se (for adrenal imaging). • As a result of the long physical half-lives of these radionuclides and their long residence times in the body, it is recommended that pregnancy be avoided for 6 and 12 months respectively. VIII.2.1. Justification 31 PREGNANCY AFTER THERAPY Radiopharmaceutical All activities up to (MBq) Au-198 colloid 10000 I-131 iodide (thyroid ca) 5000 I-131 iodide (thyrotoxicosis) 800 I-131 MIBG 5000 P-32 phosphate 200 Sr-89 chloride 150 Y-90 colloid (arthritic joints) 400 Y-90 colloid (malignancy) 4000 VIII.2.1. Justification Avoid pregnancy (months) 2 4 4 4 3 24 0 1 32 Research on Pregnant Patients Radiation research involving pregnant patients should be discouraged VIII.2.1. Justification 33 Other factors to consider Will the patient pose a risk to other persons such as members of the family or general public? Is the patient scheduled for surgery or similar intervention? Is there a risk that the patient will die within a short period of time? Is there an increased risk that the patient requires emergency treatment? VIII.2.1. Justification 34 Advise from BSS appendix II.28. “In order to restrict the exposure of any members of the household of a patient who has undergone a therapeutic procedure with sealed or unsealed radionuclides and members of the public, such a patient shall not be discharged from hospital before the activity of radioactive substances in the body falls below the level specified in Schedule III, Table III-VI. Written instructions to the patient concerning contact with other persons and relevant precautions for radiation protection shall be provided as necessary”. VIII.2.1. Justification 35 IAEA BSS (1996) App. II.28 BSS Schedule III, Table III-VI: Guidance level only given for 131-I: Maximum activity for discharge 1100MBq Other isotopes not mentioned Legal limit values are still applicable VIII.2.1. Justification 36 Also consider: What happens if the patient requires emergency treatment? Surgery? What happens if the patient dies? Autopsies? Cremation? VIII.2.1. Justification 37 Other factors to consider The other factors discussed should generally not impose on the justification of an examination or treatment of the patient. The radiation protection problems should be solved by optimization of safety and a well trained staff in case of emergencies. VIII.2.1. Justification 38