Part 2

1. Part 2

2. What can radiation do? Death Cancer Skin Burns Cataract Infertility Genetic effects 2

3. What can radiationdo? Deterministic effects death, skin burns, cataract, infertility Stochastic effects cancer, genetic effects 3

4. Early Observations of the Effects of Ionizing Radiation • 1895 X Rays discovered by Roentgen • 1896 First skin burns reported • 1896 First use of X Rays in the treatment of cancer • 1896 Becquerel: Discovery of radioactivity • 1897 First cases of skin damage reported • 1902 First report of X Ray induced cancer • 1911 First report of leukaemia in humans and lung cancer from occupational exposure • 1911 94 cases of tumour reported in Germany (50 being radiologists)

5. OBJECTIVES OF RADIATION PROTECTION • PREVENTION of deterministic effect. • LIMITING the probability of stochastic effect 5

6. Radiosensitivity [RS] • RS = Probability of a cell, tissue or organ of suffering an effect per unit of dose.

7. RADIOSENSITIVITY:

8. Why do we need protection? It is generally assumed that even very small doses of ionizing radiation can potentially be harmful . Therefore, persons must be protected from ionizing radiation at all dose levels. 8

9. Who should be protected in Hospital? Patients. Members of his/her family. Workers. General public. 9

10. Ionizing Radiation We live with 1-3 mSv/y Can kill 4000 mSv 10

11. Patients Protection: • Persons are medically exposed as part of their diagnostic or treatment • According to IAEA, ICRP and BSS, two basic principles of radiation protection are to be complied with: justification and optimization

12. Justification Optimization Dose Limitations Time (dose directly proportional to length of exposure). Shielding (b/w source and patient). Distance (Intensity and StP distance). RP Principles vs. Actions

13. Justification No use of ionizing radiation is justified if there is no benefit. All applications must be justified. This implies: All, even the smallest exposures are potentially harmful and the risk must be offset by a benefit. 13

14. The justification of a practice • The decision to adopt or continue any human activity involves a review of benefits and disadvantages of the possible options • E.g.: choosing between the use of X Rays or ultrasound Most of the assessments needed for the justification of a practice are made on the basis of experience, professional judgement, and common sense.

15. Risk/Benefit analysis: Need to evaluate the benefits of radiation - an easy task in the case of nuclear medicine. Radiation is the diagnostic and therapeutic agent. Assessment of the risks requires the knowledge of the dose received by persons. 15

16. Optimization When radiation is to be used then the exposure should be optimized to minimize any possibility of detriment. Optimization is “doing the best you can under the prevailing conditions”. Need to be familiar with techniques and options to optimize the application of ionizing radiation - this is really the main objective of the present course. 16

17. Optimization: • Reducing the patient dose may reduce the quantity as well as the quality of the information provided by the examination or may require important extra resources. • Means that doses should be “As Low As Reasonably Achievable” ALARA, economic and social factors being taken into account” compatible with achieving the required objective.

18. Optimization principle ALARA 18

19. OPTIMIZATION OFPATIENT EXAMINATION Diagnostic objective Medical exposure

20. Optimization of image quality Image quality depends on: Administered activity Technical factors - equipment used - acquisition protocol - image processing & evaluation - noise - spatial resolution - scatter Patient factors - size - age - disease - movement

21. Framework of RP for medical exposure • Justification • Optimization • The use of doses limits is NOT APPLICABLE • Dose constraints and guidance (or reference) levels ARE RECOMMENDED

22. Three types of exposure • Medical Exposure (principally the exposure of persons as part of their diagnostic or treatment) • Occupational Exposure (exposure incurred at work, and practically as a result of work) • Public Exposure (including all other exposures)

23. Medical exposure • Medical Exposure • Exposure of persons as part of their diagnostic or treatment. • Exposures incurred by volunteers as part of a program of biomedical research.

24. Responsibilities for Medical Exposure (a) No patient to be administered a diagnostic or therapeutic medical exposure unless the exposure is prescribed by a medical practitioner; (d) For therapeutic uses of radiation, the calibration, dosimetry and quality assurance requirements of the Standards be conducted by or under the supervision of a qualified expert in radiotherapy physics. 24

25. PUBLIC: • effective dose of 1 mSv/year • equivalent dose to lens of the eye 15 mSv/yr • equivalent dose to skin of 50 mSv/year.

26. Guidance levels for diagnostic radiography (typical adult patient)

27. Guidance levels for diagnostic radiography (typical adult patient)

28. Typical effective doses from diagnostic medical exposures From: Referral Criteria For Imaging. CE, 2000.

29. Typical effective doses from diagnostic medical exposures From: Referral Criteria For Imaging. CE, 2000.

30. OCCUPATIONAL - APPENDIX I Dose Limits • effective dose of 5mSv per year averaged over five consecutive years • equivalent dose to lens of eye of 150mSv in a year • equivalent dose to extremities or skin of 500mSv in a year. For apprentices (16-18 years of age) • effective dose of 6mSv in a year 30

31. OCCUPATIONAL Female workers should notify pregnancy. Working conditions shall be adapted to ensure that the embryo and fetus are afforded the same broad level of protection as for members of the public. 31

32. Class Activity 3 • Mr. Sharp, I am given to understand that 2 bone scans and a cardiac study done on me have given me 22 mSv whereas 20 mSv is the safe dose. I want to file legal suit against the doctor. What do you feel??