sivabalan presentation edited HSV encephalitis and jejunal volvulus.pptx

Case presentation

1. RADIATION HAZARDS and PROTECTION 1 MODERATORS: PROF : DR DHRUBAJYOTHI BORPATRAGOHAIN PROF & HOD : DR M.H.BHUYAN PRESENTED BY DR SIVABALAN J

2. Radiation is a form of energy that propagates through matter or space in the form of wave or particulate manner. Radiation Hazard: Risk of damage to cells or tissue from being exposed to any amount of ionizing radiation.

3. A. Natural radiation: 72% 1. External: Cosmic and gamma radiation 2. Internal: radionuclides with in the body ingested or inhaled B. Man made : 2 8 % 1. Diagnostic 83% (Medical x-ray ,CT and nuclear imaging) 2. Therapeutic , Sterilisation , 17 % 3. Nuclear weapons/industry/accidents SOURCES OF RADIATION:

4. 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 ). 4 THREE TYPES OF EXPOSURE

5. Radio-sensitivity [RS] AND ITS LAW RS = Probability of a cell, tissue or organ of suffering an effect per unit of dose. Radio-sensitivity of living tissues varies with maturation & metabolism; Stem cells are radiosensitive. More mature cells are more resistant. Younger tissues are more sensitive. Tissues with high metabolic activity are highly radiosensitive. High proliferation and growth rate, high radio-sensitivity.

6. INTRODUCTION: The first recorded biologic effect of radiation was seen by Becquerel , who developed erythema and subsequently ulceration when radium container was left accidentally in his left pocket. Clarence Dally , who had worked extensively with X-rays, died of skin cancer in 1904, it was the first death attributed to radiation effect. William Herbert Rollins developed leaded tube housings, collimators , and other techniques to limit patient dose during 1896-1904. - Also demonstrated that exposure of a pregnant guinea pig resulted in killing of the fetus.

7. PART i: Radiation hAZARDS : DETERMINISTIC Somatic Clinically attributable in the exposed individual CELL DEATH STOCHASTIC somatic & hereditary epidemiologically attributable in large populations ANTENATAL somatic and hereditary expressed in the foetus, in the live born or descendants BOTH TYPE OF EFFECTS CELL TRANSFORMATION

8. A. DETERMINISTIC EFFECTS 9 Also called Threshold/non-stochastic effect. Mechanism is cell killing. Existence of a dose threshold value (below this dose, the effect is not observable) Severity of the effect increases with dose A large number of cells are involved. Radiation injury from an industrial source

9. B. Stochastic Effects Mechanism is cell modification. No threshold. Probability of the effect increases with dose. Generally occurs with a single cell. e.g. Cancer, genetic effects.

10. Biological Damage Process occurs in three distinct modes/stages according to time frames: 1. Physical 2. Chemical 3. Biological

11. i . Physical stage- iONIZATION Radiation deposits energy. Excess energy removes an electron from an atom (ionized) Very quick!~10`-12 seconds. Leads to deterministic effects.

12. ii. CHEMICAL STAGE Ionized water can produce what are called free radicals. Radical can be very reactive chemically. The problem occurs when it reacts with DNA Ionization of DNA directly can also result in unwanted chemical reactions. Still very quick! ~10`-7 s. Leads to both deterministic and stochastic effects.

13. III. Biological Stage 1 . Cell Necrosis, Apoptosis (Deterministic effects) 2. DNA damage could lead too: - death during next division - prevention of division - mutation ( transformed- Stochastic effects ) 3. No effect(damage repaired by proof reading )

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15. DEFINITION International Atomic Energy Agency (IAEA) is defined the radiation protection as "The protection of people from harmful effects of exposure to ionizing radiation and the means for achieving this". The IAEA also states "The accepted understanding of the term radiation protection is restricted to protection of people” Part ii: RADIATION PROTECTION

16. Rome Vernon Wagner , an x-ray tube manufacturer, had begun to carry a photographic plate in his pocket and to develop the plate each evening to determine if he had been exposed (1907 ). Pioneer for personal monitoring . Died of cancer in 1908. Film badge came into effect from 1920. The first tolerance dose or permissible exposure limit was equivalent to about 0.2 rem per day. Rolf Sievert also put forth a tolerance dose- 10% of the skin erythema dose. EVALUATION

17. 2 nd International congress of radiation in 1928 set up the International X-ray and radium protection committee . International X-ray and radium protection committee was remodeled into The International Commission on Radiological Protection (ICRP) and The International Commission on Radiation Units and Measurements (ICRU ). The International Commission on Radiological Protection (ICRP) was the primary body created to assurance for the public benefit, the science of radiological protection. It is a registered charity, independent non-governmental organization.

18. It provides recommendations and guidance on protection against the risks associated with ionizing radiation, from artificial sources widely used in medicine, general industry and nuclear enterprises, and from naturally occurring sources The first report Publication 1 (ICRP, 1959)--->Publication 26(ICRP, 1977)--->Publication 60(ICRP, 1991b, international Basic Safety Standards)---> Publication 103(ICRP, 2007)

19. OTHER GOVERNING BODIES IAEA (International Atomic Energy Agency) establishes standards of safety and provides for the application of the standards National commission on radiation protection and measurement(NCRP) is recommendation body of USA

20. Atomic Energy Regulatory Board(AERB) Was constituted in 1983 by government of India. Carries out certain regulatory and safety functions under the Atomic Energy Act,1962 and Environment Protection Act, 1986, Radiation Protection Rules 2004. It is the recommendation, research and licensing body in India.

21. Atomic Energy Regulatory Board(AERB) The Mission of the AERB is to ensure the use of ionising radiation and nuclear energy in India does not cause undue risk to the health of people and the environment. & To protect people (workers, public and patients) from harmful effects of ionising radiation without unduly limiting the use of techniques that may cause radiation exposure.

22. Three Principles Of Radiation Protection JUSTIFICATION : OPTIMISATION : DOSE LIMITATION : The total dose to any individual from regulated sources in planned exposure situations other than medical exposure of patients should not exceed the appropriate limits specified by the Commission.

23. 1. JUSTIFICATION A practice involving exposure to radiation should produce sufficient benefit to the exposed individual or to society I n the case of patients, the diagnostic or therapeutic benefit should outweigh the risk of detriment. In the occupational exposure, the radiation risk must be added and compared with other risks in the workplace. In cases in which the individual receives no benefit, the benefit to society must outweigh the risks.

24. Three level of justification : 1.The proper use of radiation in medicine is accepted . (Like doing radiological investigation only when clinically indicated) 2. A specified procedure with specified objective is accepted. 3 . The application of the prcedure to an individual patient should be justified.

25. 2.OPTIMISATION Optimization of protection can be achieved by optimizing the procedure to administer a radiation dose which is a s l ow a s r easonably a chievable alara principle so as to derive maximum diagnostic information with minimum discomfort to the patient.

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27. METHODS OF RADIATION PROTECTION

28. CARDINAL PRINCIPLE OF RADIATION PROTECTION The triad of radiation protection measures is “time-distance-shielding” 1. Keep the time of exposure to radiation as short as possible. 2. Maintain as large distance as possible between the radiation and the exposed person. 3. Insert shielding material between the radiation source and the exposed person.

29. A .TIME The exposure time is related to radiation exposure and exposure rate (exposure per unit time) as follows: Exposure = Exposure rate x Time The algebraic expressions simply imply that if the exposure time is kept short, then the resulting dose to the individual is small.

30. B .DISTANCE The second radiation protection action relates to the distance between the source of radiation and the exposed individual.

31. C .SHIELDING Shielding implies that certain materials (concrete, lead) will attenuate radiation (reduce its intensity) when they are placed between the source of radiation and the exposed individual.

32. TYPES OF SHIELDING 1. X-ray tube shielding 2. Room shielding 3 . Personnel shielding 4. Patient shielding

33. X-ray Tube Shielding (Source Shielding) The X-ray tube housing is lined with thin sheets of lead because X-rays produced in the tube are scattered in all directions. This shielding is intended to protect both patients and personnel from leakage radiation. Manufacturers of X-ray devices are required to shield the tube housing so as to limit the leakage radiation exposure rate to < 0.1R/ hr at 1 meter from the tube anode. AERB recommends a maximum allowable leakage radiation from tube housing not greater than 1 mGy /hour/100 cm. i .

34. The control room of X-ray equipment is a secondary protective barrier which has two important aspects: a. The walls and viewing window of the control booth, which should have lead equivalents of 1.5 mm. b. The location of control booth, which should not be located where the primary beam falls directly, and the radiation should be scattered twice before entering the booth. Room Shielding (Structural Shielding) ii.

35. Unshielded openings in an X-ray room for ventilation or natural light, are located above a height of 2 m. Rooms housing diagnostic X-ray units and related equipment are located as far away as feasible from areas of high occupancy and general traffic, maternity and paediatric wards.

36. CT ROOM SHIELDING The size of the CT room housing the gantry of the CT unit as recommended by AERB should not be less than 25m2 . I t was proposed an additional thickness of 2.5mm of lead or 6.4` of concrete to shield the front and rear reference points, so as to reduce the absorbed dose to 1 mGy /year

37. Shielding of occupational workers can be achieved by following methods: a . The distance between the personnel and the patient should be maximized. b . Shielding apparel should be used as and when necessary which comprise of lead aprons, eye glasses with side shields, hand gloves and thyroid shields. Lead aprons are shielding apparel recommended for use by radiation workers. These are classified as a secondary barrier to the effects of ionizing radiation. These aprons protect an individual only from secondary (scattered) radiation, not the primary beam, Personal shielding iii.

38. Why LEAD BARRIERS? - has a high atomic number (i.e. 82) & has high melting point. • For the photoelectric process, the mass absorption coefficient increases with the cube of the atomic number 0.25 mm lead thickness attenuates 66% of the beam at 75kVp 1mm attenuates 99% of the beam at same kVp. • for general purpose radiography the minimum thickness of lead equivalent in the protective apparel should be 0.5mm.)

39. Operational Safety nts

40. DOSE EQUIVALENT Equivalent dose may also be called radiation protection unit as it takes into the account the potential of the radiation to cause biological damage. It is a measure of biological effectiveness of radiation.

41. E FFECTIVE DOSE EQUIVALENT takes into account the specific organs and areas of the body that are exposed. Not all parts of the body and organs are equally sensitive to the possible adverse effects of radiation, such as cancer induction and mutations. For the purpose of determining effective dose, the different areas and organs have been assigned tissue weighting factor ( wT ) values. Effective Dose Equivalent ( Sv ) = Dose Equivalent ( Sv ) × wT Purpose It is calculated by multiplying the dose equivalent received by each individual organ or tissue (DT) by an appropriate tissue weighting factor (WT) and summing for all the tissues involved.

42. DOSE LIMITATIONS In the 1930s, the concept of a tolerance dose was used, a dose to which workers could be exposed continuously without any evident deleterious acute effects such as erythema of skin. Early 1950s , emphasis shifted to late effects and maximum permissible dose was designed to ensure that probability of injury is so low that the risk would be easily acceptable to the average person. This was based on geneticist H.J Muller work who had indicated that the reproductive cells were vulnerable to even smallest doses of radiation.

43. Permissible Dose The concept of tolerance dose indicated that there was a level of radiation below which it was safe. The concept of stochastic effects of radiation invalidated this dogma. Most scientists rejected that there was a threshold dose below which exposure to radiation was harmless. The concept of permissible dose therefore introduced.

44. Maximum Permissible Dose “There is no safe level of exposure and there is no dose of radiation so low that the risk of a malignancy is zero” — Dr. Karl Z. Morgan, father of Health Physics Maximum Permissible dose (MPD) is defined as that dose which in the light of present knowledge is not expected to cause appreciable bodily injury to the person at any point during his lifetime

45. Maximum Permissible Dose Advantages - explicit acknowledgment that doses below MPD have a risk of detrimental effects. - acknowledged danger due to stochastic effects of radiation. - introduced the concept of acceptable risk- probability of the radiation induced injury was to be kept low to be easily acceptable to individual

46. Dose Limits by AERB The limits on effective dose apply to the sum of effective doses from external as well as internal sources. The limits exclude the exposures due to natural background radiation and medical exposures. Calendar year shall be used for all prescribed dose limits

47. Radiation detection and measurement The instruments used to detect radiation are referred to as radiation detection devices. The radiation measurement is a time-integrated dose, i.e., the dose summed over a period of time, usually about 3 months. The dose is subsequently stated as an estimate of the effective dose equivalent to the whole body in mSv for the reporting period. Dosimeters used for personnel monitoring have dose measurement limit of 0.1 - 0.2 mSv dose equivalent.

48. Film Badge Monitoring: These badges use small x-ray films sandwiched between several filters to help detect radiation. The photographic effect, which refers to the ability of radiation to blacken photographic films, is the basis of detectors that use film . Wearing the badge -wear the badge on the collar region, because the collar region including head, neck, and lens of the eyes are unprotected. Wearing period- Each member of staff wears film badge in working place for 4 weeks; a t the end of a period of 4 weeks the film inside is changed. The exposed film is sent to BARC. Useful for detecting radiation at or above 0.1 mSv

49. ii . Thermo luminescent dosimetry (TLD) Monitoring: Property of certain materials to emit light when they are stimulated by heat. • Materials such as lithium fluoride ( LiF ), lithium borate (Li2B4O7), calcium fluoride (CaF2), and calcium sulfate (CaSO4) have been used to make TLDs. When an LiF crystal is exposed to radiation, a few electrons become trapped in higher energy levels. For these electrons to return to their normal energy levels, the LiF crystal must be heated. As the electrons return to their stable state, light is emitted because of the energy difference between two orbital levels. The amount of light emitted is measured (by a photomultiplier tube) and it is proportional to the radiation dose.

50. Harmful effects of ionizing radiation are classified as stochastic and non stochastic . The majority of the radiation dose received by the operator (provided the primary beam is avoided) is due to scattered radiation from the patient. Use protective shields (lead apron, mounted shields/flaps, ceiling suspended screens as applicable) Stand in the correct place: opposite the X ray tube rather than near the X ray tube. Always wear your personal radiation monitoring badge and use them in the right manner. Follow Time, Distance, Shielding golden rules. SUMMARY

51. The dosimetric quantity relevant to radiation protection is the dose equivalent. Effective dose equivalent limits for occupational and general population has been recommended by the regulatory board of that country. The values quoted for radiation workers are such that the hazards that the doses represent to health is small compared with ordinary hazards of life.

52. THANK YOU!