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Radiation protection
This document discusses radiation protection and provides definitions, types of radiation effects, sources of radiation exposure, units of measurement, dose limits, and techniques to reduce radiation exposure in medical imaging. It defines radiation protection as protecting people from harmful effects of ionizing radiation. It describes stochastic and deterministic effects and lists examples of radiation anomalies. It also outlines regulatory bodies, dose limits for occupational workers and the public, and principles of radiation safety including time, distance, shielding and reducing exposure.
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Radiation protection
- 1. Dr. Umar Tauqir PGRRadiology ALNOOR DIAGNOSTICS
- 2. International AtomicEnergy Agency (IAEA) 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 DEFINITION
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- 6. 3 TYPES diagnostics XRAYS CTSCAN Nuclear medicine Theraputic MEDICAL RADIATION
- 7. In theworld today, two sets of units exist. They are the Special units (Curie, Roentgen, Rad and Rem) and SI or International Units (Becquerel, Gray and Sievert). In the United States, the Special units must be used as required by Federal law.
- 8. 1curie = 3.7x 1010 disintegrations per second 1 becquerel = 1 disintegration per second 1 millicurie (mCi) = 37 megabecquerels (MBq) 1 rad = 0.01 gray (Gy) 1 rem = 0.01 sievert (Sv) 1 roentgen (R) = 0.000258 coulomb/kilogram (C/kg) 1 megabecquerel (MBq) = 0.027 millicuries (mCi) 1 gray (Gy) = 100 rad 1 sievert (Sv) = 100 rem 1 coulomb/kilogram (C/kg) = 3,880 roentgens UNITS CONVERSION EQUILENCE
- 9. To convert fromTo Multiply by Curies (Ci) becquerels (Bq) 3.7 x 1010 millicuries (mCi) megabecquerels (MBq) 37 microcuries (µCi) megabecquerels (MBq) 0.037 millirads (mrad) milligrays (mGy) 0.01 millirems (mrem) microsieverts (µSv) 10 milliroentgens (mR) microcoulombs/kilogram (µC/kg) 0.258 becquerels (Bq) curies (Ci) 2.7 x 10-11 megabecquerels (MBq) millicuries (mCi) 0.027 megabecquerels (MBq) microcuries (µCi) 27 milligrays (mGy) millirads (mrad) 100 microsieverts (µSv) millrems (mrem) 0.1 microcoulombs/kilogram (µC/kg) milliroentgens (mR) 3.88 CONVERSION FACTORS
- 10. XRAYS BARIUM ENEMA 4.0 UPPER GI 2.45 Lumbar spine 1.43 OTHERS THORACIC SPINE 1.09 PELVIS0.7 CHEST 0.06 Radiation dose in msv
- 11. CT HEAD:- 2msv CT CHEST :- 7msv CT ABDOMEN/PELVIS :- 10MSV WHOLE BODY CT SCREENING :- 10 MSV Ct scan
- 12. ICRP :-International commission for radiation protection is the international regulatory authority PNRA:- Pakistan nuclear regulatory authority NCRP:- National commission for radiology protection American counterpart REGULATORY BODIES
- 13. • Lay downnorms for protection against radiation. • Guidelines regarding the specification of medical x– ray equipment, room layout of x– ray installation, protective devices • Responsibilities of the radiation personal, employer and radiation safety officer • Recommends the dose limits for radiation workers and general public. Approval for new models of x– ray equipment. • Registration, inspection and ISO certification
- 14. Atomic energyregulatory board (AERB) making recommendations on limits of exposure to ionizing radiation. Occupational exposed individuals General public Embryo/fetus
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- 16. CNS –Anencephaly , microcephaly , skull malformation & hydrocephalus. Ocular-absence of eyes, microphthalmia, absence of lens, cataract. Skeletal malformation- stunting, cleft palate, spina- bifida ANOMALIES
- 17. When amember of general population eg. visitor enters a radiation area , he becomes an occasionally exposed individual. Annual dose limit- - <1mSv - frequent exposure - 5 mSv - infrequent exposure GENERAL PUBLIC
- 18. AS LOWAS REASONABLY ACHIEVABLE For any given radiation source, magnitude of individual doses, number of people exposed, and likelihood of incurring exposures should be kept to as low as reasonably achievable, taking economic and social factors into considerations. ALARA
- 19. POCKET DOSIMETRE Film badge dosimeter TLD (thermo luminescent dosimeter) RADIATION MONITORING
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- 21. Exposure isthe amount of light per unit area (the image plane luminance times the exposure time) reaching a photographic film or electronic image sensor, as determined by shutter speed, lens aperture and scene luminance Exposure is measured in lux seconds, and can be computed from exposure value (EV) and scene luminance in a specified region Total dose equilant x time Exposure time
- 22. - Inverse squarelaw applies. - whenever possible , distance should be 2 meter from x-ray tube. -Distance 1 m - 400 (exposure) -Distance 2 m - 100 DISTANCE
- 23. - efficient absorberof x rays. - great reduction of exposure by placing it in between source and person. - thickness stated in HALF VALUE LAYER (HVL) for kilo voltage x rays. (HVL – any material thickness which reduces exposure rate by one –half.) LEAD BARRIERS
- 24. Half-Value Layer. The thickness of any given material where 50% of the incident energy has been attenuated is know as the half-value layer (HVL). The HVL is expressed in units of distance (mm or cm). Like the attenuation coefficient, it is photon energy dependent. Increasing the penetrating energy of a stream of photons will result in an increase in a material's HVL. HVL (HALF VALUE LAYER)
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- 26. tube mustenclosed in metal housing that reduces leakage radiation ( is radiation which penetrates the protective housing ) Protective barriers in radiation and fluoroscopy
- 27. • Useful beam( radiation pass through aperture) • Leakage radiation • Scattered radiation (radiation undergoes change in direction through its path) • Stray radiations (scattered + leakage radiation) 4 types of radiations Wall protection
- 28. PRIMARY • In radiographyup to 140 kV is about 1/16 inch lead extending 7 feet up from the floor when tube is 5-7 f.t from the wall. • protects from useful beam(mainly). SECONDARY • is about 1/32 inch lead. • - extends from the top of the 1ry barrier to ceiling. • - ordinary plaster often suffice as a 2ry barrier without added lead. PROTECTIVE BARRIER
- 29. Lead apron– worn in fluoroscopy room. - Pb equivalent 0.5 mm. Check lead protective apron periodically for cracks by means of a radiography test.
- 30. BEAM FILTRATION: -exposure greatly reduced by ALUMINIUM filter. - removes lower energy photons. - recommendations:- DOSE REDUCTION operating kVp Minimum HVL Al (mm) < 50 0.3 50-70 1.2 > 70 2.3
- 31. decrease in crosssectional area of the beam avoids unnecessary exposure of tissues outside the area of interest. - also reduces amount of scattered radiation. - modern equipment have automatic variable beam limiting device with manual override. COLLIMATION (BEAM LIMITATION)
- 32. beam should beso restricted that direct exposure of gonads does not occur. - thyroid ,testes shield must have lead equivalent 0.5 mm. - ovaries should be shielded whenever possible. GONADAL’THYROID SHIELDING
- 33. In radiography ofgirls for scoliosis should be use PA view. - Reduces breast dose at least 98 % without loss of radiographic quality. MODIFIED SHIELDING
- 34. HIGH KILOVOLTAGE:- - high kVp with low mAs delivers smaller absorbed dose to the patient. CAREFUL TECHNIQUE :- - to minimize repeat examination. Radiographic examination in fertile women preferably performed during 1st 10 days following onset of menstrual period. Ovulation and pregnancy are much less apt during this time than later menstrual cycle
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- 36. Skillful techniqueminimizes breast dose. Goal achieved by molybdenum targets and filters in mammographic tubes. Low dose screens and films, with/ without grid having ratios of 3:1 or 4:1. Efficient breast compression device :- reduces breast thickness and make more uniform. PROTECTION IN MAMOGRAPHY
- 37. ADVANTAGES 1. decreasesexposure factors with reduction of dose. 2. diminished amount of scattered thereby improving contrast. 3. improved recorded details by bringing breast closer to the image receptor.
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- 39. Dose inCT scanning , by measuring absorbed dose at the center of one “slice” with small dosimeter in water phantom. Scanning this slice and 3 adjoining slices on both side. Dosimeter record dose from direct beam through the center slice, as well as scattered radiation from adjoining slices. Collimator should also checked periodically to assure its proper function. CT SCANNING
- 40. Intermittent fluoroscopy– decreases exposure and prolong tube life. Restriction of field size – must be limited by suitably lead shutters placed between tube and patient. Correct operating factors – exposure decreases as kVp increases and mA is lowered. Recommended factors are 90-100 kVp, 2-3 mA and 2. mm aluminium filter PATIENT PROTECTION IN FLUORORSCOPY
- 41. The source-skindistance must be at least 15 inch with stationary and 12 inch with mobile fluoroscopic equipment. Filtration :- – increase in hardness of x ray beam by filter. – Filter removed relatively more soft than hard x-rays.
- 42. Medical compoundscontaining radionuclide's are called radiopharmaceuticals. Types of radiation – alpha particles – beta particles – gamma rays radiopharmaceuticals emits beta and gamma rays PROTECTON IN NUCLEAR MEDICINE
- 43. Gamma raysare electromagnetic wave and have much greater penetrability than beta particle. Beta particles consist of high-speed electrons. Beta particles are much less penetrating ,their effect limited to the skin (external source) immediate vicinity(internal source).
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