Radiation protection Petr Nádeníček Department of Radiology, University Hospital Brno 2013 c1196 X-rays nelectromagnetic radiation of short to very short wavelengths n10 - 0,001 nm nphotons narises in electron orbitals nenergy depends on the wavelength – nthe shorter the wavelength the higher the energy nradiation nbremsstrahlung – used in diagnostic and radiotherapy ncharacteristic – used in analytical chemistry > X-rays nelectromagnetic radiation of short to very short wavelengths n10 - 0,001 nm nphotons narises in electron orbitals nenergy depends on the wavelength – nthe shorter the wavelength the higher the energy nradiation nbremsstrahlung – used in diagnostic and radiotherapy ncharacteristic – used in analytical chemistry X-ray tube ncathode - tungsten filament, incandescent current, temperature up to 2000° C nelectons emitting cathode, electon field between K. and A. speeds electons nDC voltage of 10-500 kV nanode - cold copper block, target disc (Wofram, Molybdenum) nphoton emission nlow-energy radiation - soft component nhigh-energy radiation - hard component 00000467_rentgenka_2 photon ß electric interaction (Compton scattering, photoeffect, electron-positron couple) ß ionisation ß chemical changes ß biological effect 0,001 – 1 s, interaction of ions, radicals, excited atoms with biological organic molecules (DNA, proteins) minutes – tens years, functional and morfological changes in cells, organs and whole organism interaction – ionizing radiation/matter stochastic deterministic ionizing radiation - biological effect Latence: several years for cancer 100s years for genetic effects nno threshold nincreasing Def – increasing probability of stochastic effects nmagnitude of the effect do not dependent on the dose nnever effect immediately after irradiation (after several years) ncarcinogenic + genetic effects nlesion may not occure in the irradiated spot Def (Sv) stochastic effects: stochastic effects: The graph of incidence of occurence at a dose nthreshold nlesion depends on absorbed dose nafter crossing the threshold dosis - increases damage in certain organs nlocal effects nradiation damage is clinical provable nexample: acute radiation sickness, cataract, erythema, infertility etc nDekv (Sv) deterministic effects: The graph of incidence of effect at a dose radiosensitivity nactive bone marrow, lymphoid organs, gonads, GIT nskin epithelium, epithelium of esophagus, stomach, bladder), lens nvessels, growing cartilage, bone growth nmature cartilage, mature bone, respiratory tract, endocrine system nmuscles, CNS 12. w embryo •2 weeks – „everything or nothing“ •3.–8. w – organogenesis, risk of malformations •8.–15. w – risk of mental handicap •after 15. w – the same resistance as born child • • • The highest radiosensitivity – 1. third of gravidity! 8. w •natural : artificial = 5:1 •54 % Radon (Rn) •16 % cosmic radiation •19 % gama radiation •11 % inner radiation, radionuclid • 40K, 14C •93 % medical irradiation •1 % nuclear energy •2 % professional irradiation •2 % nuclear fall-out • ionizing radiation - etiology: 11 0,3 49 9 17 0,13 Radon in building Natural radionuclid in humans Gama from Earth surfice Nuclear fall-out Medical irradiation The rest Radon in building units nabsorbed dosis (D) Gray (Gy) nekvivalent dosis (Devk) Sievert (Sv) nefective dosis (Def) Sievert ncollective dosis (Def) manSv limits: nRadiation employee nDef - 5 y - 100 mSv nDef - 1 y - 50 mSv nDekv – 1 y - lens - 150 mSv n nStudents n n6 mSv n50 mSv n n A pregnant woman – during whole pregnancy - 1 mSv Def – 1 mSv •several years – external irradiation from nature sources •several years – internal irradiation from potassium in body •< 1 year – internal irradiation from Radon in buildings • •severals months – external irradiation in high altitude • • •100-1000 hours – external irradiation during long flight 1 mSv – 1 year limit for irradiation for person in population. probability of death – 50 mSv: •irradiation of 50 mSv •1 year work in „industry“ •smoke 10 packs of cigaret •15 years in household with smoker •drink 50 bottle of good wine •1500 km tour on the bicycle •45 000 km travel by car death probability - 1:10000 exposure from artificial sources Source basis of comparison The period of exposure from natural sources Medicine irradiation year experience 90 days Nuclear weapons yet all 2,3 years Nuclear energy 1 year of operation 1 day Major accidents per all the time 20 days Exposure at work per year 8 hours Exposure from natural sources 1 year Modality Effective dose (mSv) Number of x-ray pictures * Ekvivalent radiation dose ** limbs, joints less than 0,01 less than 0,5 1,5 day teeth 0,02 1 3 lung 0,02 1 3 skull 0,07 3,5 11 days mammography 0,1 5 15 days pelvis 0,7 35 7 weeks thoracic spine 0,7 35 7 weeks lumbar spine 1,3 65 7 months enteroklysis 3 150 16 months irrigography 7 350 3,2 years chest CT 8 400 3,6 years abdominal CT 10 500 4,5 years effective dosis – x-ray, CT * equivalent number of the X-ray chest examination ** approximate period at which the person received the equivalent radiation dose from natural sources Modality Typical effective doses (mSv) Number of x-ray pictures * Ekvivalent radiation dose ** pulmonary ventilation (Xe-133) 0,3 15 7 weeks pulmonary perfusion 1 50 6 month kidneys (Tc-99m) 1 50 6 month thyroid gland (Tc-99m) 1 50 6 month bones (Tc-99m) 4 200 1,8 year PET head (F-18 FDG 5 250 2,3 year dynamic myocard scintigraphy (Tc-99m) 6 300 2,7 year effective dosis – nuclear medicine * equivalent number of the X-ray chest examination ** approximate period at which the person received the equivalent radiation dose from natural sources optimalization nIt had been examinated? nThe physician should make every effort to reduce repetition of already examinated examinations (at another hospital, etc.). nDo I need it really? ndoctor should avoid unnecessary examination, which do not affect treating (for example – degenerative diseases spine….etc.) optimalization nDo I need it now? nthe doctor should not require too often the examinations. For example before the disease could further develop or retreat, or before results may affect treatment. nIs it best examination (modality)? ndoctor should consider to discuss the method of examination with a radiologist before sending the patient to optimalization nDid I explaned the problem? nthe doctor should obtain all relevant clinical informations and determine the questions which is interested in. nNot too many x-ray, CT (and other examinations)? nSome clinicians tend to rely on (X-ray) examinations more than others. Some patients like this investigation. categorization of workplaces nI. category - small sources, densitometry, dental X-ray nII. category - radiodiagnostics / therapy nIII. category - particle accelerators, sealed radionuclide sources (radiotherapy, brachytherapy) nIV. category - nuclear facilities, radioactive waste repository protective equipment ndistance ntime nshielding (alpha, beta, X-ray) naprons, collars, shields, covers the gonads and thyroid nChildren – the fuser equipment My wife recently underwent a dental x-ray examination. We found that at that time she was in the third week of pregnancy. How big is the risk? nComplete ortopantomogram of pregnant patients - the ndose receiving by embryo is around 0.001 mGy. nIn comparison with the average natural background which makes 3 mGy - the dose in such tests is less than the dose from natural exposure for one day. nCases were shown that such small doses pose none risk. nOf course, this is not conclusive evidence of absolute safety company, but provides assurance that if any risk arises as extremely small. Questions I am already three months working with a panoramic and intraoral X-rays devices. I missed one menstrual cycle and I believe that I was pregnant - approximately five to six weeks. I wonder if my child is in any danger of radiation, which I was exposed at the work. nIt is very unlikely that you and your unborn child are suffered any harm because of your professional exposure and have any significant risk. Available data indicate that a typical dose of irradiation on professional dental work is about 0.7 mSv per year. For comparison - the average natural radiation, which is exposed to each of us - is 3.5 mSv per year. Limits for workers with x-ray is 100 mSv in five consecutive years, but one year shall not be exceeded value of 50 mSv. Pregnant women must not received a dose greater than 1 mSv. The limits are chosen to avoid deterministic effects and did not lead to a significant increase in the likelihood of late effects such as cancer and genetic changes. nPregnant women should follow all steps to minimize their own irradiation. During the scan, they should be separated from the X-ray by shielding layer, preferably a wall. If this is not possible in their workplace they may stand for photographing away from the device. Discuss with your employer use of a personal dosimeter with a monthly deduction of benefits received. It should be emphasized that there is no reason to panic. Questions Thank you Department of Radiology, University Hospital Brno 2013 c1196