임신 중 방사선(X-ray) 노출이 태아에 어떤 영향을 미칠까?

Radiation in pregnancy CHA의대 강남차병원 산부인과 조연경

Definition (1)• Roentgen (R): units of exposure• Rad, Gray (Gy): absorbency into human tissue – 100rad = 1Gy (gray) = 1 J/kg• Rem, Sivert (Sv): biological effectiveness of absorbed radiation – 100rem = 1Sv

Definition (2)• Relative biological effectiveness(RBE) – correction factor for predicting the biological effect of absorbed radiation – 1 rem = 1 rad/RBE or 1 Sv = 1Gy/RBE In radiation in soft tissue, RBE is about 1  rad & rem (or Gy & Sv): used interchahgeably

Effects of radiation (1Gy) prenatal exposure in rodentsExposure group Preimplantation Embyo Fetus Spontaneous ++ ± - Abortion Congenital - + - Malformation Intrauterine - + +growth restriction Mental - + + retardation (Schull WJ & Otake. 1999)

Effects of radiation exposureGestational age Weeks after Fetal dose Observed effects conceptionPreimplantation 0-2 0.05-0.1Gy Animal data:prenatal deathmajor 1-8 0.2-0.25 Gy sensitive stage for growth restrictionorganogenesis 2-15 Small head size < 8weeks :intellectual deficit (-) Most sensitive time for induction of childhood cancerRapid neuron 8-15 > 0.1 Gy Small head size, seizure, IQ point ↓development and (↓25/0.1 Gy)migrationAfter 15- term >0.1 Gy Increased frequency of childhood cancerorganogenesis andrapid neurondevelopment > 0.5 Gy Severe mental retardation (16-25 weeks) (Schull WJ & Otake. 1999)

Ionizing radiation & malformationMalformation Estimated threshold dose Gestational age at greatest riskMicrocephaly > 20Gy 8-15 weeksmental retardation 0.06-0.31Gy (8-15 weeks) 0.25-0.28 Gy (16-25 weeks) 8-15 weeks > 0.5Gy (8-15 weeks)Reduction of IQ 0.1 Gy 8-15 weeksOther malformation > 0.2 Gy 3-11 weeks

Radiation and mental retardation• 8-15 weeks, : Risk of impaired CNS development > 5 times than 16~25 weeks• < 8 weeks, or > 25 weeks - No increased risk of mental retardation

Cancer incidence (1950-1984) & A-bomb radiation exposure DS86 maternal uterine dose (Gy) 0 0.01-0.29 0.30-0.59 > 0.6Mean dose (Gy) 0.000 0.087 0.416 1.372No. at risk 710 682 129 109Person –years 21770 21659 4095 3287Cancer cases 5 7 3 3Adjusted 22.4 32.5 77.8 97.0rate/100,000Estimated RR 1.00 1.24 2.18 4.78 [1.01-2.10] [1.06-6.32] [1.19-7.93]

Risks of leukemia in various groupsGroup Approximate risk Increased risk over occurrence control populationSiblings of leukemic 1/720 4 ~ 10 yearschildrenGestational exposure 1/2000 1.5U.S white children 1/2800 1< 15 y.o. (Brent RL, Teratology, 1986)

Estimated conceptus doses from radiographic and fluoroscopic examinations examinations Typical conceptus dose (mGy)Cervical spine < 0.001Extremities <0.001Chest 0.002T-spine 0.003Abdomen 21cm patient thickness 1 33cm patient thickness 3L-spine 1Limited IVP 6Small bowel study 7Barium enema 7 (McCollough CH 2007)

Estimated conceptus doses from single CT & Nuclear medicine examExaminations Typical conceptus doses (mGy)Extra-abdominal Head CT 0 Chest CT 0.2Abdominal Abdomen, routine 4 Abdomen/pelvis, routine 25 Early 1st trimester End of 1 st trimesterBone scan 5 4Whole body PET scan 15 10Thyroid scan 0.2 0.1 (Pavlidis NA, 2002)

Probability of birth with no malformation and no childhood cancerDoses to conceptus No malformation No childhood No malformation (mGy) (%) cancer(%) and childhood cancer (%) 0 96.00 99.93 95.93 0.5 95.999 99.926 95.928 1.0 95.998 99.921 95.922 2.5 95.995 99.908 95.91 5.0 95.99 99.89 95.88 10.0 95.98 99.84 95.83 50.0 95.90 99.51 95.43 100.0 95.80 99.07 94.91 (Wagner LK 2002)

Spontaneous risk vs additional risk Type of risk Spontaneous risk Additional risk (0Gy exposure) from 0.05Gy Spontaneous abortion 150,000/106 pregnancies 0 Major ongenital 30,000/106 pregnancies 0 malformationSevere mental retardation 5,000/106 pregnancies 0childhood leukemia/year 40,000/106 <?1-3/106year pregnancies/year prematurity 40,000/106 pregnancies 0 growth restriction 30,000/106 pregnancies 0 stillbirth 20-2,000/106 pregnancies 0 infertility 7% of couples 0

Cancer in pregnancy Tumot type incidence Breast cancer 1: 3,000-10,000 Cervical cancer 1.2 : 10,000 Hodgkin’s disease 1: 1,000-6,000Malignant melanoma 2.6: 1,000 leukemia 1: 75,000-100,000

Ultrasonography• Medical ultrasound: 1-20 MHz• No independently confirmed significant biological effects in mammals in low megahertz frequency range and < 100 mW/cm2 (American Institute of Ultrasound in Medicine, 1982)• Largely replaced X-ray as the 1’ method of fetal Imaging during pregnancy

Repeated Dx doses of x-ray/US :prenatal effect Exposure Body weight Body length Head length Brain weight groups Control 1.25 ±0.010 25.62±0.094 8.10 ±0.042 0.086 ±0.001 X+U 1.22 ±0.012 25.38 ±0.012 8.08 ±0.041 0.085 ±0.001 U+X 1.20 ± 0.011* 25.12 ±0.201 8.07 ±0.046 0.086 ±0.001 X+X 1.22±0.015 25.34±0.188 8.09±0.040 0.086±0.001 U+U 1.19±0.013* 25.03±0.205* 7.97±0.045 0.083±0.001(18-day mouse fetuses after repeated exposures to diagnostic doses of X-ray/USduring organogenesis) (Hande MP, 1995)

Repeated Dx doses of x-ray/US :postnatal effect Exposure groups Postnatal mortality Sex ratio % brain weight- body weight ratio Control 11.81 0.98 1.57±0.17 X+U 16.45 1.03 1.55 ±0.19 U+X 18.67 0.88 1.56±0.19 X+X 16.00 1.05 1.55±0.18 U+U 20.00* 0.94 1.45±0.18 (18-day mouse fetuses after repeated exposures to diagnostic doses of X-ray/US during organogenesis) (Hande MP, 1995)

Continuing a pregnancy after exposureGestational age Fetal absorbed dose Control < 5 rad 5-15 rad > 15 rad < 2 wk recommended recommended recommended 2-8 wk recommended 8-15 wk recommended 15 wk-term recommended recommended recommended (Wagner LK, 1995)

Magnetic Resonance Imaging• Magnet: alter the energy state of hydrogen protons• Mice  eye malformation (Tyndall DA, 1991)• Embryo is not sensitive to the magnetic field (more studies are needed)• But, Prudent to exclude pregnant women from MRI during the 1st trimester

Nuclear medicine• Tc 99m – brain, bone, renal, cardiovascular – < 0.5 rad• Ventilation-perfusion scan – TechTc99m, 127Xe, 133Xe – < 50 mrad• Radioactive iodine – Readily cross the placenta – Adverse effect on fetal thyroid (esp. after 10-12weeks) – Contraindicated during pregnancy – If a diagnostic scan is essential, 123I or Tecnetium Tc99m

Contrast agent• In CT, derivatives of iodine – In animals, not teratogenic/Neonatal hypothyroidism – Generally avoided unless essential for correct diagnosis• Paramagnetic contrast agent (in MRI) – In animals, abortion, skeletal/visceral abnormalities (2-7 times the human dose)• Should be used during pregnancy only if the potential benefit justifies the potential risk

Paternal irradiation• In Hiroshima & Nagasaki survivors, → No increase in malformation, fetal death, birth weight• Father received diagnostic x-ray exam → Insignificant decrease in birth weight (Avon Longitudinal Study of Pregnancy and Childhood)• Association between paternal pre-conceptional radiational dose and childhood leukemia has not been confirmed

Guidelines (1) : ACOG, 2004• X-ray exposure from a single diagnostic procedure does not result in harmful effects• Concern about effect of high-dose ionizing radiation exposure should not prevent indicated diagnostic X- ray• US / MRI :not associated with known adverse fetal efects

Guidelines (2) : ACOG, 2004• Consultation with an expert in dosimetry calculation• Use of radioactive isotope of iodine is contraindicated during pregnancy• Radiopaque and paramagnetic contrast agent : unlikely to cause harm

Abdominal radiation in women of reproductive age• Because the risk of 0.05 Gy is so small, the medical care of the mother take priority over the risks to the embryo• X-ray studies for diagnosis and treatment should not be postponed• After diagnosis, elective procedure need not be performed on a pregnant woman• Other procedure can provide information without exposing to ionizing radiation• A period when the patient is pregnant but the pregnancy test is negative – Risk: extremely small during this period of gestation (all or none period)

Counseling patientsexposed to ionizing radiation during pregnancy

Risk from ionizing radiation• Spontaneous risks vs additional risks from low exposure of ionizing radiation• Diagnostic radiology (0.2 mGy-0.05Gy) – Extremely low risk to the embryo• >15%  spontaneous abortion 3%  major malformation 3%  IUGR (Brent RL , 1986)

Case 1• Pregnant / possibly pregnant patient with clinical symptoms – Should be performed at the time clinically indicated – Should not be relegated to one portion of the menstrual cycle In follow-up study(not an emergency), – Postpone until the beginning of the next menstrual period

Case 2• Patient has completed a diagnostic procedure that has exposed her uterus to ionizing radiation – Calculate dose to the embryo • If < 5 rad, her risks have not been increased • Threshold for birth defects > 0.2 Gy – Determine stage of pregnancy

Case 3• A woman delivers a baby with a serious birth defect – Radiation induced malformation : confined group of malformation – < 0.05~0.1 Gy : not cause of the malformation Analysis about dose, timing, nature of the malformation – 15~25% of malformed children : genetic disease

Case 4• When external radiation therapy / high exposures of radionuclides – Low exposure to embryo : Head, neck, upper chest, extremities – Each radionuclides: different half-life, metabolism, excretion – Expert evaluation to determine what the fetal exposure will be or has been

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임신 중 방사선(X-ray) 노출이 태아에 어떤 영향을 미칠까?

by mothersafe on Jun 12, 2012

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임신 중 방사선(X-ray) 노출이 태아에 어떤 영향을 미칠까? Presentation Transcript