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RADIATION & PREGNANCY

Diagnostic & Therapeutic procedures causing exposure of the abdomen of women likely to be pregnant should be avoided unless there is a strong clinical indications

STOCHASTIC EFFECTS STOCHASTIC EFFECTS

Stochastic Effects are caused by mutations in a cell or in small group of cells

STOCHASTIC EFFECTS STOCHASTIC EFFECTS The absorbed dose is not important for severity of the effect, but for probability of the effect depend on the absorbed dose

STOCHASTIC EFFECTS STOCHASTIC EFFECTS Examples of stochastic effect malignancies and hereditary effects. No threshold dose.

DETERMINISTIC EFFECTS

Result from killing of cells. There is a threshold dose. e.g.: Fetal death, gross malformation

DETERMINISTIC EFFECTS Pre-Implantation: 0 – 8 days post- conception Death of embryo 5 cGy rats 0.9 cGy mice Threshold dose: 10 cGy

DETERMINISTIC EFFECTS Embryonic = 9 – 60 days Risk of embryonic death remain. higher threshold dose. Risk of malformation is in the order of 0.5% per cGy Threshold dose = 10 cGy Small head size 1% per cGy Threshold dose = 10 – 20 cGy Growth retardation threshold dose = 5 – 25 cGy

DETERMINISTIC EFFECTS Early fetal = 61 – 104 days Threshold dose for lethality = 0.5 Gy Mental retardation 0.4% per cGy Threshold dose = 12 cGy 0.3 IQ points per cGy Unprovoked seizures 4 – 8 cGy threshold dose All seizure 11 – 15 cGy threshold dose

DETERMINISTIC EFFECTS Mid fetal = 105 – 175 days post-conception Risk of fetal death remain in this period, but seems to be lower than in the earlier period Threshold doses 0.65Gy for mental retardation 0.5 Gy for small head size 0.5 Gy for growth retardation

DETERMINISTIC & EFFECTS Late fetal = more than 175 days post-conception Risk of fetal death seem to be low Risk of malformation & mental retardation are negligible

STOCHASTIC EFFECTS

Excess Fatal Cancer Natural prevalence of fatal childhood cancer up to the age of 15-year (1:1300) 0.03% per cGy 0.04% % cGy Higher risk for those irradiated in the second trimester than those in third trimester

TUMOURS

TUMOURS Leukemia, tumours of CNS

RISK OF GENETIC DISEASE

NATURAL PREVALENCE IS 1.6%

Maternal age > 35 Total chromosal abnormality is 2.26% & 9.6% age above 45 1 cGy 0.012% It is clear that risk of radiation effects is smaller than risk effect by age

Normal risk that a child will have congenital defect is 3% – 6%

When dose exceed 10 cGy probability increase to 10%

A dose of 10 cGy – 20 cGy is radiologically not accepted as an indication for an abortion

Dose to the embryo of 20 cGy at 3-Weeks could be accepted as a reason for “Therapeutic Abortion” Whalen & Batter

Dose from Nuclear Medicine Diagnostic test is at’s highest estimate 1 cGy

Threshold dose for deterministic effect is in the order of 10 cGy – 60 cGy

The risk of cancer induction is 0.03% % per cGy If patient received 0.5 cGy (1.5 – 2.5) out of 10,000 Risk of genetic defect (0.5 – 5) out of 10,000

ProjectionExamination Estimated Fetal Dose per Examination (mGy) Mean (this work) Reported Mean Range (this work) Reported Range APAbdomen a – – 9.2 PAAbdomen a – – 0.82 Abdomen b [1.4]0.26 – – 19.0 {4.2} APChest a < 0.01 PAChest a < 0.01 Chest b < [< 0.01]0.002 – 0.43< 0.01 APLumbar Spine a – – 15.0 LATLumbar Spine a – – 3.1 Lumbar Spine b [1.7]0.09 – – 40.0 {10.0} LATLumbosacral Joint a – – 2.4 APPelvis b [1.1]1.4 – – 22.0 {4.0} APThoracic Spine a < 0.01 < 0.01 – 0.03 PAThoracic Spine a < 0.01 < 0.01 – 0.01 Thoracic Spine b < 0.01< 0.1 [< 0.01]< 0.01< {<0.01} COMPARISON OF THE ESTIMATED MEAN & RANGE OF FETAL DOSE a – Reported mean & range are adapted from Shrimpton et al b – Reported mean & range are adapted from Wagner et al Mean values in square brackets & values curly brackets (representing only maximum values) are adapted from Sharp et al

ProjectionExamination Estimated Fetal Dose per Examination (mGy) Mean (this work) Reported Mean Range (this work) Reported Range IVU [1.7]2.9 – – 55.0 {10.0} Barium Enema [6.8]0.3 – – {24.0} Barium Meal1.5- [1.1]0.1 – 2.3- {5.8} Cholecystography – – 16.0 APUrinary Bladder – 11.0 COMPARISON OF THE ESTIMATED MEAN & RANGE OF FETAL DOSE a – Reported mean & range are adapted from Shrimpton et al b – Reported mean & range are adapted from Wagner et al Mean values in square brackets & values curly brackets (representing only maximum values) are adapted from Sharp et al

ProjectionExamination Fetal dose per examination (mGy) RangeMean APAbdomen0.26 – PAAbdomen0.64 – Abdomen a 0.26 – APChest< 0.01 – 0.01< 0.01 PAChest< 0.01 Chest b > 0.01 – 0.01< 0.01 a – Average for the various projections b – For only one examination MEAN FETAL ABSORBED DOSE PER EXAMINATION (GXR) Contd…

ProjectionExamination Fetal dose per examination (mGy) RangeMean APHip joint0.11 – APLumbar Spine0.31 – LATLumbar Spine0.09 – OBLLumbar Spine0.61 – Lumbar Spine a 0.09 – LATLumbosacral Joint0.10 – APPelvis1.4 – APThoracic Spine< 0.01 LATThoracic Spine< 0.01 b Thoracic Spine b < 0.01 a – Average for the various projections b – For only one examination MEAN FETAL ABSORBED DOSE PER EXAMINATION (GXR)

Examination No. of Cases Fetal dose per examination (mGy) RangeMean Liver42.0 – Lumbar Spine12.8 Lung21.0 – Pelvis265.0 – MEAN FETAL ABSORBED DOSE PER EXAMINATION (CT)

COMPARISON OF THE ESTIMATED MEAN & RANGE OF FETAL DOSE Radiopharmaceutical Conversion factor (cGy/MBq) [1,3] Activity (MBq] Route of Administration Dose to the Uterus (cGy) 123 I-Sodiumiodide1.4x i.v.2.8x I-MIBG1.1x i.v.3.3x I-MIBG8.0x i.v Ga-citrate7.9X i.v Tl-chloride5.0x i.v.5-7x m Tc-tetrofosmin (1-day protocol, rest) 8.4x i.v.1.3x m Tc-tetrofosmin (1-day protocol, effort) 7.3x i.v.3.3x10 -1 MIBG, Metaiodobenzylguanidine; MDP, methylene diphosphonate; HDP, hydroxydiphosphonate; MAA, macroaggregated albumin; MAG3, mercaptoacetyltriglycine

COMPARISON OF THE ESTIMATED MEAN & RANGE OF FETAL DOSE Radiopharmaceutical Conversion factor (cGy/MBq) [1,3] Activity (MBq] Route of Administration Dose to the Uterus (cGy) 99m Tc-sestamibi (1-day protocol, rest) 7.8x i.v.1.2x m Tc-sestamibi (1-day protocol, effort) 7.2x i.v.3.2x m Tc-MDP6.1x i.v.2.4x m Tc-HDP6.1x i.v.2.4x m Tc-MAA2.4x i.v.2.4x m Kr-gas 6.0x10 -8 (per minute) Generator: MBq/minute Inhalation< m Tc-MAG31.2x i.v.4.8x10 -2 MIBG, Metaiodobenzylguanidine; MDP, methylene diphosphonate; HDP, hydroxydiphosphonate; MAA, macroaggregated albumin; MAG3, mercaptoacetyltriglycine

131 I-Therapy & Pregnancy

10 – 12 Weeks thyroid gland of fetus start to function. For every 10mCi the mother receive, the fetus will receive 1 cGy..

Radiation Worker’s & Pregnancy Radiation worker who is pregnant should not receive more than 1 mSv during the whole pregnancy.

CONCLUSION

CONCLUSION For diagnostic examination whether radiological or Nuclear Medicine, the risks for the fetus are Extremely low For therapeutic dose The doses may be high enough to cause unacceptable tissue damage.