Pregnancy and Medical Imaging with or without Contrast

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Pregnancy and Medical Imaging with or without
Contrast
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Informed consent and understanding

• The pregnant patient has a right to know the
  magnitude and type of potential radiation effects
  on a fetus that might result from in-utero
  exposure.

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Evaluation of potentially pregnant patients

• In females of child-bearing age, an attempt
  should be made to determine who is, or could be,
  pregnant, prior to radiation exposure.

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Notices

• A missed period in a regularly menstruating woman
  should be considered due to pregnancy, until
  proven otherwise.

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MRI SCANS

• MR Imaging is known to cause slight heating of
  the body of the patient being scanned.
• There is at present no objective data to suggest
  that MR Imaging has any other adverse effects on
  the patient being scanned or on an unborn fetus.
• It is not possible to determine the true risk of
  MR Imaging on an unborn fetus.
• MR Imaging should be avoided unless a delay until
  after delivery would be dangerous to the fetus or
  mother.
• If the only other means of diagnosis is with
  ionizing radiation, MR Imaging would be the
  preferred diagnostic study.
• MR Imaging can if necessary, be performed at any
  stage in pregnancy.

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• Pregnant patients may undergo MRI scans at any
  stage of pregnancy, if the ordering physician
  determines the risk-benefit ratio for the patient
  warrants that the study be performed.
• The justification for the exam must be documented
  in the patients hospital chart by the ordering
  clinician for inpatients or emergency room
  patients prior to the exam being performed.
• For outpatients written documentation must be
  faxed to the department by the ordering clinician
  prior to the procedure being scheduled.
• Gadolinium contrast will not be used during
  pregnancy without prior approval by a radiologist

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Fetal radiation risk

• There are radiation-related risks throughout
  pregnancy that are related to the stage of
  pregnancy and absorbed dose.
• Radiation risks are most significant during
  organogenesis in the early fetal period, somewhat
  less in the 2nd trimester, and least in the 3rd
  trimester.

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Radiation-induced malformations

• Malformations have a threshold of 10-20 rad or
  higher and are typically associated with central
  nervous system problems.

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Central nervous system effects

• During 8-25 weeks post-conception the CNS is
  particularly sensitive to radiation.
• Fetal doses in excess of 10 rad can result in
  some reduction of IQ (intelligence quotient).
• Fetal doses in the range of 100 rad can result in
  severe mental retardation and microcephaly,
  particularly during 8-15 weeks and to a lesser
  extent at 16-25 weeks.
• The accepted maximum cumulative fetal dose during
  pregnancy is 5 rad.

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Breast Feeding and Contrast

• An infant absorbs approximately 0.01 of the
  maternal intravenous dose of iodinated contrast
  from breast milk, over the first 24 hours
  (equivalent to less than 1 of the recommended
  dose for an infant undergoing a contrasted
  imaging study). The ACR recommends that it is
  safe to breast feed immediately after an
  iodinated study or she may wait 24 hours, if she
  continues to be concerned about potential risk.
• An infant absorbs approximately 0.0004 of the
  maternal intravenous dose of gadolinium contrast
  from breast milk, over the first 24 hours
  (equivalent to less than 0.04 of the recommended
  dose for an infant undergoing a contrasted
  imaging study). The ACR recommends that it is
  safe to either breast feed immediately after a
  gadolinium contrast study or she may wait 24
  hours, if she continues to be concerned about
  potential risk.

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Use of contrast (iodinated or gadolinium) during
pregnancy is recommended only if

• The referring physician feels that the
  information gained by imaging with a contrasted
  study cannot be obtained by an alternative
  method.
• The results will not affect the patient/fetus
  during the pregnancy.
• Waiting after the pregnancy to obtain this
  information is not prudent for the
  patients/fetus care.
• Documentation is made on the patients chart by
  the referring physician who has approved informed
  consent.
• ACR Manual on Contrast Media (Version 5.0)

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Common Radiographic Studies
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Examination type Estimated fetal dose per examination (rad) Number of examinations required for a cumulative 5-rad dose
Plain Films
Skull 0.004 1,250
Dental 0.0001 50,000
Cervical Spine 0.002 2,500
Upper or Lower Extremity 0.001 5,000
Chest (two views) 0.00007 71,429
Mammogram 0.020 250
Abdominal (multiple views) 0.245 20
Thoracic Spine 0.009 555
Lumbosacral spine 0.359 13
Intravenous pyelogram 1.398 3
Pelvis 0.040 125
Hip (single view) 0.213 23
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Examination type Estimated fetal dose per examination (rad) Number of examinations required for a cumulative 5-rad dose
CT scans 9slice thickness 10 MM) Non-helical
Head (10 Slices) lt0.050 gt100
Chest (10 slices) lt0.100 gt50
Abdomen (10slices) 2.600 1
Lumbar Spine (5 slices) 3.500 1
Pelvimetry (1 slice with scout film) 0.250 20
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Examination type Estimated fetal dose per examination (rad) Number of examinations required for a cumulative 5-rad dose
Fluoroscopic studies
Upper GI Series 0.056 89
Barium Swallow 0.006 833
Barium Enema 3.986 1
Nuclear medicine studies
Most studies using technetium (99mTc) lt0.500 gt10
Hepatobiliary technetium HIDA scan 0.150 33
Ventilation-perfusion scan (total) 0.215 0.215 23
Perfusion portion Technetium .0175 28
Ventilation portion xenon (133 Xe) 0.040 125
Iodine ( I 131 ), at fetal thyroid tissue 590.000 Iodine (I 131) is contraindicated during pregnancy
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Examination type Estimated fetal dose per examination (rad) Number of examinations required for a cumulative 5-rad dose
Environmental sources (for comparison)
Environmental background radiation (cumulative dose over nine months) 0.100 N/A
CT computed tomographic GIgastrointestinal
HIDAhepatobiliary iminodiacetic acid N/A not
applicable --Where the reference provides a
range of estimated doses, the highest value of
the range listed here. --Authors calculation
from data provided in reference values rounded
to lowest whole number.
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Chest for Pulmonary Embolism
CT Helical Scan Estimated fetal dose per examination (rad) Estimated fetal dose per examination (rad) Estimated fetal dose per examination (rad)
1st Trimester 2nd Trimester 3rd Trimester
2.5 mm slice .00033 .00202 .00079-.00767 .000513-.001308
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Helical CT Scans
Single Slice (5 mm thick) Multi-Slice (4) Detector (5 mm thick)
Abdomen 1.25 3.5 rad 1.25 3.5 rad
Pelvis 1.25 3.5 rad 1.25 3.5 rad
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Nuclear medicine and pregnant patients

• Most diagnostic procedures are done with
  short-lived radionuclides (such as
  technetium-99m) that do not cause large fetal
  doses
• Often, fetal dose can be reduced through maternal
  hydration and encouraging voiding of urine
• Some radionuclides do cross the placenta and can
  pose fetal risks (such as iodine-131)

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Nuclear medicine and pregnant patient (contd)

• The fetal thyroid accumulates iodine after about
  10 weeks gestational age
• High fetal thyroid doses from radioiodine can
  result in permanent hypothyroidism
• If pregnancy is discovered within 12 hours of
  radio-iodine administration, prompt oral
  administration of stable potassium iodine (60-130
  mg) to the mother can reduce fetal thyroid dose.
  This may need to be repeated several times

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Approximate whole body fetal dose (rad) from
common nuclear medicine procedures
Procedure Activity (MBq) Early pregnancy 9 months
Tc-99m Bone scan Lung scan Liver colloid scan Thyroid scan Renal DTPA Red blood cell 750 240 300 400 300 930 0.47 0.09 0.06 0.44 0.9 0.6 0.18 0.09 0.11 0.37 0.35 0.25
I123 thyroid uptake 30 0.06 0.03
I131 thyroid uptake 0.55 0.004 0.015
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Nuclear medicine and breast feeding

• A number of radionuclides are excreted in breast
  milk. It is recommended that breast feeding is
  suspended as follows
• Completely after I131 therapy
• 3 weeks after I131, I125, Ga67, Na22, and Tl201
• 12 h after I131 hippurate and all 99mTc compounds
  except as below
• 4 h after 99mTc red cells, DTPA, and phosphonates

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Conversions for Absorbed Dose

• 0.001 rad 1 mrad 0.01 mGy
• 0.01 rad 10 mrad 0.1 mGy
• 0.1 rad 100 mrad 1 mGy 0.001 Gy
• 1 rad 1000 mrad 10 mGy 0.01 Gy
• 10 rad 100 mGy 0.1 Gy
• 100 rad 1000 mGy 1 Gy (Gray)
• 1000 rad 10 Gy

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Termination of pregnancy

• High fetal doses (100-1000 mGy, 10-100 rad)
  during late pregnancy are not likely to result in
  malformations or birth defects since all the
  organs have been formed
• At fetal doses in excess of 500 mGy (50 rad),
  there can be significant fetal damage, the
  magnitude and type of which is a function of dose
  and stage of pregnancy
• At fetal doses between 100 and 500 mGy (10 and 50
  rad), decisions should be based upon individual
  circumstances

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Reference List

• ICRP Publication 84, Task Group R. Brent, F.
  Mettler, L. Wagner, M. Berry, S. He, T. Kusama
• Safety of Radiographic Imaging during pregnancy.
  Kevin S. Toppenberg, M.D., Ashley Hill, M.D. and
  David Miller M.S. Florida Hospital Medical
  Center. Orlando, Florida.
• Policy for Handling Pregnant Patients. Georges
  Y. El-Khoury, M.D. and Mark Madsen, Ph.D., The
  University of Iowa Hospitals and Clinics,
  Department of Radiology.
• Pulmonary Embolism in Pregnant Patients Fetal
  Radiation Dose with Helical CT, Helen T.
  Winer-Muram, M.D. et al, Indiana Univ. School of
  Medicine, Dept. of Radiology.

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Web sites for additional information on radiation
sources and effects

• European Commission (radiological protection
  pages) europa.eu.int/comm/environment/radprot
• International Atomic Energy Agency
  www.iaea.org
• International Commission on Radiological
  Protection
  www.icrp.org
• United Nations Scientific Committee on the
  Effects of Atomic Radiation
  www.unscear.org
• World Health Organization www.who.int