Pregnancy and Medical Pregnancy and Medical Imaging with or without Imaging with or without

ContrastContrast

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Informed consent and Informed consent and understandingunderstanding

• 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 Evaluation of potentially pregnant patientspregnant 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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NoticesNotices

• 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 patient’s 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 riskFetal 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.

Most

risk Less Least

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Radiation-induced malformationsRadiation-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 effectsCentral 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:1. The referring physician feels that the information gained

by imaging with a contrasted study cannot be obtained by an alternative method.

2. The results will not affect the patient/fetus during the pregnancy.

3. Waiting after the pregnancy to obtain this information is not prudent for the patient’s/fetus’ care.

4. Documentation is made on the patient’s chart by the referring physician who has approved informed consent.

– “ACR Manual on Contrast Media (Version 5.0)”

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Common Radiographic Common Radiographic StudiesStudies

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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) <0.050 >100

Chest (10 slices) <0.100 >50

Abdomen (10slices) 2.600 1

Lumbar Spine (5 slices) 3.500 1

Pelvimetry (1 slice with scout film) 0.250 20

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) <0.500 >10

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; GI=gastrointestinal; HIDA=hepatobiliary 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 Chest for Pulmonary EmbolismEmbolism

CT Helical Scan

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 ScansHelical 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 (cont’d)

• 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

Approximate whole body fetal dose (rad) from common nuclear medicine procedures

ProcedureActivity (MBq)

Early pregnancy

9 months

Tc-99m

Bone scan Lung scan

Liver colloid scan Thyroid scan

Renal DTPA Red blood cell

750240

300400

300930

0.470.09

0.060.44

0.90.6

0.180.09

0.110.37

0.350.25

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…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