1. CT and MRI in pregnancy and lactation
Fergus Coakley MD, Professor of Radiology and Urology,
Vice Chair for Clinical Services, Chief of Abdominal Imaging, UCSF

2. Recognize early pregnancy…
5 WEEK GESTATION - ARF DUE TO OBSTRUCTION BY THECA LUTEIN CYSTS
5 WEEK GESTATION (UNKNOWN) – CT FOR STAGING BLADDER MASS
10 WEEK GESTATION – MRI FOR STAGING CERVICAL CANCER

3. Learning objectives
Detail the safety issues related to CT and MRI during pregnancy/lactation
Describe the problematic and newer applications of CT and MRI in pregnancy
Advise clinicians on appropriate use of imaging in pregnancy/lactation

4. Medline hits for “CT radiation dose”
Context
Growing demand and radiation awareness:
121% more tests over 10 years
Doctors poorly informed:
Superficial ACOG guidelines
5% would suggest TOP after CT
Radiologists need to take the lead
RSNA program 2007; 436
AJR 2004; 182:
Medline hits for “CT radiation dose”

5. Safety of CT - Safety of MRI - Indications for CT and MRI

6. Risks of CT Teratogenesis Carcinogenesis Iodinated contrast
Stochastic (threshold)
Carcinogenesis
Non-stochastic (no threshold)
Iodinated contrast

7. Teratogenesis Unlikely <4 or >17 weeks (organogenesis)
Measured from first day of LMP
Known effects mainly on CNS: Mental/growth retardation, microcephaly, microphthalmia, cataracts
Estimated threshold dose of 5 to 15 rad
Dose from standard pelvic CT: 1-10 rad
No detected teratogenic effects in human studies
Exposure of the pregnant patient to diagnostic radiations: a guide to medical management. Lippincott 1985;
AJR 1996; 167: Radiology 1986; 159:
Br J Radiol 1987; 60: 17-31

8. Carcinogenesis Endpoint Risk
Baseline risk of childhood cancer (0-15 yrs)
19/10,000
Excess risk per rad of fetal whole body dose
/10,000
Relative risk of childhood cancer after 5 rad 2
UNSCEAR 1972 Report to the UN General Assembly
National Radiological Protection Board, 1993:
Thrombosis and Haemostasis 1989; 61:

9. Basis of risk estimates
Oxford Survey of Childhood Cancer
547 case-control pairs ( ):
Child (< 10) dying of cancer in England & Wales
Matched living control (age, sex, location)
Standard questionnaire to both mothers
OSCC subsequently extended:
15,276 case-control pairs by 1981
Lancet 1956; 2: BJR Feb 1997;

10. OSCC - Results Maternal radiation Controls Cases Risk To abdomen 43 85
2.0
To other body part 55 58
1.0
None
447
404 NA

11. Gestational age & carcinogenesis
Relative risk by trimester (OSCC data):
J Radiol Prot 1988; 8: 3-8
First
(< 10 weeks)
(All)
Second
Third
4.6
3.2
1.3

12. What should we do?
Only perform CT of the pregnant abdomen and pelvis if critical:
Clear clinical justification with benefit >> risk
No non-ionizing imaging options
CT of other body areas much smaller concern
Risks and benefits should be discussed with the patient/parents and documented:
Signed informed consent may be wise
Sample form at

13. Parental counseling Absolute risks:
Baseline risk of fatal childhood cancer = 1/2000
Risk after fetal dose of 5 rads = 2/2000
Practical comparisons for excess risk:
Driving 20,000 miles in a car
Living in New York City for 3 years
ACOG guidelines are superficial:
Describe carcinogenic risk as "very small”
Conclude "abortion should not be recommended”
Do not discuss parental counseling/consent
Obstet Gynecol 2004; 104:

14. Imaging fertile women Varying historical approaches:
10 day rule, 28 day rule, limited 10 day rule
Largely based on “all or nothing” concept of early risk, and ignores carcinogenesis
What are the regulatory and practical requirements?
Statement from the 1983 Washington meeting of ICRP. Annals of International Commission on Radiological Protection 1984:14
Board statement on diagnostic medical exposure to ionising radiation during pregnancy and estimates of late radiation risks to the UK population. Documents of the NRPB 1993; 4:1-14

15. Regulatory guidelines
No requirement for pregnancy testing
ACR: “Radiologists should be advised of known or possible pregnancy”
HHS: “A woman who is or thinks she is pregnant should be encouraged to give this information to the physician”
Medical radiation: a guide to good practice. ACR 1985;4-8
DHSS publication no. HHS/FDA
AJR 1996; 167:

16. Good practice Pregnancy section on requisition forms Prominent signage
Routine questioning by technologist

17. Good practice No safe time during menstrual cycle:
Various “day rules” are obsolete
Any possibility of pregnancy:
Consult with clinician +/- perform pregnancy test
Earliest positive pregnancy test:
Serum hCG - 7 days after conception
Urinary hCG - first day of missed period
STALL!!
Request other opinions, e.g. surgical consult

18. Inadvertent exposure
Case 1
17 year old undergoing CT for incidentally discovered FNH - denied any possibility of pregnancy

19. 46 year old - denied pregnancy “irregular periods”
Inadvertent exposure
Case 2
46 year old - denied pregnancy “irregular periods”

20. Inadvertent exposure
Case 3
21 year old – post BMT for CML – no periods for 6/12 but denied pregnancy – now with nausea and cramping

21. Inadvertent exposure 27 year old - denied pregnancy
Case 4
27 year old - denied pregnancy
“late period” (5 weeks gestation)

22. Inadvertent exposure
Case 4
GESTATIONAL SAC
DECIDUAL REACTION

23. 20 year old at 7 weeks gestation with RLQ pain
Inadvertent exposure
Case 5
CORPUS LUTEUM
PLACENTA
GESTATIONAL SAC
20 year old at 7 weeks gestation with RLQ pain

24. Exposure and termination
Source
Fetal dose guideline
Hammer-Jacobsen
Advisable if > 10 rad (“Danish rule”)
Wagner et al
Consider if > 5 rad at 2 to 15 weeks
Recommend if > 15 rad
Hall
Consider if > 10 rad at 10 days to 26 weeks
Danish Med Bull 1959; 6:
Exposure of the pregnant patient to diagnostic radiations: a guide to medical management. Lippincott 1985;
Radiobiology for the radiologist, 4th ed. 1994:

25. Patel, S. J. et al. Radiographics 2007; 27: 1705-1722
Fetal doses
1 rad
2 rad
3 rad
Key point: Radiation dose from single CT of the pelvis is highly unlikely to justify termination
Patel, S. J. et al. Radiographics 2007; 27:
Copyright ©Radiological Society of North America, 2007

26. Fetal dose = 10-19 mGy (1-1.9 rad)
What about PET?
Rare - two reported cases
Fetal dose estimates vary:
0.8, 1.2, and 1.5 mGy/mCi
May vary with gestational age
J Nucl Med 2010; 51: 803-5
J Nucl Med 2008; 49: 679–82
J Nucl Med 2004; 45: 634–5
J Nucl Med 2003; 44: 1522–30
40 year old woman with metastatic breast cancer – “no periods for 5 years” mCi FDG
Fetal dose = mGy (1-1.9 rad)

27. Iodinated contrast in pregnancy
Iodinated contrast should be avoided:
Amniography can cause hypothyroidism
Mutagenic to human cells in vitro
NOT teratogenic in animals
Better than rescanning?
Invest Radiol 1982; 17:
Eur J Radiol 1994; 18 (Suppl 1): 21-31
Invest Radiol 1989; 24 (Suppl 1): 16-22
Am J Obstet Gynecol 1976; 126:

28. Neonatal hypothyroidism?
23 babies of 21 women:
All had contrast-enhanced CT during pregnancy
No cases of neonatal hypothyroidism
343 babies of 332 women:
All had CECT for PE during pregnancy
No cases of neonatal hypothyroidism (transient reduced TSH in one)
AJR 2008; 191:
Radiology 2010; 256:

29. Iodinated contrast and lactation
Standard recommendation:
Stop breast-feeding for 24 hours
Weak rationale:
Minimal passage of IV contrast into breast milk
Minimal absorption of oral iodinated contrast
No thyroid dysfunction after neonatal IV contrast
Recommendation recently questioned:
Personal approach - continue breast-feeding
Eur J Radiol 1992; 12: 22-25
Acta Radiol Suppl. 1980; 362: 87-92
Eur Radiol 2005; 15:

30. Safety of CT - Safety of MRI - Indications for CT and MRI

31. Risks of MRI
Teratogenesis
Acoustic damage
Gadolinium toxicity

32. Teratogenesis: Chick embryo study
1.5T x 6 hours Controls
19.5% abnormal/dead % abnormal/dead
JMRI 1994; 4:
Statistically significant difference

33. Acoustic damage Follow-up of 20 children after fetal EPI:
16/18 passed hearing test at 8/12 (16.7 expected)
Intragastric sound intensity measurement:
Fetal exposure < maternal
Am J Obstet Gynecol 1994; 170: 32-33
Br J Radiol 1995; 68:

34. Gadolinium toxicity Teratogenic: Skeletal malformations
0.5 mmol/kg/day x 13 days to pregnant rabbits
No adverse effect in small human studies
Use only if essential
Omniscan package insert, Nycomed, Princeton, NJ
Radiology 1997; 205: Clin Radiology 2000; 55:
Radiology 2011; 258:
Clears rapidly from fetus and amniotic fluid in mice

35. FDA and drugs in pregnancy
Category
Fetal dose (rads) A
Controlled studies in women fail to demonstrate a risk to the fetus – remote possibility of fetal harm B
Animal studies show no risks, but there are no controlled human studies
Adverse effects in animals, but not in well-controlled human studies
Use in pregnancy considered probably safe (e.g. acetaminophen) C
Studies in animals have revealed adverse effects on the fetus and no controlled studies in women, or studies in women and animals not available
Only use if benefit justifies the potential risk (most prescribed medications) D
Positive evidence of human fetal risk
Benefits may be acceptable if the risk is high (life-threatening situation or serious disease with no other options, e.g., most chemotherapy drugs) X
Studies in animals or women have demonstrated fetal abnormalities
Not to be used – absolutely contra-indication (e.g., thalidomide)
IODINATED CONTRAST
GADOLINIUM

36. Gadolinium and lactation
Package insert “recommendation”:
Unknown if this drug is excreted in human milk
“Caution should be exercised”
Recent study of 20 lactating women:
< 0.04% of maternal dose passes into milk
Less than 1% of permitted IV neonatal dose
Suspension of nursing not warranted?
Omniscan package insert - amershamhealth-us.com
Radiology 2000; 216: Eur Radiol 2005; 15:

37. Indications for CT and MRI
Safety of CT - Safety of MRI - Indications for CT and MRI
Indications for CT and MRI

38. Indications for CT/MRI in pregnancy
Fetal
Mainly MRI of CNS anomalies – some body applications
Maternal
PELVIC
EXTRA-PELVIC
Obstetric
Pelvimetry
Placenta accreta
Adnexal mass
Red degeneration of fibroid
Postpartum uterine mass
Cerebral venous thrombosis
Pulmonary embolism
HELLP syndrome
Other
Acute appendicitis
Flank pain
Trauma
Malignancy

39. Pulmonary embolism PE rate = 0.7 per 1000 pregnancies:
50% occur after Cesarean section
Imaging options:
V/Q scan, helical CT, pulmonary angiography
No comparative studies in pregnancy
25% of V/Q scans nondiagnostic in pregnancy (v. 7% in nonpregnant patients)
Angiology 2002; 53:
Obstet Gynecol 1999; 94:
Arch Intern Med 2002;162:

40. Radiation doses from PE studies
Test
Fetal dose
Helical CT
3-130 microGy
Rises from first to third trimester
V/Q scan
microGy
Assumes reduced dose of Tc 99m (37-74 MBq)
Pulmonary angiogram
500 microGy
Assumes brachial approach
Radiology 2002; 224:

41. British Medical Journal 2005; 331: 350
Perfusion only scan?
Dose
CTPA
Q scan
Maternal
2.0 Sv
0.6 Sv
Breast
10.0 mGy
0.28 mGy
Fetus
0.01 mGy
0.12 mGy
British Medical Journal 2005; 331: 350

42. Acute appendicitis in pregnancy
Major indication for surgery in pregnancy:
1 in 1500 pregnancies
Diagnosis clinically difficult, 25% perforation rate
Limited data on role of imaging:
CT 100% accurate (n = 2 of 7)
US 100% sensitive & 96% specific (n = 15 of 42)
US could not be performed in 3 (all > 35 weeks)
Mil Med. 1999; 164:
Am J Obstet Gynecol 2001; 184:
AJR 1992; 159:

43. Appendix hard to see near term
37 weeks
34 weeks
APPENDIX
APPENDIX?

44. MRI for appendicitis in pregnancy
Dutch study of 12 suspected cases:
Mean gestational age of 17 weeks (range, 7-35)
3 with surgically proven appendicitis
*17 and 35 weeks gestation
AJR 2004; 183:
True positive
True negative
Not seen US 1 11
MRI 3 7 2*

45. MRI for appendicitis in pregnancy
Beth Israel study of 51 suspected cases:
Mean gestational age of 20 weeks (range, 4-38)
Oral Gastromark/Readi-Cat mix (dark on T1 & T2)
Three planes of SSFSE
Sensitivity of 100%, specificity of 93.6%
Only 4 “proven” appendicitis (3 surgical, 1 CT)
Gestational ages of 13, 20, 27, and 31 weeks
Normal
Positive
Radiology 2006; 238:

46. MRI for appendicitis in pregnancy
Normal
Positive

47. UCSF experience
TRUE NEGATIVE T2
TRUE POSITIVE T1
34 weeks
31 weeks

48. UCSF experience ? 26 weeks CT prior to pregnancy 32 weeks
TRUE NEGATIVE
26 weeks
TRUE NEGATIVE ?
TRUE NEGATIVE
CT prior to pregnancy
32 weeks

49. SMALL BOWEL OBSTRUCTION
UCSF experience
SMALL BOWEL OBSTRUCTION
FORNICEAL RUPTURE
18 weeks
14 weeks

50. Flank pain Hydronephrosis common in pregnancy: Imaging options:
Probably mechanical
Consider stones, etc if symptomatic
Imaging options:
US, NECT, IVP, isotope renography, MRU
No established optimal approach

51. Imaging stones in pregnancy
Incidence: 0.3 per 1000 deliveries
Detection of calculi by first test ( n = 57):
Renal US - 21 of 35 (60%)
AXR - 4 of 7 (57%)
IVP - 13 of 14 (93%)
Estimated fetal doses:
IVP = 1.4 rad
CT = 2.6 rad
Obstet Gynecol 2000; 96:
Am Fam Physician 1999; 59:
AJR 2002; 178:

52. Examples
38 weeks
LEFT URETERAL STONE
31 weeks
FORNICEAL RUPTURE

53. 2. Clinical Radiology 2000; 55: 446-453
MRU in pregnancy
FSE MRU
Two techniques for MRU:
Static - heavily T2W images
Dynamic (MREU) - serial T1W images after standard dose of gadolinium
BUT gadolinium is teratogenic!!
Alternative to IVU?
Stones seen in 4/15 patients1
MREU/MAG3 concordant in 8/9 cases2
1. Magn Reson Imaging 1995; 13:
2. Clinical Radiology 2000; 55:

54. Take home points CT and pregnancy: MRI and pregnancy:
Teratogenesis unlikely at diagnostic doses
Carcinogenesis is a real risk
Document risk/benefit discussion, or signed consent
MRI and pregnancy:
No proven risk, but avoid first trimester studies
Contrast and pregnancy/lactation:
Iodinated contrast is (probably) safe
Gadolinium is (relatively) contraindicated
No need to stop breast-feeding

55. Take home points Suspected PE in pregnancy:
CT preferred to V/Q scans throughout pregnancy
Suspected appendicitis in pregnancy:
All modalities limited near term - US worth trying
MRI may help if US inconclusive
Flank pain in pregnancy:
US first – but may be indeterminate
Manage symptomatically versus limited IVP?
Remember forniceal rupture
Obstet & Gynecol 2008; 112:

56. Case study
CONTRAST-ENHANCED CT OR
GAD-ENHANCED MRI?
20 year with SEVERE flare of known Crohn’s disease at 19 weeks gestation
“Must rule out abscess” - GI attending

57. “We’ve created a safe, nonjudgmental environment that will leave your child ill prepared for real life”