Imaging of Pregnant and
Lactating Patients
Evidence-based review and
recommendations
Dr. Robert Walter,
Department of Medical Imaging
Royal Inland Hospital
Declaration of conflicts of interest:
 None
Outline:
 Discuss basic concepts of ionizing radiation
 Ionizing radiation effects on teratogenesis and
carcinogenesis
 IV contrast use during pregnancy and lactation
 CT / MRI safety in pregnancy
Con’t:




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Trauma imaging in pregnancy
Pulmonary embolism imaging
Imaging of acute appendicitis
Imaging of urolithiasis
Imaging in cholecystitis
X-rays, gamma rays, alpha, beta particles
TISSUE IONIZATION
Deterministic
effects
Stochastic
effects
Radiation units SI units
Exposure
Non-SI units
Roentgens
Absorbed dose
Gray
100 Rads
Equivalent dose
Sievert
100 Rem
Effective dose
Sievert
100 Rem
10 mSv = 1 Rem
Natural background radiation
Mother
3 mSv / year
Fetus
0.1 mSv / gestation
MPR (NRCP)
Fetus of Radiation worker allowed
5 mSv / gestation
Relative radiation levels
Effects of
ionizing
radiation on
fetus
Teratogenic
(deterministic)
Carcinogenic
(Stochastic)
Summary of deterministic effects:
Gestational
Age
Radiation dose
<50 mGy
50 – 100 mGy
> 100 mGy
0 – 2 wks
None
None
3 – 4 wks
Probably none
Possible spontaneous abortion
5 – 10 wks
Subtle/uncertain
Possible malformations
dose
11 – 17 wks
Subtle/uncertain
Risk of
IQ
with
dose
18 – 27 wk
None
IQ not measurably affected
> 27 wks
None
None
Estimated fetal dose:
Estimated CT fetal dose:
Consensus statements:
 NCRP
 ICRP
 BIER VII
 CDC
 ACR
 ACOG
Risk of malignancy,
miscarriage, major
malformations:
NEGLIGIBLE
@ < 50 mGy
Spontaneous pregnancy risks:
Spontaneous abortion
Major malformation
Prematurity / IUGR
Mental retardation
15%
3%
4%
1%
Carcinogenic risks to fetus less wellestablished:
Increased risk of childhood cancer
with in-utero irradiation:
 Patel el al. Radiographics 2007
 Valentin. Annals ICRP 2000
 Doll et al. British Journal of Radiology 1997
Childhood Carcinogenic Risk:
1 cancer / 500
fetuses
[ICRP estimate]
30 mGy dose
Lifetime Carcinogenic Risk:
40 cancer / 5000
fetuses
20 mGy dose
[ACR practice
guidelines]
Post natal Carcinogenic Risk
1 cancer / 100 people
100 mSv
[BIER VII Lifetime risk
model]
42 cancer / 100
people
Non-radiation
causes
Risks of Pediatric CT
The bottom line:
Minimize the
radiation
exposure and
dose in
accordance with
ALARA principle.
IV Contrast Agent Use During
Pregnancy and Lactation
 Literature is limited
Lactation
 Less than 1% of maternal dose excreted
in milk
 Less than of that absorbed by neonate
 No reports of toxicity or allergy
 Option to pump and discard
Pregnancy
 Gadolinium and iodinated agents
 cross the placenta
 Iodine-based contrast
 No teratogenic affects reported
 No reports of sequelae from IV use
 Use only as needed
 Gadolinium
 is a teratogen in high and multiple doses in
animal models
 No harm reported in human fetuses
exposed
ACR – use only if benefit to the mother is
overwhelming
CAR – IV Contrast should not be used
CT and MRI Safety in Pregnancy
 CT
 Avoid if alternative, but may be essential
 Dose reduction strategies
 MRI
 No deleterious fetal effects shown
 Safety during pregnancy not established
 Potential risk of RF heating effects and acoustic noise on
fetus not validated
 CAR recommends if information cannot be acquired by US
Acute Trauma in Pregnancy
 6 – 7 % of pregnancy will have
significant trauma
 A leading cause of nonobstetrical maternal death
First line trauma imaging modality
 Ultrasound
 If hemodynamically stable
 Assess gestation
 Assess for free fluid, if present go to CT
 61 – 83% sensitive
 94 – 100% specific for visceral injury
Second line imaging in pregnancy
 CT with contrast
 Reference standard for organ injury in trauma
 No delay, IV contrast is safe
 C+ abdomen dose is well-below 50 mSv
 Acute Multi-trauma
 If CT dose is above 100 mGy due to multiple studies,
elevated risk of malformation and childhood cancer
 If termination is being considered, consult medical
physicist
Acute Pulmonary Embolism
 Venous thromboembolism is the number 1
cause of maternal mortality in the developed
world.
 Pregnancy associated PE is 7 – 10 times the
incidence in age-matched controls
 15 – 24% of untreated DVTs develop PE
 PE has 15% fatality rate
Diagnosis of PE in Pregnancy
 Usual signs and symptoms overlap with
standard symptoms of pregnancy
 D-dimer can be false positive and false
negative
 Wells criteria and Geneva scores are less
reliable
Suspect PE
do
D-Dimer
Positive
Negative
(98%) specific
STOP
do leg US
Negative
BUT ???
do CXR
Negative
do
V/Q scan
Negative
STOP
Positive
STOP AND TREAT
Positive
??? Pneumonia
Indeterminate
do
Chest CT
High probability
STOP AND TREAT
Acute (and not so cute) Appendicitis
 Leading cause of nonobstetrical surgery in
pregnancy
 1 / 1700 pregnancies
 Pregnant patient
more likely to present
with appendix rupture
 Diagnosis is
challenging
Suspected appendicitis
 Graded compression sonography
 Reported sensitivity 85 – 100%
 Specificity 92 – 96%
 Recent CT and MR studies not supportive of these
claims.
If study indeterminate?
 MRI




Sensitivity 90 – 100%
Specificity 93 – 98%
Identification of alternative disease processes
Availability issue
Suspected appendicitis
 CT
 Sensitivity 92%
 Specificity 99%
 Dose reduction strategies
Wallace et al. Journal Gastrointestinal Surg 2008
Dx appendicitis clinically
Add ultrasound
Add CT
-
54% negative
36%
8%
Acute urolithiasis
 1 / 3300 pregnant patients develops obstructive renal
stones
 70 – 80% pass spontaneously
 Ultrasound primary modality with 34 – 95% sensitivity
for stone
 If US equivocal / non-diagnostic, do CT KUB
 Possible second line test = MR Urography, but less
sensitive for stones
Acute cholecystitis
 Second most common non-obstetrical emergency
requiring surgery during pregnancy
 Pregnant females at increased risk
 Abdominal US = primary modality
 Positive predictive value 94% with gallstones, gall
bladder wall thickening, and sonographic Murphy’s
sign
Normal gall bladder, bile duct
dilatation by ultrasound
 MRCP (MR cholangiopancreatography) = most
appropriate second line imaging test
 More sensitive than ultrasound for bile duct stones
 98% sensitive for biliary disease
 94% specific
 ERCP
 Restricted to therapeutic intervention for bile duct stones
 Multiple risk factors
In Summary:
 At typical diagnostic CT doses, teratogenicity is not an
issue but in-utero exposure does increase the risk of
carcinoma
 CT or MR contrast agent use during lactation has no
reports of sequelae
 CT contrast during pregnancy, no fetal problems
reported
 Gadolinium contrast in pregnancy is relatively
contraindicated
In Summary:
 MRI safety in pregnancy not definitely established
 Theoretic risks at 1.5 T but no adverse effects reported
 Acute trauma US first if pt stable, CT scanning if
free fluid present
 Pulmonary embolus Test sequence is D-dimer, leg
US, CXR, V/Q scan, CT for Pulmonary Embolus
 Appendicitis Test sequence is US, MRI if feasible,
CT-abdomen+pelvis with contrast
In Summary:
 Urolithiasis
Test sequence is US, Renal colic CT, (MRU)
 Cholecystitis
Test sequence is US, MRCP, ERCP only for
stone removal
ALARA