CT and MRI in pregnancy and lactation Fergus Coakley MD, Professor of Radiology and Urology, Vice...
Transcript of CT and MRI in pregnancy and lactation Fergus Coakley MD, Professor of Radiology and Urology, Vice...
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
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
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; 436AJR 2004; 182: 1107-1109
Safety of CT
Safety of CT - Safety of MRI - Indications for CT and MRI
Risks of CT
Teratogenesis
– Stochastic (threshold) Carcinogenesis
– Non-stochastic (no threshold) Iodinated contrast
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; 19-223
AJR 1996; 167: 1377-1379 Radiology 1986; 159: 787-792Br J Radiol 1987; 60: 17-31
Endpoint Risk
Baseline risk of childhood cancer (0-15 yrs) 19/10,000
Excess risk per rad of fetal whole body dose 4.6-6.4/10,000
Relative risk of childhood cancer after 5 rad 2
UNSCEAR 1972 Report to the UN General AssemblyNational Radiological Protection Board, 1993: 15-157
Thrombosis and Haemostasis 1989; 61: 189-196
Carcinogenesis
Basis of risk estimates
Oxford Survey of Childhood Cancer
547 case-control pairs (1953-55):– 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: 447 BJR Feb 1997; 130-139
Maternal radiation
Controls
Cases Risk
To abdomen 43 85 2.0
To other body part
55 58 1.0
None 447 404 NA
OSCC - Results
Gestational age & carcinogenesis
Relative risk by trimester (OSCC data):
J Radiol Prot 1988; 8: 3-8
First (< 10 weeks)
First(All)
Second Third
4.6 3.2 1.3 1.3
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 www.radiology.ucsf.edu
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
http://www.physics.isu.edu/radinf/risk.htmObstet Gynecol 2004; 104: 647-651
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
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;4-8DHSS publication no. HHS/FDA-86-8254
AJR 1996; 167: 1377-1379
Good practice
Pregnancy section on requisition forms
Prominent signage
Routine questioning by technologist
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
Inadvertent exposure
17 year old undergoing CT for incidentally discovered FNH - denied any possibility of
pregnancy
Case 1
Inadvertent exposure
Case 2
46 year old - denied pregnancy “irregular periods”
Inadvertent exposure
Case 3
21 year old – post BMT for CML – no periods for 6/12 but denied pregnancy – now with
nausea and cramping
Inadvertent exposure
Case 4
27 year old - denied pregnancy“late period” (5 weeks gestation)
Inadvertent exposure
GESTATIONAL SAC
DECIDUAL REACTION
Case 4
Inadvertent exposure
Case 5
20 year old at 7 weeks gestation with RLQ pain
GESTATIONAL SAC
PLACENTA
CORPUS LUTEUM
Source Fetal dose guideline
Hammer-Jacobsen Advisable if > 10 rad (“Danish rule”)
Wagner et alConsider 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: 113-122Exposure of the pregnant patient to diagnostic radiations: a guide to
medical management. Lippincott 1985; 19-223Radiobiology for the radiologist, 4th ed. 1994: 363-452
Exposure and termination
Fetal doses
Patel, S. J. et al. Radiographics 2007; 27: 1705-1722
Key point: Radiation dose from single CT of the pelvis is highly unlikely to justify termination
Copyright ©Radiological Society of North America, 2007
1 rad 2 rad 3 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: 803-5J Nucl Med 2008; 49: 679–82J 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” - 12.4 mCi FDG
Fetal dose = 10-19 mGy (1-1.9 rad)
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: 183-185Eur J Radiol 1994; 18 (Suppl 1): 21-31Invest Radiol 1989; 24 (Suppl 1): 16-22
Am J Obstet Gynecol 1976; 126: 723-726
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: 268-71Radiology 2010; 256: 744-50
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: 22-25Acta Radiol Suppl. 1980; 362: 87-92
Eur Radiol 2005; 15: 1234-1240
Safety of MRI
Safety of CT - Safety of MRI - Indications for CT and MRI
Risks of MRI
Teratogenesis
Acoustic damage
Gadolinium toxicity
Teratogenesis: Chick embryo study
304 chick embryos
1.5T x 6 hours Controls
19.5% abnormal/dead 10.7% abnormal/dead
JMRI 1994; 4: 742-748
Statistically significant difference
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: 32-33Br J Radiol 1995; 68: 1090-1094
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, NJRadiology 1997; 205: 493-496 Clin Radiology 2000; 55: 446-453
Radiology 2011; 258: 455-460
Clears rapidly from fetus and amniotic fluid in mice
Category
Fetal dose (rads)
A Controlled studies in women fail to demonstrate a risk to the fetus – remote possibility of fetal harm
BAnimal studies show no risks, but there are no controlled human studiesAdverse effects in animals, but not in well-controlled human studiesUse in pregnancy considered probably safe (e.g. acetaminophen)
CStudies 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)
DPositive evidence of human fetal riskBenefits 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 abnormalitiesNot to be used – absolutely contra-indication (e.g., thalidomide)
FDA and drugs in pregnancy
IODINATED CONTRAST
GADOLINIUM
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.comRadiology 2000; 216: 555-558 Eur Radiol 2005; 15: 1234-1240
Indications for CT and MRI
Safety of CT - Safety of MRI - Indications for CT and MRI
Maternal PELVIC EXTRA-PELVIC
Obstetric
Pelvimetry Placenta accretaAdnexal massRed degeneration of fibroidPostpartum uterine mass
Cerebral venous thrombosisPulmonary embolismHELLP syndrome
OtherAcute appendicitisFlank pain
TraumaMalignancy
Indications for CT/MRI in pregnancy
Fetal Mainly MRI of CNS anomalies – some body applications
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: 429-434Obstet Gynecol 1999; 94: 730-734
Arch Intern Med 2002;162:1170-1175
Test Fetal dose
Helical CT3-130 microGyRises from first to third trimester
V/Q scan100-370 microGy Assumes reduced dose of Tc 99m (37-74 MBq)
Pulmonary angiogram
500 microGyAssumes brachial approach
Radiology 2002; 224: 487-492
Radiation doses from PE studies
Perfusion only scan?
British Medical Journal 2005; 331: 350
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
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: 671-674 Am J Obstet Gynecol 2001; 184: 954-957
AJR 1992; 159: 539-542
Appendix hard to see near term
APPENDIX
34 weeks
APPENDIX?
37 weeks
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: 671-675
True positive True negative Not seen
US 1 0 11
MRI 3 7 2*
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
Radiology 2006; 238: 891-899
Normal Positive
MRI for appendicitis in pregnancy
Normal Positive
UCSF experience
TRUE POSITIVE
34 weeks
TRUE NEGATIVE
31 weeks
T2
T1
TRUE NEGATIVE
32 weeks
TRUE NEGATIVE
UCSF experience
?
26 weeks
TRUE NEGATIVE
CT prior to pregnancy
UCSF experienceSMALL BOWEL OBSTRUCTION
18 weeks
FORNICEAL RUPTURE
14 weeks
Flank pain
Hydronephrosis common in pregnancy:– Probably mechanical– Consider stones, etc if
symptomatic
Imaging options:– US, NECT, IVP, isotope
renography, MRU– No established optimal approach
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: 753-756 Am Fam Physician 1999; 59: 1813-1818
AJR 2002; 178:1285-1286
Examples38 weeks
FORNICEAL RUPTURE 31 weeks
LEFT URETERAL STONE
MRU in pregnancy
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; 13:767-7722. Clinical Radiology 2000; 55: 446-453
FSE MRU
Take home points
CT 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
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: 333-340
Case study
20 year with SEVERE flare of known Crohn’s disease at 19 weeks gestation
“Must rule out abscess” - GI attending
CONTRAST-ENHANCED CT
OR
GAD-ENHANCED MRI?
“We’ve created a safe, nonjudgmental environment that will leave your child ill
prepared for real life”