Transcript INTERESTING CASES IN ABDOMINAL IMAGING

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
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: 1107-1109
Medline hits for “CT
radiation dose”
Safety of CT - Safety of MRI - Indications for CT and MRI
Safety of CT
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: 787-792
Br J Radiol 1987; 60: 17-31
Carcinogenesis
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 Assembly
National Radiological Protection Board, 1993: 15-157
Thrombosis and Haemostasis 1989; 61: 189-196
Basis of risk estimates
 Oxford
 547
Survey of Childhood Cancer
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
OSCC - Results
Maternal
radiation
Control
s
Cases
Risk
To abdomen
43
85
2.0
To other body part
55
58
1.0
None
447
404
NA
Gestational age & carcinogenesis
 Relative
risk by trimester (OSCC data):
First
(< 10 weeks)
First
(All)
Second
Third
4.6
3.2
1.3
1.3
J Radiol Prot 1988; 8: 3-8
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.htm
Obstet 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;4-8
DHSS 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
Case 1
Inadvertent exposure
17 year old undergoing CT for
incidentally discovered FNH - denied
any possibility of pregnancy
Case 2
Inadvertent exposure
46 year old - denied pregnancy
“irregular periods”
Case 3
Inadvertent exposure
21 year old – post BMT for CML – no
periods for 6/12 but denied pregnancy –
now with nausea and cramping
Case 4
Inadvertent exposure
27 year old - denied pregnancy
“late period” (5 weeks gestation)
Case 4
Inadvertent exposure
GESTATIONAL SAC
DECIDUAL REACTION
Case 5
Inadvertent exposure
PLACENTA
CORPUS
LUTEUM
GESTATIONAL SAC
20 year old at 7 weeks gestation with RLQ pain
Exposure and termination
Source
Hammer-Jacobsen
Wagner et al
Hall
Fetal dose guideline
Advisable if > 10 rad (“Danish rule”)
Consider if > 5 rad at 2 to 15 weeks
Recommend if > 15 rad
Consider if > 10 rad at 10 days to 26 weeks
Danish Med Bull 1959; 6: 113-122
Exposure of the pregnant patient to diagnostic radiations: a guide to
medical management. Lippincott 1985; 19-223
Radiobiology for the radiologist, 4th ed. 1994: 363-452
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: 1705-1722
Copyright ©Radiological Society of North America, 2007
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” - 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
 Better
teratogenic in animals
than rescanning?
Invest Radiol 1982; 17: 183-185
Eur J Radiol 1994; 18 (Suppl 1): 21-31
Invest 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: 268-71
Radiology 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: 22-25
Acta Radiol Suppl. 1980; 362: 87-92
Eur Radiol 2005; 15: 1234-1240
Safety of CT - Safety of MRI - Indications for CT and MRI
Safety of MRI
Risks of MRI
 Teratogenesis
 Acoustic
damage
 Gadolinium
toxicity
Teratogenesis: Chick embryo study
304 chick embryos
1.5T x 6 hours
19.5% abnormal/dead
Controls
10.7% abnormal/dead
Statistically significant difference
JMRI 1994; 4: 742-748
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: 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
 Clears
rapidly from
fetus and amniotic
fluid in mice
Omniscan package insert, Nycomed, Princeton, NJ
Radiology 1997; 205: 493-496 Clin Radiology 2000; 55: 446-453
Radiology 2011; 258: 455-460
FDA and drugs in pregnancy
Categor
y
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 consideredGADOLINIUM
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
IODINATED CONTRAST
Studies in animals or women have demonstrated fetal abnormalities
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: 555-558
Eur Radiol 2005; 15: 1234-1240
Safety of CT - Safety of MRI - Indications for CT and MRI
Indications for CT and MRI
Indications for CT/MRI in pregnancy
Fetal
Maternal
Mainly MRI of CNS anomalies – some body applications
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
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: 429-434
Obstet Gynecol 1999; 94: 730-734
Arch Intern Med 2002;162:1170-1175
Radiation doses from PE studies
Test
Fetal dose
Helical CT
3-130 microGy
Rises from first to third trimester
V/Q scan
100-370 microGy
Assumes reduced dose of Tc 99m (37-74 MBq)
Pulmonary 500 microGy
angiogram Assumes brachial approach
Radiology 2002; 224: 487-492
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
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
34 weeks
APPENDIX
37 weeks
APPENDIX?
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
True positive True negative
Not seen
US
1
0
11
MRI
3
7
2*
*17 and 35 weeks gestation
AJR 2004; 183: 671-675
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: 891-899
MRI for appendicitis in pregnancy
Normal
Positive
UCSF experience
TRUE NEGATIVE
T2
T1
TRUE POSITIVE
34 weeks
31 weeks
UCSF experience
TRUE NEGATIVE
TRUE NEGATIVE
26 weeks
?
TRUE NEGATIVE
32 weeks
CT prior to
pregnancy
UCSF experience
SMALL 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:
 Detection
0.3 per 1000 deliveries
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
Examples
38 weeks
FORNICEAL RUPTURE
LEFT URETERAL STONE
31 weeks
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; 13:767-772
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”