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Imaging of Pregnant and Lactating Patients Evidence-based review and recommendations Dr. Robert Walter, Department of Medical Imaging Royal Inland Hospital.

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Presentation on theme: "Imaging of Pregnant and Lactating Patients Evidence-based review and recommendations Dr. Robert Walter, Department of Medical Imaging Royal Inland Hospital."— Presentation transcript:

1 Imaging of Pregnant and Lactating Patients Evidence-based review and recommendations Dr. Robert Walter, Department of Medical Imaging Royal Inland Hospital

2  None Declaration of conflicts of interest:

3  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 Outline:

4  Trauma imaging in pregnancy  Pulmonary embolism imaging  Imaging of acute appendicitis  Imaging of urolithiasis  Imaging in cholecystitis Con’t:

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9 Radiation unitsSI unitsNon-SI units ExposureRoentgens Absorbed doseGray100 Rads Equivalent doseSievert100 Rem Effective doseSievert100 Rem 10 mSv = 1 Rem

10 Mother3 mSv / year Fetus0.1 mSv / gestation MPR (NRCP)Fetus of Radiation worker allowed 5 mSv / gestation Natural background radiation

11 Relative radiation levels

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13 Gestational Age Radiation dose <50 mGy50 – 100 mGy> 100 mGy 0 – 2 wksNone 3 – 4 wksProbably nonePossible spontaneous abortion 5 – 10 wksSubtle/uncertain Possible malformations dose 11 – 17 wks Subtle/uncertain Risk of IQ with dose 18 – 27 wkNoneIQ not measurably affected > 27 wksNone Summary of deterministic effects: None

14 Estimated fetal dose:

15 Estimated CT fetal dose:

16 Consensus statements:  NCRP  ICRP  BIER VII  CDC  ACR  ACOG Risk of malignancy, miscarriage, major malformations: < 50 mGy

17 Spontaneous abortion15% Major malformation 3% Prematurity / IUGR 4% Mental retardation 1% Spontaneous pregnancy risks:

18 Carcinogenic risks to fetus less well- established:

19  Patel el al. Radiographics 2007  Valentin. Annals ICRP 2000  Doll et al. British Journal of Radiology 1997 Increased risk of childhood cancer with in-utero irradiation:

20 Childhood Carcinogenic Risk: 1 cancer / 500 fetuses [ICRP estimate] 30 mGy dose

21 Lifetime Carcinogenic Risk: 40 cancer / 5000 fetuses [ACR practice guidelines] 20 mGy dose

22 Post natal Carcinogenic Risk 100 mSv Non-radiation causes 1 cancer / 100 people [BIER VII Lifetime risk model] 42 cancer / 100 people

23 Risks of Pediatric CT

24 Minimize the radiation exposure and dose in accordance with ALARA principle. The bottom line:

25  Literature is limited IV Contrast Agent Use During Pregnancy and Lactation

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27  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 Lactation

28  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 Pregnancy

29  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

30  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 CT and MRI Safety in Pregnancy

31 Acute Trauma in Pregnancy  6 – 7 % of pregnancy will have significant trauma  A leading cause of non- obstetrical maternal death

32  Ultrasound  If hemodynamically stable  Assess gestation  Assess for free fluid, if present go to CT  61 – 83% sensitive  94 – 100% specific for visceral injury First line trauma imaging modality

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34  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 Second line imaging in pregnancy

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36  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 Acute Pulmonary Embolism

37  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 Diagnosis of PE in Pregnancy

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39 Suspect PE do D-Dimer Suspect PE do D-Dimer Negative (98%) specific STOP Negative (98%) specific STOP Positive do leg US Positive do leg US Positive STOP AND TREAT Positive STOP AND TREAT Negative BUT ??? do CXR Negative BUT ??? do CXR Negative do V/Q scan Negative do V/Q scan Positive ??? Pneumonia Positive ??? Pneumonia Negative STOP Negative STOP Indeterminate do Chest CT Indeterminate do Chest CT High probability STOP AND TREAT High probability STOP AND TREAT

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42  Leading cause of non- obstetrical surgery in pregnancy  1 / 1700 pregnancies  Pregnant patient more likely to present with appendix rupture  Diagnosis is challenging Acute (and not so cute) Appendicitis

43  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

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47  CT  Sensitivity 92%  Specificity 99%  Dose reduction strategies Wallace et al. Journal Gastrointestinal Surg 2008 Dx appendicitis clinically - 54% negative Add ultrasound - 36% Add CT - 8% Suspected appendicitis

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51  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 urolithiasis

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55  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 Acute cholecystitis

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57  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 Normal gall bladder, bile duct dilatation by ultrasound

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59  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:

60  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:

61  Urolithiasis Test sequence is US, Renal colic CT, (MRU)  Cholecystitis Test sequence is US, MRCP, ERCP only for stone removal  A L A R A In Summary:

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