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Ob Gyn: Pregnant Patient and CT Imaging Pearls - Educational Tools | CT Scanning | CT Imaging | CT Scan Protocols - CTisus
Imaging Pearls ❯ OB GYN ❯ Pregnant Patient and CT

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  • " In cases where CT is needed, protocols should be optimized for the individual with careful planning, with use of dose reduction techniques that allow adequate imaging without unnecessary radiation exposure. As in all cases, the benefit of an imaging diagnosis needs to be weighed against theoretical risks."
    Invited Commentary
    Levine D
    RadioGraphics 2010; 30:1230-1233
  • " The risk associated with a radiologic examination appears to be rather low compared with the natural risk. However, any added risk, no matter how small, is unacceptable if it does not benefit the patient."
    Radiation Risk: What You Should Know to Tell your Patient
    Verdun FR et al.
    RadioGraphics 2008:28:1807-1816
  • " The risk burden of radiation exposure to the fetus has to be carefully weighed against the benefits of obtaining a critical diagnosis quickly and using a single tailored imaging exam ."
    Imaging in Pregnant Patients: Examination Appropriateness
    Wieseler KM et al.
    RadioGraphics 2010; 30:1215-1233
  • "We aimed to combine previously described pregnancy specific CTPA technique alterations with a dose reduction strategy and a low kVp technique to yield a low dose CTPA protocol specifically tailored to pregnant patients, without a reduction in clinical image quality. The results demonstrate that by using a low kVp CTPA technique tailored to pregnancy, effective doses under 1 mSv are routinely achievable in a pregnant population."
    Low dose computed tomography pulmonary angiography protocol for imaging pregnant patients: Can dose reduction be achieved without reducing image quality?
    Halpenny D et al.
    Clinical Imaging: Volume 44, July–August 2017, Pages 101-105
  • "Pregnancy is a hypercoagulable state, and consequently pregnant patients are at high risk for PE. The diagnosis of PE can be challenging in pregnant patients, as the clinical signs and symptoms of PE can mimic the physiological effects of pregnancy. In the ATS/STR guidelines, CTPA is the recommended when a chest radiograph is abnormal and therefore maintains an important role in the evaluation of PE. While both V/Q scintigraphy and CTPA have high sensitivities and specificities, CTPA is quick to perform and interpret, and provides a higher rate of alternate diagnoses."
    Low dose computed tomography pulmonary angiography protocol for imaging pregnant patients: Can dose reduction be achieved without reducing image quality?
    Halpenny D et al.
    Clinical Imaging: Volume 44, July–August 2017, Pages 101-105
  • "CTPA image quality is potentially impacted by the hemodynamic changes of pregnancy. Increased plasma volume, cardiac output, total vascular resistance, and heart rate can lead to hemodilution of injected intravenous contrast with decreased peak arterial enhancement and shorter contrast material arrival time in the pulmonary arteries. Additionally, the gravid uterus increases IVC pressure and can accentuate transient contrast interruption."
    Low dose computed tomography pulmonary angiography protocol for imaging pregnant patients: Can dose reduction be achieved without reducing image quality?
    Halpenny D et al.
    Clinical Imaging: Volume 44, July–August 2017, Pages 101-105
  • “ In major trauma, when there is concern for maternal injury, CT is the mainstay of imaging. The risks of radiation to the pregnancy are small compared with the risk of missed or delayed diagnosis of trauma.”
    Imaging of Trauma: Part 2, Abdominal trauma and Pregnancy---A radiologists Guide to Doing What is Best for the Mother and Baby
    Sadro C et al.
    AJR 2012;199:1207-1219
  • “ Trauma is the leading cause of non-obstetric maternal mortality affecting up to 7% of pregnancies and is a significant cause of fetal loss. Approximately 2% of level-1 trauma patients have a positive pregnancy test.”
    Imaging of Trauma: Part 2, Abdominal trauma and Pregnancy---A radiologists Guide to Doing What is Best for the Mother and Baby
    Sadro C et al.
    AJR 2012;199:1207-1219
  • “ Causes of trauma in pregnancy include motor vehicle injury (49%), falls (25%), assaults and domestic violence( 18%), and gunshot wounds (4%).”
    Imaging of Trauma: Part 2, Abdominal trauma and Pregnancy---A radiologists Guide to Doing What is Best for the Mother and Baby
    Sadro C et al.
    AJR 2012;199:1207-1219
  • “Certain injuries in pregnancy are associated with an increased risk of fetal loss.Pelvic and acetabular fractures occurring in pregnancy are associated with a high maternal (9%) and higher fetal mortality (35%), increasing to 75% for severe fracture patterns.”
    Imaging of Trauma: Part 2, Abdominal trauma and Pregnancy---A radiologists Guide to Doing What is Best for the Mother and Baby
    Sadro C et al.
    AJR 2012;199:1207-1219
  • "Placental abruptions are often overlooked on CT scans. Sensitivity may be improved by systematic evaluation of the placenta and specificity by training on normal placental morphology."

    CT Evaluation of Placental Abruption in Pregnenet Trauma Patients
    Wei SH et al.
    Emerg Radiol (2009) 16:365-373

  • "True placental abruptions were characterized by large, contiguous, and retroplacental and/or full-thickness areas of low enhancement that form acute angles with myometrium."

    CT Evaluation of Placental Abruption in Pregnenet Trauma Patients
    Wei SH et al.
    Emerg Radiol (2009) 16:365-373

  • Placental Abruption: Complications
    - Pre-term labor
    - Fetal distress
    - Fetal death in 20-60%
    - Maternal shock
    - DIC
    - Maternal death
  • Conclusion

    "In cases where CT is needed, protocols should be optimized for the individual with careful planning, with use of dose reduction techniques that allow adequate imaging without unnecessary radiation exposure. As in all cases, the benefit of an imaging diagnosis needs to be weighed against theoretical risks."

    Invited Commentary
    Levine D
    RadioGraphics 2010; 30:1230-1233

  • Suspected Acute Abdomen
    - There are numerous causes for the acute abdomen
    - When a diagnosis can not be made CT is the study of choice
  • Urolithiasis (r/o)
    - Calculi in pregnancy are uncoomon
    - Ultrasound is done first but if not helpful CT is done to r/o stone and also look for other causes of flank pain.
    - If CT is done low dose non-contrast CT is fine
  • Trauma
    - The severity of the injury determines workup but priority is given to maternal survival
    - CT is used as needed in the chest and abdomen
    - Most common uterine injury is placental abruption which occurs in up to 40% of patients with severe injury. Uterine rupture is rare
  • Appendicitis (rule out)
    - Most common cause of surgical abdomen in pregnancy (50-70 per 1000 patients)
    - Ultrasound can be used first and in some institututions MR is done
    - If indeterminate a CT is done using oral and IV contrast material
  • Pulmonary Embolism
    - Leading cause of maternal morbidity
    - Pregnancy increases risk of PE by a factor of 5
    - Chest x-ray and ultrasound are often first test used to screen
    - If chest x-ray and ultrasound are negative and high suspicion CT is done
    - VQ scan is done if patients allergic to IV contrast
  • Common Clinical Scenarios in the Pregnant Patient
    - r/o pulmonary embolism
    - Trauma
    - r/o appendicits
    - Urolithiasis
    - Acute abdomen
  • 2008 ACR Practice Guidelines

    "To maintain a high standard of safety, particularly when imaging potentially pregnant patients, imaging radiation must be applied at levels as low as reasonably achieveable (ALARA), while the degree of medical benefit must counterbalance the well managed levels of risk."

    ACR Practice Guideline for imaging pregnant and potentially pregnant adolescents and woman with ionizing radiation (American College of Radiology)

     

  • At 150 mGy the risks will vary on stage of pregnancy but include
    - 3% chance of cancer development
    - 6% chance of mental retardation
    - Loss of 30 IQ points per 100 mGy
    - 15% chance of microcephaly
  • Nonstochastic Effects
    - Threshold effects or deterministic effects are caused by exposure to radiation at a high level
    - These effects are predictable and involve multicellular injury including chromosomal alterations
    - Threshold dose is usually 150 mGy and these patients need to be accessed for termination
  • "As shown in table 1, the ACR suggested that the theoretical risks are not likely at doses less than 100 mGy."

    Imaging in Pregnant Patients: Examination Appropriateness
    Wieseler KM et al.
    RadioGraphics 2010; 30:1215-1233

  • Stochastic effects
    - Are the results of cellular damage likely at the DNA level causing cancer or other germ cell mutations
    - They have no threshold dose and are theorized to any with exposure to any amount of radiation
    - The threshold for radiation induced Stochastic effects was established at 50mGy
  • Radiation Effects and Risk
    - Stochastic effects
    - Nonstochastic effects
  • Practical Points in Performing CT in the Pregnant Patients
    - Make sure that CT is the study of choice
    - Prepare the patient for the study as completely as possible (oral contrast etc. done early)
    - Design the optimal protocol for that patient (kVp, mAs, etc)
    - Scan only the area needed to be scanned
    - Monitor the scan to make sure you have a dx
  • Estimated Average Fetal Radiation Dose from a Single Acquisition with 64 MDCT

    Type of CT exam

    Dos
    mGy

    Section thickness (mm)

    Noise index

    mAs

    pitch

    CT  of the Chest

    0.02

    2.5

    30

    80

    1.375

    CT for PE

    0.02

    1.25

    30

    88

    0.984

    CT of the Abdomen

    1.3

    2.5

    36

    110

    1.375

    CT of the Kidney and bladder

    11

    2.5

    36

    110

    1.375

    CT of the Pelvis

    13

    2.5

    36

    130

    1.375

    CT of the Abdomen and Pelvis

    13

    2.5

    36

    130

    1.375

    CT Angiography

    13

    2.5

    30

    130

    1.375

  • Estimated Average Fetal Radiation Dose from a Single Acquisition with 64 MDCT

    Type of CT exam

    Dos
    mGy

    Section thickness (mm)

    Noise index

    mAs

    pitch

    CT  of the Chest

    0.02

    2.5

    30

    80

    1.375

  • Potential Radiation Effects on the Fetus by Gestational Age and Radiation Exposure
    Potential Effects by Radiation Exposure  

    Gestational age (weeks)

    <50 mDy

    50-100mGy

    >100 mGy

    0-2nonenonenone
    3-4noneprobably nonepossible spontaneous abortion
    5-10noneuncertain

    Possible malformations

    11-17noneuncertain

    Possible defects in IQ or mental retardation

    18-27nonenone

    IQ deficits not detectable at diagnostic doses

    >27nonenone

    None applicable to diagnostic radiology

  • Potential Radiation Effects on the Fetus by Gestational Age and Dose
    - Under 50 mGy there is none
    - With 50-100 mGy there is none at over 18 weeks and probably none under 4 weeks and uncertain at 5-17 weeks
    - Over 100 mGy there are typically no issues over 18 weeks and possible issues between 4 and 17 weeks Data from ACR practice guidelines
  • "However, no examination should be withheld when an important clinical diagnosis is under consideration. Exposure to ionizing radiation may be unavoidable, but there is no evidence to suggest that the risk to the fetus after a single imaging study and an interventional procedure is significant."

    Imaging in Pregnant Patients: Examination Appropriateness
    Wieseler KM et al.
    RadioGraphics 2010; 30:1215-1233

  • "The risk burden of radiation exposure to the fetus has to be carefully weighed against the benefits of obtaining a critical diagnosis quickly and using a single tailored imaging exam ."

    Imaging in Pregnant Patients: Examination Appropriateness
    Wieseler KM et al.
    RadioGraphics 2010; 30:1215-1233

     

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