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Ct Of The Pregnant Patient

  • Fetal and Maternal Doses Associated with Diagnostic Tests for PE
  • Some Explanations for the Decision Process
    - “ In pregnant woman with suspected PE and a normal CXR, we recommend lung scintigraphy as the next imaging test rather than CTPA.” (strong recommendation, low quality evidence)
    - “ The recommendation puts a high value on minimizing radiation dose to the mother. It puts a lower value on rapidity of the diagnostic test and the possibility of alternate diagnoses afforded by CTPA.”
  • Some Explanations for the Decision Process
    - “ In pregnant woman with suspected PE and a nondiagnostic V/Q scan we suggest further diagnostic testing rather than clinical management alone (weak recommendation, low quality evidence). In patients with a nondiagnostic V/Q scan in whom a decision is made to further investigate, we recommend CTPA rather than DSA (strong recommendation, very low quality evidence)”
    - “ This recommendation puts a high value on diagnostic certainty given the potential morbid consequences if PE is undiagnosed due to a nondiagnostic V/Q scan.”
  • “ The federal government has the authority, precedents, and mechanisms to address CT safety concerns through comprehensive regulatory schemes. Federal activities to date, namely imaging facility accreditation under MIPPA and increased FDA oversight, signify important steps aimed at eliminating the risk of accidental radiation overdoses.”
    The Federal Government’s Oversight of CT Safety: Regulatory Possibilities
    Harvey HB, Pandharipande PV
    Radiology 2012; 262;391-398
  • “ However, alone these measures only partially address the CT safety problem as defined by experts in Congressional testimony. Working together with states and the radiologic community, the federal government could further leverage its authority to provide more comprehensive regulatory solutions that attend to overutilization and dose optimization.”
    The Federal Government’s Oversight of CT Safety: Regulatory Possibilities
    Harvey HB, Pandharipande PV
    Radiology 2012; 262;391-398
  • "According to the phantom data, patients are subject to different organ doses in the lens and brain depending on scanner assignment. At our institution with existing protocols, absorbed dose at brain CT are lowest with the single detector CT scanner, followed by MDCT scanners capable of gantry tilt"

    Radiation Dose for Routine Clinical Adult Brain CT: Variability on Different Scanners at One Institution
    Jaffe TA et al.
    AJR 2010; 195:433-438

  • 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
  • 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

  • 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

  • "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

  • When indicated, major radiodiagnostic testing in pregnancy should be carried out, along with brief counseling [37]. The latter will hopefully lessen the level of anxiety experienced by an expectant mother (and her family), not only at the time of illness, but after her child is born
  • Conclusion

    Although major radiodiagnostic testing is now performed in about 1 in 160 pregnancies in Ontario, the absolute annual risk of childhood malignancy following exposure in utero remains about 1 in 10,000. Since the upper confidence limit of the relative risk of malignancy may be as high as 1.8 times that of an unexposed pregnancy, we cannot exclude the possibility that fetal exposure to CT or radionuclide imaging is carcinogenic.

    Ray JG, Schull MJ, Urquia ML, You JJ, Guttmann A, et al. (2010) Major Radiodiagnostic Imaging in Pregnancy and the Risk of Childhood Malignancy: APopulation-Based Cohort Study in Ontario. PLoS Med 7(9): e1000337. doi:10.1371/journal.pmed.1000337
  •  

  • What is the science behind the facts?

    Major radiodiagnostic imaging in pregnancy and the risk of childhood malignancy: a population-based cohort study in Ontario.

    Ray JG, Schull MJ, Urquia ML, You JJ, Guttmann A, Vermeulen MJ.

    Department of Medicine, St. Michael's Hospital, Toronto, Ontario, Canada. rayj@smh.toronto.on.ca

    Abstract

    BACKGROUND: The association between fetal exposure to major radiodiagnostic testing in pregnancy-computed tomography (CT) and radionuclide imaging-and the risk of childhood cancer is not established.

    METHODS AND FINDINGS: We completed a population-based study of 1.8 million maternal-child pairs in the province of Ontario, from 1991 to 2008. We used Ontario's universal health care-linked administrative databases to identify all term obstetrical deliveries and newborn records, inpatient and outpatient major radiodiagnostic services, as well as all children with a malignancy after birth. There were 5,590 mothers exposed to major radiodiagnostic testing in pregnancy (3.0 per 1,000) and 1,829,927 mothers not exposed. The rate of radiodiagnostic testing increased from 1.1 to 6.3 per 1,000 pregnancies over the study period; about 73% of tests were CT scans. After a median duration of follow-up of 8.9 years, four childhood cancers arose in the exposed group (1.13 per 10,000 person-years) and 2,539 cancers in the unexposed group (1.56 per 10,000 person-years), a crude hazard ratio of 0.69 (95% confidence interval 0.26-1.82). After adjusting for maternal age, income quintile, urban status, and maternal cancer, as well as infant sex, chromosomal or congenital anomalies, and major radiodiagnostic test exposure after birth, the risk was essentially unchanged (hazard ratio 0.68, 95% confidence interval 0.25-1.80).

    CONCLUSIONS: Although major radiodiagnostic testing is now performed in about 1 in 160 pregnancies in Ontario, the absolute annual risk of childhood malignancy following exposure in utero remains about 1 in 10,000. Since the upper confidence limit of the relative risk of malignancy may be as high as 1.8 times that of an unexposed pregnancy, we cannot exclude the possibility that fetal exposure to CT or radionuclide imaging is carcinogenic.