Imaging Pearls ❯ Radiation Dose ❯ CT of the Pregnant Patient
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- “Imaging studies are important adjuncts in the diagnostic evaluation of acute and chronic conditions. However, confusion about the safety of these modalities for pregnant and lactating women and their infants often results in unnecessary avoidance of useful diagnostic tests or the unnecessary interruption of breastfeeding.”
Guidelines for Diagnostic Imaging During Pregnancy and Lactation
ACOG COMMITTEE OPINION
Obstet Gynecol. 2017 Oct;130(4):933-93 - Ultrasonography and magnetic resonance imaging (MRI) are not associated with risk and are the imaging techniques of choice for the pregnant patient, but they should be used prudently and only when use is expected to answer a relevant clinical question or otherwise provide medical benefit to the patient.”
Guidelines for Diagnostic Imaging During Pregnancy and Lactation
ACOG COMMITTEE OPINION
Obstet Gynecol. 2017 Oct;130(4):933-93 - “With few exceptions, radiation exposure through radiography, computed tomography (CT) scan, or nuclear medicine imaging techniques is at a dose much lower than the exposure associated with fetal harm. If these techniques are necessary in addition to ultrasonography or MRI or are more readily available for the diagnosis in question, they should not be withheld from a pregnant patient.”
Guidelines for Diagnostic Imaging During Pregnancy and Lactation
ACOG COMMITTEE OPINION
Obstet Gynecol. 2017 Oct;130(4):933-93 - “Use of CT and associated contrast material should not be withheld if clinically indicated, but a thorough discussion of risks and benefits should take place. In the evaluation for acute processes such as appendicitis or small-bowel obstruction, the maternal benefit from early and accurate diagnosis may outweigh the theoretical fetal risks.”
Guidelines for Diagnostic Imaging During Pregnancy and Lactation
ACOG COMMITTEE OPINION
Obstet Gynecol. 2017 Oct;130(4):933-93 - “Although iodinated contrast media can cross the placenta and either enter the fetal circulation or pass directly into the amniotic fluid, animal studies have reported no teratogenic or mutagenic effects from its use. Additionally, theoretical concerns about the potential adverse effects of free iodide on the fetal thyroid gland have not been borne out in human studies.”
Guidelines for Diagnostic Imaging During Pregnancy and Lactation
ACOG COMMITTEE OPINION
Obstet Gynecol. 2017 Oct;130(4):933-93 - “Traditionally, lactating women who receive intravascular iodinated contrast have been advised to discontinue breastfeeding for 24 hours. However, because of its water solubility, less than 1% of iodinated contrast administered to a lactating woman is excreted into the breast milk, and less than 1% of this amount of contrast will be absorbed through the infant’s gastrointestinal tract. Therefore, breastfeeding can be continued without interruption after the use of iodinated contrast.”
Guidelines for Diagnostic Imaging During Pregnancy and Lactation
ACOG COMMITTEE OPINION
Obstet Gynecol. 2017 Oct;130(4):933-93 
NOVEMBER 2010 / WWW.IMAGEWISELY.ORG- The objective of this practice parameter is to assist practitioners to identify pregnant patients, prevent their unnecessary radiation exposure, tailor examinations to effectively manage radiation dose, and develop strategies to quantify and evaluate the potential effects of radiation delivered to pregnant patients. This practice parameter :
1) outlines the body of knowledge on the risks to the conceptus from ionizing radiation during the various stages of pregnancy, 2) provides guidance on when and how to screen for pregnancy prior to imaging examinations using ionizing radiation,
3) recommends means to control, manage, and practically minimize radiation dose to pregnant or potentially pregnant patients, and
4) discusses evaluation of dose assessment, risk assessment, and communication issues following exposure of pregnant patients. 
ACR–SPR PRACTICE PARAMETER FOR IMAGING PREGNANT OR POTENTIALLY PREGNANT ADOLESCENTS AND WOMEN WITH IONIZING RADIATION (2018)- Examinations That Do Not Require Verification of Pregnancy Status
In general, x-ray–based examinations that do not directly expose the pelvis or gravid uterus to the x-ray beam do not require verification of pregnancy status. Such studies include, but are not limited to:
- Chest radiography
- Extremity radiography.
- Any diagnostic examination of the head or neck.
- Mammography
- Any CT imaging outside of the abdomen or pelvis (with the possible exception of the hip)
ACR–SPR PRACTICE PARAMETER 2018 - Examinations That May Require Verification of Pregnancy Status
- Interventional fluoroscopic procedures of the abdomen or pelvis
- Diagnostic angiography of the abdomen or pelvis
- Hysterosalpingography
- Standard-dose CT protocols of the abdomen or pelvis
- Diagnostic Nuclear Medicine PET/CT
- ACR–SPR PRACTICE PARAMETER 2018 - Patient History for Possible Pregnancy
“Patients usually can supply adequate information to help assess the possibility of pregnancy. All patients of childbearing age (typically at least ages 12 years to 50 years) should be questioned about pregnancy status using a standardized form and/or through direct questioning by the technologist. The guidance is based on a minimum practical and balanced approach that considers patient and facility convenience, fertility (extremely rare without medical intervention beyond age 50 despite menstruation status), safety, and efficiency. A standardized form has the advantage of ensuring uniformity and can serve as documentation of pregnancy status for the medical record.”
ACR–SPR PRACTICE PARAMETER 2018 - Pregnancy Tests
“If the results of a pregnancy test are positive, the information must be brought to the attention of a radiologist or nuclear medicine physician prior to proceeding with an examination, except in the case of a life-saving emergency procedure. A negative pregnancy test should not be used by technologists as a reason to forgo standard screening procedures for pregnancy. If, following questioning of the patient, there is uncertainty in regard to her pregnancy status, the radiologist or nuclear medicine physician should be notified prior to performing the study, and the date and results of the negative pregnancy test should be included in the notification.”
ACR–SPR PRACTICE PARAMETER 2018 - Emergency Situations
If the procedure is of a critically urgent nature and pregnancy status cannot be verified, a note should be entered in the patient’s record that verification of pregnancy status was waived because of the critically urgent nature of the study. Documentation that is consistent with institutional policies should be entered in the patient’s medical record, indicating the circumstances of the waiver and the physician who directed the waiver.
ACR–SPR PRACTICE PARAMETER 2018 - Emergency Situations
For an imaging examination of the abdomen or pelvis using ionizing radiation, obtaining consent from a patient known to be pregnant is an essential component of providing comprehensive medical care in certain situations. This process requires: 1) a realistic overview of the limited risk to the patient and conceptus from the examination, and 2) the beneficial role of this imaging procedure in maternal or fetal health evaluation. Whether particular institutions use written consent forms or verbal consent, this interaction should be documented in the patient’s medical record and in compliance with state law. The written consent form should be retained in the medical record.
ACR–SPR PRACTICE PARAMETER 2018 - Patient Consent
Conveying information in a positive, rather than negative, format is useful in helping a patient understand an accurate perspective of risk. Rather than telling the patient what the likelihood is that her child could develop cancer later in life, the message with a positive, accurate perspective is that the cancer risk is small and that the likelihood the child will remain healthy with no adverse radiation effects is only slightly different from that of any other child .
ACR–SPR PRACTICE PARAMETER 2018 - Study Selection
What study can be used?
- Ultrasound
- MRI
- Computed Tomography - If CT is the study of choice optimize the exam
- Oral and/or IV contrast
- Single phase acquisition if possible
- Limit the volume scanned to the volume that needs to be scanned
- Use dose reduction techniques for a quality study at the lowest dose (do not get a low dose unreadable study) - CT Accreditation Program Requirements
- Resources
- “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 - “ 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 - “ 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 - 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 - Appendicitis (rule out)
- Most common cause of surgical abdomen in pregnancy (50-70 per 1000 patients)
- Ultrasound can be used first and in some institutions MR is done
- If indeterminate a CT is done using oral and IV contrast material - 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 - OBJECTIVE. Patient shielding is standard practice in diagnostic imaging, despite growing evidence that it provides negligible or no benefit and carries a substantial risk of increasing patient dose and compromising the diagnostic efficacy of an image. The historical rationale for patient shielding is described, and the folly of its continued use is discussed.
CONCLUSION. Although change is difficult, it is incumbent on radiologic technologists, medical physicists, and radiologists to abandon the practice of patient shielding in radiology.
Patient Shielding in Diagnostic Imaging: Discontinuing a Legacy Practice
Marsh RM, Silosky M
AJR 2019; 212:1–3 - “Last, it is important to give technologists discretion to provide shielding in certain cir- cumstances. Patients who are extremely anx- ious about the lack of shielding should be ad- vised of the potential risks. If the technologist still determines that shielding would provide a substantial psychologic benefit to the patient, he or she should be allowed to make this pro- fessional judgment. However, it is important to emphasize to medical staff that shielding should be avoided whenever possible.”
Patient Shielding in Diagnostic Imaging: Discontinuing a Legacy Practice
Marsh RM, Silosky M
AJR 2019; 212:1–3 - Patient shielding persists despite growing evidence that the practice should be aban- doned. Although change is difficult, it is in- cumbent on radiologic technologists, medical physicists, and radiologists to finally step up as reasonable voices on the subject. Until then, training programs, health care facilities, and accreditation and regulatory bodies will continue to encourage and engage in a legacy practice that presents substantial risk but negligible (or no) benefit to patient health.
Patient Shielding in Diagnostic Imaging: Discontinuing a Legacy Practice
Marsh RM, Silosky M
AJR 2019; 212:1–3 - “In addition, information in the form of posters or brochures can provide in- formation to patients before an appointment, either online or in a waiting room. The concerns of many patients may be alleviated if the patients know that someone is paying attention to their safety and that the lack of shielding is intentional rather than negligent.”
Patient Shielding in Diagnostic Imaging: Discontinuing a Legacy Practice
Marsh RM, Silosky M
AJR 2019; 212:1–3
- 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; 195:433-438Conclusion
"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; 30:1230-12332008 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
mGySection 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
0-2 none none none 3-4 none probably none possible spontaneous abortion 5-10 none uncertain Possible malformations
11-17 none uncertain Possible defects in IQ or mental retardation
18-27 none none IQ deficits not detectable at diagnostic doses
>27 none none 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. [email protected]
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.