ACR–SPR PRACTICE PARAMETER FOR IMAGING

PREGNANT OR POTENTIALLY PREGNANT

PATIENTS WITH IONIZING RADIATION

The American College of Radiology, with more than 30,000 members, is the principal organization of radiologists,

radiation oncologists, and clinical medical physicists in the United States. The College is a nonprofit professional

society whose primary purposes are to advance the science of radiology, improve radiologic services to the

patient, study the socioeconomic aspects of the practice of radiology, and encourage continuing education for

radiologists, radiation oncologists, medical physicists, and persons practicing in allied professional fields.

The American College of Radiology will periodically define new practice parameters and technical standards for

radiology requires specific training, skills, and techniques, as described in each document. Reproduction or

modification of the published practice parameter and technical standard by those entities not providing these

services is not authorized.

PREAMBLE

This document is an educational tool designed to assist practitioners in providing appropriate radiologic care for

patients. Practice Parameters and Technical Standards are not inflexible rules or requirements of practice and are

not intended, nor should they be used, to establish a legal standard of care

1

. For these reasons and those set

forth below, the American College of Radiology and our collaborating medical specialty societies caution against

the use of these documents in litigation in which the clinical decisions of a practitioner are called into question.

after publication of this document. However, a practitioner who employs an approach substantially different from

the guidance in this document may consider documenting in the patient record information sufficient to explain

the approach taken.

The practice of medicine involves the science, and the art of dealing with the prevention, diagnosis, alleviation,

and treatment of disease. The variety and complexity of human conditions make it impossible to always reach the

most appropriate diagnosis or to predict with certainty a particular response to treatment. Therefore, it should be

recognized that adherence to the guidance in this document will not assure an accurate diagnosis or a successful

outcome. All that should be expected is that the practitioner will follow a reasonable course of action based on

current knowledge, available resources, and the needs of the patient to deliver effective and safe medical care.

The purpose of this document is to assist practitioners in achieving this objective.

procedures in light of the standard’s stated purpose that ACR standards are educational tools and not intended to

establish a legal standard of care. See also, Stanley v. McCarver, 63 P.3d 1076 (Ariz. App. 2003) where in a

concurring opinion the Court stated that “published standards or guidelines of specialty medical organizations are

useful in determining the duty owed or the standard of care applicable in a given situation” even though ACR

standards themselves do not establish the standard of care.

I. INTRODUCTION

This practice parameter was revised collaboratively by the American College of Radiology (ACR) and the Society

for Pediatric Radiology (SPR).

Radiation exposure to a pregnant or potentially pregnant patient from a medical imaging procedure and the

argued that there is "no safe level” of radiation exposure. The risk of adverse effects from ionizing radiation

should always be weighed against the risk of not performing the procedure and the benefit derived from the

procedure . Many people are exposed to higher amounts of natural background radiation, including people who

live at mountain elevations or those who frequently use air travel. These lifestyle-related activities are generally

not considered risky. Even during pregnancy, the majority of the population does not avoid activities with natural

background radiation over concern of ionizing radiation exposure. The use of the term "safe” in any setting,

clinical or nonclinical, should be understood within the context of benefit versus risk. Safety is a matter of taking

appropriate actions to limit risk to a level justified by the benefit. To maintain a high standard of safety,

particularly when imaging pregnant or potentially pregnant patients, the degree of medical benefit should

outweigh the well-managed levels of risk.

technologist is referred to as the most likely person to communicate potential risks to pregnant patients. Nurses,

registered radiologist assistants, physician assistants, physicians, and other staff may also fill this role. Therefore,

whenever this practice parameter refers to technologists, it should be understood that others may share or be

assigned this responsibility.

When managing a pregnant patient potentially exposed to a high dose of radiation, the radiologist or nuclear

medicine physician should involve a Qualified Medical Physicist or Radiation Safety Officer to estimate absorbed

dose to the conceptus from the diagnostic or interventional procedure(s). This can be completed either

prospectively or retrospectively. The Qualified Medical Physicist should also advise the radiologist means by which

risk can be reasonably limited.

This practice parameter addresses the imaging of pregnant and possibly pregnant patients with ionizing radiation

The objective of this practice parameter is to assist practitioners in identifying pregnant patients, preventing

unnecessary radiation exposure, tailoring examinations to effectively manage radiation dose, and developing

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 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.

II. RADIATION RISKS TO THE CONCEPTUS

Potential effects of radiation have been extensively researched, resulting in a broad body of knowledge. As with

management of pregnant or potentially pregnant patients. A more complete review is provided in Appendix A.

3rd and 4th weeks

(15–28 days)

5th–10th weeks

(29–70 days)

18th–27th weeks

(120–189 days)

>27 weeks

(>189 days)

uncertainties in this estimate are considerable.

III. SCREENING FOR PREGNANCY

According to the International Commission on Radiological Protection, thousands of pregnant patients are

exposed to medically indicated ionizing radiation each year [4]. The frequency at which pregnant patients are

unintentionally exposed to ionizing radiation is unknown. One study reported that 1% of patients of childbearing

potential who underwent abdominal imaging were unknowingly pregnant in their first trimester [7]. Another

study of female trauma patients reported that 2.9% were pregnant and that the unidentified pregnancy rate was

0.3% [8].

The purpose of screening patients for the possibility of pregnancy is to minimize radiation exposure to the

from radiation exposure is much less than previously thought [12]. In the past, the use of shielding was optional

but not required. In light of the new data, the use of protective shielding for the pelvis, when it is outside the field

of view, is not recommended [13].

Standard-dose CT protocols of the abdomen or pelvisd.

99mTc-MDP Bone scan

with an examination. A negative pregnancy test should not be a reason to forgo standard screening procedures

for pregnancy. If, after questioning the patient, there is uncertainty in regard to their pregnancy status, the

radiologist or nuclear medicine physician should be notified prior to performing the study. The date of the

negative pregnancy test should be included in the notification.

Procedures that require a pregnancy test should be documented in the department policies

III. SCREENING FOR PREGNANCY

The definition and age of a minor may vary depending on state law; typically a person under the age of 18 is a

requirements.

In 1996, the US Congress passed the Health Insurance Portability and Accountability Act (HIPAA). The resulting

regulations contain numerous provisions that affect patients’ health care privacy rights, including those of minors.

The regulations recognize that, in specific circumstances, parents are not necessarily the personal representatives

of their minor children 1) when under state law the minor is legally able to consent to their care; 2) when the

minor may legally receive the care without the consent of a parent, and the minor or someone else has consented

to the care; or 3) when a parent or guardian assents to a confidential relationship between a health care provider

and the minor. In these situations, the radiologic or nuclear medicine technologist may ask a minor about their

pregnancy status prior to an imaging procedure involving ionizing radiation. The minor may exercise most of the

same rights as an adult under the regulations including limiting access of the parent or guardian to the minor’s

or ask the patient to fill out the standard form about menstrual history and the potential for pregnancy. If the

parent refuses, then a backup screening policy may be put in place. If the responses indicate that the patient is or

could be pregnant, verbal consent for a pregnancy test should be obtained from the patient and, when

examination. If consent is declined, the radiologist should be informed of the circumstance before any

examination is conducted. It should be documented in the patient’s medical record that the patient and/or the

guardian declined the pregnancy test.

Alternatively, the institutional policy might indicate that:

The pregnancy test should be ordered by the appropriate clinician.

If a pregnancy test is refused, this should be documented in the patient’s medical record and the radiologist

should be notified.

Such a policy has the advantage of:

incapable of conceiving), then the examination can be performed.

When the patient does not meet these criteria, and when the need for the examination is not critically urgent, the

technologist should contact the radiologist or nuclear medicine physician for further guidance. The technologist

may also follow procedural instructions defined in a written protocol [1].

If pregnancy is established, the patient should be informed in a timely manner. Although it is preferable that the

referring physician inform the patient, this might not be practical, and the radiologist or nuclear medicine

physician should ensure the patient is informed. The patient, referring physician, and radiologist/nuclear medicine

physician can then make decisions on the optimal patient management and imaging needs.

If the procedure is critically urgent, it must be performed without determining the patient’s pregnancy status.

That the determination of the pregnancy status was waived must be documented in the patient’s record [17].

IV. IMAGING THE PREGNANT PATIENT

For an imaging examination of the abdomen or pelvis using ionizing radiation, obtaining consent from a confirmed

pregnant patient is essential to provide comprehensive medical care . This process requires:

retained in the medical record.

The format of the consent may vary based on the clinical situation and local institutional guidelines. Because a

detailed quantitative list of risks may be beyond the comprehension of some patients, institutions may prefer a

limited consent process in which generalized benefits and risks to the pregnant patient and conceptus are

described (see Appendix C). Other facilities might prefer a detailed, numerically oriented consent form that lists

the radiation risks and potential adverse effects. Regardless of the format, the information communicated should

accurately convey benefits and risks posed by the procedure, in language understandable to the layperson.

Conveying information in a positive, rather than negative, manner is useful in helping a patient accurately

positive, accurate perspective is that the cancer risk is extremely small and it is likely the child will remain healthy

with no adverse radiation effects (see Appendix C for sample consent form).

achieved, discussion between the referring physician and the radiologist or the nuclear medicine physician may

need to occur. The imaging technologist and the imaging physician should work together to assure the best

benefit/risk for the patient and conceptus. Establishment of guidelines for imaging acute disease processes in

pregnant patients can expedite patient evaluation.

It is best to have written imaging protocols in place before imaging pregnant patients to ensure uniform and

optimized patient care. Protocols may be based on accumulated experience, literature reviews, and respected

medical opinions . When necessary, dose estimation can be facilitated by documenting relevant technique factors

[16] and machine-recorded dose surrogates, such as kerma-area product (also known as dose-area product) and

cumulative reference-point air kerma [18]. For nuclear medicine procedures, the conceptus dose can be estimated

from published tables of organ doses per unit of administered activity by radiopharmaceutical [19].

patient and conceptus, including reducing the number of images or limiting CT phases through the

abdomen/pelvis. When possible, imaging should be confined to the area of interest to avoid unnecessary pelvic

exposure.

Improvements in imaging equipment can also aid in reducing radiation exposure to the conceptus. One example is

automatic exposure control software on multirow-detector CT (MDCT) scanners, which limit patient exposure by

instantaneously modifying X-ray tube output to produce diagnostic images at a preset noise level. In the MDCT

assessment of abdominal/pelvic trauma, the data from a single phase through the patient’s body provide both a

comprehensive evaluation of the abdominal contents and diagnostic-quality reconstructed images of the spine,

eliminating the need for additional series. CT scanners with iterative reconstruction techniques have improved

image quality and reduced radiation dose in CT relative to the filtered back–projection techniques. Historically

12.

13.

17.

18.

19.

20.

23.

24.

25.

26.

27.

31.

32.

33.

36.

A.

B.

The weeks prior to conception

During the preconception interval, between last menstruation and just prior to conception, the ovum

is potentially susceptible to the genetic effects of radiation, a stochastic effect. Although heritable

effects have been demonstrated in experiments involving large doses of radiation to populations of

interval is extremely unlikely and has not been documented as a result of imaging examinations.

1.

Conception to implantation and preorganogenesis

For about 2 weeks after conception, the only established deterministic effect of radiation is induced

abortion [4]. Much of the experimental data assessing this effect involved rodents. Although doses of

1,000 mGy (1 Gy) or more result in a high rate of lethality, the likelihood of inducing this effect at

doses less than 50 mGy (0.05 Gy), in the upper range of diagnostic examinations, is low and not

distinguishable from zero [26]. Data from animal experiments suggest the risk of embryonic loss at

this stage increases incrementally between 0.5% and 1% per 10 mGy. Surviving conceptuses develop

2.

There is increased radiosensitivity to potential teratogenic effects during the period of

organogenesis. These are deterministic effects and therefore do not occur unless the dose to the

embryo exceeds the threshold necessary to induce the effect. Organogenesis occurs after

implantation and throughout the remainder of gestation and can be divided into 4 distinct intervals

with different vulnerabilities.

Embryonic stage or major organogenesis (~15–56 days after conception)

In the embryonic stage, beginning near the end of the second postconception week and

stage of differentiated and differentiating cells. The likelihood and severity of the effect

increase as the dose increases beyond the threshold.

A finding of small head circumference, without cognitive defect, has also been reported in

atomic- bomb survivors exposed during the organogenesis stage of intrauterine life [37]. There

was no discernible threshold for this effect. The mechanism for such an effect is unclear, and

the finding has been hypothesized to be a result of generalized growth retardation. In the

dose range of diagnostic examinations (less than 0.1 Gy), the effect, if truly existing, is subtle.

Small head circumference resulting from exposure to radiation secondary to diagnostic

a.

Early fetal stage

In the early fetal stage, after the eighth and through the 15th week postconception (after the

10th and through the 17th weeks menstrual age or approximately days 56–105

mGy, using the Japanese DS86 radiation data [39]. The broad range of the threshold estimate

is a consequence of the very small sample size at this radiation level. Furthermore, this

threshold range is determined on the basis of one model for statistical analysis. Higher

thresholds are predicted by other models. The lowest clinically documented dose producing

severe mental retardation is 610 mGy. The putative threshold is an extrapolation from data

observed at higher doses. The absolute risk of mental retardation is estimated at 44% for a

1,000 mGy exposure. The threshold range for CNS effects is significantly higher than the range

of doses delivered from a single well-managed imaging examinations ( less than 50 mGy).

Dose-dependent radiation-mediated deficits in Intelligence Quotient (IQ) have also been

beyond those normally delivered by radiological examinations.

Mid fetal stage

Beginning with the 16th week and extending through the 25th week postconception, the risk

for mental retardation remains but is less pronounced than in the preceding 8–15-week stage.

The estimated threshold dose for severe mental retardation is 250 to 280 mGy. The decline in

IQ is also less pronounced compared with the early fetal stage. Beyond a dose of 100 mGy, the

decline is estimated at 13 to 25 points per 1,000 mGy. The threshold dose during this period

for other types of malformation is about 1,000 mGy.

c.

neoplasia. These are discussed below.

APPENDIX B

should proceed according to verbal or written policy instructions of the radiologist. If a required pregnancy test is

refused, the radiologist should provide instructions on how to proceed.

This form and the one in Appendix C are provided as EXAMPLES ONLY. They are not intended to be used without

first consulting with legal counsel regarding your facility, local, or state law requirements.

PATIENT: MRN: DATE: TIME:

TECHNOLOGIST:

Yes No Possibly

Patient/guardian signature: Date:

Pregnancy testing required (per department guideline)? Yes No

Type: urine serum

Pregnancy Test Performed in Diagnostic Imaging

Verbal consent to test from: Patient Guardian (if appropriate) Results: Negative Positive

Testing tech/nurse initials:

Pregnancy Test Performed Outside the Radiology Practice

Results: Negative Positive

Source of results:

APPENDIX C

DATE: ________________________________ TIME: _________________________________

To the patient:

You are scheduled for an X-ray examination of your body. You and your unborn child will be exposed to X-rays.

The risk to you is very small. The examination might slightly increase the possibility of cancer later in the child’s

life, but the actual potential for a healthy life is very nearly the same as that of other children in circumstances

similar to yours but who are not provided the benefit of this medical examination. The examination does not add

to risks for birth defects or miscarriage. Your physician has considered the risks associated with this examination

and believes it is in your and your child’s best interests to proceed. Any questions you have regarding this

examination should be directed to the radiologist.

Radiologist or referring physician: Date:

Patients of childbearing potential will be screened for pregnancy.1.

Screening of patients <12 will be conducted at the discretion of the patient’s care providers.2.

Emergency procedures and examinations1.

Patients for whom pregnancy is anatomically impossible2.

Patients receiving human chorionic gonadotropin (hCG) therapy3.

Patients undergoing diagnostic/therapeutic oncology procedures (eg, bone marrow biopsy, lumbar

puncture, intrathecal chemotherapy) .

4.

These include all examinations that do not directly involve exposure of the pelvis (other than

Interventional Radiology; IR).

Low Risk

No probable (ie, deterministic) radiation effect, but a theoretical (ie, stochastic) risk.i.

These include abdomen/pelvic images and single-phase abdominal/pelvic CT.ii.

b.

See APPENDIX E: Imaging Examinations Requiring Pregnancy Testing.d.

Elective surgical procedures performed in the perioperative area

Note: Because of the operational complexity of limiting screening by laboratory test only to those

procedures believed to pose a substantial risk (such as abdominal and pelvic procedures and

procedures involving radiation exposure due to use of C arm), all patients of reproductive potential

scheduled for elective procedures in the perioperative area (See section I.A.1.a-f above) will be

screened for pregnancy by urine or serum test.

2.

Negligible risk

For negligible risk examinations (eg, chest or extremity imaging), the pregnancy screening is

1.

accompanying them.

Document response in the patient’s chart.c.

If the patient response is other than "no” or is thought to be unreliable for any reason, an hCG

test should be performed.

d.

Substantial risk

Examinations with possible deterministic radiation effects during some portions of the

pregnancy (ie, dual-phase abdominal and/or pelvic CT), and any examination that involves an

unpredictable duration of fluoroscopy including IR procedures, procedures expected to exceed

a conceptus dose of 50 mGy.

a.

Obtain a urine hCG test prior to examination.b.

3.

Low exposure examinations The benefit of providing the diagnostic imaging study outweighs the very

low potential risk to the fetus during a well-shielded patient examination.

1.

Examinations categorized as substantial risk Risk versus benefit dialogue provides rationale to move2.