Radiologists seek national guidelines for imaging of pregnant women

National societies and individual institutions need to firm up guidelines governing the imaging of pregnant women, according to several presenters at a special focus session Wednesday.

"Welcome to the third rail of radiology," said Dr. Andrew LeRoy, a professor of radiology at the Mayo Clinic in Rochester, MN.

LeRoy cited 2 a.m. arguments about how to deal with pregnant women who need some kind of imaging. One way to mitigate such disagreements is to establish firm protocols addressing a variety of imaging scenarios.

Dr. Louis Wagner, a professor of radiological physics at the University of Texas, opened up the session by outlining risk and dose issues. A fetus exposed to specific radiation doses may have increased risks for malformations, induced neoplasms such as leukemia, and induced terminations, according to Wagner.

"A rough estimate of risk is that one extra mortality and up to four extra cancers occur for every 1000 fetuses exposed to 100 mGy of radiation," he said. "Put another way, if you expose 1000 pregnant patients to a single CT pass, eight fetuses may go on to develop cancer, with two possibly dying from the cancer."

Wagner listed his own rules of radiation management:

• Radiation to the conceptus should never go above 100 mGy.

• Cumulative doses of between 50 and 100 mGy reside in a worrisome gray zone.

• Less than 50 mGy should be acceptable if the benefit to risk ratio is kept high.

At Mayo, LeRoy developed guidelines and a simple reference sheet to ameliorate those 2 a.m. disputes. In thinking about protocols for the pregnant patient, the department learned four different lessons:

• Imaging protocols need to be developed in every area and modality of the practice.

• Iodinated IV is probably acceptable, but the jury is still out for gadolinium.

• For every imaging exam that is performed, there is always something the radiologist can do to reduce radiation dose.

LeRoy described several imaging protocols that had been changed to accommodate pregnant women. For appendicitis, he and his colleagues first turn to ultrasound, and if that is nondiagnostic, they go to MR. The protocol is not feasible, of course, for facilities that have no or limited access to MR equipment, he said.

Dr. Kimberley Applegate, an associate professor of radiology at the Indiana University School of Medicine, noted the surprising lack of literature regarding the topic of imaging pregnant or potentially pregnant women. The topic is a complicated one, encompassing different categories of patients: abdominal versus extra-abdominal imaging candidates, emergency versus scheduled imaging candidates, known pregnancies versus unsure/unknown, and minors versus adults.

Citing earlier research, Applegate said that approximately 1% of all pregnant women are given abdominal radiography during the first trimester of pregnancy.

In terms of screening and imaging protocols for pregnant patients, policies vary at institutions across the nation. Some have no written consent or screening questionnaire, some have the technologist ask all females from 12 to 52 years of age if they are pregnant, and others perform urine tests in those patients where pregnancy is unknown, she said.

Many are looking to the American College of Radiology to develop national guidelines to bring some uniformity to the process, Applegate said. Meanwhile, radiology departments can develop brochures informing pregnant women about the risks as well as the benefits of imaging. Facilities and organizations should update their Web sites to include imaging information for the pregnant patient.

Developing national guidelines and standards is no easy task. It will require collaboration between radiologists, clinicians, legal experts, and radiation risk experts, according to Applegate.