CT use in pregnant women skyrockets at Rhode Island hospital

The CT imaging rate for pregnant women at two hospitals affiliated with Brown University's medical school grew at an explosive 25.3% annual rate from 1997 and 2006, while medical imaging involving ionizing radiation for this population more than doubled.

A study that in appeared in March on the online edition of Radiology raised concern among radiologists who have suspected that pregnant women and their fetuses have been exposed to increasing amounts of ionizing radiation because of the growing popularity of CT and nuclear imaging.

"This study is a yellow light for radiologists," said Dr. Fergus Coakley, a professor of radiology and biomedical imaging at the University of California, San Francisco.

Physicians need to be very conscious of the use of imaging studies in pregnancy, especially those that involve substantial doses of radiation to the fetus, he said in an interview with Diagnostic Imaging.

The 10-year retrospective review at the Rhode Island Hospital and Women and Infants' Hospital in Providence focused on CT, fluoroscopy, nuclear medicine, and plain-film x-ray studies, all of which involve exposure to ionizing radiation. Both facilities are affiliated with the Brown Alpert Medical School, where the study was performed.

Lead investigator Dr. Elizabeth Lazarus and colleagues evaluated 5270 exams and 3285 patients. Over the 10-year duration of the study, the number of patients imaged annually rose from 237 to 449, and the number of exams increased from 331 to 732. This represented an 89% increase in patients and a 121% increase in the number of exams. During the same 10 years, the number of deliveries increased 7% from 8661 to 9264, resulting in a rise in the imaging utilization rate per 1000 deliveries of 107%.

Lazarus reported that nuclear medicine use rose 11.6% per year, while fluoro use jumped 10.6% per year, and plain-film x-rays increased 6.8% per year.

The study estimated that each CT exam exposed the fetus to 4.3 mGy of radiation. Fetal exposures for fluoro, nuclear imaging, and plain-film x-ray exams were 2.91 mGy, 0.4 mGy, and 0.43 mGy, respectively.

CT exams are not routinely ordered for pregnant women, but they may be needed to detected suspected life-threatening conditions such as brain hemorrhage, pulmonary embolism, or appendicitis. The Rhode Island study broke down the studies:
• Head: 37%
• Abdomen and pelvis: 32%
• Pulmonary angiograms: 27%
• Limbs, spine, neck, and chest: 4%

"Our study did not examine the causes of the increases," Lazarus said in an interview with Diagnostic Imaging. "We know from other studies that imaging, particularly CT and MR, has been increasing in the general population." The causes of the increase could be more awareness of CT's usefulness in diagnosing and triaging patients as well as replacing other exams like intravenous urography, she said.

"We also think, due to the risks of surgery during pregnancy, that CT has been used to help avoid surgery or to increase clinical confidence in a surgically relevant diagnosis prior to surgery," she said.

Lazarus expressed confidence in the safety of imaging involving ionizing radiation when performed during pregnancy, though the study should raise awareness about imaging trends in pregnant patients. The study may help efforts by radiologists to minimize radiation exposure, she said.

Lazarus predicted that the trend toward higher CT use will continue. She touted the potential value of electronic medical records to help physicians track imaging procedures performed on pregnant patients and to recognize the potential value of nonionizing MRI and ultrasound for this population.

For more information from the Diagnostic Imaging and SearchMedica archives:

MR offers different option for pregnant appendicitis patientsRadiation dose reduction themes color RSNA 2008Protocols for pregnant patients increase safety