Who should tell pregnant women about the potential risks of radiation exposure? And what should happen if an accidental dose is administered?
These two burning questions prompted a lively discussion during Sunday’s session about diagnostic radiology and pregnancy.
Dr. John Damilakis, an associate professor and the chair of medical physics at the University of Crete in Iraklion, Greece, thinks medical physicists should play a central role in informing gynecologists, patients, and their relatives and physicians about dose and risk.
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| Dr. John Damilakis |
In the case of accidental exposure, the gynecologist is the best person to inform the patient and address her anxiety, he said. This view was supported by a delegate who sprang to her feet and spoke eloquently on the topic.
“I think it’s vital that the person looking after the patient is the one who is giving the information. What happens in real life is that there is a lot of anxiety and misinformation. When these patients actually come to someone who understands the subject, then you will save lives,” said Dr Josephine McHugo, a consultant radiologist at Birmingham Women’s Hospital in the U.K.
She doesn’t think there should be any termination of pregnancy because of exposure to radiation.
“If you know when radiation’s been given and at what dose, then you can manage it appropriately,” she said.
Damilakis described two particularly complex cases. A 22-year-old woman who is 15 weeks pregnant is admitted to rule out appendicitis, but her appendix cannot be visualized adequately with ultrasound and the referring clinician recommends a CT examination of the abdomen, with and without contrast. Similarly, a woman in her sixth week of pregnancy requires a cardiac ablation procedure involving a total fluoroscopy time of 42 minutes.
In such situations, radiologists must ask themselves if the risk of irradiating the fetus is less than that of not making the necessary diagnosis and whether a termination should be recommended, he said. Conceptus doses below 100 mGy should not be considered a reason for termination.
It is essential to investigate thoroughly the reproductive status of a woman of childbearing age prior to imaging and ensure that posters are displayed prominently in the hospital to encourage patients to inform staff before an x-ray examination if they think they may be pregnant, he said.
Damilakis and his colleagues have recently submitted a paper to Radiology about the measurement of conceptus dose from multislice CT examinations during early gestation. The researchers tested a method that considers maternal body size and conceptus position variations. They assessed patient-specific Monte Carlo simulations based on 117 patient models created using image data of young women who underwent abdominal CT studies.
When performing MRI on pregnant women, be careful to avoid scanning above the normal controlled limit, said Dr. Janet De Wilde, SINAPSE coordinator at the University of Edinburgh in the U.K. If you need to exceed the limit, high specific absorption rate sequences should be applied for as short a time as possible, and high SAR sequences should be interspersed with low SAR sequences.
“If the fetus or maternal abdomen are not the target organs of interest, then the fetus should be kept out of the transmit field of the RF coil, if possible,” she said. “Particular care must be taken when scanning fetuses with poor placental function, for example in fetal growth restriction.”
Also, be aware that maternal heat stress may reduce placental perfusion, De Wilde said. Special care must be taken when scanning pregnant women with conditions leading to impaired thermoregulation, and pregnant women who are febrile should never be scanned. Make sure the patient’s heat loss pathways are optimal (no blankets, good bore air flow, reasonable room temperature).
“Overall there is no indication that the use of clinical MR procedures during pregnancy produces adverse effects,” she said.
Note: a version of this article appeared in the 2010 ECR Today newspaper.
