Shlomit Goldberg-Stein MD, Presenter: Nothing to Disclose

Bob Liu PhD, Abstract Co-Author: Nothing to Disclose

Peter F. Hahn MD, PhD, Abstract Co-Author: Nothing to Disclose

Susanna In-Sun Lee MD, PhD, Abstract Co-Author: Nothing to Disclose

To examine CT utilization trends, indications, yields, and radiation doses in pregnancy over a decade to identify factors that most impact on fetal radiation exposure.

Following human research committee approval, from a single institution database of 46,100 chest, abdomen, and pelvic CT’s from 1998-2007, all exams of known pregnant patients were identified. For abdominopelvic CT, demographics, fetal gestational age, exam indication, diagnostic yield, and scanning parameters were abstracted from the clinical record and scan images. A CT dose calculation software package from IMPACT.ORG was used to estimate uterine radiation dose for those examinations with complete direct fetal irradiation.

105 chest and 84 abdominopelvic CT’s on women known to be pregnant at time of scanning were identified. Incidence of chest CT increased annually 58% in pregnancy vs. 16% overall (p=0.24); abdominopelvic CT increased 64% in pregnancy vs. 11% overall (p=0.36). Most common indications for abdominopelvic CT in pregnancy were suspected appendicitis (61%, 51/84) and trauma (17%, 14/84) with an overall positive yield of 25% (21/84). Average fetal radiation dose calculated from the 59 exams with complete direct fetal irradiation was 24.8 mGy (range 7.8- 74.0) with 5% (3/59) of exams exceeding 50 mGy. Scan parameters most strongly associated with a high dose exam(i.e. >40 mGy) were kVp>120 (p=0.006), pitch<1 (p=0.017) and >1 series (p=0.046).

Over the past decade, body CT utilization has increased in both general and pregnant populations. Suspected appendicitis was the most common reason for abdominopelvic CT in pregnancy. Fetal radiation doses administered by abdominopelvic CT were well below the 150 mGy threshold for malformation or miscarriage risk; however, 5% exceeded the 50mGy threshold for risk of childhood cancer. High dose (>40 mGy) exams were associated with high kVp (>120), low pitch (<1) and multiple (>1) series.

To minimize fetal radiation exposure from diagnostic CT, scan series should be limited to 1. When tube current modulation is used, the low noise and thin slice technique should be used with caution.

Goldberg-Stein, S, Liu, B, Hahn, P, Lee, S, Body CT in Pregnancy: How to Best Minimize Fetal Radiation Exposure.  Radiological Society of North America 2008 Scientific Assembly and Annual Meeting, February 18 - February 20, 2008 ,Chicago IL. http://archive.rsna.org/2008/6015168.html