Low-dose fetal CT in the prenatal evaluation of skeletal dysplasias and other severe skeletal abnormalities

OBJECTIVE. Prenatal diagnosis of skeletal dysplasia is often difficult and based on findings with ultrasound, a technique with 40-60% sensitivity. The purpose of this study was to evaluate a preliminary experience in assessing severe prenatal osseous abnormalities with low-dose fetal CT. The hypothesis was that use of CT may improve the prenatal diagnosis of skeletal dysplasia beyond the available capabilities of ultrasound. MATERIALS AND METHODS. Retrospective search of a radiology database (July 2008-February 2011) yielded the records of unenhanced CT examinations of patients referred because of abnormal fetal bones. The original ultrasound and CT reports as interpreted at image acquisition were independently analyzed by two radiologists blinded to the final diagnosis and to the findings of the opposing imaging modality. Blinded review of the images was also performed. Correlation was made with the postmortem and postnatal findings. RESULTS. According to the reports of the studies, 5 of 21 cases were interpreted correctly with CT and incorrectly with ultrasound. In 17 cases, CT revealed additional osseous findings not in the ultrasound report. There were no cases in which ultrasound findings were correct and CT findings were incorrect. Blinded review of the images revealed that CT outperformed ultrasound (p < 0.001). There were a total of four CT errors among 218 total measures recorded and a total of 19 ultrasound errors among 218 total measures. CONCLUSION. Although low-dose fetal CT should never be used as the initial diagnostic modality in cases of suspected skeletal dysplasia, it is a powerful imaging adjunct that depicts the fetal bones in exquisite detail. Use of CT of fetuses at risk of skeletal dysplasia may provide clinicians with more accurate information for counseling of families regarding neonatal morbidity and mortality.