title: Three-dimensional US of the fetus: volume imaging.
abstract: OBJECTIVE
  To retrospectively compare the rapidity, efficiency, and accuracy of three-dimensional (3D) and two-dimensional (2D) ultrasonography (US) for complete anatomic survey in fetuses at 17-21 weeks of gestation.
  
  
  METHODS
  Institutional review board approval was obtained, informed consent was waived, and the study was HIPAA compliant. Fifty consecutive women undergoing fetal anatomic survey at 17-21 weeks of gestation formed the study cohort. After standard 2D US was performed by one of eight sonographers, the same sonographer also obtained five 3D volumes to encompass the entire fetal anatomy. Three physicians interpreting the scans independently evaluated the completeness of the examination and time needed to read the scans, comparing the standard 2D method with the 3D volume reconstruction technique. The paired t test was used to compare biparietal diameter (BPD), femur length, and performance times between the 3D measurements and the 2D measurement. The t test was used to compare fetal anatomy according to volume angle. Differences were significant when P < .05.
  
  
  RESULTS
  Mean time to perform 2D US was 19.6 minutes per examination, whereas mean time to perform complete 3D volume acquisition was 1.8 minutes. Mean times needed to interpret 3D images and measure the BPD and femur were 5.53, 4.79, and 5.34 minutes for the three interpreting physicians. Compared with complete fetal surveys performed with 2D US, individual fetal anatomic landmarks (except for fetal arms and cavum septum pellucidum) were identified more than 94% of the time by using 3D US. Grouping anatomic views by region, the heart, head, extremities, and abdominal views were completely seen in 88%, 90%, 90%, and 95% of patients, respectively. No significant difference was seen between the three physicians regarding completeness of the 3D examinations (P = .7). One fetus had multiple anomalies, with 3D volumes identified as abnormal by all three physicians. Overall, 74% of 3D BPD measurements were within 1 mm of the 2D measurements, and 64% of 3D femur measurements were within 1 mm of the 2D measurements.
  
  
  CONCLUSIONS
  The standard fetal anatomic survey can be performed in less than 2 minutes with 3D volume US, and the volumes can be interpreted in 6-7 minutes, compared with a mean of 19.6 minutes to perform standard 2D US.
authors.affiliation: Department of Obstetrics and Gynecology, Division of Maternal-Fetal Medicine, Brigham and Women's Hospital, Boston, Mass, USA. bbsono@aol.com
authors.forename: Beryl R
authors.initials: BR
authors.lastname: Benacerraf
authors.forename: Thomas D
authors.initials: TD
authors.lastname: Shipp
authors.forename: Bryann
authors.initials: B
authors.lastname: Bromley
mesh_terms: D000328:Adult; D016009:Chi-Square Distribution; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional; D011247:Pregnancy; D011262:Pregnancy Trimester, Second; D012189:Retrospective Studies; D013997:Time Factors; D016216:Ultrasonography, Prenatal / Q000379:methods*