title: Gestational sac fluid volume measurements in virtual reality.
abstract: OBJECTIVE
  To evaluate a virtual reality (VR) application for gestational sac fluid volume (GSFV) measurements in first-trimester pregnancies and to study the correlation between different embryonic growth parameters.
  
  
  METHODS
  This was a prospective cohort study analyzing 180 three-dimensional (3D) ultrasound scans of 42 healthy women, performed between 5 + 5 and 12 + 6 weeks' gestational age (GA). The 3D datasets were transferred to the I-Space immersive VR system. The V-Scope application was used to create a 'hologram' of the ultrasound image, allowing depth perception and interaction with the rendered objects. Volumes were measured semi-automatically using a segmentation algorithm. In addition to the GSFV, the total gestational sac volume (GSV) and its diameter (GSD) were measured. The GSV was also calculated using the ellipsoid formula. Previously obtained measurements of embryonic volume and crown-rump length (CRL) were included in the study. The outcomes were analyzed using repeated-measures analysis of variance.
  
  
  RESULTS
  The GSFV was measured in 78 scans, and varied from 434 to 81 491 mm(3). A positive correlation between GSFV and GA, CRL and GSD was found. Comparison of the GSD formula constructed in our study in relation to GA with a formula that is commonly used clinically showed an increasing difference with increasing GA either side of 8 + 5 weeks. The GSFV/embryonic volume ratio showed a decrease with GA. The GSV calculated using the ellipsoid formula was on average 19.8% larger compared with the GSV measured in VR.
  
  
  CONCLUSIONS
  New charts for first-trimester GSFV were constructed using VR. These growth charts could be promising tools for studying normal and abnormal embryonic development.
authors.affiliation: Department of Obstetrics and Gynaecology, Division of Obstetrics and Prenatal Medicine, Erasmus MC, Rotterdam, The Netherlands. m.rousian@erasmusmc.nl
authors.forename: M
authors.initials: M
authors.lastname: Rousian
authors.forename: A H J
authors.initials: AH
authors.lastname: Koning
authors.forename: W C
authors.initials: WC
authors.lastname: Hop
authors.forename: P J
authors.initials: PJ
authors.lastname: van der Spek
authors.forename: N
authors.initials: N
authors.lastname: Exalto
authors.forename: E A P
authors.initials: EA
authors.lastname: Steegers
mesh_terms: D000465:Algorithms; D000653:Amniotic Fluid / Q000000981:diagnostic imaging*; D015331:Cohort Studies; D003198:Computer Simulation / Q000592:standards; D018568:Crown-Rump Length; D005260:Female; D005865:Gestational Age; D058746:Gestational Sac / Q000000981:diagnostic imaging*; D006801:Humans; D021621:Imaging, Three-Dimensional; D011247:Pregnancy; D011261:Pregnancy Trimester, First; D011446:Prospective Studies; D016216:Ultrasonography, Prenatal; D014584:User-Computer Interface