title: Embryo volume measurement: an intraobserver, intermethod comparative study of semiautomated and manual three-dimensional ultrasound techniques.
abstract: OBJECTIVE
  To compare the reliability of our recently introduced technique for first-trimester embryo volume measurement, the 'semiautomated technique' using both Virtual Organ Computer-aided AnaLysis (VOCAL(™) ) and Sonography-based Automated Volume Count (SonoAVC) with a manual technique using VOCAL alone.
  
  
  METHODS
  Seventy-four subjects with viable, singleton first-trimester in-vitro fertilization (IVF) pregnancies were recruited. Each subject underwent transvaginal sonography, at which a three-dimensional ultrasound dataset of the entire gestational sac was acquired. Each embryo volume was measured by two techniques, each performed twice. In the semiautomated technique VOCAL was used to calculate the volume of the gestational and yolk sacs, and SonoAVC was used to quantify the fluid volume within the amniotic and extra-amniotic cavities. Embryo volume was calculated by subtracting the sum of yolk sac, amniotic and extra-amniotic fluid volumes from gestational sac volume. In the manual technique, VOCAL was used to delineate the entire embryo using 9° rotations. Reliability was assessed using limits of agreement and intraclass correlation coefficient.
  
  
  RESULTS
  Datasets were included from 52 eligible subjects. Median gestational age was 7 + 4 weeks; median crown-rump length (CRL) was 13 (range, 2-29) mm; and median embryo volume was 1.8 (range, 0.03-8.1) cm(3) using the semiautomated technique and 0.7 (range 0.009-3.6) cm(3) using the manual technique. There was a significant discrepancy in the volumes measured by the two different techniques. Assessment of the limits of agreement suggested that the semiautomated technique (-15.8% to 14.0% of the mean embryo volume) was more reliable than was the manual technique (-22.4% to 26.6%).
  
  
  CONCLUSIONS
  The semiautomated technique is more reliable than is the manual technique for embryo volume measurement. However, the discrepancy in measurements between the two methods raises concerns over the validity of the semiautomated technique that require further investigation.
authors.affiliation: Nottingham University Research and Treatment Unit in Reproduction (NURTURE), Division of Obstetrics and Gynaecology, School of Clinical Sciences, University of Nottingham, Nottingham, UK. Shyamaly.Sur@nottingham.ac.uk
authors.forename: S D
authors.initials: SD
authors.lastname: Sur
authors.forename: J S
authors.initials: JS
authors.lastname: Clewes
authors.forename: B K
authors.initials: BK
authors.lastname: Campbell
authors.forename: N J
authors.initials: NJ
authors.lastname: Raine-Fenning
mesh_terms: D018568:Crown-Rump Length; D004622:Embryo, Mammalian / Q000033:anatomy & histology / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods; D021621:Imaging, Three-Dimensional / Q000379:methods; D015588:Observer Variation; D011247:Pregnancy; D011446:Prospective Studies; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D016216:Ultrasonography, Prenatal / Q000379:methods