title: Reliability and validity of tissue volume measurement by three-dimensional ultrasound: an experimental model.
abstract: OBJECTIVE
  To determine the validity and the intra- and interobserver reliability of volume measurements of an endometrium-like model using a three-dimensional (3D) ultrasound rotational technique.
  
  
  METHODS
  A 3D ultrasound dataset was obtained from a sample of bovine liver containing a portion of chicken chest muscle (CCM). The process was repeated seven times using pieces of CCM of different sizes, resulting in seven datasets. Each portion of CCM was then placed in a water-filled volume-scaled tube and the 'actual' volumes were calculated by water displacement. For each dataset, ten volumes were calculated by each of two observers using a (VOCAL) with a 15 degrees rotational step. Reliability was assessed by calculating intraclass correlation coefficients (ICC) and validity by examining the percentage difference from the actual volume using limits of agreement.
  
  
  RESULTS
  The volume measurement of organic tissues using the 3D ultrasound rotational method was highly reliable (intraobserver ICC, 0.998 for Observer 1 and 0.997 for Observer 2; interobserver ICC, 0.997) and valid (the bias and 95% limits of agreement of the percentage difference from the actual volume was only 0.57 (-3.07 to 4.21) % for Observer 1 and - 0.17 (-4.34 to 4.0) % for Observer 2).
  
  
  CONCLUSIONS
  The 3D sonographic measurement, using VOCAL with a 15 degrees rotational step, of small and irregular tissues is reliable and valid, suggesting that it is a useful technique for measurement of the endometrial volume and other volumes of similar size.
authors.affiliation: Departamento de Ginecologia e Obstetrícia da Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo and Escola de Ultra-sonografia de Ribeirão Preto, Ribeirão Preto, Brazil. wpmartins@gmail.com
authors.forename: W P
authors.initials: WP
authors.lastname: Martins
authors.forename: R A
authors.initials: RA
authors.lastname: Ferriani
authors.forename: D A
authors.initials: DA
authors.lastname: Barra
authors.forename: R M
authors.initials: RM
authors.lastname: Dos Reis
authors.forename: M A V
authors.initials: MA
authors.lastname: Bortolieiro
authors.forename: C O
authors.initials: CO
authors.lastname: Nastri
authors.forename: F Mauad
authors.initials: FM
authors.lastname: Filho
mesh_terms: D000818:Animals; D001717:Birds; D002417:Cattle; D002645:Chickens; D004717:Endometrium / Q000000981:diagnostic imaging*; D005260:Female; D021621:Imaging, Three-Dimensional / Q000295:instrumentation / Q000379:methods / Q000592:standards*; D008099:Liver; D008954:Models, Biological; D018482:Muscle, Skeletal; D011247:Pregnancy; D015203:Reproducibility of Results; D016216:Ultrasonography, Prenatal / Q000295:instrumentation / Q000379:methods / Q000592:standards*