title: Fetal thymus: visualization rate and volume by integrating 2D- and 3D-ultrasound during 2nd trimester echocardiography.
abstract: OBJECTIVE
  To assess the visualization rate and transverse diameter of fetal thymus by two-dimensional ultrasound (2DUS) as well as the fetal thymus volume by three-dimensional ultrasound (3DUS) during the 2nd trimester echocardiography.
  
  
  METHODS
  A prospective cross-sectional study involving 100 normal fetuses between 18w0d and 23w6d was performed. The identification of fetal thymus and peri-thymic vessels was realized at level of three vessels and trachea (3VT). The transverse diameter was obtained placing a line cursor perpendicular to the line connecting the sternum and the spine. The fetal thymus volume was obtained by virtual organ computer-aided analysis (VOCAL) with 30° of rotation. We used the percentage of visualization rate of 2D structures and means and 95% confidence intervals (CI) for fetal thymus transverse diameter and volume.
  
  
  RESULTS
  The visualization rate of fetal thymus by 2DUS was of 100% in all gestational ages using the 3VT view. Addition of color Doppler ultrasound facilitates identification of the thy-box and enhanced the calculation of both fetal thymus transverse diameter and volume. The mean fetal thymus transverse diameter by 2DUS ranged from 11 mm at 18 weeks to 19 mm at 23 weeks of gestation. The mean fetal thymus volume by 3DUS ranged from 1.25 cm(3) at 18 weeks to 2.61 cm(3) at 23 weeks of gestation.
  
  
  CONCLUSIONS
  We demonstrated a high visualization rate of fetal thymus and peri-thymic vessels by 2DUS during the 2nd trimester echocardiography. The measurements of transverse diameter by 2DUS and the volume by 3DUS also showed a high success rate.
authors.affiliation: a Department of Obstetrics & Gynaecology , Guastalla Civil Hospital , AUSL Reggio Emilia , Reggio Emilia , Italy .
authors.forename: Gabriele
authors.initials: G
authors.lastname: Tonni
authors.affiliation: b Department of Obstetrics & Gynaecology , Meyer University Hospital , Florence , Italy .
authors.forename: Lucia
authors.initials: L
authors.lastname: Rosignoli
authors.affiliation: b Department of Obstetrics & Gynaecology , Meyer University Hospital , Florence , Italy .
authors.forename: Ettore
authors.initials: E
authors.lastname: Cariati
authors.affiliation: c Department of Obstetrics and Gynecology , Ribeirão Preto Medical School, University of São Paulo (FMRP-USP) , Ribeirão Preto-SP , Brazil .
authors.forename: Wellington P
authors.initials: WP
authors.lastname: Martins
authors.affiliation: c Department of Obstetrics and Gynecology , Ribeirão Preto Medical School, University of São Paulo (FMRP-USP) , Ribeirão Preto-SP , Brazil .
authors.forename: André H
authors.initials: AH
authors.lastname: Miyague
authors.affiliation: d Department of Obstetrics and Gynecology , Federal University of Paraná (UFPR) , Curitiba-PR , Brazil , and.
authors.forename: Rafael F
authors.initials: RF
authors.lastname: Bruns
authors.affiliation: e Department of Obstetrics , Paulista School of Medicine - Federal University of São Paulo (EPM-UNIFESP) , São Paulo-SP , Brazil.
authors.forename: Edward
authors.initials: E
authors.lastname: Araujo Júnior
mesh_terms: D003430:Cross-Sectional Studies; D004452:Echocardiography; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional; D011247:Pregnancy; D011262:Pregnancy Trimester, Second; D011446:Prospective Studies; D015203:Reproducibility of Results; D012984:Software; D013950:Thymus Gland / Q000000981:diagnostic imaging*; D016216:Ultrasonography, Prenatal
keywords: Diameter; fetal thymus; peri-thymic vessels; three-dimensional ultrasound; two-dimensional ultrasound; volume