title: Sonographic Evaluation of the Fetal Thymus Using the Thy-Box Technique Between 13 and 16 Weeks' Gestation.
abstract: OBJECTIVE
  The purposes of this study were to assess the feasibility of fetal thymus measurement between 13 and 16 weeks' gestation, to evaluate the potential difference using color Doppler sonography with the thy-box technique, and to construct normal percentile ranges.
  
  
  METHODS
  This retrospective study included 287 healthy singleton pregnancies. The fetal thymus was shown in an axial plane of the upper mediastinum. Color Doppler imaging was applied to outline the thy-box: ie, the area between the brachiocephalic artery posteriorly and internal mammary arteries laterally. Measurements of the lateral and anteroposterior diameters of the thymus with and without color Doppler imaging were compared.
  
  
  RESULTS
  The thymus was shown in 95% of the cases (273 of 287) between 13 and 16 weeks' gestation. The mean lateral thymus diameter ± SD with color Doppler imaging (5.30 ± 0.7 mm) was significantly longer in comparison to the measurement without color Doppler imaging (5.06 ± 0.8 mm; P < .001), whereas the anteroposterior diameter was significantly shorter (3.19 ± 0.9 versus 3.26 ± 0.8 mm; P = .044). Normal percentiles of thymus measurements for gestational age were constructed.
  
  
  CONCLUSIONS
  The fetal thymus can be clearly and accurately shown as early as 13 weeks' gestation by using the thy-box. Measurements with color Doppler imaging were significantly different from those without and hence are preferable, as color Doppler imaging can delineate the thymus borders more accurately.
authors.affiliation: Department of Obstetrics and Gynecology, Chaim Sheba Medical Center, Tel Hashomer, Ramat Gan, Israel; affiliated with the Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel. alinabrenner@yahoo.com.
authors.forename: Alina
authors.initials: A
authors.lastname: Weissmann-Brenner
authors.affiliation: Department of Obstetrics and Gynecology, Chaim Sheba Medical Center, Tel Hashomer, Ramat Gan, Israel; affiliated with the Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel.
authors.forename: Roni
authors.initials: R
authors.lastname: Zemet
authors.affiliation: Department of Obstetrics and Gynecology, Chaim Sheba Medical Center, Tel Hashomer, Ramat Gan, Israel; affiliated with the Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel.
authors.forename: Zvi
authors.initials: Z
authors.lastname: Kivilevitch
authors.affiliation: Department of Obstetrics and Gynecology, Chaim Sheba Medical Center, Tel Hashomer, Ramat Gan, Israel; affiliated with the Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel.
authors.forename: Yaron
authors.initials: Y
authors.lastname: Zalel
mesh_terms: D000465:Algorithms; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008297:Male; D015588:Observer Variation; D011247:Pregnancy; D011262:Pregnancy Trimester, Second; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013950:Thymus Gland / Q000002:abnormalities* / Q000000981:diagnostic imaging* / Q000196:embryology; D013952:Thymus Hyperplasia / Q000000981:diagnostic imaging*; D018615:Ultrasonography, Doppler, Color / Q000379:methods*
keywords: Doppler sonography; fetal thymus; obstetric ultrasound; prenatal diagnosis; thy-box