title: A mathematical formula to estimate in vivo thyroid volume from two-dimensional ultrasonography.
abstract: BACKGROUND
  The determination of thyroid volume (TV) is required for the management of thyroid diseases. Since two-dimensional ultrasonography (2D-US) has become the accepted method for the assessment of TV (2D-US-TV), we verified whether it accurately assesses postsurgical measured TV (PS-TV).
  
  
  METHODS
  In 92 patients who underwent total thyroidectomy by conventional cervicotomy, 2D-US-TV obtained by the ellipsoid volume formula was compared to PS-TV, determined by the Archimedes' principle.
  
  
  RESULTS
  Mean 2D-US-TV (23.9 +/- 14.8 mL) was significantly lower than mean PS-TV (33.4 +/- 20.1 mL). Underestimation was observed in 77% of cases, and it was related to gland multinodularity and/or nodular involvement of the isthmus, while 2D-US-TV matched the PS-TV in the remaining 21 cases (23%). A mathematical formula, to estimate PS-TV from US-TV, was derived using a linear model (Calculated-TV = [1.24 x 2D-US-TV]+ 3.66). Calculated-TV (mean value 33.4 +/- 18.3 mL) significantly (p < 0.01) increased from 21 (23%) to 31 (34%) of the cases that matched PS-TV. In addition, it significantly (p < 0.01) decreased from 77% to 27% the percentage of cases where PS-TV was underestimated as well as the range of the disagreement from 245% to 92%.
  
  
  CONCLUSIONS
  This study shows that 2D-US does not provide an accurate estimation of TV and suggests that it can be improved by a mathematical model different from the ellipsoid model. If confirmed in prospective studies, this may contribute to a more appropriate management of thyroid diseases.
authors.affiliation: Department of Experimental Medicine, Sapienza University of Rome, Viale del Policlinico 155, Rome, Italy.
authors.forename: Pierpaolo
authors.initials: P
authors.lastname: Trimboli
authors.forename: Massimo
authors.initials: M
authors.lastname: Ruggieri
authors.forename: Angela
authors.initials: A
authors.lastname: Fumarola
authors.forename: Michele
authors.initials: M
authors.lastname: D'Alò
authors.forename: Andrea
authors.initials: A
authors.lastname: Straniero
authors.forename: Amelia
authors.initials: A
authors.lastname: Maiuolo
authors.forename: Salvatore
authors.initials: S
authors.lastname: Ulisse
authors.forename: Massimino
authors.initials: M
authors.lastname: D'Armiento
mesh_terms: D000328:Adult; D000368:Aged; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D013961:Thyroid Gland / Q000033:anatomy & histology* / Q000000981:diagnostic imaging*; D013965:Thyroidectomy; D014463:Ultrasonography