title: Radiographic reference limits for cardiac width in peregrine falcons (Falco peregrinus).
abstract: OBJECTIVE
  To determine radiographic reference limits for cardiac width (CW) in peregrine falcons.
  
  
  METHODS
  Retrospective cross-sectional study. Animals-100 peregrine falcons.
  
  
  METHODS
  CW, thoracic width (TW), and sternal width (SW) were measured at the level of maximum CW on ventrodorsal radiographs of 64 falcons. Ratios of CW:TW and CW:SW were compared between positive pressure insufflation (PPI) radiographs and standard radiographs in 6 falcons. A hypothesis for the most accurate predictor of CW was formulated and validated in a new set of 36 falcons.
  
  
  RESULTS
  PPI radiographs had a significantly lower CW:TW ratio than did standard radiographs. The CW:SW ratio was unaffected. The 95% confidence interval for a regression-based predicted CW was 19% larger for any given TW, compared with SW. The difference between predicted and measured CW was significantly smaller with SW, compared with TW. Validation of these findings in a new data set of 36 falcons confirmed that prediction of CW when SW was used as the independent variable in a regression equation was superior to use of the CW:SW ratio or the CW:TW ratio and was superior to prediction of CW when TW was used as the independent variable in a regression equation.
  
  
  CONCLUSIONS
  Of the variables examined, SW seemed to be the most precise and most accurate predictor for CW in peregrine falcons. Thoracic width seemed inferior as a predictor for CW because TW was influenced by respiratory movements. The following formula can be used to predict the 95% confidence interval for CW in peregrine falcons: CW = 0.83SW + 0.37 ± 0.16.
authors.affiliation: Souq Waqif Falcon Hospital, Abdullah Bin Jassim St, Al-Jasra, Doha, Qatar., Division of Zoological Medicine, Department of Clinical Sciences of Companion Animals, Faculty of Veterinary Medicine, Utrecht University, 3584 CM Utrecht, The Netherlands. j.t.lumeij@uu.nl
authors.forename: Johannes T
authors.initials: JT
authors.lastname: Lumeij
authors.forename: Muneer A S
authors.initials: MA
authors.lastname: Shaik
authors.forename: Mohammed
authors.initials: M
authors.lastname: Ali
mesh_terms: D000818:Animals; D003430:Cross-Sectional Studies; D046093:Falconiformes / Q000033:anatomy & histology*; D005260:Female; D006321:Heart / Q000033:anatomy & histology* / Q000000981:diagnostic imaging*; D008297:Male; D013902:Radiography, Thoracic / Q000662:veterinary*; D012016:Reference Values; D013045:Species Specificity