title: Changes in Cross-Sectional Area and Transverse Diameter of the Heart on Inspiratory and Expiratory Chest CT: Correlation with Changes in Lung Size and Influence on Cardiothoracic Ratio Measurement.
abstract: OBJECTIVE
  The aim of this study was to investigate physiological changes in cardiac area and diameters between inspiratory and expiratory chest computed tomography (CT), and to assess their correlation with lung size change and influence on cardiothoracic ratio (CTR) measurements.
  
  
  METHODS
  The institutional review board of our institution approved this study, and informed consent was waived. Forty-three subjects underwent inspiratory and expiratory chest CT as part of routine clinical care. On both inspiratory and expiratory scans, lung volumes and maximum lung diameters (transverse and vertical directions) were measured. The maximum cardiac cross-sectional area (CSA) and the maximum transverse cardiac diameter were measured on both scans, and the CT-based CTR was calculated. Changes in the lung and cardiac measurements were expressed as the expiratory/inspiratory (E/I) ratios. Comparisons between inspiratory and expiratory measurements were made by the Wilcoxon signed-rank test. Correlations between the E/I ratios of lung and heart measurements were evaluated by Spearman's rank correlation analysis.
  
  
  RESULTS
  Cardiac CSA and transverse cardiac diameter was significantly larger on expiratory than on inspiratory CT (p < 0.0001). Significant negative correlations were found between the E/I ratios of these cardiac measurements and the E/I ratios of lung volume and vertical lung diameter (p < 0.01). CT-based CTR was significantly larger on expiration than on inspiration (p < 0.0001).
  
  
  CONCLUSIONS
  Heart size on chest CT depends on the phase of ventilation, and is correlated with changes in lung volume and craniocaudal lung diameter. The CTR is also significantly influenced by ventilation.
authors.affiliation: Department of Radiology, St. Marianna University School of Medicine, Kawasaki, Kanagawa, Japan.
authors.forename: Hayato
authors.initials: H
authors.lastname: Tomita
authors.affiliation: Department of Radiology, St. Marianna University School of Medicine, Kawasaki, Kanagawa, Japan; Department of Radiology, Graduate School of Medical Science, University of the Ryukyus, Nishihara, Okinawa, Japan.
authors.forename: Tsuneo
authors.initials: T
authors.lastname: Yamashiro
authors.affiliation: Department of Radiology, St. Marianna University School of Medicine, Kawasaki, Kanagawa, Japan.
authors.forename: Shin
authors.initials: S
authors.lastname: Matsuoka
authors.affiliation: Department of Radiology, St. Marianna University School of Medicine, Kawasaki, Kanagawa, Japan.
authors.forename: Shoichiro
authors.initials: S
authors.lastname: Matsushita
authors.affiliation: Department of Radiology, St. Marianna University School of Medicine, Kawasaki, Kanagawa, Japan.
authors.forename: Yasuyuki
authors.initials: Y
authors.lastname: Kurihara
authors.affiliation: Department of Radiology, St. Marianna University School of Medicine, Kawasaki, Kanagawa, Japan.
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Nakajima
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006321:Heart / Q000000981:diagnostic imaging / Q000502:physiology*; D006801:Humans; D008168:Lung / Q000000981:diagnostic imaging / Q000502:physiology*; D008171:Lung Diseases / Q000175:diagnosis / Q000000981:diagnostic imaging; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D013990:Tidal Volume / Q000502:physiology*; D014057:Tomography, X-Ray Computed; D055815:Young Adult