title: Three-dimensional volumetric assessment of abnormally low attenuation of the lung from routine helical CT: inspiratory and expiratory quantification.
abstract: OBJECTIVE
  The purpose of this investigation was to quantitatively assess abnormally low attenuation of the lung by use of three-dimensional volumetric reconstructions from routine helical CT and to assess their correlation with pulmonary function tests.
  
  
  METHODS
  Helical CT was performed in 100 patients in full inspiration. Examination was also performed in full expiration in 53 of these patients. Three-dimensional volumetric reconstructions were performed for total lung volumes at inspiration and at expiration, with a threshold of -896 H on inspiratory CT and -790 H on expiratory CT, to quantify emphysematous change. Correlation was made with pulmonary function tests in 79 patients.
  
  
  RESULTS
  CT volumetric assessments of abnormally low attenuation of the lung at inspiration and expiration had a high correlation (r2 = .84, p < or = .0001). In comparison with pulmonary function tests, both inspiratory low attenuation of the lung and expiratory low attenuation of the lung correlated well with the logarithm of the ratio of the forced expiratory volume in 1 sec (FEV1) to the forced vital capacity (r2 = .74, p < or = .0001 and r2 = .74, p < or = .0001, respectively) and with the percentage of predicted ratio of the FEV1 to the forced vital capacity (r2 = .69, p < or = .0001 and r2 = .69, p < or = .0001, respectively). Linear correlations were also seen with FEV1, residual volume, and forced residual capacity.
  
  
  CONCLUSIONS
  Three-dimensional volumetric reconstructions of hypoattenuating lung correlate well with pulmonary function tests. In addition, inspiratory and expiratory data are also correlative, suggesting that a dedicated expiratory examination is not needed. This easily obtainable information will prove useful for patients with obstructive lung disease from emphysema, providing a measure of pulmonary function status in this population.
authors.affiliation: Department of Radiology, University of Florida College of Medicine, Gainesville 32610, USA.
authors.forename: P J
authors.initials: PJ
authors.lastname: Mergo
authors.forename: W F
authors.initials: WF
authors.lastname: Williams
authors.forename: R
authors.initials: R
authors.lastname: Gonzalez-Rothi
authors.forename: R
authors.initials: R
authors.lastname: Gibson
authors.forename: P R
authors.initials: PR
authors.lastname: Ros
authors.forename: E V
authors.initials: EV
authors.lastname: Staab
authors.forename: T
authors.initials: T
authors.lastname: Helmberger
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D005541:Forced Expiratory Volume / Q000502:physiology; D005544:Forecasting; D005652:Functional Residual Capacity / Q000502:physiology; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D001239:Inhalation / Q000502:physiology*; D016014:Linear Models; D008168:Lung / Q000000981:diagnostic imaging* / Q000503:physiopathology; D008171:Lung Diseases / Q000000981:diagnostic imaging / Q000503:physiopathology; D008173:Lung Diseases, Obstructive / Q000000981:diagnostic imaging / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D011656:Pulmonary Emphysema / Q000000981:diagnostic imaging / Q000503:physiopathology; D012123:Pulmonary Ventilation / Q000502:physiology*; D012115:Residual Volume / Q000502:physiology; D012129:Respiratory Function Tests; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed / Q000379:methods*; D014109:Total Lung Capacity / Q000502:physiology; D014797:Vital Capacity / Q000502:physiology