Measuring lung volumes from chest films using equations derived from computed tomography.
Computed tomographic scans show true cross-sectional area of a segment of the chest. Measurement of the cross-sectional area of the lung at several adjacent levels permits calculation of a geometrically defined volume. CT scans from 26 cases were used to derive equations to predict regional volume from measurements which can be obtained from plain PA and lateral chest films. Separate equations were derived for slices above and below the top of the diaphragm. The best correlation between linear dimensions and true volume was obtained with equations that used lung width and antero-posterior (AP) diameter of each scan, maximum AP lung diameter, and relative scan level (apex to base). These equations predicted the volumes of individual slices above the diaphragm with a correlation coefficient (r) of 0.99 on the right, 0.97 on the left. Below top of the diaphragm, r was 0.91 on the right, 0.92 on the left. Total lung volume was predicted with an r of 0.98 (s.e. 4.8%) on the right and 0.97 (s.e. 5.3%) on the left. Using total chest width instead of AP diameter of each slice reduced r to 0.96 for the volume of either lung. This method compares favorably with previous regression or geometric approximation methods for total lung volume and also makes it possible to obtain estimates of portions of lung volume from chest films.
D006801:Humans; D008168:Lung / Q000000981:diagnostic imaging*; D008176:Lung Volume Measurements / Q000379:methods*; D014057:Tomography, X-Ray Computed