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Assessment of Airways with Three-dimensional Quantitative Thin-Section CT: In Vitro and in Vivo Validation¹

¹ From the Laboratory of Cellular Respiratory Physiology, Université Bordeaux 2, Bordeaux, France, and Institut National de la Santé et de la Recherche Médicale, E 356, F 33076, Bordeaux, France (M.M., P.B., R.M., J.M.T.d.L., F.L.); Department of Thoracic and Cardiovascular Imaging, CHU de Bordeaux, Hôpital du Haut-Lévêque, F 33604, Hôpital Cardiologique, avenue de Magellan, 33604 Pessac, France (M.M., F.L.); and Université Bordeaux 1, Talence, France (G.d.D., A.B.). Received January 6, 2006; revision requested March 7; revision received March 31; accepted May 3; final version accepted May 10. Supported by grants from Programme Hospitalier de Recherche Clinique received in 2002. Address correspondence to F.L. (e-mail: francois.laurent{at}chu-bordeaux.fr).

View larger version (107K): [in this window] [in a new window] [Download PPT slide]   Figure 1: A dedicated software tool that was used to analyze bronchi in three dimensions was applied to chest multi–detector row CT images. A, Volumetric data acquired with thoracic CT were used to reconstruct 1-mm-thick images (arrows indicate the direction of the propagation algorithm) from which, B, a propagation algorithm was used to obtain a binary volume based on bi-thresholding (frontal view). The area in which measurements were obtained is shown (arrowhead). The resulting image was automatically generated after the observer placed a seed point in the trachea. The airway skeleton was computed and superimposed on the binary volume. C, The resulting 3D image can be seen at various angles (oblique view). The accuracy of the central computation of the central axis can be checked to choose the most appropriate segment for orthogonal two-dimensional reformation. The area in which measurements were obtained is shown (arrowhead). D, A peripheral obliquely orientated bronchus (arrow) is shown on a native transverse thin-section CT scan. Reconstructions of cross-sectional 1-mm-thick CT scans of the selected bronchus perpendicular to the central axis were obtained. E, Three contiguous magnified thin-section CT scans are shown. F, The thin-section CT scan on which measurements were obtained was carefully selected by the observer. Scans that showed the least contiguity with surrounding vessels were chosen. G, A Laplacian of Gaussian algorithm was used to segment the designed airway and measure LA and WA.

View larger version (13K): [in this window] [in a new window] [Download PPT slide]   Figure 2a: (a) Graphs of data from correlation over time for x, y, and z spatial coordinates (left, middle, and right graphs, respectively) of each bronchial bifurcation. (b) Graphs of means of measurements over time for x, y, and z spatial coordinates (left, middle, and right graphs, respectively) are plotted against their difference according to Bland-Altman analysis. Solid lines correspond to the mean difference. Dashed lines correspond to the mean difference ± 2 standard deviations and the 95% confidence interval. Lack of agreement was greater for z coordinates. ICC = intraclass correlation coefficient, Obs1 = observer 1.

View larger version (19K): [in this window] [in a new window] [Download PPT slide]   Figure 2b: (a) Graphs of data from correlation over time for x, y, and z spatial coordinates (left, middle, and right graphs, respectively) of each bronchial bifurcation. (b) Graphs of means of measurements over time for x, y, and z spatial coordinates (left, middle, and right graphs, respectively) are plotted against their difference according to Bland-Altman analysis. Solid lines correspond to the mean difference. Dashed lines correspond to the mean difference ± 2 standard deviations and the 95% confidence interval. Lack of agreement was greater for z coordinates. ICC = intraclass correlation coefficient, Obs1 = observer 1.

View larger version (114K): [in this window] [in a new window] [Download PPT slide]   Figure 3: Images obtained during the in vivo examination. A, Native transverse thin-section CT scan shows the selected bronchus is B2a (arrow). B, Binary volume and skeleton of right S2 shows B2a (arrowhead) and the location in which reformatted thin-section CT scans were obtained. C, Multiplanar reformatted thin-section CT scan perpendicular to the main bronchial axis. Outlined area indicates the area shown in E. D, Corresponding CT scan reconstructed with dedicated software. Outlined area indicates the area shown in F. E, Magnified image of C shows internal and external contours of the bronchus as assessed by an observer using the manual method. (Original magnification, x3.) F, Magnified image of D with automatic detection of internal and external airway contours with dedicated software. (Original magnification, x3.)

View larger version (24K): [in this window] [in a new window] [Download PPT slide]   Figure 4a: Graphs of data collected during the in vivo examination. x = WA, = LA. (a) WA and LA measurements obtained with dedicated software were plotted against measurements obtained manually. The diagonal line corresponds to the line of equality. There was a strong correlation between data obtained with software and data obtained manually, as assessed with the intraclass correlation coefficient (ICC). r1 = Pearson correlation coefficient. (b) Means of measurements are plotted against their difference according to Bland-Altman analysis. The solid line corresponds to the mean difference. The dashed lines correspond to the 2 standard deviations. For each standard deviation, a 95% confidence interval that corresponds to the irregular lines can be calculated. (c) Means of measurements are plotted against their standard deviations. r2 = Pearson correlation coefficient.

View larger version (26K): [in this window] [in a new window] [Download PPT slide]   Figure 4b: Graphs of data collected during the in vivo examination. x = WA, = LA. (a) WA and LA measurements obtained with dedicated software were plotted against measurements obtained manually. The diagonal line corresponds to the line of equality. There was a strong correlation between data obtained with software and data obtained manually, as assessed with the intraclass correlation coefficient (ICC). r1 = Pearson correlation coefficient. (b) Means of measurements are plotted against their difference according to Bland-Altman analysis. The solid line corresponds to the mean difference. The dashed lines correspond to the 2 standard deviations. For each standard deviation, a 95% confidence interval that corresponds to the irregular lines can be calculated. (c) Means of measurements are plotted against their standard deviations. r2 = Pearson correlation coefficient.

View larger version (26K): [in this window] [in a new window] [Download PPT slide]   Figure 4c: Graphs of data collected during the in vivo examination. x = WA, = LA. (a) WA and LA measurements obtained with dedicated software were plotted against measurements obtained manually. The diagonal line corresponds to the line of equality. There was a strong correlation between data obtained with software and data obtained manually, as assessed with the intraclass correlation coefficient (ICC). r1 = Pearson correlation coefficient. (b) Means of measurements are plotted against their difference according to Bland-Altman analysis. The solid line corresponds to the mean difference. The dashed lines correspond to the 2 standard deviations. For each standard deviation, a 95% confidence interval that corresponds to the irregular lines can be calculated. (c) Means of measurements are plotted against their standard deviations. r2 = Pearson correlation coefficient.