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Application of an Optical Flow Method to Inspiratory and Expiratory Lung MDCT to Assess Regional Air Trapping: A Feasibility Study

Drew A. Torigian1, Warren B. Gefter, John D. Affuso, Kiarash Emami and Lawrence Dougherty

1 All authors: Department of Radiology, University of Pennsylvania School of Medicine and Hospital of the University of Pennsylvania, 3400 Spruce St., Philadelphia, PA 19104-4283.


Figure 1
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  		Fig. 1A —74-year-old woman with multifocal air trapping. End-expiratory axial CT image through upper chest shows multiple hyperlucent regions of air trapping.

 

Figure 2
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  		Fig. 1B —74-year-old woman with multifocal air trapping. End-inspiratory axial CT reference image through upper chest. Note subtle mosaic attenuation of lung.

 

Figure 3
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  		Fig. 1C —74-year-old woman with multifocal air trapping. Resultant end-expiratory axial CT image aligned to end-inspiratory axial CT reference image using optical flow method.

 

Figure 4
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  		Fig. 1D —74-year-old woman with multifocal air trapping. Quantitative attenuation difference color maps for images obtained in axial (D), coronal (E), and sagittal (F) planes reveal multifocal regions of air trapping throughout right lung as dark blue to black regions. Color scale ranges from 0 H (dark blue to black) to 366 H (bright orange to yellow). Note white areas in periphery of axial and coronal images with corresponding values of more than 366 H are predominantly due to incomplete segmentation of chest wall.

 

Figure 5
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  		Fig. 1E —74-year-old woman with multifocal air trapping. Quantitative attenuation difference color maps for images obtained in axial (D), coronal (E), and sagittal (F) planes reveal multifocal regions of air trapping throughout right lung as dark blue to black regions. Color scale ranges from 0 H (dark blue to black) to 366 H (bright orange to yellow). Note white areas in periphery of axial and coronal images with corresponding values of more than 366 H are predominantly due to incomplete segmentation of chest wall.

 

Figure 6
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  		Fig. 1F —74-year-old woman with multifocal air trapping. Quantitative attenuation difference color maps for images obtained in axial (D), coronal (E), and sagittal (F) planes reveal multifocal regions of air trapping throughout right lung as dark blue to black regions. Color scale ranges from 0 H (dark blue to black) to 366 H (bright orange to yellow). Note white areas in periphery of axial and coronal images with corresponding values of more than 366 H are predominantly due to incomplete segmentation of chest wall.

 

Figure 7
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  		Fig. 1G —74-year-old woman with multifocal air trapping. Attenuation difference histogram of entire right lung shows peak pixel frequency of 5.0%, mean attenuation difference of 151.4 H, and SD of 141.0 H. Color scale ranges from 0 H (dark blue to black) to 366 H (bright orange to yellow), with black for all values less than 0 H and white for all values greater than 366 H, both of which are thought to be due to misregistration, incomplete segmentation, or both.

 

Figure 8
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  		Fig. 1H —74-year-old woman with multifocal air trapping. Gaussian curve fit (red) of attenuation difference histogram (blue) of entire right lung has peak pixel frequency of 4.4%, mean attenuation difference of 117.5 H, SD of 83.0 H, and full width at half maximum of 195.5 H. Area under the curve percentages for pixel values less than 0, 50, 100, and 200 H arbitrary threshold attenuation difference values were 6.0%, 16.1%, 36.7%, and 73.9%, respectively.

 

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