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Obstructive Lung Diseases: Texture Classification for Differentiation at CT¹

¹ From the Department of Visual Information Processing (F.C., G.Z.Y.) and Division of Investigative Sciences (D.M.H.), Imperial College of Science, Technology and Medicine, Royal Brompton Hospital, Sydney St, London SW3 6NP, England. Received April 30, 2002; revision requested July 10; final revision received December 19; accepted January 13, 2003. F.C. supported by Imatron, San Francisco, Calif. Address correspondence to D.M.H. (e-mail: d.hansell@rbh.nthames.nhs.uk).

View larger version (76K): [in a new window]   Figure 1a. Transverse thin-section CT scans of the chest (window level, -500 HU; width, 1,000 HU). On each image, the circle highlights a region of interest (ROI) that is typical of a particular condition. An enlarged view of the ROI is shown on the left side of each image. (a) Panlobular emphysema: Destruction of the lung parenchyma results in areas of homogeneously decreased attenuation. (b) Severe centrilobular emphysema: The CT appearance of the disease superficially resembles that of air cysts. (c) Mild centrilobular emphysema: The features of centrilobular emphysema are visible but less obvious. (d) Constrictive obliterative bronchiolitis results in homogeneously decreased lung attenuation. (e) Normal lung tissue: The mean CT attenuation value of the lung parenchyma is higher than that in cases of obstructive lung disease.

View larger version (76K): [in a new window]   Figure 1b. Transverse thin-section CT scans of the chest (window level, -500 HU; width, 1,000 HU). On each image, the circle highlights a region of interest (ROI) that is typical of a particular condition. An enlarged view of the ROI is shown on the left side of each image. (a) Panlobular emphysema: Destruction of the lung parenchyma results in areas of homogeneously decreased attenuation. (b) Severe centrilobular emphysema: The CT appearance of the disease superficially resembles that of air cysts. (c) Mild centrilobular emphysema: The features of centrilobular emphysema are visible but less obvious. (d) Constrictive obliterative bronchiolitis results in homogeneously decreased lung attenuation. (e) Normal lung tissue: The mean CT attenuation value of the lung parenchyma is higher than that in cases of obstructive lung disease.

View larger version (73K): [in a new window]   Figure 1c. Transverse thin-section CT scans of the chest (window level, -500 HU; width, 1,000 HU). On each image, the circle highlights a region of interest (ROI) that is typical of a particular condition. An enlarged view of the ROI is shown on the left side of each image. (a) Panlobular emphysema: Destruction of the lung parenchyma results in areas of homogeneously decreased attenuation. (b) Severe centrilobular emphysema: The CT appearance of the disease superficially resembles that of air cysts. (c) Mild centrilobular emphysema: The features of centrilobular emphysema are visible but less obvious. (d) Constrictive obliterative bronchiolitis results in homogeneously decreased lung attenuation. (e) Normal lung tissue: The mean CT attenuation value of the lung parenchyma is higher than that in cases of obstructive lung disease.

View larger version (71K): [in a new window]   Figure 1d. Transverse thin-section CT scans of the chest (window level, -500 HU; width, 1,000 HU). On each image, the circle highlights a region of interest (ROI) that is typical of a particular condition. An enlarged view of the ROI is shown on the left side of each image. (a) Panlobular emphysema: Destruction of the lung parenchyma results in areas of homogeneously decreased attenuation. (b) Severe centrilobular emphysema: The CT appearance of the disease superficially resembles that of air cysts. (c) Mild centrilobular emphysema: The features of centrilobular emphysema are visible but less obvious. (d) Constrictive obliterative bronchiolitis results in homogeneously decreased lung attenuation. (e) Normal lung tissue: The mean CT attenuation value of the lung parenchyma is higher than that in cases of obstructive lung disease.

View larger version (72K): [in a new window]   Figure 1e. Transverse thin-section CT scans of the chest (window level, -500 HU; width, 1,000 HU). On each image, the circle highlights a region of interest (ROI) that is typical of a particular condition. An enlarged view of the ROI is shown on the left side of each image. (a) Panlobular emphysema: Destruction of the lung parenchyma results in areas of homogeneously decreased attenuation. (b) Severe centrilobular emphysema: The CT appearance of the disease superficially resembles that of air cysts. (c) Mild centrilobular emphysema: The features of centrilobular emphysema are visible but less obvious. (d) Constrictive obliterative bronchiolitis results in homogeneously decreased lung attenuation. (e) Normal lung tissue: The mean CT attenuation value of the lung parenchyma is higher than that in cases of obstructive lung disease.

View larger version (19K): [in a new window]   Figure 2. Line graph shows relationship between the threshold pthreshold on a posteriori probabilities and the overall sensitivity and specificity of the classifier. As pthreshold increases, and only samples with increasing confidence are classified, the overall sensitivity and specificity of the technique improve. However, a larger proportion of samples are then rejected and remain unclassified. A trade-off can be obtained with a value of pthreshold such that half the samples are reclassified confidently, for instance. Corresponding overall sensitivity and overall specificity are 73.6% and 91.2%.

View larger version (63K): [in a new window]   Figure 3a. Application of the classifier to segmentation of lung parenchyma. At pixels where the confidence of the classifier is low (smaller than the p1 threshold), no label is assigned. (a) Left: Transverse CT scan obtained in a healthy subject (window level, -800 HU; width, 1,000 HU). Right: Transverse CT scan obtained with automated classification. Samples classified confidently are labeled as normal. (b) Left: Transverse CT scan obtained in a patient with signs of centrilobular emphysema. Right: In transverse CT scan, most of the classified samples are labeled as centrilobular emphysema. Some areas of lung with homogeneously decreased attenuation are classified as constrictive obliterative bronchiolitis. (c) Left: Transverse CT scan in a patient with constrictive obliterative bronchiolitis. Right: In transverse CT scan, most of the parenchyma is labeled as constrictive obliterative bronchiolitis. Some areas are classified as normal. Areas of lung with increased attenuation adjacent to areas of decreased attenuation make the classifier identify the texture of centrilobular emphysema in the vicinity of the major bronchi. (d) Left: Transverse CT scan obtained in a patient with panlobular emphysema. Right: In transverse CT scan, most of the parenchyma is labeled as panlobular emphysema, with some areas classified as constrictive obliterative bronchiolitis.

View larger version (71K): [in a new window]   Figure 3b. Application of the classifier to segmentation of lung parenchyma. At pixels where the confidence of the classifier is low (smaller than the p1 threshold), no label is assigned. (a) Left: Transverse CT scan obtained in a healthy subject (window level, -800 HU; width, 1,000 HU). Right: Transverse CT scan obtained with automated classification. Samples classified confidently are labeled as normal. (b) Left: Transverse CT scan obtained in a patient with signs of centrilobular emphysema. Right: In transverse CT scan, most of the classified samples are labeled as centrilobular emphysema. Some areas of lung with homogeneously decreased attenuation are classified as constrictive obliterative bronchiolitis. (c) Left: Transverse CT scan in a patient with constrictive obliterative bronchiolitis. Right: In transverse CT scan, most of the parenchyma is labeled as constrictive obliterative bronchiolitis. Some areas are classified as normal. Areas of lung with increased attenuation adjacent to areas of decreased attenuation make the classifier identify the texture of centrilobular emphysema in the vicinity of the major bronchi. (d) Left: Transverse CT scan obtained in a patient with panlobular emphysema. Right: In transverse CT scan, most of the parenchyma is labeled as panlobular emphysema, with some areas classified as constrictive obliterative bronchiolitis.

View larger version (57K): [in a new window]   Figure 3c. Application of the classifier to segmentation of lung parenchyma. At pixels where the confidence of the classifier is low (smaller than the p1 threshold), no label is assigned. (a) Left: Transverse CT scan obtained in a healthy subject (window level, -800 HU; width, 1,000 HU). Right: Transverse CT scan obtained with automated classification. Samples classified confidently are labeled as normal. (b) Left: Transverse CT scan obtained in a patient with signs of centrilobular emphysema. Right: In transverse CT scan, most of the classified samples are labeled as centrilobular emphysema. Some areas of lung with homogeneously decreased attenuation are classified as constrictive obliterative bronchiolitis. (c) Left: Transverse CT scan in a patient with constrictive obliterative bronchiolitis. Right: In transverse CT scan, most of the parenchyma is labeled as constrictive obliterative bronchiolitis. Some areas are classified as normal. Areas of lung with increased attenuation adjacent to areas of decreased attenuation make the classifier identify the texture of centrilobular emphysema in the vicinity of the major bronchi. (d) Left: Transverse CT scan obtained in a patient with panlobular emphysema. Right: In transverse CT scan, most of the parenchyma is labeled as panlobular emphysema, with some areas classified as constrictive obliterative bronchiolitis.

View larger version (54K): [in a new window]   Figure 3d. Application of the classifier to segmentation of lung parenchyma. At pixels where the confidence of the classifier is low (smaller than the p1 threshold), no label is assigned. (a) Left: Transverse CT scan obtained in a healthy subject (window level, -800 HU; width, 1,000 HU). Right: Transverse CT scan obtained with automated classification. Samples classified confidently are labeled as normal. (b) Left: Transverse CT scan obtained in a patient with signs of centrilobular emphysema. Right: In transverse CT scan, most of the classified samples are labeled as centrilobular emphysema. Some areas of lung with homogeneously decreased attenuation are classified as constrictive obliterative bronchiolitis. (c) Left: Transverse CT scan in a patient with constrictive obliterative bronchiolitis. Right: In transverse CT scan, most of the parenchyma is labeled as constrictive obliterative bronchiolitis. Some areas are classified as normal. Areas of lung with increased attenuation adjacent to areas of decreased attenuation make the classifier identify the texture of centrilobular emphysema in the vicinity of the major bronchi. (d) Left: Transverse CT scan obtained in a patient with panlobular emphysema. Right: In transverse CT scan, most of the parenchyma is labeled as panlobular emphysema, with some areas classified as constrictive obliterative bronchiolitis.