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Normal Lung Quantification in Usual Interstitial Pneumonia Pattern: The Impact of Threshold-based Volumetric CT Analysis for the Staging of Idiopathic Pulmonary Fibrosis.

Ohkubo H, Kanemitsu Y, Uemura T, Takakuwa O, Takemura M, Maeno K, Ito Y, Oguri T, Kazawa N, Mikami R, Niimi A - PLoS ONE (2016)

Bottom Line: NL% showed a large area under the receiver operating characteristic curve for detecting patients in the moderate or advanced stages of IPF.Multivariable logistic regression analyses showed that NL% is significantly more useful than the percentages of predicted FVC and predicted diffusing capacity of the lungs for carbon monoxide (Japanese stage II/III/IV [odds ratio, 0.73; 95% confidence intervals (CI), 0.48 to 0.92; P < 0.01]; III/IV [odds ratio. 0.80; 95% CI 0.59 to 0.96; P < 0.01]; GAP stage II/III [odds ratio, 0.79; 95% CI, 0.56 to 0.97; P < 0.05]).The measurement of NL% by threshold-based volumetric CT analysis may help improve IPF staging.

View Article: PubMed Central - PubMed

Affiliation: Department of Respiratory Medicine, Allergy and Clinical Immunology, Nagoya City University Graduate School of Medical Sciences, Nagoya, Japan.

ABSTRACT

Background: Although several computer-aided computed tomography (CT) analysis methods have been reported to objectively assess the disease severity and progression of idiopathic pulmonary fibrosis (IPF), it is unclear which method is most practical. A universal severity classification system has not yet been adopted for IPF.

Objective: The purpose of this study was to test the correlation between quantitative-CT indices and lung physiology variables and to determine the ability of such indices to predict disease severity in IPF.

Methods: A total of 27 IPF patients showing radiological UIP pattern on high-resolution (HR) CT were retrospectively enrolled. Staging of IPF was performed according to two classification systems: the Japanese and GAP (gender, age, and physiology) staging systems. CT images were assessed using a commercially available CT imaging analysis workstation, and the whole-lung mean CT value (MCT), the normally attenuated lung volume as defined from -950 HU to -701 Hounsfield unit (NL), the volume of the whole lung (WL), and the percentage of NL to WL (NL%), were calculated.

Results: CT indices (MCT, WL, and NL) closely correlated with lung physiology variables. Among them, NL strongly correlated with forced vital capacity (FVC) (r = 0.92, P <0.0001). NL% showed a large area under the receiver operating characteristic curve for detecting patients in the moderate or advanced stages of IPF. Multivariable logistic regression analyses showed that NL% is significantly more useful than the percentages of predicted FVC and predicted diffusing capacity of the lungs for carbon monoxide (Japanese stage II/III/IV [odds ratio, 0.73; 95% confidence intervals (CI), 0.48 to 0.92; P < 0.01]; III/IV [odds ratio. 0.80; 95% CI 0.59 to 0.96; P < 0.01]; GAP stage II/III [odds ratio, 0.79; 95% CI, 0.56 to 0.97; P < 0.05]).

Conclusion: The measurement of NL% by threshold-based volumetric CT analysis may help improve IPF staging.

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Related in: MedlinePlus

Volumetric analysis of normally attenuated lung.Chest computed tomography (CT) image of a 79-year-old man with IPF showing UIP pattern. This CT slice shows peripheral honeycomb lung predominantly on the right side (A). The CT image showing extracted whole lungs (in green) (B). The volume of the whole lungs (WL) is 2,438 milliliter (mL). The CT image showing normally attenuated lung, as defined between −950 Hounsfield units (HU) and −701 HU (in yellow) (C). The volume of normally attenuated lung (NL) is 1,346 mL. Although some parts of honeycombing are marked as normally attenuated lung (in yellow) by the workstation, most areas of normally attenuated lung are considered to be identical to normal lung tissue. The yellow area under the histogram curve represents the NL (D). The percentage of NL (NL%) is 55.2%. Forced vital capacity and diffusing capacity of the lungs for carbon monoxide of this patient are 1.59 L (52.1%, %predicted) and 6.6 mL/min/mmHg (59.2%, %predicted), respectively. His partial pressure of arterial oxygen is 65.9 Torr, and the lowest percutaneous oxygen saturation is 84% during the 6-min walk test. The patient was classified in Japanese stage IV and GAP stage II.
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pone.0152505.g001: Volumetric analysis of normally attenuated lung.Chest computed tomography (CT) image of a 79-year-old man with IPF showing UIP pattern. This CT slice shows peripheral honeycomb lung predominantly on the right side (A). The CT image showing extracted whole lungs (in green) (B). The volume of the whole lungs (WL) is 2,438 milliliter (mL). The CT image showing normally attenuated lung, as defined between −950 Hounsfield units (HU) and −701 HU (in yellow) (C). The volume of normally attenuated lung (NL) is 1,346 mL. Although some parts of honeycombing are marked as normally attenuated lung (in yellow) by the workstation, most areas of normally attenuated lung are considered to be identical to normal lung tissue. The yellow area under the histogram curve represents the NL (D). The percentage of NL (NL%) is 55.2%. Forced vital capacity and diffusing capacity of the lungs for carbon monoxide of this patient are 1.59 L (52.1%, %predicted) and 6.6 mL/min/mmHg (59.2%, %predicted), respectively. His partial pressure of arterial oxygen is 65.9 Torr, and the lowest percutaneous oxygen saturation is 84% during the 6-min walk test. The patient was classified in Japanese stage IV and GAP stage II.

Mentions: All patients underwent HRCT using a single CT scan machine (SOMATOM Definition Flash; Siemens Healthcare, Tokyo, Japan). The settings of CT machine were as follows: detector-row configuration acquired as 128 x 0.6 mm by double sampling in the z-direction, 120 kVp, and quality mAs by CARE Dose4D. Mean and standard deviation (SD) of the effective mAs were 176.9 mAs and 44.2 mAs, respectively. The reconstruction algorithm for CT data comprised Sinogram-Affirmed Iterative Reconstruction (SAFIRE), and a sharp kernel of I70. CT images of 2-mm slice thickness for 2-mm intervals in the lung parenchyma [window level: −600 HU; window width: 1500 HU] were used for analysis. All patients underwent CT scan examinations in the supine position at full inspiration without intravenous contrast. Before CT, patients were instructed to maintain full inspiration without coughing during CT. Synapse VINCENT version 3.5 (Fujifilm Medical Systems, Tokyo, Japan) [13,14], a commercially available CT imaging analysis workstation, was used. Digital imaging and communications in medicine (DICOM) data for each patient were transferred to this workstation anonymously. Using this system, whole lung extraction from the chest CT imaging is automatically available by excluding the thoracic wall, mediastinum, large vessels, and airways toward tertiary bronchi (Fig 1A and 1B). This lung extraction was performed by using both threshold values and anatomical knowledge-based algorithms. After this, the observer (HO) checked the automatic lung extraction. The observer is a pulmonary physician with four years of experience checking automated segmentation. In cases that have very large cysts or strong architectural distortion, such as cystic bronchiectasis, whole lungs cannot be extracted correctly by this workstation. In these cases, the extraction of whole lungs can be made by adding manual operation. The mean CT value (MCT) was also available. In addition, threshold-based volumetric CT analysis was available, in which threshold CT values can be flexibly determined by all users. CT values for the whole lung were defined as between -1000 HU and 0 HU. The volume of the extracted whole lungs (WL), the volumes of normally attenuated lung (NL), as defined from −950 HU to −701 HU, and its percentage of the whole lung volume (NL%) were calculated (Fig 1C and 1D).


Normal Lung Quantification in Usual Interstitial Pneumonia Pattern: The Impact of Threshold-based Volumetric CT Analysis for the Staging of Idiopathic Pulmonary Fibrosis.

Ohkubo H, Kanemitsu Y, Uemura T, Takakuwa O, Takemura M, Maeno K, Ito Y, Oguri T, Kazawa N, Mikami R, Niimi A - PLoS ONE (2016)

Volumetric analysis of normally attenuated lung.Chest computed tomography (CT) image of a 79-year-old man with IPF showing UIP pattern. This CT slice shows peripheral honeycomb lung predominantly on the right side (A). The CT image showing extracted whole lungs (in green) (B). The volume of the whole lungs (WL) is 2,438 milliliter (mL). The CT image showing normally attenuated lung, as defined between −950 Hounsfield units (HU) and −701 HU (in yellow) (C). The volume of normally attenuated lung (NL) is 1,346 mL. Although some parts of honeycombing are marked as normally attenuated lung (in yellow) by the workstation, most areas of normally attenuated lung are considered to be identical to normal lung tissue. The yellow area under the histogram curve represents the NL (D). The percentage of NL (NL%) is 55.2%. Forced vital capacity and diffusing capacity of the lungs for carbon monoxide of this patient are 1.59 L (52.1%, %predicted) and 6.6 mL/min/mmHg (59.2%, %predicted), respectively. His partial pressure of arterial oxygen is 65.9 Torr, and the lowest percutaneous oxygen saturation is 84% during the 6-min walk test. The patient was classified in Japanese stage IV and GAP stage II.
© Copyright Policy
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4816297&req=5

pone.0152505.g001: Volumetric analysis of normally attenuated lung.Chest computed tomography (CT) image of a 79-year-old man with IPF showing UIP pattern. This CT slice shows peripheral honeycomb lung predominantly on the right side (A). The CT image showing extracted whole lungs (in green) (B). The volume of the whole lungs (WL) is 2,438 milliliter (mL). The CT image showing normally attenuated lung, as defined between −950 Hounsfield units (HU) and −701 HU (in yellow) (C). The volume of normally attenuated lung (NL) is 1,346 mL. Although some parts of honeycombing are marked as normally attenuated lung (in yellow) by the workstation, most areas of normally attenuated lung are considered to be identical to normal lung tissue. The yellow area under the histogram curve represents the NL (D). The percentage of NL (NL%) is 55.2%. Forced vital capacity and diffusing capacity of the lungs for carbon monoxide of this patient are 1.59 L (52.1%, %predicted) and 6.6 mL/min/mmHg (59.2%, %predicted), respectively. His partial pressure of arterial oxygen is 65.9 Torr, and the lowest percutaneous oxygen saturation is 84% during the 6-min walk test. The patient was classified in Japanese stage IV and GAP stage II.
Mentions: All patients underwent HRCT using a single CT scan machine (SOMATOM Definition Flash; Siemens Healthcare, Tokyo, Japan). The settings of CT machine were as follows: detector-row configuration acquired as 128 x 0.6 mm by double sampling in the z-direction, 120 kVp, and quality mAs by CARE Dose4D. Mean and standard deviation (SD) of the effective mAs were 176.9 mAs and 44.2 mAs, respectively. The reconstruction algorithm for CT data comprised Sinogram-Affirmed Iterative Reconstruction (SAFIRE), and a sharp kernel of I70. CT images of 2-mm slice thickness for 2-mm intervals in the lung parenchyma [window level: −600 HU; window width: 1500 HU] were used for analysis. All patients underwent CT scan examinations in the supine position at full inspiration without intravenous contrast. Before CT, patients were instructed to maintain full inspiration without coughing during CT. Synapse VINCENT version 3.5 (Fujifilm Medical Systems, Tokyo, Japan) [13,14], a commercially available CT imaging analysis workstation, was used. Digital imaging and communications in medicine (DICOM) data for each patient were transferred to this workstation anonymously. Using this system, whole lung extraction from the chest CT imaging is automatically available by excluding the thoracic wall, mediastinum, large vessels, and airways toward tertiary bronchi (Fig 1A and 1B). This lung extraction was performed by using both threshold values and anatomical knowledge-based algorithms. After this, the observer (HO) checked the automatic lung extraction. The observer is a pulmonary physician with four years of experience checking automated segmentation. In cases that have very large cysts or strong architectural distortion, such as cystic bronchiectasis, whole lungs cannot be extracted correctly by this workstation. In these cases, the extraction of whole lungs can be made by adding manual operation. The mean CT value (MCT) was also available. In addition, threshold-based volumetric CT analysis was available, in which threshold CT values can be flexibly determined by all users. CT values for the whole lung were defined as between -1000 HU and 0 HU. The volume of the extracted whole lungs (WL), the volumes of normally attenuated lung (NL), as defined from −950 HU to −701 HU, and its percentage of the whole lung volume (NL%) were calculated (Fig 1C and 1D).

Bottom Line: NL% showed a large area under the receiver operating characteristic curve for detecting patients in the moderate or advanced stages of IPF.Multivariable logistic regression analyses showed that NL% is significantly more useful than the percentages of predicted FVC and predicted diffusing capacity of the lungs for carbon monoxide (Japanese stage II/III/IV [odds ratio, 0.73; 95% confidence intervals (CI), 0.48 to 0.92; P < 0.01]; III/IV [odds ratio. 0.80; 95% CI 0.59 to 0.96; P < 0.01]; GAP stage II/III [odds ratio, 0.79; 95% CI, 0.56 to 0.97; P < 0.05]).The measurement of NL% by threshold-based volumetric CT analysis may help improve IPF staging.

View Article: PubMed Central - PubMed

Affiliation: Department of Respiratory Medicine, Allergy and Clinical Immunology, Nagoya City University Graduate School of Medical Sciences, Nagoya, Japan.

ABSTRACT

Background: Although several computer-aided computed tomography (CT) analysis methods have been reported to objectively assess the disease severity and progression of idiopathic pulmonary fibrosis (IPF), it is unclear which method is most practical. A universal severity classification system has not yet been adopted for IPF.

Objective: The purpose of this study was to test the correlation between quantitative-CT indices and lung physiology variables and to determine the ability of such indices to predict disease severity in IPF.

Methods: A total of 27 IPF patients showing radiological UIP pattern on high-resolution (HR) CT were retrospectively enrolled. Staging of IPF was performed according to two classification systems: the Japanese and GAP (gender, age, and physiology) staging systems. CT images were assessed using a commercially available CT imaging analysis workstation, and the whole-lung mean CT value (MCT), the normally attenuated lung volume as defined from -950 HU to -701 Hounsfield unit (NL), the volume of the whole lung (WL), and the percentage of NL to WL (NL%), were calculated.

Results: CT indices (MCT, WL, and NL) closely correlated with lung physiology variables. Among them, NL strongly correlated with forced vital capacity (FVC) (r = 0.92, P <0.0001). NL% showed a large area under the receiver operating characteristic curve for detecting patients in the moderate or advanced stages of IPF. Multivariable logistic regression analyses showed that NL% is significantly more useful than the percentages of predicted FVC and predicted diffusing capacity of the lungs for carbon monoxide (Japanese stage II/III/IV [odds ratio, 0.73; 95% confidence intervals (CI), 0.48 to 0.92; P < 0.01]; III/IV [odds ratio. 0.80; 95% CI 0.59 to 0.96; P < 0.01]; GAP stage II/III [odds ratio, 0.79; 95% CI, 0.56 to 0.97; P < 0.05]).

Conclusion: The measurement of NL% by threshold-based volumetric CT analysis may help improve IPF staging.

Show MeSH
Related in: MedlinePlus