Normal Lung Quantification in Usual Interstitial Pneumonia Pattern: The Impact of Threshold-based Volumetric CT Analysis for the Staging of Idiopathic Pulmonary Fibrosis |
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| Authors: | Hirotsugu Ohkubo Yoshihiro Kanemitsu Takehiro Uemura Osamu Takakuwa Masaya Takemura Ken Maeno Yutaka Ito Tetsuya Oguri Nobutaka Kazawa Ryuji Mikami Akio Niimi |
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| Institution: | 1Department of Respiratory Medicine, Allergy and Clinical Immunology, Nagoya City University Graduate School of Medical Sciences, Nagoya, Japan;2Department of Radiology, Nagoya City University Graduate School of Medical Sciences, Nagoya, Japan;3Department of Radiology, Tokyo Medical University, Tokyo, Japan;University of Allabama at Birmingham, UNITED STATES |
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| Abstract: | BackgroundAlthough 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.ObjectiveThe 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.MethodsA 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.ResultsCT 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]).ConclusionThe measurement of NL% by threshold-based volumetric CT analysis may help improve IPF staging. |
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