title: Normal Lung Quantification in Usual Interstitial Pneumonia Pattern: The Impact of Threshold-based Volumetric CT Analysis for the Staging of Idiopathic Pulmonary Fibrosis.
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]).
  
  
  CONCLUSIONS
  The measurement of NL% by threshold-based volumetric CT analysis may help improve IPF staging.
authors.affiliation: Department of Respiratory Medicine, Allergy and Clinical Immunology, Nagoya City University Graduate School of Medical Sciences, Nagoya, Japan.
authors.forename: Hirotsugu
authors.initials: H
authors.lastname: Ohkubo
authors.affiliation: Department of Respiratory Medicine, Allergy and Clinical Immunology, Nagoya City University Graduate School of Medical Sciences, Nagoya, Japan.
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Kanemitsu
authors.affiliation: Department of Respiratory Medicine, Allergy and Clinical Immunology, Nagoya City University Graduate School of Medical Sciences, Nagoya, Japan.
authors.forename: Takehiro
authors.initials: T
authors.lastname: Uemura
authors.affiliation: Department of Respiratory Medicine, Allergy and Clinical Immunology, Nagoya City University Graduate School of Medical Sciences, Nagoya, Japan.
authors.forename: Osamu
authors.initials: O
authors.lastname: Takakuwa
authors.affiliation: Department of Respiratory Medicine, Allergy and Clinical Immunology, Nagoya City University Graduate School of Medical Sciences, Nagoya, Japan.
authors.forename: Masaya
authors.initials: M
authors.lastname: Takemura
authors.affiliation: Department of Respiratory Medicine, Allergy and Clinical Immunology, Nagoya City University Graduate School of Medical Sciences, Nagoya, Japan.
authors.forename: Ken
authors.initials: K
authors.lastname: Maeno
authors.affiliation: Department of Respiratory Medicine, Allergy and Clinical Immunology, Nagoya City University Graduate School of Medical Sciences, Nagoya, Japan.
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Ito
authors.affiliation: Department of Respiratory Medicine, Allergy and Clinical Immunology, Nagoya City University Graduate School of Medical Sciences, Nagoya, Japan.
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Oguri
authors.affiliation: Department of Radiology, Nagoya City University Graduate School of Medical Sciences, Nagoya, Japan.
authors.forename: Nobutaka
authors.initials: N
authors.lastname: Kazawa
authors.affiliation: Department of Radiology, Tokyo Medical University, Tokyo, Japan.
authors.forename: Ryuji
authors.initials: R
authors.lastname: Mikami
authors.affiliation: Department of Respiratory Medicine, Allergy and Clinical Immunology, Nagoya City University Graduate School of Medical Sciences, Nagoya, Japan.
authors.forename: Akio
authors.initials: A
authors.lastname: Niimi
mesh_terms: D000368:Aged; D019540:Area Under Curve; D054893:Cone-Beam Computed Tomography; D005260:Female; D006801:Humans; D054990:Idiopathic Pulmonary Fibrosis / Q000000981:diagnostic imaging / Q000473:pathology*; D007564:Japan; D016015:Logistic Models; D008168:Lung / Q000000981:diagnostic imaging / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D012372:ROC Curve; D012129:Respiratory Function Tests; D012189:Retrospective Studies; D012720:Severity of Illness Index