title: Clinical impact of high-attenuation and cystic areas on computed tomography in fibrotic idiopathic interstitial pneumonias.
abstract: BACKGROUND
  Quantitative computed tomography (CT) analysis has been proposed as a means of objectively assessing fibrotic interstitial pneumonia (IP) including idiopathic pulmonary fibrosis (IPF). We investigated whether percentages of high-attenuation areas (HAA%) and cystic areas (CA%) quantified from CT images were useful as indices of fibrotic IP.
  
  
  METHODS
  CT images of 74 patients with fibrotic idiopathic interstitial pneumonias (IPF, 36; non-specific interstitial pneumonia, 9; unclassifiable idiopathic interstitial pneumonia, 29) were analyzed via in-house computer software, which automatically calculated HAA%, CA%, mean lung density (MLD), standard deviation of lung density (SD-LD), kurtosis, and skewness from CT attenuation histograms. These indices were compared in each instance with physiologic measures, visual fibrosis score, clinical diagnosis, radiologic CT pattern, and prognosis.
  
  
  RESULTS
  HAA% correlated significantly with physiologic measures and visual fibrosis score to a moderate extent (%forced vital capacity, rs = -0.59; % carbon monoxide diffusion capacity, rs = -0.43; fibrosis score, rs = 0.23). Densitometric parameters (MLD, SD-LD, kurtosis, and skewness) correlated significantly with physiologic measures and fibrosis score (|rs| = 0.28-0.59). CA% showed no association with pulmonary functions but differed significantly between IPF and other interstitial pneumonias (IPs) (1.50 ± 2.41% vs. 0.41 ± 0.80%; P < 0.01) and between the definite usual interstitial pneumonia (UIP) pattern and other patterns (1.48 ± 2.38% vs. 0.55 ± 1.19%; P < 0.01). On univariate analysis, HAA%, MLD, SD-LD, kurtosis, skewness, fibrosis score, and definite UIP pattern all correlated with survival, with kurtosis alone identified as a significant predictor of mortality on multivariate analysis (hazard ratio = 0.67; 95% CI, 0.44-0.96; P = 0.03).
  
  
  CONCLUSIONS
  CA% and HAA% are novel quantitative CT indices with differing properties in fibrotic IP evaluations. HAA% largely reflects physiologic impairments, whereas CA% corresponds with diagnosis and HRCT pattern. Of the CT indices examined, kurtosis constituted the strongest predictor of mortality.
authors.affiliation: Department of Respiratory Care and Sleep Medicine, Graduate School of Medicine, Kyoto University, Kyoto, Japan. tanizawa@kuhp.kyoto-u.ac.jp.
authors.forename: Kiminobu
authors.initials: K
authors.lastname: Tanizawa
authors.affiliation: Department of Respiratory Medicine, Graduate School of Medicine, Kyoto University, 54 Shogoin Kawaharacho, Sakyo-ku, Kyoto, 606-8507, Japan. hanta@kuhp.kyoto-u.ac.jp.
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Handa
authors.affiliation: Kyoto Central Clinic, Clinical Research Center, Kyoto, Japan. nagai@chuo-c.jp.
authors.forename: Sonoko
authors.initials: S
authors.lastname: Nagai
authors.affiliation: Department of Respiratory Medicine, Graduate School of Medicine, Kyoto University, 54 Shogoin Kawaharacho, Sakyo-ku, Kyoto, 606-8507, Japan. t_hirai@kuhp.kyoto-u.ac.jp.|Kyoto Central Clinic, Clinical Research Center, Kyoto, Japan. t_hirai@kuhp.kyoto-u.ac.jp.
authors.forename: Toyohiro
authors.initials: T
authors.lastname: Hirai
authors.affiliation: Department of Diagnostic Imaging and Nuclear Medicine, Graduate School of Medicine, Kyoto University, Kyoto, Japan. tkubo@kuhp.kyoto-u.ac.jp.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Kubo
authors.affiliation: Department of Respiratory Medicine, Graduate School of Medicine, Kyoto University, 54 Shogoin Kawaharacho, Sakyo-ku, Kyoto, 606-8507, Japan. toguma@kuhp.kyoto-u.ac.jp.
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Oguma
authors.affiliation: Department of Respiratory Medicine, Graduate School of Medicine, Kyoto University, 54 Shogoin Kawaharacho, Sakyo-ku, Kyoto, 606-8507, Japan. isaoito@kuhp.kyoto-u.ac.jp.
authors.forename: Isao
authors.initials: I
authors.lastname: Ito
authors.affiliation: Department of Respiratory Medicine, Allergy and Clinical Immunology, School of Medical Sciences, Nagoya City University, Nagoya, Japan. yutaka@kuhp.kyoto-u.ac.jp.
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Ito
authors.affiliation: Department of Respiratory Medicine, Fukui Red-Cross Hospital, Fukui, Japan. watanabe@kuhp.kyoto-u.ac.jp.
authors.forename: Kizuku
authors.initials: K
authors.lastname: Watanabe
authors.affiliation: Department of Respiratory Medicine, Saiseikai-Noe Hospital, Osaka, Japan. aiharak@kuhp.kyoto-u.ac.jp.
authors.forename: Kensaku
authors.initials: K
authors.lastname: Aihara
authors.affiliation: Department of Respiratory Medicine, Graduate School of Medicine, Kyoto University, 54 Shogoin Kawaharacho, Sakyo-ku, Kyoto, 606-8507, Japan. koikezoe@kuhp.kyoto-u.ac.jp.
authors.forename: Kohei
authors.initials: K
authors.lastname: Ikezoe
authors.affiliation: Department of Respiratory Care and Sleep Medicine, Graduate School of Medicine, Kyoto University, Kyoto, Japan. ogato@kuhp.kyoto-u.ac.jp.
authors.forename: Toru
authors.initials: T
authors.lastname: Oga
authors.affiliation: Department of Respiratory Care and Sleep Medicine, Graduate School of Medicine, Kyoto University, Kyoto, Japan. chink@kuhp.kyoto-u.ac.jp.
authors.forename: Kazuo
authors.initials: K
authors.lastname: Chin
authors.affiliation: Kyoto Central Clinic, Clinical Research Center, Kyoto, Japan. izumi@chuo-c.jp.
authors.forename: Takateru
authors.initials: T
authors.lastname: Izumi
authors.affiliation: Department of Respiratory Care and Sleep Medicine, Graduate School of Medicine, Kyoto University, Kyoto, Japan. mishima@kuhp.kyoto-u.ac.jp.
authors.forename: Michiaki
authors.initials: M
authors.lastname: Mishima
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D054988:Idiopathic Interstitial Pneumonias / Q000401:mortality*; D054990:Idiopathic Pulmonary Fibrosis / Q000000981:diagnostic imaging*; D008168:Lung / Q000000981:diagnostic imaging* / Q000473:pathology; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D011379:Prognosis; D016016:Proportional Hazards Models; D012129:Respiratory Function Tests; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed