title: Effect of threshold on the correlation between airflow obstruction and low attenuation volume in smokers assessed by inspiratory and expiratory MDCT.
abstract: BACKGROUND
  The estimation of emphysematous changes is very sensitive to computed tomography (CT) threshold level. In clinical practice, the predetermined threshold is usually set at -950 Hounsfield units (HU) for the detection of low attenuation volume (LAV). However, threshold levels that are tightly connected to pulmonary function abnormalities have not been determined.
  
  
  OBJECTIVE
  To determine the threshold level for calculating an LAV that closely reflects airflow limitation in patients with chronic obstructive pulmonary disease (COPD).
  
  
  METHODS
  Seventy-six consecutive non-COPD smokers and COPD patients underwent paired inspiratory and expiratory multidetector CT (MDCT). LAV% was segmented every 10 HU between -1000 and -750 HU to examine the correlation between LAV% and indexes of obstructive impairment.
  
  
  RESULTS
  LAV% gradually increased as the threshold level increased on both inspiratory and expiratory images. LAV% on inspiratory images was higher than that on expiratory images at all threshold levels between -1000 and -750 HU. The threshold level that correlated with obstructive impairment differed between the two images: -930 HU on inspiratory and -870 or -880 HU on expiratory images.
  
  
  CONCLUSIONS
  LAV% dramatically changed according to the threshold level on both inspiratory and expiratory images, indicating that LAV% is dependent on the attenuation threshold level in patients with COPD. The threshold linking LAV% to airflow limitation was higher on expiratory than on inspiratory images.
authors.affiliation: Department of Respirology, Graduate School of Medicine, Chiba University, Chiba, Japan.
authors.forename: Noriyuki
authors.initials: N
authors.lastname: Yanagawa
authors.affiliation: Department of Respirology, Graduate School of Medicine, Chiba University, Chiba, Japan chumito_03@yahoo.co.jp.
authors.forename: Naoko
authors.initials: N
authors.lastname: Kawata
authors.affiliation: Department of Respirology, Graduate School of Medicine, Chiba University, Chiba, Japan.
authors.forename: Yukiko
authors.initials: Y
authors.lastname: Matsuura
authors.affiliation: Department of Respirology, Graduate School of Medicine, Chiba University, Chiba, Japan.
authors.forename: Toshihiko
authors.initials: T
authors.lastname: Sugiura
authors.affiliation: Department of Respirology, Graduate School of Medicine, Chiba University, Chiba, Japan.
authors.forename: Toshio
authors.initials: T
authors.lastname: Suzuki
authors.affiliation: Department of Respirology, Graduate School of Medicine, Chiba University, Chiba, Japan.
authors.forename: Hajime
authors.initials: H
authors.lastname: Kasai
authors.affiliation: Department of Respirology, Graduate School of Medicine, Chiba University, Chiba, Japan.
authors.forename: Ryosuke
authors.initials: R
authors.lastname: Irie
authors.affiliation: Department of Respirology, Graduate School of Medicine, Chiba University, Chiba, Japan.
authors.forename: Ken
authors.initials: K
authors.lastname: Iesato
authors.affiliation: Department of Respirology, Graduate School of Medicine, Chiba University, Chiba, Japan.
authors.forename: Yuji
authors.initials: Y
authors.lastname: Tada
authors.affiliation: Department of Respirology, Graduate School of Medicine, Chiba University, Chiba, Japan.
authors.forename: Nobuhiro
authors.initials: N
authors.lastname: Tanabe
authors.affiliation: Department of public Health, Graduate School of Medicine, Chiba University, Chiba, Japan.
authors.forename: Yoichi
authors.initials: Y
authors.lastname: Suzuki
authors.affiliation: Department of Respirology, Graduate School of Medicine, Chiba University, Chiba, Japan.
authors.forename: Koichiro
authors.initials: K
authors.lastname: Tatsumi
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000402:Airway Obstruction / Q000000981:diagnostic imaging* / Q000209:etiology / Q000503:physiopathology; D005260:Female; D006801:Humans; D008168:Lung / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D061330:Multidetector Computed Tomography / Q000379:methods*; D029424:Pulmonary Disease, Chronic Obstructive / Q000000981:diagnostic imaging* / Q000209:etiology / Q000503:physiopathology; D011656:Pulmonary Emphysema / Q000000981:diagnostic imaging / Q000209:etiology / Q000503:physiopathology; D012119:Respiration; D012907:Smoking / Q000009:adverse effects / Q000503:physiopathology*
keywords: Chronic obstructive pulmonary disease; low attenuation volume; multidetector computed tomography; threshold