title: A size-based emphysema severity index: robust to the breath-hold-level variations and correlated with clinical parameters.
abstract: OBJECTIVE
  To determine the power-law exponents (D) of emphysema hole-size distributions as a competent emphysema index. Robustness to extreme breath-hold-level variations and correlations with clinical parameters for chronic obstructive pulmonary disease (COPD) were investigated and compared to a conventional emphysema index (EI%).
  
  
  METHODS
  A total of 100 patients with COPD (97 males and three females of mean age 67±7.9 years) underwent multidetector row computed tomography scanning at full inspiration and full expiration. The diameters of the emphysematous holes were estimated and quantified with a fully automated algorithm. Power-law exponents (D) of emphysematous hole-size distribution were evaluated.
  
  
  RESULTS
  The diameters followed a power-law distribution in all cases, suggesting the scale-free nature of emphysema. D of inspiratory and expiratory computed tomography of patients showed intraclass correlation coefficients >0.8, indicating statistically absolute agreement of different breath-hold levels. By contrast, the EI% failed to agree. Bland-Altman analysis also revealed the superior robustness of D to EI%. D also significantly correlated with clinical parameters such as airflow limitation, diffusion capacity, exercise capacity, and quality of life.
  
  
  CONCLUSIONS
  The D of emphysematous hole-size distribution is robust to breath-hold-level variations and sensitive to the severity of emphysema. This measurement may help rule out the confounding effects of variations in breath-hold levels.
authors.affiliation: Asan Institute for Life Sciences.
authors.forename: Jeongeun
authors.initials: J
authors.lastname: Hwang
authors.affiliation: Department of Radiology.
authors.forename: Minho
authors.initials: M
authors.lastname: Lee
authors.affiliation: Department of Radiology.
authors.forename: Sang Min
authors.initials: SM
authors.lastname: Lee
authors.affiliation: Department of Radiology.
authors.forename: Sang Young
authors.initials: SY
authors.lastname: Oh
authors.affiliation: Department of Convergence Medicine; Department of Pulmonary and Critical Care Medicine, University of Ulsan College of Medicine, Asan Medical Center, Seoul, Republic of Korea.
authors.forename: Yeon-Mok
authors.initials: YM
authors.lastname: Oh
authors.affiliation: Department of Radiology; Department of Convergence Medicine.
authors.forename: Namkug
authors.initials: N
authors.lastname: Kim
authors.affiliation: Department of Radiology.
authors.forename: Joon Beom
authors.initials: JB
authors.lastname: Seo
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D062485:Breath Holding; D017079:Exercise Tolerance; D005260:Female; D005541:Forced Expiratory Volume; D006304:Health Status; D006801:Humans; D008168:Lung / Q000000981:diagnostic imaging* / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D061330:Multidetector Computed Tomography; D011237:Predictive Value of Tests; D029424:Pulmonary Disease, Chronic Obstructive / Q000000981:diagnostic imaging* / Q000503:physiopathology; D011656:Pulmonary Emphysema / Q000000981:diagnostic imaging* / Q000503:physiopathology; D011857:Radiographic Image Interpretation, Computer-Assisted; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012720:Severity of Illness Index; D000070857:Walk Test
keywords: breath-hold; chronic obstructive pulmonary disease; computed tomography; emphysema; power law; quantitative imaging