title: Application of the homology method for quantification of low-attenuation lung region inpatients with and without COPD.
abstract: BACKGROUND
  Homology is a mathematical concept that can be used to quantify degree of contact. Recently, image processing with the homology method has been proposed. In this study, we used the homology method and computed tomography images to quantify emphysema.
  
  
  METHODS
  This study included 112 patients who had undergone computed tomography and pulmonary function test. Low-attenuation lung regions were evaluated by the homology method, and homology-based emphysema quantification (b0,b1,nb0,nb1, andR) was performed. For comparison, the percentage of low-attenuation lung area (LAA%) was also obtained. Relationships between emphysema quantification and pulmonary function test results were evaluated by Pearson's correlation coefficients. In addition to the correlation, the patients were divided into the following three groups based on guidelines of the Global initiative for chronic Obstructive Lung Disease: Group A, nonsmokers; Group B, smokers without COPD, mild COPD, and moderate COPD; Group C, severe COPD and very severe COPD. The homology-based emphysema quantification and LAA% were compared among these groups.
  
  
  RESULTS
  For forced expiratory volume in 1 second/forced vital capacity, the correlation coefficients were as follows: LAA%, -0.603;b0, -0.460;b1, -0.500;nb0, -0.449;nb1, -0.524; andR, -0.574. For forced expiratory volume in 1 second, the coefficients were as follows: LAA%, -0.461;b0, -0.173;b1, -0.314;nb0, -0.191;nb1, -0.329; andR, -0.409. Between Groups A and B, difference innb0was significant (P-value = 0.00858), and those in the other types of quantification were not significant.
  
  
  CONCLUSIONS
  Feasibility of the homology-based emphysema quantification was validated. The homology-based emphysema quantification was useful for the assessment of emphysema severity.
authors.affiliation: Clinical PET Center, Institute of Biomedical Research and Innovation, Hyogo, Japan.
authors.forename: Mizuho
authors.initials: M
authors.lastname: Nishio
authors.affiliation: Department of Molecular Pathology, Osaka University Graduate School of Medicine and Health Science, Osaka, Japan.
authors.forename: Kazuaki
authors.initials: K
authors.lastname: Nakane
authors.affiliation: Department of Radiology, Chibune General Hospital, Osaka, Japan.
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Tanaka
keywords: COPD; emphysema; homology; low-attenuation lung region