title: DERIVATION OF A TEST STATISTIC FOR EMPHYSEMA QUANTIFICATION.
abstract: Density masking is the de-facto quantitative imaging phenotype for emphysema that is widely used by the clinical community. Density masking defines the burden of emphysema by a fixed threshold, usually between -910 HU and -950 HU, that has been experimentally validated with histology. In this work, we formalized emphysema quantification by means of statistical inference. We show that a non-central Gamma is a good approximation for the local distribution of image intensities for normal and emphysema tissue. We then propose a test statistic in terms of the sample mean of a truncated non-central Gamma random variable. Our results show that this approach is well-suited for the detection of emphysema and superior to standard density masking. The statistical method was tested in a dataset of 1337 samples obtained from 9 different scanner models in subjects with COPD. Results showed an increase of 17% when compared to the density masking approach, and an overall accuracy of 94.09%.
authors.affiliation: Applied Chest Imaging Lab., Brigham and Women's Hospital, Harvard Medical School, Boston, USA; Biomedical Image Technologies, Universidad Politécnica de Madrid & CIBER-BBN, Madrid, Spain.
authors.forename: Gonzalo
authors.initials: G
authors.lastname: Vegas-Sanchez-Ferrero
authors.affiliation: Applied Chest Imaging Lab., Brigham and Women's Hospital, Harvard Medical School, Boston, USA.
authors.forename: George
authors.initials: G
authors.lastname: Washko
authors.affiliation: Applied Chest Imaging Lab., Brigham and Women's Hospital, Harvard Medical School, Boston, USA.
authors.forename: Farbod N
authors.initials: FN
authors.lastname: Rahaghi
authors.affiliation: Biomedical Image Technologies, Universidad Politécnica de Madrid & CIBER-BBN, Madrid, Spain.
authors.forename: Maria J
authors.initials: MJ
authors.lastname: Ledesma-Carbayo
authors.affiliation: Applied Chest Imaging Lab., Brigham and Women's Hospital, Harvard Medical School, Boston, USA.
authors.forename: R San José
authors.initials: RS
authors.lastname: Estépar
keywords: Emphysema quantification; non-central Gamma; statistical test; truncated random variable