Variation of quantitative emphysema measurements from CT scans

Brad M. Keller, Anthony P. Reeves, Claudia I. Henschke, R. Graham Barr, David F. Yankelevitz

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review

6 Scopus citations


Emphysema is a lung disease characterized by destruction of the alveolar air sacs and is associated with long-term respiratory dysfunction. CT scans allow for imaging of the anatomical basis of emphysema, and several measures have been introduced for the quantification of the extent of disease. In this paper we compare these measures for repeatability over time. The measures of interest in this study are emphysema index, mean lung density, histogram percentile, and the fractal dimension. To allow for direct comparisons, the measures were normalized to a 0-100 scale. These measures have been computed for a set of 2,027 scan pairs in which the mean interval between scans was 1.15 years (σ: 93 days). These independent pairs were considered with respect to three different scanning conditions (a) 223 pairs where both were scanned with a 5 mm slice thickness protocol, (b) 695 with the first scanned with the 5 mm protocol and the second with a 1.25 mm protocol, and (c) 1109 pairs scanned both times using a 1.25 mm protocol. We found that average normalized emphysema index and histogram percentiles scores increased by 5.9 and 11 points respectively, while the fractal dimension showed stability with a mean difference of 1.2. We also found, a 7 point bias introduced for emphysema index under condition (b), and that the fractal dimension measure is least affected by scanner parameter changes.

Original languageEnglish
Title of host publicationMedical Imaging 2008 - Computer-Aided Diagnosis
StatePublished - 2008
Externally publishedYes
EventMedical Imaging 2008 - Computer-Aided Diagnosis - San Diego, CA, United States
Duration: 19 Feb 200821 Feb 2008

Publication series

NameProgress in Biomedical Optics and Imaging - Proceedings of SPIE
ISSN (Print)1605-7422


ConferenceMedical Imaging 2008 - Computer-Aided Diagnosis
Country/TerritoryUnited States
CitySan Diego, CA


  • COPD
  • CT
  • Computer aided diagnosis
  • Emphysema
  • Lung disease


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