How is emphysema visualized on a CT scan?

Updated: Mar 13, 2019
  • Author: Ali Nawaz Khan, MBBS, FRCS, FRCP, FRCR; Chief Editor: Eugene C Lin, MD  more...
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Müller et al [31] and Kinsella et al [32] used a CT attenuation mask to highlight voxels in a given attenuation range to quantitate emphysema and define areas of abnormally low attenuation. They compared different masks, mean lung attenuations, and visual appearances and pathologic grades of emphysema in 28 patients undergoing lung resection for tumor. In each patient, a single representative CT image was compared with corresponding pathologic specimens. They found good correlation between the extent of emphysema as assessed by using the attenuation mask and the pathologic grade. Such methods not only eliminate interobserver and intraobserver variability but also enable reproducible assessment of the percentage of lung that is affected. Although quantitative CT measurements have problems, they may improve our understanding of lung function. [33]

Kuwano et al [34] visually quantified emphysema on 1- and 5-mm HRCT scans by using resected specimens. They found an excellent correlation; however, as expected, the 5-mm sections tended to cause underestimation of the degree of emphysema. They concluded that HRCT scans could depict mild emphysema in patients without clinical evidence of airflow limitation and that they could be used to exclude emphysema in patients with moderate or severe airflow limitation.

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