Quantitative <scp>CT</scp> measurements of small pulmonary vessels in chronic obstructive pulmonary disease: do they change on follow‐up scans?

<jats:title>Summary</jats:title><jats:p>The aims of this study were to perform a longitudinal evaluation of the cross‐sectional area (<jats:styled-content style="fixed-case">CSA</jats:styled-content>) of small pulmonary vessels and the extent of emphysema measured on computed tomography (<jats:styled-content style="fixed-case">CT</jats:styled-content>) scans of patients with chronic obstructive pulmonary disease (<jats:styled-content style="fixed-case">COPD</jats:styled-content>), and to correlate the pulmonary vascular measurements with extent of emphysema. The institutional review board approved this retrospective study and waived the need for patients' informed consent. Seventy‐four patients with <jats:styled-content style="fixed-case">COPD</jats:styled-content> who underwent both initial and follow‐up <jats:styled-content style="fixed-case">CT</jats:styled-content> scans at an interval of ≥12 months were analysed. The <jats:styled-content style="fixed-case">CSA</jats:styled-content> of small pulmonary vessels <5 mm<jats:sup>2</jats:sup> was measured, and the percentage of total <jats:styled-content style="fixed-case">CSA</jats:styled-content> of the area of the lung (%<jats:styled-content style="fixed-case">CSA</jats:styled-content><jats:sub><5</jats:sub>) was calculated. The extent of emphysema was assessed as the percentage of low attenuation area (%<jats:styled-content style="fixed-case">LAA</jats:styled-content>, <−950 Hounsfield units). Comparisons between initial and follow‐up measurements were performed using the Wilcoxon signed‐rank test. The relationship between longitudinal changes in %<jats:styled-content style="fixed-case">CSA</jats:styled-content><jats:sub><5</jats:sub> and %<jats:styled-content style="fixed-case">LAA</jats:styled-content> during the follow‐up period was assessed using the Spearman rank correlation. The %<jats:styled-content style="fixed-case">LAA</jats:styled-content> increased significantly on follow‐up <jats:styled-content style="fixed-case">CT</jats:styled-content> scans (<jats:italic>P</jats:italic><0·0001). The %<jats:styled-content style="fixed-case">CSA</jats:styled-content><jats:sub><5</jats:sub> was slightly decreased on follow‐up scans, but the difference was not significant. Although longitudinal change in %<jats:styled-content style="fixed-case">LAA</jats:styled-content> was positively correlated with duration of follow‐up period (ρ = 0·505, <jats:italic>P</jats:italic><0·0001), longitudinal change in %<jats:styled-content style="fixed-case">CSA</jats:styled-content><jats:sub><5</jats:sub> was not. In conclusion, there was a progressive increase in the extent of emphysema over time, but no significant decrease in the <jats:styled-content style="fixed-case">CSA</jats:styled-content> of small pulmonary vessels over the same time period.</jats:p>