Abstract
Knowledge of the lung vessel morphology in healthy subjects is necessary to improve our understanding about the functional network of the lung and to recognize pathologic deviations beyond the normal inter-subject variation. Established values of normal lung morphology have been derived from necropsy material of only very few subjects. In order to determine morphologic readouts from a large number of healthy subjects, computed tomography pulmonary angiography (CTPA) datasets, negative for pulmonary embolism, and other thoracic pathologies, were analyzed using a fully-automatic, in-house developed artery/vein separation algorithm. The number, volume, and tortuosity of the vessels in a diameter range between 2 and 10 mm were determined. Visual inspection of all datasets was used to exclude subjects with poor image quality or inadequate artery/vein separation from the analysis. Validation of the algorithm was performed manually by a radiologist on randomly selected subjects. In 123 subjects (men/women: 55/68), aged 59 ± 17 years, the median overlap between visual inspection and fully-automatic segmentation was 94.6% (69.2–99.9%). The median number of vessel segments in the ranges of 8–10, 6–8, 4–6, and 2–4 mm diameter was 9, 34, 134, and 797, respectively. Number of vessel segments divided by the subject's lung volume was 206 vessels/L with arteries and veins contributing almost equally. In women this vessel density was about 15% higher than in men. Median arterial and venous volumes were 1.52 and 1.54% of the lung volume, respectively. Tortuosity was best described with the sum-of-angles metric and was 142.1 rad/m (138.3–144.5 rad/m). In conclusion, our fully-automatic artery/vein separation algorithm provided reliable measures of pulmonary arteries and veins with respect to age and gender. There was a large variation between subjects in all readouts. No relevant dependence on age, gender, or vessel type was observed. These data may provide reference values for morphometric analysis of lung vessels.
Highlights
Morphometric information on the lung vasculature in healthy subjects is necessary to improve our understanding about the complex and interconnected functional network of the lung and to recognize pathologic deviations beyond the normal variation expected between subjects (Weibel, 2009, 2017)
The artery/vein separation algorithm was applied to all datasets
The visual inspection of all datasets resulted in a median percentage of correctly labeled vessels of 89%
Summary
Morphometric information on the lung vasculature in healthy subjects is necessary to improve our understanding about the complex and interconnected functional network of the lung and to recognize pathologic deviations beyond the normal variation expected between subjects (Weibel, 2009, 2017). Quantitative measures of the lung vessel morphology were shown to have diagnostic and/or prognostic value in diseases like pulmonary hypertension (Matsuoka et al, 2010b; Helmberger et al, 2014; Rahaghi et al, 2016a), chronic obstructive pulmonary disease (COPD) (Matsuoka et al, 2010a; Estépar et al, 2013; Rahaghi et al, 2016b), or idiopathic pulmonary fibrosis (IPF) (Jacob et al, 2016, 2017) For these applications it is important to know the normal ranges of the morphologic readouts (Li et al, 2003, 2012; Hansell, 2010; Hoffman et al, 2014)
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