Fig. 1.

Segmentation algorithm basic steps. Upper left: sub-pleural selection from the original ultrasound scan. Upper right: K-means classification to divide pixels into two subsets. Bottom right: alternated sequential filter consisting in iterative morphological openings and closings, with an axial-line structuring element which closes small (10-pixel) gaps axially and isolates the objects laterally, thus enhancing the B-line contours. Bottom left: B-line detection scanning the images along their columns selecting those with ≥ 50% of white pixels over 70% of their total vertical length