Fig. 2.

In a 26-yr-old mild-to-moderate asthmatic subject, a three-dimensional (3D) resolution-matched proton image was acquired. A: coronal slice reformat of a proton acquisition overlaid with the lung segmentation. B: extracted lung segmentation from the slice in A. C: matched coronal slice reformation of a helium acquisition overlaid with the lung segmentation. Note the mismatch between the helium acquisition and the mask at the defect region. D: extracted lung segmentation from the slice in C. Note that although parts A–D were done in 3D, they are shown here in two dimensions for clarity. E: final mask generated by combining the proton segmentations (B) and helium segmentations (D) using an affine transformation of the proton mask to the helium mask, with additional editing by hand done when necessary. F: 3D rendering of the final mask after removing the trachea and large airways.