Fig. 4.

Ratio of normalized ¹²⁹Xe pixel count in barrier and RBC images vs. pixel count in the airspace images in each lung. Pixel counts were separated by right and left lung to take into account reduced lung volume in injured lungs and to allow one lung to serve as a control. A strong correlation (R² = 0.93) is seen between barrier and airspace pixel counts, as would be expected, because they are directly adjacent. The regression line is a fit to all of the barrier pixel counts in injured and uninjured lungs. In injured lungs, the RBC pixel count fell well below the regression line in five of seven lungs, whereas in control lungs, the RBC pixel count fell on the regression line.