Fig. 2

X-ray images of differently-sized MCT tracking particles. Images of (a) 52 μm, (b) 78 μm and (c) 103 μm HRI glass beads on Kapton tape, taken at 30 keV with the field of view set to ~ 16.6 mm x 14 mm to image the full width of the tracheal segments. The contrast is primarily due to absorption. The insets show a 4x magnification of the beads. The brightness and contrast of the three images have been altered in the same way to improve particle visualisation for publication and allow visual comparisons. The 103 μm beads were chosen for the ex vivo experiments. Scale bar 2 mm