Kaiser et al. 10.1073/pnas.0611544104. |
Fig. 5. Stereological point count method. Ultrathin slices (A, gray planes) of the region of interest are overlaid with a grid of points (B). Points that cover the structures of interest are counted (B, white on blue). The relation of counted (white) points to total number of points in the grid gives a number for area density in the slice. The mean value of area densities from multiple slices determines the volume density of the objects in the region of interest (1).
1. Weibel ER (1979) Stereological Methods (Academic, London), Vol. 1.
Fig. 6. Adapted stereological point count method. Images obtained by x-ray microscopy are two-dimensional projections (B) of 3D regions of interest (A). Because the tubes overlap, the point count method alone overestimates the area density. The true volume density must be calculated by applying a correction factor. The factor is determined by the number of layers that can be filled by the objects perpendicular to the beam; in this case, the number of tracheae that can be stacked into the beetle dorsoventrally (C).