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Fig. 4 | Respiratory Research

Fig. 4

From: A short primer on lung stereology

Fig. 4

Stereological test systems and their relation to parameters of interest. The dimension of the parameter that is estimated plus the dimension of the test system containing geometric probes that is used to estimate it equals at least 3. Therefore, test points (dimension 0) “feel” volume (dimension 3), test lines (dimension 1) “feel” surface area (dimension 2), test planes (dimension 2) “feel” length (dimension 1), and only test volumes (dimension 3) “feel” number (dimension 0). In practice, test volumes are generated by using section pairs or thick sections (disectors) from one tissue block. For volume density estimation, test points are counted if they lie in the volume, i.e. hit the cut area in the section (red). For surface area density estimation, intersections are counted if the test line intersects the surface, i.e. hit the cut boundary line in the section (red). For length density estimation, transects are counted if the test plane transects the line, i.e. hits the line to create cut profiles (red). For number density estimation, particles are counted if their top lies in the test volume (disector), i.e. either they are present in one disector section but not the other (physical disector) (red), or their tops become visible while focussing through a thick section (optical disector). To avoid the “reference trap”, these estimates of densities (ratios) per unit reference volume have to be converted to total values by multiplying them with the total volume of the reference space (see Fig. 1). From [34]

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