VERTICAL LM SECTIONING AND PARALLEL CT SCANNING DESIGNS FOR STEREOLOGY - APPLICATION TO HUMAN LUNG

Practical, unbiased stereological methods are described to estimate lu ng volume and external surface area, and total volume and surface area of relatively large and anisotropic structures (bronchi and arteries) inside the lung. The volume of each of five lung strata was estimated first by fluid displacement and then by computed tomography (CT) usin g Cavalieri's method; the reliability of CT was assessed through a cal ibration procedure, and image thresholding criteria for an accurate vo lume estimation using CT were established. The parallel, perfectly reg istered CT section images were also used to estimate the external surf ace area of each stratum by the spatial grid method. Unbiased estimati on of internal surface areas in lung is a long-standing problem: since the structures are large and essentially void, large sections are nee ded; to facilitate identification, thin sections have to be used for l ight microscopy, and since such structures are anisotropic, the sectio ns should be vertical. A practical stereological design is demonstrate d here on an infant lung, which fulfils all these requirements. This s tudy illustrates the potential of using unbiased stereology to charact erize infant pulmonary hypoplasia.