The use of simple image analysers in lung morphometry

We have used several commercially available image analysers to measure the inter-alveolar wall distance on histologic sections of animal and human lungs. Inter- and intra-observer variations using these machines are small, and very similar results are obtained using different machines. The recorded result depends on the magnification used since higher resolution produces more intercepts. The plane in which the measurement is made affects the result, representing the difference in shrinkage from fixed tissue to stained slides in the horizontal and vertical planes. Machine-measured inter-alveolar wall distances are smaller than those measured by humans because of the spurious intercepts made by the image analysers. However, the measurements are highly correlated and human-measured inter-alveolar wall distances can be closely predicted from the machine-measured ones. The number of alveoli per unit volume is less well predicted from the average inter-alveolar wall distance. Image analysers may possibly play a useful role in making similar simple measurements in other organs.