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Measurements
Measurements can be classed generally into two groups: those for the entire image or scene (usually extrapolated to the entire specimen represented by the sample), and those performed on each individual feature or object present (and usually summarized statistically or used for feature recognition).
Stereology - In most microscopy applications, the sample is a thin slice or surface through a three-dimensional specimen, and the proper interpretation of the structure measurements is based on stereological rules. Modern stereological procedures emphasize the efficient and unbiased sampling of the specimen, and make use of relatively simple measurement or counting procedures, often using grids placed on the image, to obtain the desired results. The metric properties of a structure such as the volume fraction, surface area, length, and curvature, can all be determined by the examination of representative section planes. Topological properties such as the number of discrete objects and the connectivity of networks require at a minimum the comparison of two parallel sections.
Feature Measurements - There are four basic classes of measurements on individual features: those involving the pixel values (color, brightness, or derived values such as density); measures of size (such as area, diameter, perimeter or length); information on position (either absolute coordinates, or position relative to other objects); and finally values that characterize shape.
Contributing Authors
John C. Russ - Materials Science and Engineering Dept., North Carolina State University, Raleigh, North Carolina, 27695.
Matthew Parry-Hill and Michael W. Davidson - National High Magnetic Field Laboratory, 1800 East Paul Dirac Dr., The Florida State University, Tallahassee, Florida, 32310.
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