Stereology Glossary

Property of an object or tissue whose geometric characteristics vary according to the direction of observation. Anisotropic structures require specific sampling methods (IUR, VUR) to obtain unbiased estimates.

Systematic error introduced into an estimate when the sampling method favours certain elements over others. In stereology, bias is avoided through the use of random geometric methods.

Method for estimating the volume of an object from the areas of its equidistant plane sections. Volume V is estimated by V = T × Σ Ai, where T is the sampling interval and Ai is the area of section i.

Measure of the precision of a stereological estimate. It represents the ratio between the standard error and the estimated mean. A CE below 0.05 is generally considered acceptable.

Three-dimensional probe used to count objects within a defined volume of tissue, using two focal planes (upper and lower look-up planes). Provides an unbiased estimate of object number.

Version of the disector using two adjacent physical sections instead of two focal planes within a thick section.

Method for estimating the total number of objects in a tissue by counting only a known fraction of that tissue. Highly efficient for large structures such as the whole brain.

Geometric object (point, line, plane, volume) used to sample the structure of interest and estimate its geometric properties.

Sampling method ensuring that all orientations in space are equally probable. Essential for unbiased estimation of surface area and length.

Property of an object or tissue whose geometric characteristics are identical in all directions. Isotropic structures can be analysed with geometric probes in any orientation.

Total length of a filamentous structure per unit volume of the reference space. Estimated by counting intersections with test planes.

Absolute number of discrete objects within a defined reference space. Estimated using the optical or physical disector, or the fractionator.

Number of objects per unit volume of reference space. Expressed as number/mm³ or number/cm³.

See Disector (Optical).

Method for estimating volume fraction by superimposing a grid of points on a section. Volume fraction is estimated as the ratio of points falling on the structure of interest to the total number of test points.

A point in a grid used to estimate volume fraction by the point counting method.

Volume, surface, length or total number to which stereological estimates are related. The choice of reference space is critical for the interpretation of results.

Total volume of the reference space within which estimates are made. Estimated using the Cavalieri method.

Distance between two consecutive sections in a systematic uniform sampling scheme. Expressed in the same unit as the dimension of the object under study.

Science that allows estimation of three-dimensional geometric parameters (volume, surface area, length, number) from two-dimensional observations on plane sections.

Total surface area of a structure per unit volume of reference space. Expressed in mm²/mm³. Estimated by counting intersections with test lines.

Sampling method in which sections are taken at regular intervals with a random starting point. Guarantees uniform representation of the entire object.

Straight or cycloid line used to count intersections with the boundaries of a structure. Used to estimate surface density and length density.

Set of stereological methods guaranteeing estimates free from systematic bias. Title of the reference textbook by Prof. Vyvyan Howard and co-authors.

Section obtained according to a protocol guaranteeing isotropy in the plane of the section, while maintaining a fixed vertical direction. Allows surface estimation on anisotropic structures.

Proportion of the volume of a structure relative to the total volume of the reference space. Estimated by point counting. Dimensionless, expressed between 0 and 1 or as a percentage.

Sampling protocol for obtaining vertical isotropic sections for surface estimation on anisotropic structures.