Table 2 Glossary of stereological terms
Stereological term | Definition |
|---|---|
Bias | Systematic error. A systematic deviation of the average estimate from the true value. Absence of bias is termed accuracy |
Cavalieri estimator | An unbiased method for estimating the volume of an object by slicing it in parallel sections of a known thickness and estimating the area of the cut surfaces with a point grid. The volume is calculated by multiplying the total surface area of all sections with the section thickness |
CE | Coefficient of error. A mathematical expression of the imprecision (variance) of an estimate. Can be predicted to adjust the sampling effort in relation to the overall coefficient of variation (CV) of a study group |
Disector | A 3D stereological test system (test volume) for sampling and counting objects. By either using two sections (physical disector) or by focussing through one thick section in z direction (optical disector), a known z distance with a defined counting area is sampled, and particle number in 3D space can be estimated |
Fractionator | An unbiased sampling design that is based on keeping track of sampling fractions at each subsampling step to obtain total values by multiplying the counted objects at the final sampling step with the inverse of the sampling fraction. The method can optimally be combined with the optical disector (optical fractionator) |
Isector | A method for generating IUR sections by embedding the tissue in spherical molds to randomize orientation in further tissue processing |
IUR | Isotropic uniform random. An unbiased sampling design that randomizes for spatial orientation of microscopic sections (IUR sections). Tools to generate IUR sections are the isector or the orientator |
Orientator | A method for generating IUR sections via a two-step process, including randomized dis-orientation along two different axes |
Reference volume | The space from which samples are taken and in which particular stereological measurements are performed, e.g. total lung volume. Knowledge of the reference volume is crucial to convert densities estimated with stereological test systems to total quantities |
SURS | Systematic uniform random sampling. An unbiased sampling design that randomizes for location (e.g. the selection of tissue blocks or fields of view). Includes a systematic and a random component, by selecting the first position at random and the selection of all other positions with a constant sampling interval |
VUR | Vertical uniform random. An unbiased sampling design for randomization of spatial orientation. Combines randomization of microscopic sections in two dimensions (VUR sections), thus maintaining a specific horizontal plane, with a sine-weighted curved test line orientation (cycloids) to randomize the interaction with test lines in the third dimension |