# Stereology Symbols

### A

Stereology differentiates between the area in a plane (profile area, cross-sectional area) and surface area which is area in 3-D. A thin section of tissue has profiles on it that have area. A photograph or other image is flat and shows cross-sectional area. In cross-section, surface area will look like line-segments.

### B

The outlines of objects on a plane have length, boundary length. Stereology differentiates between the length of objects in 3-D and the lengths of boundaries just as area and surface are seen as two distinct quantities.

### N

The number of particles. The number of cells in the kidneys and the number of synapses in the brain are examples of numbers of objects.

### L

Length is a 3-d quantity. This might be the length of dendrites or capillaries. Length is seen as being distinct from boundary.

### S

Surface area is a 3-d quantity. Stereologists are clear to distinguish surface area from the area seen in something flat such as a thin section of rock or an image. A cell is bounded by a surface.

### V

Volume is a 3-d quantity. The size of a ventricle is an example of volume.

### I

Intersections are the places where a line probe pierces a surface that is being probed.

### Q

From the German word querschnitt that means something like ‘cross-section’. It indicates when a surface area probe is pierced by a string whose length is being probed. This symbol is also used to indicate a cross-section through a particle.

### Q–

To indicate that a cross-section of a particle is in one physical or optical section, but not the next (in other words to indicate the leading edge of a particle).

### V

Volume of an individual member of the population. The volume of a cell, rather than the volume of all of the cells is a good example of the use of a lower case v.

These basic symbols are often used in a subscript form. The subscript can be read as per unit. An example makes this easy to understand. Suppose the estimate is capillary length per unit volume. The quantity is written as L v . The symbol L stands for 3-d length and the subscript V is per unit volume. Another common symbol is N v. This stands for number per unit volume. This might be the number of cells per unit volume. The notation V v is volume per unit volume. An example of this is how much plaques there is in the hippocampus. A value of 0.2 means that the hippocampus is 20 percent plaque by volume.

There are a number of symbols that are used less frequently. These symbols are more common in some disciplines within stereology than in others.

### J

The symbol J is occasionally used in place of L.

### C

Total curvature of a curve in the plane. This is the net angle through which the unit tangent vector rotates as a point traverses the curve.

### K

Integral of mean curvature

Other symbols that might be seen in stereological work are:

### *

The asterisk is often used to denote the star volume. This symbol appears as a superscript.

### ^

An upwards pointing arrow is often used to denote the intersections between a probe and the region of interest.

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