Stereology derives three-dimensional information from two-dimensional samples. It is often used to study or compare tissues and organs in the body.
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This technique implements stereological ‘probes’ to study the shapes and sizes of cells and tissues. These probes take the shape of virtual objects oriented in space such that the size or distribution of cells can be studied. The probe is chosen to suit sample dimensions, and the interaction of the probe with the sample is used to quantify the sample using different mathematical equations.
Stereological probes examine either a specific point in space, a line or area with a specific position in space as well as an orientation. This allows the sample to be compared and studied. Several different probes can be used on a sample, for example, the 3D structure of a sample can be measured using probes with certain lines, cross sections and areas together, called a dissector probe.
These probes are commonly used to determine the length of capillaries in certain areas of the circulatory system, the volume of tumors, and the number of cells in different areas of an organ.
What characteristics can be measured?
One common aspect of a sample that needs to be studied is the length of various fibers or vessels. This can be measured by quantifying the number of interactions the sample has with the chosen probe. This information can be feeded into mathematical equations which can then assess the relationship between sample and probe and provide the output data.
The number of cells in a culture is another common example, which can also be measured using different probes and methods, such as a disector or fractionator. This method randomly samples the culture and estimates the number of cells present using the interaction with the probes.
There are many other structural characteristics, such as surface area of membranes and tissues can be measured using stereology. They all based on measuring interactions with the sample and providing estimates of the data needed.
Why is stereology important?
2D images are frequently generated during analysis of tissue, and it is often difficult to draw conclusions about overall structure or function of tissues without determining how these 2D structures form a 3D tissue. Stereology is therefore often used to make estimations and predictions about the three-dimensional structural features of different tissues.
However, large number of samples are needed to produce accurate results which can be time-consuming. It is an efficient and consistent method compared to other simple quantitative analyses and reduce sampling biases.