IUR sections, also known as isotropic or random sections, are random in all three planes. Important to stereologists, but usually not popular with anatomists, they are used by probes including the nucleator, and length or surface probes in thin sections. IUR sections are more random than vertical sections in that three planes are randomized instead of two. For instance, systematically and randomly selected pieces of tissue can be embedded in spheres and rolled along the lab bench until they come to rest. This is called the isector and is good for small tissue samples, while the orientator is better for larger pieces of tissue.
Mattfeldt, T., Mall, G., Gharehbagi, H., and P. Möller, 1990, Estimation of Surface Area and Length with the Orientator. J. Microsc., 159, pp. 301-317.
Nyengaard JR, and Gundersen HJG, 1992, The Isector: A Simple and Direct Method for Generating Isotropic, Uniform Random Sections from Small Specimens. J. Microsc., 165, pp 427-431.
Mark J. West, 2012, sections 4.1 to 4.5, Isotropy, Isectors, and Vertical sections, ‘Basic Stereology for Biologists and Neuroscientists’. Cold Spring Harbor Laboratory Press, Cold Spring Harbor, NY.
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