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Updated: Jun 24, 2026

Immunohistochemical Analysis in the Rat Central Nervous System and Peripheral Lymph Node Tissue Sections
Published on: November 14, 2016
Aldehyde fixative solutions alter the water relaxation and diffusion properties of nervous tissue
Timothy M Shepherd1, Peter E Thelwall, Greg J Stanisz
1Department of Radiology and Biomedical Imaging, University of California, San Francisco, San Francisco, California 94143-0628, USA. tim.shepherd@radiology.ucsf.edu
Abstract:
Chemically-fixed nervous tissues are well-suited for high-resolution, time-intensive MRI acquisitions without motion artifacts, such as those required for brain atlas projects, but the aldehyde fixatives used may significantly alter tissue MRI properties. To test this hypothesis, this study characterized the impact of common aldehyde fixatives on the MRI properties of a rat brain slice model. Rat cortical slices immersion-fixed in 4% formaldehyde demonstrated 21% and 81% reductions in tissue T(1) and T(2), respectively (P < 0.001). The T(2) reduction was reversed by washing slices with phosphate-buffered saline (PBS) for 12 h to remove free formaldehyde solution. Diffusion MRI of cortical slices analyzed with a two-compartment analytical model of water diffusion demonstrated 88% and 30% increases in extracellular apparent diffusion coefficient (ADC(EX)) and apparent restriction size, respectively, when slices were chemically-fixed with 4% formaldehyde (P
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