The choice of embedding media affects image quality, tissue R(2)*, and susceptibility behaviors in post‐mortem brain MR microscopy at 7.0T

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Item Type:	Article
Title:	The choice of embedding media affects image quality, tissue R(2)*, and susceptibility behaviors in post‐mortem brain MR microscopy at 7.0T
Creators Name:	Dusek, P., Madai, V.I., Huelnhagen, T., Bahn, E., Matej, R., Sobesky, J., Niendorf, T., Acosta-Cabronero, Julio and Wuerfel, J.
Abstract:	PURPOSE: The quality and precision of post‐mortem MRI microscopy may vary depending on the embedding medium used. To investigate this, our study evaluated the impact of 5 widely used media on: (1) image quality, (2) contrast of high spatial resolution gradient-echo (T(1) and T(2)-weighted) MR images, (3) effective transverse relaxation rate (R(2)), and (4) quantitative susceptibility measurements (QSM) of post-mortem brain specimens. METHODS: Five formaldehyde-fixed brain slices were scanned using 7.0T MRI in: (1) formaldehyde solution (formalin), (2) phosphate-buffered saline (PBS), (3) deuterium oxide (D(2)O), (4) perfluoropolyether (Galden), and (5) agarose gel. SNR and contrast-to-noise ratii (SNR/CNR) were calculated for cortex/white matter (WM) and basal ganglia/WM regions. In addition, median R(2)* and QSM values were extracted from caudate nucleus, putamen, globus pallidus, WM, and cortical regions. RESULTS: PBS, Galden, and agarose returned higher SNR/CNR compared to formalin and D(2)O. Formalin fixation, and its use as embedding medium for scanning, increased tissue R(2). Imaging with agarose, D(2)O, and Galden returned lower R(2) values than PBS (and formalin). No major QSM offsets were observed, although spatial variance was increased (with respect to R(2)* behaviors) for formalin and agarose. CONCLUSIONS: Embedding media affect gradient-echo image quality, R(2), and QSM in differing ways. In this study, PBS embedding was identified as the most stable experimental setup, although by a small margin. Agarose and Galden were preferred to formalin or D(2)O embedding. Formalin significantly increased R(2) causing noisier data and increased QSM variance.
Keywords:	Ex Vivo Imaging, Formaldehyde Fixation, Post-Mortem Imaging, Quantitative Susceptibility Mapping, Ultra-High Field MRI
Source:	Magnetic Resonance in Medicine
ISSN:	0740-3194
Publisher:	Wiley
Volume:	81
Number:	4
Page Range:	2688-2701
Date:	April 2019
Official Publication:	https://doi.org/10.1002/mrm.27595
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