Off‐resonance saturation as an MRI method to quantify mineral‐ iron in the post‐mortem brain

Abstract

Purpose:To employ an off-resonance saturation method to measure the mineraliron pool in the postmortem brain, which is an endogenous contrast agent that can give information on cellular iron status.Methods: An off-resonance saturation acquisition protocol was implemented on a 7 Tesla preclinical scanner, and the contrast maps were fitted to an established analytical model. The method was validated by correlation and Bland-Altman analysis on a ferritin-containing phantom. Mineral-iron maps were obtained from postmortem tissue of patients with neurological diseases characterized by brain iron accumulation, that is, Alzheimer disease, Huntington disease, and aceruloplasminemia, and validated with histology. Transverse relaxation rate and magnetic susceptibility values were used for comparison. Results: In postmortem tissue, the mineral-iron contrast colocalizes with histological iron staining in all the cases. Iron concentrations obtained via the off-resonance saturation method are in agreement with literature. Conclusions:Off-resonance saturation is an effective way to detect iron in gray matter structures and partially mitigate for the presence of myelin. If a reference region with little iron is available in the tissue, the method can produce quantitative iron maps. This method is applicable in the study of diseases characterized by brain iron accumulation and can complement existing iron-sensitive parametric methods.

Quantitative MRI maps of human neocortex explored using cell type-specific gene expression analysis

“…2019 )), this could give rise to spatial variance in MTsat, explaining the observed relationship between MTsat and endothelial cells. Relatedly, the robust association of MTsat with microglia could be due to “off-resonance saturation” ( Bossoni et al. 2022 , Delangre et al.…”

In-depth magnetometry and EPR analysis of the spin structure of human-liver ferritin: from DC to 9 GHz

“…As such, the magnetism of the protein influences the contrast of R2 and R2*-weighted MRI images. [7][8][9] In the past decades, 'bulk' magnetometry techniques have been used to characterize the magnetic and mineral state of ferritin, 10,11 along with spectroscopy techniques such as Mo ¨ssbauer spectroscopy, 11,12 electron paramagnetic resonance (EPR), 13,14 nuclear magnetic resonance (NMR), [15][16][17] as well as electron and X-ray microscopy techniques, 18,19 and diamondbased quantum spin relaxometry to study the ferritin room temperature magnetic properties. 20 Electron paramagnetic resonance (EPR), sometimes also referred to by the more general term electron magnetic resonance (EMR), has also been applied to ferritin, 13,14,[21][22][23][24][25] in spite of intrinsic challenges related to extreme spectral broadening.…”

“…As such, the magnetism of the protein influences the contrast of R2 and R2*-weighted MRI images. 7–9…”