Biophysical contrast sources for magnetic susceptibility and R2* mapping: A combined 7 Tesla, mass spectrometry and electron paramagnetic resonance study
Year: 2024
Type: article
Abstract: • R2* and QSM show variable regional contrast patterns. With similar contrast in iron-rich structures. • Iron and its molecular form as ferritin were shown to be the main contributors for the overall R2* and QSM contrast. • Analysis individualized by ROI showed different contributions of iron and ferritin to R2* and QSM, resulting in three groups of structures according to the correlation of iron/ferritin to R2* and QSM. • Iron-rich structures displayed strong correlation to iron/ferritin, low-iron structures displayed no correlation to iron/ferritin, and the substantia nigra displayed partial correlation to iron and no correlation to ferritin. Iron is the most abundant trace metal in the human brain and consistently shown elevated in prevalent neurological disorders. Because of its paramagnetism, brain iron can be assessed in vivo by quantitative MRI techniques such as R 2 * mapping and Quantitative Susceptibility Mapping (QSM). While Inductively Coupled Plasma Mass Spectrometry (ICP-MS) has demonstrated good correlations of the total iron content to MRI parameters in gray matter, the relationship to ferritin levels as assessed by Electron Paramagnetic Resonance (EPR) has not been systematically analyzed. Therefore, we included 15 postmortem subjects (age: 26–91 years) which underwent quantitative in-situ MRI at 7 Tesla within a post-mortem interval of 24 h after death. ICP-MS and EPR were used to measure the total iron and ferritin content in 8 selected gray matter (GM) structures and the correlations to R 2 * and QSM were calculated. We found that R 2 * and QSM in the iron rich basal ganglia and the red nucleus were highly correlated with iron (R² > 0.7) and ferritin (R² > 0.6), whereas those correlations were lost in cortical regions and the hippocampus. The neuromelanin-rich substantia nigra showed a different behavior with a correlation with total iron only (R² > 0.5) but not with ferritin. Although qualitative results were similar for both qMRI techniques the observed correlation was always stronger for QSM than R 2 *. This study demonstrated the quantitative correlations between R 2 *, QSM, total iron and ferritin levels in an in-situ MRI setup and therefore aids to understand how molecular forms of iron are responsible for MRI contrast generation.
Source: NeuroImage
Language: English
Subfield: Radiology, Nuclear Medicine and Imaging
Field: Medicine
Domain: Health Sciences
Open Access status: gold
Estimated APC paid: $3,450
Awards: End-to-End Quantitative Susceptibility Mapping, G2526514380, G2604241884, G2638626260, Postmortem Validation of Quantitative Susceptibility Mapping, G3030194232, G3914732244, G4402799499, G4895942499, G5140418445, G9000348328, Clinical Features and Neuropathological Basis of Sleep Wake Behavior in Alzheimer's and PSP
OpenAlex ID: W4403564984