Otsuka Fábio Seiji, Otaduy Maria Concepción Garcia, Rodriguez Roberta Diehl, Langkammer Christian, Barbosa Jeam Haroldo Oliveira, Salmon Carlos Ernesto Garrido
InBrain, Departamento de Física, Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto (FFCLRP), Universidade de São Paulo USP, Avenida Bandeirantes 3900, Vila Monte Alegre, Ribeirão Preto, São Paulo CEP 14040-901, Brazil.
LIM44, Instituto de Radiologia (InRad), Hospital das Clínicas da Faculdade de Medicina da Universidade de São Paulo (HCFMUSP), São Paulo, São Paulo, Brazil.
Neuroimage. 2024 Nov 15;302:120892. doi: 10.1016/j.neuroimage.2024.120892. Epub 2024 Oct 19.
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* 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* and QSM were calculated. We found that R* 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*. This study demonstrated the quantitative correlations between R*, 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.
铁是人类大脑中含量最丰富的痕量金属，在常见的神经系统疾病中一直呈现升高状态。由于其顺磁性，脑铁可以通过诸如R图谱和定量磁化率图谱（QSM）等定量MRI技术在体内进行评估。虽然电感耦合等离子体质谱法（ICP-MS）已证明灰质中总铁含量与MRI参数具有良好的相关性，但尚未对通过电子顺磁共振（EPR）评估的与铁蛋白水平之间的关系进行系统分析。因此，我们纳入了15名死后受试者（年龄：26 - 91岁），他们在死后24小时内于7特斯拉磁场下接受了定量原位MRI检查。使用ICP-MS和EPR测量了8个选定灰质（GM）结构中的总铁和铁蛋白含量，并计算了与R和QSM的相关性。我们发现，富含铁的基底神经节和红核中的R和QSM与铁（R² > 0.7）和铁蛋白（R² > 0.6）高度相关，而在皮质区域和海马体中这些相关性消失。富含神经黑色素的黑质表现出不同的行为，仅与总铁相关（R² > 0.5），而与铁蛋白无关。尽管两种定量MRI技术的定性结果相似，但观察到的相关性对于QSM总是比R更强。这项研究证明了在原位MRI设置中R*、QSM、总铁和铁蛋白水平之间的定量相关性，因此有助于理解铁的分子形式如何产生MRI对比度。
