A variety of Magnetic Resonance Imaging (MRI) techniques are known to be sensitive to brain iron content. In principle, iron sensitive MRI techniques are based on local magnetic field variations caused by iron particles in tissue. The purpose of this study was to investigate the sensitivity of MR relaxation and magnetization transfer parameters to changes in iron oxidation state compared to changes in iron concentration. Therefore, quantitative MRI parameters including R1, R2, R2∗, quantitative susceptibility maps (QSM) and magnetization transfer ratio (MTR) of post mortem human brain tissue were acquired prior and after chemical iron reduction to change the iron oxidation state and chemical iron extraction to decrease the total iron concentration. All assessed parameters were shown to be sensitive to changes in iron concentration whereas only R2, R2∗ and QSM were also sensitive to changes in iron oxidation state. Mass spectrometry confirmed that iron accumulated in the extraction solution but not in the reduction solution. R2∗ and QSM are often used as markers for iron content. Changes in these parameters do not necessarily reflect variations in iron content but may also be a result of changes in the iron's oxygenation state from ferric towards more ferrous iron or vice versa.

中文翻译：

---

铁氧化态对死后人脑MRI定量参数的影响

已知多种磁共振成像 (MRI) 技术对脑铁含量敏感。原则上，铁敏感 MRI 技术基于组织中铁粒子引起的局部磁场变化。本研究的目的是研究与铁浓度变化相比，MR 弛豫和磁化转移参数对铁氧化态变化的敏感性。因此，在化学铁还原改变铁氧化态和化学铁提取前后获得包括R1、R2、R2*、定量磁化率图（QSM）和磁化转移比（MTR）在内的定量MRI参数。以降低总铁浓度。所有评估的参数都显示对铁浓度的变化敏感，而只有 R2，R2∗ 和 QSM 也对铁氧化态的变化敏感。质谱证实铁在提取溶液中积累，但在还原溶液中没有积累。R2∗ 和 QSM 通常用作铁含量的标记。这些参数的变化不一定反映铁含量的变化，但也可能是铁的氧化状态从三价铁向更多亚铁质变化的结果，反之亦然。