Radiology, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts.
Athinoula A. Martinos Center for Biomedical Imaging, Boston, Massachusetts.
Hum Brain Mapp. 2019 Apr 1;40(5):1654-1665. doi: 10.1002/hbm.24477. Epub 2018 Nov 20.
During the past several decades there has been much interest in the existence of magnetite particles in the human brain and their accumulation with age. These particles also appear to play an important role in neurodegenerative diseases of the brain. However, up to now the amount and distribution of these particles has been measured only in post-mortem brain tissue. Although in-vivo MRI measurements do show iron compounds generally, MRI cannot separate them according to their magnetic phases, which are associated with their chemical interactions. In contrast, we here offer a new noninvasive, in-vivo method which is selectively sensitive only to particles which can be strongly magnetized. We magnetize these particles with a strong magnetic field through the head, and then measure the resulting magnetic fields, using the dcMagnetoencephalogram (dcMEG). From these data, the mass and locations of the particles can be estimated, using a distributed inverse solution. To test the method, we measured 11 healthy male subjects (ages 19-89 year). Accumulation of magnetite, in the hippocampal formation or nearby structures, was observed in the older men. These in-vivo findings agree with reports of post-mortem measurements of their locations, and of their accumulation with age. Thus, our findings allow in-vivo measurement of magnetite in the human brain, and possibly open the door for new studies of neurodegenerative diseases of the brain.
在过去的几十年中，人们对人类大脑中磁铁矿颗粒的存在及其随年龄增长的积累产生了浓厚的兴趣。这些颗粒似乎在大脑的神经退行性疾病中也起着重要作用。然而，到目前为止，这些颗粒的数量和分布仅在死后脑组织中进行了测量。尽管体内 MRI 测量通常确实显示出铁化合物，但 MRI 无法根据它们的磁相对其进行分离，而磁相与它们的化学相互作用有关。相比之下，我们在这里提供了一种新的非侵入性、体内方法，该方法仅对可以强烈磁化的颗粒具有选择性敏感性。我们通过头部用强磁场磁化这些颗粒，然后使用直流磁脑图（dcMEG）测量产生的磁场。从这些数据中，使用分布式逆解来估计颗粒的质量和位置。为了测试该方法，我们测量了 11 名健康男性（年龄 19-89 岁）。在年龄较大的男性中，观察到在海马结构或附近结构中磁铁矿的积累。这些体内发现与死后测量其位置以及随年龄积累的报告相符。因此，我们的发现允许在体内测量人类大脑中的磁铁矿，并可能为大脑的神经退行性疾病的新研究打开大门。
