死后猪脑的超低场和自旋锁定弛豫弥散。

Ultralow-field and spin-locking relaxation dispersion in postmortem pig brain.

机构信息

Department of Physics, University of California, Berkeley, California, USA.

State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences (CAS), Shanghai, China.

出版信息

Magn Reson Med. 2017 Dec;78(6):2342-2351. doi: 10.1002/mrm.26621. Epub 2017 Feb 5.

DOI:10.1002/mrm.26621

PMID:28164366

Abstract

PURPOSE

To investigate tissue-specific differences, a quantitative comparison was made between relaxation dispersion in postmortem pig brain measured at ultralow fields (ULF) and spin locking at 7 tesla (T). The goal was to determine whether ULF-MRI has potential advantages for in vivo human brain imaging.

METHODS

Separate specimens of gray matter and white matter were investigated using an ULF-MRI system with superconducting quantum interference device (SQUID) signal detection to measure T1ULF at fields from 58.7 to 235.0 μT and using a commercial MRI scanner to measure T1ρ7T at spin-locking fields from 5.0 to 235.0 μT.

RESULTS

At matched field strengths, T1ρ7T is 50 to 100% longer than T1ULF. Furthermore, dispersion in T1ULF is close to linear between 58.7 and 235 µT, whereas dispersion in T1ρ7T is highly nonlinear over the same range. A subtle elbow in the T1ULF dispersion at approximately 140 µT is tentatively attributed to the local dipolar field of macromolecules. It is suggested that different relaxation mechanisms dominate each method and that ULF-MRI has a fundamentally different sensitivity to the macromolecular structure of neural tissue.

CONCLUSIONS

Ultralow-field MRI may offer distinct, quantitative advantages for human brain imaging, while simultaneously avoiding the severe heating limitation imposed on high-field spin locking. Magn Reson Med 78:2342-2351, 2017. © 2016 International Society for Magnetic Resonance in Medicine.

摘要

目的

为了研究组织特异性差异，我们对在超低场（ULF）下测量的死后猪脑的弛豫弥散与在 7 特斯拉（T）下的自旋锁定进行了定量比较。我们的目的是确定 ULF-MRI 是否有可能成为用于活体人脑成像的一种优势技术。

方法

使用超导量子干涉器件（SQUID）信号检测的 ULF-MRI 系统分别对灰质和白质标本进行研究，以测量场强范围为 58.7 至 235.0 μT 的 T1ULF，并使用商用 MRI 扫描仪测量场强范围为 5.0 至 235.0 μT 的 T1ρ7T。

结果

在匹配的场强下，T1ρ7T 比 T1ULF 长 50%至 100%。此外，T1ULF 的弥散在 58.7 至 235 μT 之间接近线性，而 T1ρ7T 的弥散在相同范围内则具有高度非线性。在大约 140 μT 处 T1ULF 弥散的轻微弯曲，我们推测这是由于大分子的局部偶极场所致。这表明，每种方法都由不同的弛豫机制主导，而 ULF-MRI 对神经组织的大分子结构具有根本不同的敏感性。