Whole-brain 3D mapping of oxygen metabolism using constrained quantitative BOLD.
Whole-brain 3D mapping of oxygen metabolism using constrained quantitative BOLD.
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DOI：
10.1016/j.neuroimage.2022.118952
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发表时间：
2022-04-15
期刊：
影响因子：
5.7
通讯作者：
Wehrli, Felix W.
中科院分区：
文献类型：
--
作者：
Lee, Hyunyeol;Wehrli, Felix W.
关键词：
定量 BOLD (qBOLD) MRI 通过量化脱氧血量 (DBV) 和静脉血血红蛋白氧饱和度水平 (Yv) 的参数图，以及脑血流量 (CBF) 和脑氧代谢率 (CMRO2) 的测量，可以无创评估大脑的血流动力学和代谢状态。因此，该方法应该有可能提供有关许多神经系统疾病以及正常脑生理学的重要信息。 qBOLD 的一项主要挑战是将脱氧血红蛋白对 R2' 的贡献与调节体素信号的其他来源分开，例如 R2、R2' 与非血红素铁 (R'2,nh) 以及宏观磁场变化。此外，即使成功分离了几个混杂因素，由于 qBOLD 模型的灵敏度有限，从血红素来源的 R2' 中提取 DBV 和 Yv 仍然具有挑战性。这些问题在目前实践的 qBOLD 方法中尚未得到完全解决，迄今为止阻碍了 qBOLD 的 3D 全脑实施。因此，这项工作的目的是开发一种新的 3D MRI 血氧测定技术，该技术能够在整个大脑中实现稳健的 qBOLD 参数映射。为了实现这一目标，我们采用快速、R2'敏感、稳态 3D 脉冲序列（称为“AUSFIDE”）进行数据采集，并实现了先验约束的 qBOLD 处理流程，该流程利用通过 AUSFIDE 获得的多个初步参数以及额外测量的脑静脉血量。进行了 3 T 的数值模拟和体内研究，以评估所提出的约束 qBOLD 映射与父 qBOLD 方法相比的性能。 10 名健康受试者的测量参数（Yv、DBV、R'2,nh、非血磁化率）显示了预期的脑区对比度，同时在皮质灰质和白质中 Yv 的组平均值分别为 64.0 ± 2.3 % 和 62.2 ± 3.1 %，DBV 的组平均值为 2.8 ± 0.5 % 和 1.8 ± 0.4 %。根据 Yv 测量值，另外对 10 个研究对象中的 7 个进行了量化 CBF，从而实现了全脑 3D CMRO2 绘图，皮质灰质和白质的组平均值为 134.2 ± 21.1 和 79.4 ± 12.6 µmol/100 g/min，与文献值非常一致。结果表明，所提出的方法作为在扩展的大脑覆盖范围内测量神经代谢参数的实用且可靠的方法是可行的。
Quantitative BOLD (qBOLD) MRI permits noninvasive evaluation of hemodynamic and metabolic states of the brain by quantifying parametric maps of deoxygenated blood volume (DBV) and hemoglobin oxygen saturation level of venous blood (Yv), and along with a measurement of cerebral blood flow (CBF), the cerebral metabolic rate of oxygen (CMRO2). The method, thus should have potential to provide important information on many neurological disorders as well as normal cerebral physiology. One major challenge in qBOLD is to separate de-oxyhemoglobin’s contribution to R2′ from other sources modulating the voxel signal, for instance, R2, R2′ from non-heme iron (R′2,nh), and macroscopic magnetic field variations. Further, even with successful separation of the several confounders, it is still challenging to extract DBV and Yv from the heme-originated R2′ because of limited sensitivity of the qBOLD model. These issues, which have not been fully addressed in currently practiced qBOLD methods, have so far precluded 3D whole-brain implementation of qBOLD. Thus, the purpose of this work was to develop a new 3D MRI oximetry technique that enables robust qBOLD parameter mapping across the entire brain. To achieve this goal, we employed a rapid, R2′-sensitive, steady-state 3D pulse sequence (termed ‘AUSFIDE’) for data acquisition, and implemented a prior-constrained qBOLD processing pipeline that exploits a plurality of preliminary parameters obtained via AUSFIDE, along with additionally measured cerebral venous blood volume. Numerical simulations and in vivo studies at 3 T were performed to evaluate the performance of the proposed, constrained qBOLD mapping in comparison to the parent qBOLD method. Measured parameters (Yv, DBV, R′2,nh, nonblood magnetic susceptibility) in ten healthy subjects demonstrate the expected contrast across brain territories, while yielding group-averages of 64.0 ± 2.3 % and 62.2 ± 3.1 % for Yv and 2.8 ± 0.5 % and 1.8 ± 0.4 % for DBV in cortical gray and white matter, respectively. Given the Yv measurements, additionally quantified CBF in seven of the ten study subjects enabled whole-brain 3D CMRO2 mapping, yielding group averages of 134.2 ± 21.1 and 79.4 ± 12.6 µmol/100 g/min for cortical gray and white matter, in good agreement with literature values. The results suggest feasibility of the proposed method as a practical and reliable means for measuring neurometabolic parameters over an extended brain coverage.
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