<br>使用 Z 光谱拟合方法评估肌酸加权 CEST MRI 在 7 T 人脑中的可行性。,NMR in Biomedicine

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使用 Z 光谱拟合方法评估肌酸加权 CEST MRI 在 7 T 人脑中的可行性。
NMR in Biomedicine ( IF 2.7 ) Pub Date : 2019-10-14 , DOI: 10.1002/nbm.4176
Anup Singh _{1,

2} , Ayan Debnath _{1,

3} , Kejia Cai ₄ , Puneet Bagga ₃ , Mohammad Haris _{3,

5} , Hari Hariharan ₃ , Ravinder Reddy ₃

Affiliation

本研究旨在通过优化饱和脉冲参数并使用 Z 光谱拟合方法计算对比度，评估肌酸（Cr）化学交换饱和转移（CEST）加权 MRI 在人脑中 7 T 的可行性。Cr 加权（Cr-w） CEST 对比度是根据体模数据计算的。进行模拟以获得 Cr-w CEST 的最佳饱和参数，其他脑代谢物的贡献较低。CEST-w 图像是从 4 名人类受试者的大脑中以不同饱和度参数获取的。Cr-w CEST 对比度是使用不对称分析和基于洛伦兹函数的 Z 光谱拟合方法（分别为模型 1 和 2）计算的。对于宽磁化转移（MT）效应，还评估了高斯和超洛伦兹线形状。在体模研究中，Cr-w CEST 造影剂显示出对生理范围内浓度的线性依赖性和对饱和度参数的非线性依赖性。使用大脑不对称分析生成的体内 Cr-w CEST 图代表了与其他代谢物的贡献以及中继核 Overhauser 效应（rNOE）的混合对比。模拟为用于获取脑 CEST 数据的最佳饱和参数范围提供了估计值。用于脑数据的 Cr-w CEST 的最佳饱和参数约为 B1rms = 1.45 μT 和持续时间 = 2 秒。Z 光谱拟合方法支持计算单个分量。这也导致减轻了 MT 和 rNOE 对 Cr-w CEST 对比的贡献，这是不对称分析中低估的主要来源。与模型 1 相比，所提出的改进的 z 光谱拟合方法（模型 2）对噪声更稳定。使用拟合获得的 Cr-w CEST 造影剂在灰质中为 6.98 ± 0.31%，在白质中为 5.45 ± 0.16%。最佳饱和度参数减少了其他 CEST 效应对 Cr-w CEST 对比度的贡献，并且提出的 Z 光谱拟合方法能够计算大脑 Z 光谱中的各个分量。因此，以其他 CEST 和 rNOE 的较低贡献计算 Cr-w CEST 对比度是可行的。

"点击查看英文标题和摘要"

Evaluating the feasibility of creatine-weighted CEST MRI in human brain at 7 T using a Z-spectral fitting approach.

The current study aims to evaluate the feasibility of creatine (Cr) chemical exchange saturation transfer (CEST)-weighted MRI at 7 T in the human brain by optimizing the saturation pulse parameters and computing contrast using a Z-spectral fitting approach. The Cr-weighted (Cr-w) CEST contrast was computed from phantoms data. Simulations were carried out to obtain the optimum saturation parameters for Cr-w CEST with lower contribution from other brain metabolites. CEST-w images were acquired from the brains of four human subjects at different saturation parameters. The Cr-w CEST contrast was computed using both asymmetry analysis and Z-spectra fitting approaches (models 1 and 2, respectively) based on Lorentzian functions. For broad magnetization transfer (MT) effect, Gaussian and Super-Lorentzian line shapes were also evaluated. In the phantom study, the Cr-w CEST contrast showed a linear dependence on concentration in physiological range and a nonlinear dependence on saturation parameters. The in vivo Cr-w CEST map generated using asymmetry analysis from the brain represents mixed contrast with contribution from other metabolites as well and relayed nuclear Overhauser effect (rNOE). Simulations provided an estimate for the optimum range of saturation parameters to be used for acquiring brain CEST data. The optimum saturation parameters for Cr-w CEST to be used for brain data were around B1rms = 1.45 μT and duration = 2 seconds. The Z-spectral fitting approach enabled computation of individual components. This also resulted in mitigating the contribution from MT and rNOE to Cr-w CEST contrast, which is a major source of underestimation in asymmetry analysis. The proposed modified z-spectra fitting approach (model 2) is more stable to noise compared with model 1. Cr-w CEST contrast obtained using fitting was 6.98 ± 0.31% in gray matter and 5.45 ± 0.16% in white matter. Optimal saturation parameters reduced the contribution from other CEST effects to Cr-w CEST contrast, and the proposed Z-spectral fitting approach enabled computation of individual components in Z-spectra of the brain. Therefore, it is feasible to compute Cr-w CEST contrast with a lower contribution from other CEST and rNOE.

更新日期：2019-10-14

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