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R1ρ sensitivity to pH and other compounds at clinically accessible spin-lock fields in the presence of proteins.
NMR in Biomedicine ( IF 2.9 ) Pub Date : 2019-11-19 , DOI: 10.1002/nbm.4217
Nana Owusu 1, 2 , Casey P Johnson 3 , William Kearney 1 , Dan Thedens 1 , John Wemmie 4 , Vincent A Magnotta 1, 2, 4
Affiliation  

Numerous human diseases involve abnormal metabolism, and proton exchange is an effective source of magnetic resonance imaging (MRI) contrast for assessing metabolism. One MRI technique that capitalizes on proton exchange is R1 relaxation in the rotating frame (R1ρ ). Here, we investigated the sensitivity of R1ρ to various proton-exchange mechanisms at spin-lock pulses within Food and Drug Administration (FDA) safety guidelines for radiofrequency-induced heating. We systematically varied pH known to change the rate of proton exchange as well as the glucose and lysine concentrations, thus changing the number of amide, hydroxyl and amine exchangeable sites in a series of egg-white albumin phantoms. The resulting effects on quantitative relaxation time measurements of R1ρ , R1 and R2 were observed at 3 T. Using spin-lock amplitudes available for human imaging (less than 23.5 μT) at near physiologic temperatures, we found R1ρ was more sensitive to physiologic changes in pH than to changes in glucose and lysine concentrations. In addition, R1ρ was more sensitive to pH changes than R1 and R2 . Models of proton exchange fitted to the relaxation measurements suggest that amide groups were the primary source of pH sensitivity. Together, these experiments suggest an optimal spin-lock amplitude for measuring pH changes while not exceeding FDA-subject heating limitations.

中文翻译:

在蛋白质存在的情况下,R1ρ 在临床上可接近的自旋锁场对 pH 值和其他化合物的敏感性。

许多人类疾病都涉及代谢异常,而质子交换是磁共振成像 (MRI) 对比评估代谢的有效来源。一种利用质子交换的 MRI 技术是旋转框架中的 R1 弛豫 (R1ρ)。在这里,我们在食品和药物管理局 (FDA) 射频诱导加热安全指南中研究了 R1ρ 对自旋锁定脉冲中各种质子交换机制的敏感性。我们系统地改变已知会改变质子交换速率以及葡萄糖和赖氨酸浓度的 pH 值,从而改变一系列蛋清白蛋白幻影中酰胺、羟基和胺可交换位点的数量。在 3 T 下观察到对 R1ρ、R1 和 R2 的定量弛豫时间测量产生的影响。在接近生理温度下使用可用于人体成像的自旋锁振幅(小于 23.5 μT),我们发现 R1ρ 对 pH 的生理变化比对葡萄糖和赖氨酸浓度的变化更敏感。此外,R1ρ 比 R1 和 R2 对 pH 变化更敏感。适合弛豫测量的质子交换模型表明酰胺基团是 pH 敏感性的主要来源。总之,这些实验提出了测量 pH 变化的最佳自旋锁幅度,同时不超过 FDA 主题的加热限制。适合弛豫测量的质子交换模型表明酰胺基团是 pH 敏感性的主要来源。总之,这些实验提出了测量 pH 变化的最佳自旋锁幅度,同时不超过 FDA 主题的加热限制。适合弛豫测量的质子交换模型表明酰胺基团是 pH 敏感性的主要来源。总之,这些实验提出了测量 pH 变化的最佳自旋锁幅度,同时不超过 FDA 主题的加热限制。
更新日期:2020-01-21
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