COMBINING CEST AND SPIN-LOCK TECHNIQUES TO STUDY INTERMEDIATE CHEMICAL EXCHANGE

这个子项目是利用资源的许多研究子项目之一。 由NIH/NCRR资助的中心拨款提供。对子项目的主要支持 子项目的首席调查员可能是由其他来源提供的， 包括美国国立卫生研究院的其他来源。为子项目列出的总成本可能 表示该子项目使用的中心基础设施的估计数量， 不是由NCRR赠款提供给次级项目或次级项目工作人员的直接资金。 质子交换成像很重要，因为它可以用常规MRI显示和量化特定代谢物的分布。目前的汇率调节磁共振成像方法存在对比度差以及影响汇率的混杂因素。化学交换饱和转移(CEST)已成为间接检测溶质含量和交换相关性质的最常用机制。CEST对比要求保留水和CEST试剂上的可交换质子之间的离散化学位移差异，因此对慢到中等交换速率域(Ksw d？)最敏感。虽然CEST对慢质子交换最敏感，但旋转框架中的自旋-晶格弛豫时间(t1？)是另一种依赖于化学交换的技术，该技术对较快的交换过程更敏感，但不是特定于一个化学交换位置。 在这项研究中，我们正在开发一种方法，将CEST MRI对慢交换过程的敏感性与T1？MRI对快速交换过程的敏感性(CESTrho)相结合。由此得到的水信号，称为CESTrho信号，将专用于CEST饱和脉冲的自旋晶格驰豫效应以及T1p脉冲的依赖于化学交换的横向驰豫效应。我们假设，这一序列应该在较大的汇率范围内表现出更高的敏感性。此外，CESTrho信号随溶质浓度线性变化，可用于量化质子浓度。最后，我们认为这个新的序列可以被定制为对大范围汇率的汇率变化不敏感。 研究目标： 1.开发一种将CEST和自旋锁定技术相结合的方法，可用于产生图像对比度和量化具有可交换质子的代谢物。 2.确定这一新序列对质子浓度的依赖关系，以及设计一种磁化准备方案，使其对化学交换的变化不敏感。 3.在动物体内测试这个新序列，以检测代谢物浓度的变化

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. Proton exchange imaging is important as it allows for visualization and quantification of the distribution of specific metabolites with conventional MRI. Current exchange mediated MRI methods suffer from poor contrast as well as confounding factors that influence exchange rates. Chemical Exchange Saturation Transfer (CEST) has become the most popular mechanism to indirectly detect solute content and exchange-related properties. CEST contrast requires that a discrete chemical shift difference between water and the exchangeable proton on the CEST agent is preserved, and is thus most sensitive to the slow to intermediate exchange rate domain (ksw d ¿). While CEST is most sensitive to slow proton exchange, spin-lattice relaxation time in the rotating frame (T1¿) is another technique that depends on chemical exchange which is more sensitive to faster exchange processes but is not specific to one chemical exchange site. In this study, we are developing a method that combines the sensitivities of CEST MRI to slow exchange processes with the sensitivity of T1¿ MRI to fast exchange processes (CESTrho). The resulting acquired water signal, referred to as the CESTrho signal, will be specific to the spin-lattice relaxation effects of the CEST saturation pulse as well as the chemical exchange dependent transverse relaxation effects of the T1p pulse. We hypothesize that this sequence should show increased sensitivity along a large spectrum of exchange rates. Further, the CESTrho signal varies linearly with solute concentration and can be used to quantify proton concentration. Finally, we believe that this new sequence can be customized to be insensitive to changes in exchange rate for a large range of exchange rates. Study Aims: 1. To develop a method to that combines CEST and spin locking techniques that can be used to create image contrast and quantify metabolites with exchangeable protons. 2. To determine the dependence of this new sequence on proton concentration, as well as to devise a magnetization preparation scheme to make it insensitive to changes in chemical exchange. 3. To test this new sequence in vivo in animals to detect changes in metabolite concentrations