Simplified quantification of labile proton concentration-weighted chemical exchange rate (k(ws) ) with RF saturation time dependent ratiometric analysis (QUESTRA): normalization of relaxation and RF irradiation spillover effects for improved quantitative chemical exchange saturation transfer (CEST) MRI.
Simplified quantification of labile proton concentration-weighted chemical exchange rate (k(ws) ) with RF saturation time dependent ratiometric analysis (QUESTRA): normalization of relaxation and RF irradiation spillover effects for improved quantitative chemical exchange saturation transfer (CEST) MRI.
复制标题
使用RF饱和时间依赖性比率分析（QUESTRA）的简化质子浓度加权化学汇率（K（WS））的简化定量：弛豫和RF辐照溢出效应的归一化，以改善定量化学交换饱和转移（CEST）MRI。
DOI：
10.1002/mrm.23068
复制
发表时间：
2012-04
影响因子：
3.3
通讯作者：
Sun, Phillip Zhe
中科院分区：
文献类型：
--
作者：
Sun, Phillip Zhe
关键词：
化学交换饱和转移（CEST） MRI是一种新兴的成像技术，能够检测稀释蛋白/肽和微环境特性，在体内应用前景广阔。然而，CEST MRI对比比较复杂，不仅与不稳定质子浓度和交换速率有关，还与场强、射频照射方案等实验条件有关。此外，最佳射频辐照功率取决于交换率，为了优化CEST MRI实验，必须估计交换率。虽然已经提出了使用修正Bloch-McConnell方程进行数值拟合、量化汇率随RF饱和时间和功率（QUEST和QUESP）的方法来解决这种关系，但它们需要多参数非线性拟合和精确的弛豫测量。我们在这里的工作扩展了QUEST算法，采用比率分析（QUESTRA）对不稳定和参考频率下的磁化传递比（MTR）进行归一化，有效地消除了混杂松弛和射频溢出效应。具体来说，QUESTRA对比剂以逆汇率（kws）决定的速率接近其稳态单指数，对体积水T1、T2、射频功率和化学位移的依赖很小。所提出的算法在数值上得到了证实，并使用连续滴定pH区室的组织样幻影进行了实验验证。
Chemical exchange saturation transfer (CEST) MRI is an emerging imaging technique capable of detecting dilute proteins/peptides and microenvironmental properties, with promising in vivo applications. However, CEST MRI contrast is complex, varying not only with the labile proton concentration and exchange rate, but also with experimental conditions such as field strength and RF irradiation scheme. Furthermore, the optimal RF irradiation power depends on the exchange rate, which must be estimated in order to optimize the CEST MRI experiments. Although methods including numerical fitting with modified Bloch-McConnell equations, quantification of exchange rate with RF saturation time and power (QUEST and QUESP), have been proposed to address this relationship, they require multiple-parameter non-linear fitting and accurate relaxation measurement. Our work here extended the QUEST algorithm with ratiometric analysis (QUESTRA) that normalizes the magnetization transfer ratio (MTR) at labile and reference frequencies, which effectively eliminates the confounding relaxation and RF spillover effects. Specifically, the QUESTRA contrast approaches its steady state mono-exponentially at a rate determined by the reverse exchange rate (kws), with little dependence on bulk water T1, T2, RF power and chemical shift. The proposed algorithm was confirmed numerically, and validated experimentally using a tissue-like phantom of serially titrated pH compartments.
登录
查看更多内容
影响因子：
3.3
作者：
Stollberger, R;Wach, P
通讯作者：
Wach, P
CEST-FISP：一种在7 t处的快速化学交换饱和转移MRI的新技术。
影响因子：
3.3
作者：
Shah, T.;Lu, L.;Dell, K. M.;Pagel, M. D.;Griswold, M. A.;Flask, C. A.
通讯作者：
Flask, C. A.
影响因子：
3.3
作者：
McMahon, Michael T.;Gilad, Assaf A.;DeLiso, Marco A.;Berman, Stacey D. Cromer;Bulte, Jeff W. M.;van Zijl, Peter C. M.
通讯作者：
van Zijl, Peter C. M.
影响因子：
4.4
作者：
FORSEN, S;HOFFMAN, RA
通讯作者：
HOFFMAN, RA
影响因子：
3.3
作者：
Sun, Phillip Zhe;Cheung, Jerry S.;Wang, Enfeng;Benner, Thomas;Sorensen, A. Gregory
通讯作者：
Sorensen, A. Gregory