Sensitivity-enhanced chemical exchange saturation transfer (CEST) MRI with least squares optimization of Carr Purcell Meiboom Gill multi-echo echo planar imaging.
Sensitivity-enhanced chemical exchange saturation transfer (CEST) MRI with least squares optimization of Carr Purcell Meiboom Gill multi-echo echo planar imaging.
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DOI：
10.1002/cmmi.1546
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发表时间：
2014-03
影响因子：
--
通讯作者：
Lu, Jie
中科院分区：
文献类型：
--
作者：
Sun, Phillip Zhe;Wang, Yu;Lu, Jie
关键词：
化学交换饱和转移（CEST）成像是一种新的MRI技术，对生物分子、局部pH值和温度敏感，并为体内应用提供了相当大的优势。然而，对于经历缓慢或中间化学交换的稀释CEST试剂，CEST效应的幅度通常很小，需要使用信号平均来增强其灵敏度。考虑到T2引起的信号损失可以通过不对称性分析进行归一化，CEST效应的幅度与回波时间无关。因此，具有多回波回波平面成像（EPI）读出的CEST成像应产生与常规单回波采集相同的CEST效果。重要的是，可以对CEST多回波（CESTme）EPI图像进行平均，以增强CEST MRI灵敏度。本研究的目的是使用具有与生物组织相似的T2的肌酸-琼脂糖凝胶CEST体模来验证CESTme EPI。使用最小二乘优化，我们发现，CESTme序列的灵敏度显着高于传统的单回波CEST-EPI采集。具体而言，来自所提出的CESTme EPI的信噪比（SNR）和对比噪声比（CNR）近似等于通过将标准单回波CEST MRI序列的信号平均值的数量加倍获得的信噪比和对比噪声比。总之，我们的研究结果表明CESTme EPI用于灵敏度增强的CEST成像。
Chemical exchange saturation transfer (CEST) imaging is a novel MRI technique that is sensitive to biomolecules, local pH and temperature, and offers considerable advantages for in vivo applications. However, the magnitude of CEST effect for dilute CEST agents undergoing slow or intermediate chemical exchange is typically small, requiring the use of signal averaging to enhance its sensitivity. Given that T2-induced signal loss can be normalized by asymmetry analysis, the magnitude of CEST effect is independent of echo time. Therefore, CEST imaging with multi-echo echo planar imaging (EPI) readout should yield the same CEST effect as conventional single echo acquisition. Importantly, CEST multi-echo (CESTme) EPI images can be averaged to enhance CEST MRI sensitivity. The goal of this study was to validate CESTme EPI using a creatine-agarose gel CEST phantom with similar T2 as biological tissue. Using least-squares optimization, we found that the sensitivity of CESTme sequence is significantly higher than that obtained by conventional single echo CEST-EPI acquisition. Specifically, signal to noise ratio (SNR) and contrast to noise ratio (CNR) from the proposed CESTme EPI were approximately equivalent to that obtained by doubling the number of signal averages of the standard single echo CEST MRI sequence. In summary, our results demonstrate CESTme EPI for sensitivity-enhanced CEST imaging.
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