On the origins of chemical exchange saturation transfer (CEST) contrast in tumors at 9.4 T.
On the origins of chemical exchange saturation transfer (CEST) contrast in tumors at 9.4 T.
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DOI：
10.1002/nbm.3075
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发表时间：
2014-04
影响因子：
2.9
通讯作者：
Gore, John C.
中科院分区：
文献类型：
--
作者：
Xu, Junzhong;Zaiss, Moritz;Zu, Zhongliang;Li, Hua;Xie, Jingping;Gochberg, Daniel F.;Bachert, Peter;Gore, John C.
化学交换饱和转移 (CEST) 提供了一种通过其对水信号的影响来检测组织内可交换质子的间接方法。先前的研究表明，酰胺质子转移 (APT) 成像（CEST 的一种特殊形式）可检测内源性酰胺质子，共振频率偏移距水低场 3.5 ppm，因此可能对肿瘤中移动蛋白/肽的变化敏感。然而，由于CEST测量受到各种混杂效应的影响，例如溢出饱和、磁化转移（MT）和MT不对称性，肿瘤中APT信号增加的机制或程度尚不确定。除了 APT 之外，来自水的核奥弗豪瑟增强 (NOE) 效应也可能提供有关组织成分的独特信息。本研究对APT、NOE等几个磁共振参数进行了综合测量和比较，以阐明9.4T肿瘤中APT和NOE对比的起源。除了传统的 CEST 方法之外，还应用了新的内在逆度量来校正松弛和其他效应。经过溢出、MT和T1效应的校正后，发现肿瘤中校正的APT与正常组织没有显着差异，但肿瘤中校正的NOE效应与正常组织相比显着降低。生化测量证实，所研究的肿瘤中蛋白质含量没有显着增加，与校正的 APT 测量和之前的文献一致，而 qMT 数据显示肿瘤中固定大分子的分数减少。我们的结果可能有助于更好地理解肿瘤中 CEST 成像所描绘的对比度，以及改进癌症成像的 APT 和 NOE 测量的开发。
Chemical exchange saturation transfer (CEST) provides an indirect means to detect exchangeable protons within tissues through their effects on the water signal. Previous studies have suggested that amide proton transfer (APT) imaging, a specific form of CEST, detects endogenous amide protons with a resonance frequency offset 3.5 ppm downfield from water, and thus may be sensitive to variations of mobile proteins/peptides in tumors. However, since CEST measurements are influenced by various confounding effects, such as spillover saturation, magnetization transfer (MT) and MT asymmetry, the mechanism or degree of increased APT signal in tumors are not certain. In addition to APT, nuclear Overhauser enhancement (NOE) effects upfield from water may also provide distinct information about tissue composition. In the current study, APT, NOE and several other magnetic resonance parameters were measured and compared comprehensively in order to elucidate the origins of APT and NOE contrasts in tumors at 9.4T. In addition to conventional CEST methods, a new intrinsic inverse metric was applied to correct for relaxation and other effects. After corrections for spillover, MT and T1 effects, corrected APT in tumors was found not significantly different from normal tissues, but corrected NOE effects in tumors showed significant decreases compared with normal tissues. Biochemical measurements verified that there is no significant enhancement of protein contents in the tumors studied, consistent with corrected APT measurements and previous literature while qMT data showed decreases in the fractions of immobile macromolecules in tumors. Our results may assist better understanding the contrast depicted by CEST imaging in tumors, and the development of improved APT and NOE measurements for cancer imaging.
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影响因子：
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作者：
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