Development and validation of a smoothing-splines-based correction method for improving the analysis of CEST-MR images
Development and validation of a smoothing-splines-based correction method for improving the analysis of CEST-MR images
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DOI：
10.1002/cmmi.240
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发表时间：
2008-07-01
影响因子：
--
通讯作者：
Aime, S.
中科院分区：
文献类型：
--
作者：
Stancanello, J.;Terreno, E.;Aime, S.
化学交换饱和转移（CEST）成像是一种依赖于含有可交换质子池的内源性或外源分子的新兴MRI技术。水谐振频率的异质性抵消在CEST-MR图像中的伪影中起关键作用。为了限制这一缺点，一种基于平滑序列的新方法，用于拟合和纠正Z-Spectra，以补偿没有任何先验模型的低信噪比（SNR）。通过旨在抑制噪声的平滑术语平滑的花纹，通过平滑的花键来插值。因此，使用水频率偏移量（“零”地图）的图来正确计算每个体素的饱和转移（ST）。进行仿真以根据SNR的改进将方法与多项式和零校正的花样进行比较。在不同浓度下含有含有Lipocest剂溶液的毛细血管的体外采集进行了实验验证模拟的结果。此外，对注射Lipocest剂的牛肌肉质量的离体研究是作为增加脉冲功率的函数。模拟和实验的结果强调了适当的“零”校正的重要性（幻象和离体制剂中虚拟的CEST信号降低了15％），并证明了与先前发布的方法相比，该方法通常是更准确的，通常提供SNR在不同的模拟和实验嘈杂条件下高于5。总之，提出的方法为CEST研究提供了准确的工具。版权（C）2008 John Wiley＆Sons，Ltd。
Chemical exchange saturation transfer (CEST) imaging is an emerging MRI technique relying on the use of endogenous or exogenous molecules containing exchangeable proton pools. The heterogeneity of the water resonance frequency offset plays a key role in the occurrence of artifacts in CEST-MR images. To limit this drawback, a new smoothing-splines-based method for fitting and correcting Z-spectra in order to compensate for low signal-to-noise ratio (SNR) without any a priori model was developed. Global and local voxel-by-voxel Z-spectra were interpolated by smoothing splines with smoothing terms aimed at suppressing noise. Thus, a map of the water frequency offset ('zero' map) was used to correctly calculate the saturation transfer (ST) for each voxel. Simulations were performed to compare the method to polynomials and zero-only-corrected splines on the basis of SNR improvement. In vitro acquisitions of capillaries containing solutions of LIPOCEST agents at different concentrations were performed to experimentally validate the results from simulations. Additionally, ex vivo investigations of bovine muscle mass injected with LIPOCEST agents were performed as a function of increasing pulse power. The results from simulations and experiments highlighted the importance of a proper 'zero' correction (15% decrease of fictitious CEST signal in phantoms and ex vivo preparations) and proved the method to be more accurate compared with the previously published ones, often providing a SNR higher than 5 in different simulated and experimentally noisy conditions. In conclusion, the proposed method offers an accurate tool in CEST investigation. Copyright (C) 2008 John Wiley & Sons, Ltd.