Noise correlations and SNR in phased-array MRS
Noise correlations and SNR in phased-array MRS
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DOI：
10.1002/nbm.1429
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发表时间：
2010-01-01
影响因子：
2.9
通讯作者：
Landini, L.
中科院分区：
文献类型：
--
作者：
Martini, N.;Santarelli, M. F.;Landini, L.
通过多个接收器线圈对磁共振光谱（MRS）信号的采集可以提高信噪比（SNR），或者可以减少维持可靠SNR的扫描时间。但是，在MRS研究中使用分阶段的阵列线圈需要有效的数据处理和数据组合技术，以利用阶段阵列线圈采集方法的灵敏度提高。本文介绍了一种新的方法，即使在采集通道之间存在相关噪声的情况下，通过分阶段阵列线圈获得的MRS信号组合。实际上，尽管已经显示出电气和磁耦合机制在线圈中产生相关噪声，但先前为MRS数据组合开发的算法忽略了这种效果。提出的方法利用了噪声去相关阶段来最大化组合光谱的SNR。在噪声向量是正交的子空间中，特别利用主体成分分析（PCA）将获得的光谱投射出来。在此子空间中，SNR加权方法将提供最佳的总体SNR。该方法的性能评估是在模拟的H-1-MRS信号上进行的，并使用市售的8个基于分阶段的阵列线圈在Phantom H-1-MR光谱上获得实验结果。由于最佳的线圈设计，元素之间的噪声相关性通常很低，从而导致视野中心（FOV）中的SNR增益（约0.5％）。在外围FOV区域发现了更大的SNR改进。版权（C）2009 John Wiley＆Sons，Ltd。
The acquisition of magnetic resonance spectroscopy (MRS) signals by multiple receiver coils can improve the signal-to-noise ratio (SNR) or alternatively can reduce the scan time maintaining a reliable SNR. However, using phased array coils in MRS studies requires efficient data processing and data combination techniques in order to exploit the sensitivity improvement of the phased array coil acquisition method. This paper describes a novel method for the combination of MRS signals acquired by phased array coils, even in presence of correlated noise between the acquisition channels. In fact, although it has been shown that electric and magnetic coupling mechanisms produce correlated noise in the coils, previous algorithms developed for MRS data combination have ignored this effect. The proposed approach takes advantage of a noise decorrelation stage to maximize the SNR of the combined spectra. In particular Principal Component Analysis (PCA) was exploited to project the acquired spectra in a subspace where the noise vectors are orthogonal. In this subspace the SNR weighting method will provide the optimal overall SNR. Performance evaluation of the proposed method is carried out on simulated H-1-MRS signals and experimental results are obtained on phantom H-1-MR spectra using a commercially available 8-element phased array coil. Noise correlations between elements were generally low due to the optimal coil design, leading to a fair SNR gain (about 0.5%) in the center of the field of view (FOV). A greater SNR improvement was found in the peripheral FOV regions. Copyright (C) 2009 John Wiley & Sons, Ltd.