Martinez Luque Eva, Sung Dongsuk, Risk Benjamin B, Goldberg Rachel M, Fleischer Candace C
Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, Georgia, USA.
Department of Biostatistics and Bioinformatics, Emory University, Atlanta, Georgia, USA.
NMR Biomed. 2025 Jun;38(6):e70044. doi: 10.1002/nbm.70044.
Magnetic resonance spectroscopy (MRS) enables noninvasive quantification of metabolites, but its utility in vivo can be limited by low signal-to-noise ratios (SNRs) and long acquisition times. The use of ultrahigh-field (UHF) strengths (> 3 T) combined with multichannel phased receive arrays can improve spectral SNR. A crucial step in the use of multichannel arrays is the combination of spectra acquired from individual coil channels. We previously developed a coil combination method at 3 T, optimized truncation to integrate multichannel MRS data using rank-R singular value decomposition (OpTIMUS), which uses noise-whitened windowed spectra and iterative rank-R singular value decomposition (SVD) to combine multichannel MRS data. Here, we evaluated OpTIMUS for combination of MR spectra acquired using a multichannel phased array at 7 T and compared spectral SNR and metabolite quantification with spectra combined using whitened SVD (WSVD), signal/noise squared (S/N), and the Brown method. Data were acquired from 14 healthy volunteers, including five with data acquired at both 3 and 7 T, and from nine people living with HIV. Spectra combined using OpTIMUS resulted in a higher SNR compared to the three other methods, consistent with our prior results at 3 T. With half the number of averages (N = 32), spectra combined with OpTIMUS had higher SNR compared to spectra using the Brown method with 64 averages. Additionally, spectra combined using OpTIMUS at 7 T were compared to spectra acquired at 3 T with the same number of averages (N = 64) or matched acquisition times (N = 110 averages), and spectral fitting was consistently improved at 7 T even when comparable SNR was obtained at 3 T. The ability to increase SNR and maintain spectral quality by optimizing spectral coil combination has the potential to reduce scan time, a key challenge for routine clinical use of MRS.
磁共振波谱（MRS）能够对代谢物进行无创定量分析，但其在体内的应用可能会受到低信噪比（SNR）和长采集时间的限制。使用超高场（UHF）强度（> 3 T）并结合多通道相控接收阵列可以提高谱线的SNR。使用多通道阵列的一个关键步骤是将从各个线圈通道采集的谱线进行合并。我们之前开发了一种3 T场强下的线圈合并方法，即使用秩-R奇异值分解（OpTIMUS）优化截断以整合多通道MRS数据，该方法使用噪声白化窗口谱线和迭代秩-R奇异值分解（SVD）来合并多通道MRS数据。在此，我们评估了OpTIMUS用于合并7 T场强下使用多通道相控阵列采集的磁共振谱线，并将谱线的SNR和代谢物定量分析结果与使用白化SVD（WSVD）、信号/噪声平方（S/N）和布朗方法合并的谱线进行了比较。数据采集自14名健康志愿者，其中5名同时在3 T和7 T场强下采集了数据，另外还采集自9名艾滋病病毒感染者。与其他三种方法相比，使用OpTIMUS合并的谱线具有更高的SNR，这与我们之前在3 T场强下的结果一致。在平均次数减半（N = 32）的情况下，使用OpTIMUS合并的谱线比使用64次平均的布朗方法合并的谱线具有更高的SNR。此外，将7 T场强下使用OpTIMUS合并的谱线与相同平均次数（N = 64）或匹配采集时间（N = 110次平均）的3 T场强下采集的谱线进行了比较，即使在3 T场强下获得了可比的SNR，7 T场强下的谱线拟合也始终得到改善。通过优化谱线线圈合并来提高SNR并保持谱线质量的能力有可能减少扫描时间，这是MRS在常规临床应用中的一个关键挑战。
