Rowland Benjamin, Merugumala Sai K, Liao Huijun, Creager Mark A, Balschi James, Lin Alexander P
Center for Clinical Spectroscopy, Department of Radiology, Brigham and Women's Hospital, Boston, Massachusetts, USA.
Cardiovascular Division, Department of Medicine, Brigham and Women's Hospital, Boston, Massachusetts, USA.
Magn Reson Med. 2016 Sep;76(3):978-85. doi: 10.1002/mrm.25976. Epub 2015 Oct 7.
MR spectroscopy (MRS) typically requires averaging of multiple acquisitions to achieve adequate signal-to-noise ratio (SNR). In systems undergoing dynamic changes this can compromise the temporal resolution of the measurement. One such example is (31) P MRS of exercising skeletal muscle. Spectral improvement by Fourier thresholding (SIFT) offers a way of suppressing noise without averaging. In this study, we evaluate the performance of SIFT in healthy subjects and clinical cases.
(31) P MRS of the calf or thigh muscle of subjects (n = 12) was measured continuously before, during, and after exercise. The data were processed conventionally and with the addition of SIFT before quantifying peak amplitudes and frequencies. The postexercise increase in the amplitude of phosphocreatine was also characterized by fitting with an exponential function to obtain the recovery time constant.
Substantial reductions in the uncertainty of peak fitting for phosphocreatine (73%) and inorganic phosphate (60%) were observed when using SIFT relative to conventional processing alone. SIFT also reduced the phosphocreatine recovery time constant uncertainty by 38%.
SIFT considerably improves SNR, which improved quantification and parameter estimation. It is suitable for any type of time varying MRS and is both straightforward and fast to apply. Magn Reson Med 76:978-985, 2016. © 2015 Wiley Periodicals, Inc.
磁共振波谱（MRS）通常需要对多次采集的数据进行平均处理，以获得足够的信噪比（SNR）。在经历动态变化的系统中，这可能会损害测量的时间分辨率。运动骨骼肌的磷-31磁共振波谱（³¹P MRS）就是这样一个例子。傅里叶阈值光谱改进法（SIFT）提供了一种无需平均即可抑制噪声的方法。在本研究中，我们评估了SIFT在健康受试者和临床病例中的性能。
对12名受试者小腿或大腿肌肉进行³¹P MRS测量，在运动前、运动中和运动后连续进行。在对峰值幅度和频率进行量化之前，对数据进行常规处理，并添加SIFT处理。运动后磷酸肌酸幅度的增加也通过拟合指数函数来表征，以获得恢复时间常数。
与单独的常规处理相比，使用SIFT时观察到磷酸肌酸（73%）和无机磷酸盐（60%）峰值拟合的不确定性大幅降低。SIFT还将磷酸肌酸恢复时间常数的不确定性降低了38%。
SIFT显著提高了信噪比，从而改善了定量分析和参数估计。它适用于任何类型的随时间变化的MRS，应用起来既简单又快速。《磁共振医学》76:978 - 985, 2016。© 2015威利期刊公司。
