Department of Radiology, University of Washington, Seattle, Washington, United States of America.
PLoS One. 2010 Dec 28;5(12):e15166. doi: 10.1371/journal.pone.0015166.
Accurate conversion of magnetic resonance spectra to quantitative units of concentration generally requires compensation for differences in coil loading conditions, the gains of the various receiver amplifiers, and rescaling that occurs during post-processing manipulations. This can be efficiently achieved by injecting a precalibrated, artificial reference signal, or pseudo-signal into the data. We have previously demonstrated, using in vitro measurements, that robust pseudo-signal injection can be accomplished using a second coil, called the injector coil, properly designed and oriented so that it couples inductively with the receive coil used to acquire the data. In this work, we acquired nonlocalized phosphorous magnetic resonance spectroscopy measurements from resting human tibialis anterior muscles and used pseudo-signal injection to calculate the Pi, PCr, and ATP concentrations. We compared these results to parallel estimates of concentrations obtained using the more established phantom replacement method. Our results demonstrate that pseudo-signal injection using inductive coupling provides a robust calibration factor that is immune to coil loading conditions and suitable for use in human measurements. Having benefits in terms of ease of use and quantitative accuracy, this method is feasible for clinical use. The protocol we describe could be readily translated for use in patients with mitochondrial disease, where sensitive assessment of metabolite content could improve diagnosis and treatment.
准确地将磁共振波谱转换为浓度的定量单位通常需要补偿线圈负载条件、各个接收器放大器的增益以及在后处理操作过程中发生的重新缩放之间的差异。通过向数据中注入经过预校准的人工参考信号或伪信号，可以有效地实现这一点。我们之前已经通过体外测量证明，通过适当设计和定向的第二个线圈（称为注入线圈）可以实现稳健的伪信号注入，该线圈与用于获取数据的接收线圈进行感应耦合。在这项工作中，我们从休息的人类胫骨前肌采集了非局部磷磁共振波谱测量值，并使用伪信号注入来计算 Pi、PCr 和 ATP 浓度。我们将这些结果与使用更成熟的伪影替换方法获得的浓度的平行估计进行了比较。我们的结果表明，感应耦合的伪信号注入提供了一个稳健的校准因子，该因子不受线圈负载条件的影响，适合用于人体测量。该方法在易用性和定量准确性方面具有优势，在临床应用中是可行的。我们描述的方案可以很容易地转化为用于线粒体疾病患者，其中对代谢物含量的敏感评估可以改善诊断和治疗。
