Department of Radiology, University of Washington, Seattle, Washington, USA; Department of Radiology, Seattle Children's Hospital, Seattle, Washington, USA.
J Magn Reson Imaging. 2011 Dec;34(6):1414-21. doi: 10.1002/jmri.22679. Epub 2011 Oct 5.
To demonstrate that, when injecting an artificial reference signal for quantitation purposes, the real and artificial signals can be acquired separately, using a single radiofrequency (RF) channel, with no loss of fidelity. Conversion of MR signals to units of concentration can be simplified by injection of a precalibrated, artificial reference signal, or pseudo-signal. In previous implementations, the pseudo-signal was acquired simultaneously with the real signals arising from the sample and this requires a second, integrated RF channel.
We used in vivo spectroscopy and in vitro imaging measurements to test the validity of the separate acquisition method.
There was very strong correlation (r = 0.94; P = 0.02) between the in vivo concentrations determined with separate and simultaneous acquisition methods. The in vitro measurements validated that the separate acquisition method compensates for differences in coil loading conditions as well as the simultaneous acquisition method.
Separate acquisition eliminates the need for a second RF channel, which allows easier implementation at sites that have only one channel available, and relaxes the constraints on the number and amplitude of pseudo-signals. This flexibility can be exploited to increase the signal to noise ratio of the pseudo-signal and reduce variability when making the conversion to units of concentration.
证明在为定量目的注入人工参考信号时，可以使用单个射频 (RF) 通道分别获取真实信号和人工信号，而不会损失保真度。通过注入经过预校准的人工参考信号或伪信号，可以简化将 MR 信号转换为浓度单位。在以前的实现中，伪信号是与样品产生的真实信号同时采集的，这需要第二个集成的 RF 通道。
我们使用体内光谱和体外成像测量来测试单独采集方法的有效性。
单独采集和同时采集方法确定的体内浓度之间存在很强的相关性（r = 0.94；P = 0.02）。体外测量验证了单独采集方法可以补偿线圈加载条件的差异以及同时采集方法。
单独采集消除了对第二个 RF 通道的需求，这使得在只有一个通道可用的站点更容易实现，并放宽了对伪信号数量和幅度的限制。这种灵活性可以用来提高伪信号的信噪比，并在转换为浓度单位时减少可变性。
