Beck Michael J, Parker Dennis L, Hadley J Rock
Department of Radiology and Imaging Sciences, Utah Center for Advanced Imaging Research, University of Utah, Salt Lake City 84132, USA.
Concepts Magn Reson Part B Magn Reson Eng. 2020;2020. doi: 10.1155/2020/8828047. Epub 2020 Dec 15.
Phased array (PA) receive coils are built such that coil elements approximate independent antenna behavior. One method of achieving this goal is to use an available decoupling method to decouple adjacent coil elements. The purpose of this work was to compare the relative performance of two decoupling methods as a function of variation in sample load. Two PA receive coils with 5 channels (5-ch) each, equal outer dimensions, and formed on 12 cm diameter cylindrical phantoms of conductivities 0.3, 0.6, and 0.9 S/m were evaluated for relative signal-to-noise ratio (SNR) and parallel imaging performance. They were only tuned and matched to the 0.6 S/m phantom. Simulated and measured axial, sagittal, and coronal 5-ch PA coil SNR ratios were compared by dividing the overlap by the capacitive decoupled coil SNR results. Issues related to the selection of capacitor values for the two decoupling methods were evaluated by taking the ratio of the match and tune capacitors for large and small 2 channel (2-ch) PA coils. The SNR ratios showed that the SNR of the two decoupling methods were very similar. The inverse geometry-factor maps showed similar but better overall parallel imaging performance for the capacitive decoupled method. The quotients for the 2-ch PA coils' maximum and minimum capacitor value ratios are 3.28 and 1.38 for the large and 3.28 and 2.22 for the small PA. The results of this paper demonstrate that as the sample load varies, the capacitive and overlap decoupling methods are very similar in relative SNR and this similarity continues for parallel imaging performance. Although, for the 5-ch coils studied, the capacitive decoupling method has a slight SNR and parallel imaging advantage and it was noted that the capacitive decoupled coil is more likely to encounter unbuildable PA coil configurations.
相控阵（PA）接收线圈的构建方式使得线圈元件近似独立天线行为。实现这一目标的一种方法是使用可用的去耦方法来解耦相邻线圈元件。这项工作的目的是比较两种去耦方法在样本负载变化时的相对性能。对两个各有5个通道（5-ch）、外径相等且形成于直径12 cm、电导率分别为0.3、0.6和0.9 S/m的圆柱形体模上的PA接收线圈，评估其相对信噪比（SNR）和平行成像性能。它们仅针对0.6 S/m的体模进行调谐和匹配。通过将重叠去耦线圈的SNR结果除以电容性去耦线圈的SNR结果，比较模拟和测量的轴向、矢状面和冠状面5-ch PA线圈的SNR比值。通过计算大、小2通道（2-ch）PA线圈的匹配电容和调谐电容的比值，评估与两种去耦方法的电容值选择相关的问题。SNR比值表明，两种去耦方法的SNR非常相似。反几何因子图显示，电容性去耦方法的整体平行成像性能相似但更好。对于大的2-ch PA线圈，最大和最小电容值的商分别为3.28和1.38，对于小的PA线圈则为3.28和2.22。本文结果表明，随着样本负载的变化，电容性和重叠去耦方法在相对SNR方面非常相似，并且这种相似性在平行成像性能方面也持续存在。尽管对于所研究的5-ch线圈，电容性去耦方法在SNR和平行成像方面有轻微优势，但需要注意的是，电容性去耦线圈更有可能遇到无法构建的PA线圈配置。
