3T人腦磁共振多通道勻場線圈之優化

Abstract

一個均勻的主磁場是高品質磁共振影像或是頻譜的重要保障。然而，主磁場的靜態或者動態的擾動，使得磁共振信號減弱，並產生相應的偽影。 使用多通道勻場線圈能夠幫助克服主磁場局部不均勻多問題。在此基礎之上，發展出了整合射頻信號接收的均場線圈（iPRES）。然而， 將勻場線圈整合到多通道射頻線圈中，往往會導致射頻線圈的信噪比下降。在這篇文章中，我們發現，將勻場線圈與射頻線圈垂直放置，不僅僅能夠減少勻場線圈對於射頻線圈的干擾，還能夠保持勻場線圈的勻場效果。我們設計、製作了一個7通道的正交均場線圈，用來展示我們的想法

High-quality magnetic resonance imaging and spectroscopic measurements require a highly homogeneous magnetic field. However, both static and dynamic variations in the main magnetic field (B0) cause various artifacts. These artifacts can be corrected by providing a compensating magnetic field generated by shim coils. Different from correcting global magnetic field inhomogeneity by large volume shim coils, localized off-resonance can be corrected by using multiple shim coils. Previously, arrays of circular shim coils and integrated radio-frequency (RF)-shimming coils have been implemented. However, these designs cause non-negligible interference to RF coils and consequent image quality degradation. Here we propose a new design of multi-coil shimming, where shim coils and nearby RF coils are arranged on two orthogonal planes. This orthogonal positioning minimizes the interference between RF coils and shim coils, while multiple shim coils provide similar shimming performance like previous multi-coil shim array designs. We use both simulatiosn and phantom experiments to demonstrate the feasibility of this design.