Optimizing the ICE decoupling element distance to improve monopole antenna arrays for 7 Tesla MRI

Abstract

The induced current elimination (ICE) method has been previously applied to decouple monopole coil arrays in ultrahigh field MRI. However, the method creates low B1+ spots near the decoupling elements. In this study, we aim to improve the performance of ICE-decoupled monopole array in human head imaging at 7 Tesla. Eight-channel ICE-decoupled monopole arrays were optimized by varying the position of the decoupling elements. A series of numerical studies were performed using the co-simulation method. In simulation, decoupling performance, quality (Q−) values and transmit field (B1+) were comparatively investigated. In addition, we constructed an optimized ICE-decoupled monopole array and compared its performance with the unoptimized array. The simulation results showed that a good trade-off between decoupling and B1+ loss can be obtained when decoupling elements were moved 2.5-cm away from coil elements. This was validated by in-vivo MR imaging using the constructed array. Compared with the unoptimized ICE decoupled monopole array, the optimized array had a more homogeneous transmit field and no dark spots or signal cancellations in the MR images.

A Tiny 2.4 GHz Monopole Water Antenna

“…The same results are expected to be obtained by replacing the monopole electrode with a planar or three-dimensional antenna [6,8,17,21,23]. This research method can be applied to seawater and freshwater wireless communication and biotechnology fields [4,7,10,22].…”

The dual‐mode dipole: A new array element for 7T body imaging with reduced SAR

“…To avoid mutual coupling between two dipoles, several resonant decoupling techniques can be used. [20][21][22][23] However, no resonant decoupling techniques applicable to multi-element dipole arrays for body imaging with arbitrary shimming phases have been demonstrated so far. In this situation, the only way to increase the number of array channels and avoid any further reduction in inter-element distance, is to use modified multi-mode elements instead of single-mode dipoles.…”

“…However, increasing the number of elements in dipole arrays is intrinsically limited by inter‐element coupling, which leads to difficulties in tuning and matching of individual array elements and unacceptably high scattering power losses. To avoid mutual coupling between two dipoles, several resonant decoupling techniques can be used . However, no resonant decoupling techniques applicable to multi‐element dipole arrays for body imaging with arbitrary shimming phases have been demonstrated so far.…”

New resonator geometries for ICE decoupling of loop arrays

“…The method was later extended for L / C loop arrays [25], monopole arrays [26] and dipole arrays [27]. Compared to traditional decoupling methods that are challenged in light loading cases, ICE decoupling shows excellent decoupling performance in both heavy and light loading conditions [25,28].…”