Over-overlapped loop arrays: A numerical study

Abstract

Arrays of coils are commonly used in MRI both for reception and in parallel transmission to alleviate radiofrequency field inhomogeneities at high fields. Most designs typically overlap loop elements by a critical area (approximately 10 %) to minimize mutual inductive couplings. With this geometrical constraint, loop sizes have to be reduced to accommodate large numbers of coils for a given coverage. However, the contribution of coil noise to total noise increases as each coil size decreases, which reduces overall signal-to-noise ratio (SNR), especially in deeper regions of the sample volume. Here we propose arrays designs using elements that overlap much more (overoverlapped), and using numerical calculations we investigate their performance compared to two kinds of conventionally overlapped arrays (one with the same coil size but smaller coil number, and one with the same coil number but smaller coil size). Our simulation results show that the over-overlapped array can considerably increase the central SNR when coil noise dominates.

Effects of Non-symmetrical Current Distribution Controlled by Capacitor Placement in Loop Coils at 300 MHz MRI

“…FDTD simulations of array coil with phantom and Duke model. We also performed EM simulations on combinations of two coils to analyze the performance in terms of coupling [25,26], as shown in Fig. 4c.…”

Investigating Local Receive Arrays in tcMRgFUS System and Their Influence by Passive Antennas: A Simulation Study

“…The coil noise matrices ( R c ), including the conductor noise and component noise, were calculated by integrating power dissipation over all conductors ( P cond ) and all components ( P compon ), as shown in Equation (3) [ 28 ]. SNR is proportional to the ratio between the and the total noise and is evaluated using Equation (4) .…”

Study on the Effect of Non-Symmetrical Current Distribution Controlled by Capacitor Placement in Radio-Frequency Coils for 7T MRI

“…The coils were placed on top of the phantom as the loading condition ( Figure 3 b) for tuning and matching. We tested the coupling between each pair of coils with the same capacitor positions by measuring the S 21 parameter [ 36 , 37 ]. We performed the test on three separation distances: 55, 60 and 65 mm between the centers of the coils.…”