Design of Crisscrossed Double-Layer Birdcage Coil for Improving B₁⁺Field Homogeneity for Small-Animal Magnetic Resonance Imaging at 300 MHz

Abstract

We design a crisscrossed double-layer birdcage (DLBC) coil by modifying the coil geometry of a standard single-layer BC (SLBC) coil to enhance the homogeneity of transmitting magnetic flux density (B 1 + ) along the main magnetic field (B 0 )-direction for small-animal magnetic resonance imaging (MRI) at 300 MHz. The performance assessment of the crisscrossed DLBC coil is conducted by computational analysis with the finitedifference time domain method (FDTD) and compared with SLBC coil in terms of the B 1 and the B 1 + distribution. As per the computational calculation studies, the mean value in the two-dimensional B 1 + map obtained at the mid-axial slice with the proposed DLBC coil is slightly lower than that obtained with the SLBC coil, but the B 1 + value of the DLBC coil in the outermost plane (40 mm away from the central plane) shows improvements of 19.3% and 24.8% over the SLBC coil B 1 + value when simulating a spherical phantom and realistic mouse body modeling. These simulation results indicate that, the B 1 + homogeneity along the z-direction was improved by using DLBC configuration. Our approach enables B 1 + homogeneity improvement along the zdirection, and it can also be applied to ultra-high field (UHF) MRI systems.

A Preliminary Study for Reference RF Coil at 11.7 T MRI: Based on Electromagnetic Field Simulation of Hybrid-BC RF Coil According to Diameter and Length at 3.0, 7.0 and 11.7 T

“…In particular, an EM-field simulation is essential to more accurately predict the safety of RF coils as EM-fields play an important role in the generation of B 1 -fields and SAR distributions . Owing to these problems, various studies have been conducted with an aim to increase the uniformity of the B 1 -field [26][27][28][29][30][31][32][33][34][35][36][37] and to improve the sensitivity of the B 1 -field [38][39][40][41][42][43][44][45] along with RF safety [46][47][48][49][50][51][52][53][54][55][56][57].…”

Simulation Study of Radio Frequency Safety and the Optimal Size of a Single-Channel Surface Radio Frequency Coil for Mice at 9.4 T Magnetic Resonance Imaging

“…For this reason, preclinical researches in UHF MRI have been actively underway, and the importance of high-performance radiofrequency (RF) coils has emerged to obtain high-resolution anatomical images in preclinical MRI systems for small animals [14][15][16][17][18][19]. The researches to improve the performance of RF coils have been conducted in various ways in both preclinical MRI and clinical MRI fields, of which studies using additional structures (such as wireless element and HPM) [20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35], transmission line based RF coil to allow it to be independent of the length of the RF coil [36][37][38][39][40][41], and researches on the dedicated shapes of RF coils themselves have mainly focused [15,[42][43][44][45][46][47][48]. In addition, research on volume coils such as birdcage coils at various magnetic field strengths [49] and the development of new RF coil techniques have been actively conducted [50].…”

A study on multiple array method of birdcage coils to improve the signal intensity and homogeneity in small‐animal whole‐body magnetic resonance imaging at 7 T

“…15 In general, the diameter of a BC coil for an animal is much smaller than that for a human; therefore, the capacitor value is larger. 22 However, a BC coil covering the whole body length of a small animal exhibits a lower j B + 1 j-field strength and signal-to-noise ratio (SNR) compared to a BC coil of the same diameter and half the length. 16,17 This type of coil has been widely used as a body coil in clinical MR systems.…”

“…In smallanimal (mouse or rat) whole-body imaging, the use of volume-type RF coils (eg, BC) is preferred because they can produce homogeneous fields. 22 However, a BC coil covering the whole body length of a small animal exhibits a lower j B + 1 j-field strength and signal-to-noise ratio (SNR) compared to a BC coil of the same diameter and half the length. Therefore, we performed a study using multiple arrangements of BC coils to find the configuration that can produce a better coil performance in the jB 0 j direction.…”