Reengineered helmet coil for human brain studies at 3 Tesla

Abstract

ABSTRACT:We describe the further development of a circularly polarized helmet coil for magnetic resonance imaging (MRI) of the human brain at 3 T. The coil is used in transmit and receive (transceive) mode, a useful alternative over commercially available quadrature headcoils with scanners where phased arrays are unavailable. The coil is simple to build. Its structure is based on an assembly of two coplanar dual-loop coils of the split-circle design, which are arranged in crossed fashion. Both coils circumscribe dome-like the human head. Because of the symmetry of the assembly, a high degree of circularly polarized radiofrequency (RF) is obtained within the brain. Bench and in situ measurements of the RF magnetic field, B 1 , indicated good axial homogeneity and a moderate gradient along the symmetry axis. Compared to a commercial birdcage coil, the signal-to-noise ratio was increased up to a factor of 1.7 as a result of its superior filling factor. Initial applications in healthy volunteers included anatomical MRI and functional imaging with a cognitive paradigm.

Simple partial volume transceive coils for in vivo 1H MR studies at high magnetic fields

“…3(E) and (F), respectively. Further development of these coil designs has been described previously (9)(10)(11)(12). In Driesel et al's (12) article, the coil spokes were enlarged in the z axis for increased B 1 homogeneity at the expense of sensitivity and rotated by 458 in contrast to the coil design in Fig.…”

A microstrip helmet coil for human brain imaging at high magnetic fields

“…The B 1 gradient along the z-axis [ Fig. 10(c)] was reduced when compared with previous conventional helmet coil designs (14). Figure 11 shows the phantom images recorded with the four-channel array in a plane that was tilted by 2458 from the sagittal direction (i.e., aligned parallel to A/C and perpendicular to the B/D MTL elements; cf.…”

“…Using finite-element modeling of the RF field, this design, which may be described as an assembly of two crossed pairs of surface coils, was recently optimized for whole-brain imaging (14). With the current work, we introduce a new helmet coil concept based on microstrip transmission-line (MTL) technology with further improved RF field homogeneity and low spillover to regions outside the object under investigation.…”

“…Previously, an anatomically shaped, quadrature helmet transmit/receive (T/R) coil was introduced by Merkle et al (11)(12)(13)(14)(15) for improving the SNR in studies of superior brain areas, such as the motor cortex. Using finite-element modeling of the RF field, this design, which may be described as an assembly of two crossed pairs of surface coils, was recently optimized for whole-brain imaging (14). With the current work, we introduce a new helmet coil concept based on microstrip transmission-line (MTL) technology with further improved RF field homogeneity and low spillover to regions outside the object under investigation.…”

Imaging Adult Zebrafish Brain Structures Using Micro-fabricated RF Coil on 3T MRI System

“…Because only transverse component of EM field was concerned, the z-component of the phasor was subsequently set to zero. To maximize the sensitivity of RF coil, the coil element was designed close to the sample [5]. The geometry design of our micro-fabricated coil was illustrated in Fig.…”