A 64‐channel 3T array coil for accelerated brain MRI

Abstract

A 64-channel brain array coil was developed and compared to a 32-channel array constructed with the same coil former geometry in order to precisely isolate the benefit of the two-fold increase in array coil elements. The constructed coils were developed for a standard clinical 3T MRI scanner and used a contoured head-shape curved former around the occipital pole and tapered in at the neck to both improve sensitivity and patient comfort. Additionally, the design is a compact, split-former design intended for robust daily use. Signal-to-noise ratio (SNR) and noise amplification (G-factor) for parallel imaging were quantitatively evaluated in human imaging and compared to a size and shape-matched 32-channel array coil. For unaccelerated imaging, the 64-channel array provided similar SNR in the brain center to the 32-channel array and 1.3-fold more SNR in the brain cortex. Reduced noise amplification during highly parallel imaging of the 64-channel array provided the ability to accelerate at approximately one unit higher at a given noise amplification compared to the sized-matched 32-channel array. For example, with a 4-fold acceleration rate, the central brain and cortical SNR of the 64-channel array was 1.2 and 1.4-fold higher, respectively, compared to the 32-channel array. The characteristics of the coil are demonstrated in accelerated brain imaging.

Signal-to-noise ratio and parallel imaging performance of commercially available phased array coils in 3.0 T brain magnetic resonance imaging

“…However, both coils showed similar SNRs at the anterior region. Previous studies have shown that an increase in the number of coil elements improves the SNR near the coil surface [21,23]. Our results, therefore, suggest that many elements are arranged in the posterior region of the 32-channel coil.…”

“…Generally, the SNR in regions distant from the coil surfaces is independent of the number of coil elements [1]. Wiggins et al and Keil et al have also shown that an increase in the number of coil elements does not result in an improvement in the central SNR [21,23]. On the other hand, some previous reports on custom coils have shown that a narrower inner space of the coil results in an increase in the SNR at the center of a phantom [20,22] and a narrower inner space of the coil permits the surfaces of the coil to be closer to the center of the object.…”

“…There are several reports on the usefulness of customized coils with many elements in MRI of the brain [20][21][22][23]. The number of the elements present in commercially available PACs is continually increasing.…”

“…Therefore, noise measurements with PI techniques often use subtracted images obtained from two images with identical parameters [18]. Furthermore, the g-factor map, in which the noise amplification is mapped in a pixel-by-pixel manner, is often used for estimating the location dependence [19][20][21][22][23].…”

The Structural Connectome of the Human Central Homeostatic Network

“…A custom-made 64-channel phased array coil was used for signal reception (Keil et al, 2013). We utilized probabilistic tractography for quantitative connectivity measurements and deterministic tractography for qualitative visualization of the pathways by which streamlines travel between seed and target nodes (Edlow et al, 2012;McNab et al, 2013).…”