Stephan Biber

A 64-channel 3T array coil for accelerated brain MRI.

A 64‐channel brain array coil was developed and compared to a 32‐channel array constructed with the same coil former geometry to precisely isolate the benefit of the 2‐fold increase in array coil elements. The constructed coils were developed for a standard clinical 3T MRI scanner and used a contoured head‐shaped 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 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 signal‐to‐noise ratio in the brain center to the 32‐channel array and 1.3‐fold more signal‐to‐noise ratio 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 signal‐to‐noise ratio 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. Magn Reson Med, 2013.

Comparison of local transmit antennas for extremity imaging in MRI

MRI rf excitation with various local transmit antennas has been compared to the commonly used full-body transmit antenna in terms of transmit field distribution, field strength and local SAR. The antennas (volume and surface coils) have been designed, decoupled and matched by using a 3D field simulation software. The examined objects, a liquid-filled cylindric phantom and the arm of a human body model have been included in the simulation setup. According to this study, the use of local transmit coils results in an immense reduction of required transmit power and a saving potential of local SAR, independent of the choice of local antenna type. However, concerning homogeneity birdcage coils offer the best performance.