A stripline-like coil element structure for high field phased array coils and its application for a 8-channel 9.4T small animal transceive array

Introduction Ultra-high magnetic field strength, as widely utilised in small animal MRI systems, has advantages of being able to enhance signal-to-noise ratio (SNR) and gain high spectral resolution [1]. However, the homogeneity of B1 field worsens along with the move to higher RF-frequencies. Methods such as RF shimming and transmit SENSE, which require transceive volume-arrays had been proposed to circumvent the high-field inhomogeneity problem [2]. Currently, the trend in designing transceive volume arrays is to fit the highest feasible number of coil-elements within a given geometry. Consequently, the aperture of each coil element will be small and RF field penetration depth is sacrificed. In addition, with increased number of coil elements, mutual decoupling is harder to control and good channel isolation is difficult to achieve. Therefore, it is very important to consider these two issues when designing a transceive volume-array system. In this work, the development of an optimized, shielded 8-element transceive volume-array for small animal MRI applications at 9.4T is discussed. To take into consideration the mentioned designing issues, a novel radiating structure for the coil element has been proposed. A prototype was constructed and tested in a Bruker 9.4T Biospec MRI system. Simulated and experimental results presented herein demonstrate the potential of the design.