A Birdcage Volume Transmit Coil and 8 Channel Receive Array for Marmoset Brain Imaging at 7T

Objective: To design and fabricate a band-pass birdcage volume resonator and eight channel, conformal receive array coil for MRI of both awake and anesthetized marmoset brain at 7T. The coil is compatible with a whole body 7T clinical MRI scanner running in single channel transmit (sTx) mode. Methods: The marmoset head coil included a shielded, band-pass birdcage transmit coil with 24 legs, as well as 8 overlapped receive elements. Electromagnetic (EM) field simulation was performed for the 24 leg band pass birdcage Tx coil to calculate the B1 + efficiency. The efficacy of both transmit and receive coil designs were evaluated by measuring standard coil performance metrics. This was done while imaging a marmoset head phantom, as well as by acquiring in vivo, anesthetized and awake marmoset images. Results: The transmit coil along with the optimized receive array produced high resolution (0.8 mm isotropic for EPI images; 0.36 mm isotropic for structural images) and high SNR (between 50 and 80) images of the marmoset brain. The simulated B1 + efficiency of the birdcage at the center of the phantom was 2.6 μT/sqrt (W). Conclusion and significance: A shielded, band-pass birdcage transmit coil was designed and fabricated for marmoset brain imaging at 7T. An 8-channel receive array consisting of eight overlapped loops, covering the whole brain of the marmoset, was also constructed and applied for signal reception. The system successfully allowed scanning of both young and older marmosets. It is well-suited for longitudinal studies of marmoset brain structure. The coil advantageously allows the study of neurodevelopment and primate brain function.