Scalable and modular 8-channel transmit and 8-channel flexible receive coil array for F-19 MRI of large animals

Purpose To introduce an RF coil system consisting of an 8-channel transmit (Tx) and 8-channel receive (Rx) coil arrays for F-19 MRI of large animals. Methods The Tx efficiency and homogeneity of the 8-element loop coil array (loop size: 6 x 15 cm(2)) were simulated for two different pig models rendered from MR images. An 8-channel Rx coil array consisting of a flexible 6-channel posterior and a 2-channel planar anterior array was designed to fit on the abdomen of an average-sized pig in supine position. Measurements were performed in a grid phantom and ex vivo on a pig model with perfluoroctylbromide (PFOB)-filled tubes inserted in the thorax. Results Measured and simulated Tx efficiency and homogeneity for the 8-channel and 5-channel arrays were in good agreement: 1.87 +/- 0.22 mu T/root kW versus 1.96 +/- 0.29 mu T/root kW, and 2.29 +/- 0.39 mu T/root kW versus 2.41 +/- 0.37 mu T/root kW. An isolation of 38 +/- 8 dB is achieved between the F-19 Tx and Rx elements, and over 30 dB between the H-1 and F-19 elements. The PFOB-filled vials could be clearly identified within the cadaver abdomen with an SNR of 275 +/- 51 for a 3D gradient-echo sequence with 2-mm isotropic resolution and 12 averages, acquired in 9:52 min:s. Performance of the Tx array was robust against phase and amplitude mismatches at the input ports. Conclusions A modular and scalable Tx array offers improved Tx efficiency in F-19 MRI of large animals with various sizes. Although conventional birdcage coils have superior Tx efficiency within the target region of interest, scalability of the Tx array to animal size is a major benefit. The described F-19 coil provides homogeneous excitation and high sensitivity detection in large pig models.