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

Abstract

Purpose To introduce an RF coil system consisting of an 8‐channel transmit (Tx) and 8‐channel receive (Rx) coil arrays for 19F MRI of large animals. Methods The Tx efficiency and homogeneity of the 8‐element loop coil array (loop size: 6 × 15 cm2) 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 ± 0.22μT/√kW versus 1.96 ± 0.29μT/√kW, and 2.29 ± 0.39μT/√kW versus 2.41 ± 0.37μT/√kW. An isolation of 38 ± 8 dB is achieved between the 19F Tx and Rx elements, and over 30 dB between the 1H and 19F 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 19F 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 19F coil provides homogeneous excitation and high sensitivity detection in large pig models.

Biot–Savart-Based Design and Workbench Validation at 100 MHz of Transverse Field Surface RF Coils

“…The utility of a dual-tuned RF coil configuration constituted by a 1 H circular loop and a 31 P FC coil for MRI/MRS applications at 1.5 T was also reported in [21]. This configuration was able to provide a high SNR in 1 H images and 31 P spectra thanks to the excellent isolation between the RF coils, guaranteed by the optimal geometric decoupling, as confirmed in very recent literature [32]. Moreover, this RF coil configuration provides overlapping sensitive volume for the two nuclei and the ability to control both frequencies independently, with the further advantage of not requiring additional lossy elements [33].…”

Open‐source magnetic resonance imaging: Improving access, science, and education through global collaboration

“…98,217 Another scalable 3-T pTx RF coil design has been applied for 19 F imaging and could in principle also be tuned to 1 H frequency. 218,219 To characterize and investigate the electromagnetic fields of these or similar RF coils, the open-source electromagnetic simulation package MARIE is available. 69,220 While MARIE might be an alternative to costly proprietary EM simulation software, other open-source software tools expand the functionality of proprietary software, such as CoSimPy, 51,221 which allows speedy circuit co-simulations (e.g., for fast RF coil optimizations).…”

“…A similar sized eight‐channel RF coil was also constructed for 3 T, allowing an easy measurement‐based comparison of pTx techniques between these field strengths 98,217 . Another scalable 3‐T pTx RF coil design has been applied for 19 F imaging and could in principle also be tuned to 1 H frequency 218,219 …”

Wireless, customizable coaxially shielded coils for magnetic resonance imaging

“…These methods have proven their reliability as viable alternatives to traditional coils, providing enhanced patient comfort and comparable SNR by conforming more closely to average anatomy. Simultaneously, the next generation of receive-only MRI coils is poised to adopt a more modular approach, enhancing versatility to mitigate the current challenges of high costs and limited utility associated with MRI coils (32)(33)(34)(35). Modular coil systems offer flexibility in customizing the field-of-view (FOV) coverage based on specific applications.…”