An iPRES‐W Coil Array for Simultaneous Imaging and Wireless Localized B₀ Shimming of the Cervical Spinal Cord

Abstract

Purpose: To develop a wireless integrated parallel reception, excitation, and shimming (iPRES-W) coil array for simultaneous imaging and wireless localized B 0 shimming, and to demonstrate its ability to correct for distortions in DTI of the spinal cord in vivo.Methods: A 4-channel coil array was modified to allow an RF current at the Larmor frequency and a direct current to flow on each coil element, enabling imaging and localized B 0 shimming, respectively. One coil element was further modified to allow additional RF currents within a wireless communication band to flow on it to wirelessly control the direct currents for shimming, which were supplied from a battery pack within the scanner bore. The RF signals for imaging were transferred via conventional wired connections. Experiments were conducted to evaluate the RF, B 0 shimming, and wireless performance of this coil design. Results:The coil modifications did not degrade the SNR. Wireless localized B 0 shimming with the iPRES-W coil array substantially reduced the B 0 RMSE (−57.5% on average) and DTI distortions in the spinal cord. The antenna radiation efficiency, antenna gain pattern, and battery power consumption of an iPRES-W coil measured in an anechoic chamber were minimally impacted by the introduction of a saline phantom representing tissue. Conclusion:The iPRES-W coil array can perform imaging and wireless localized B 0 shimming of the spinal cord with no SNR degradation, with minimal change in wireless performance and without any scanner modifications or additional antenna systems within the scanner bore.

Flexible multi‐purpose integrated RF/shim coil array for MRI and localized B0 shimming

“…Integrated RF/shim coil arrays, 2,3 also known as integrated parallel reception, excitation, and shimming (iPRES) coil arrays [4][5][6][7] or AC/DC (alternating current/direct current) coil arrays, 8,9 allow both RF currents and a DC current to flow on each coil element, thereby enabling MR imaging and localized B 0 shimming with a single coil array without requiring additional space in the scanner bore or reducing the SNR. Because the coil elements are smaller and closer to the subject compared to spherical harmonic shim coils, such coil arrays can effectively shim localized B 0 inhomogeneities, as previously demonstrated in the human brain, [2][3][4]8 spinal cord, 5,9 breast, 6 and abdomen. 7 However, existing implementations are rigid, bulky, and heavy, and they cannot conform to the subject's anatomy to minimize the distance between the coil elements and the subject and to achieve an optimal SNR and shimming performance.…”

Numerical simulations of an integrated radio-frequency/wireless coil design for simultaneous acquisition and wireless transfer of magnetic resonance imaging data

“…In previous proof-of-concept experiments, this coil design was used to acquire MR images with multiple pulse sequences and to wirelessly transfer non-image data at a low data rate (LDR) of ∼11 Mbps between the coil and the AP, with no degradation in the image or wireless data quality (Darnell et al 2019). It has further been used for LDR applications such as wireless localized B 0 shimming of the spinal cord (Cuthbertson et al 2022) and brain (Cuthbertson et al 2020) with integrated RF/shim coil arrays, wireless respiratory monitoring with a respiratory belt (Cuthbertson et al 2020), wireless Q-spoiling (Cuthbertson et al 2021), and wireless physiological motion monitoring with an ultrasound sensor (Willey et al 2022).…”