An 8‐channel Tx dipole and 20‐channel Rx loop coil array for MRI of the cervical spinal cord at 7 Tesla

Abstract

The quality of cervical spinal cord images can be improved by the use of tailored radiofrequency (RF) coil solutions for ultrahigh field imaging; however, very few commercial and research 7‐T RF coils currently exist for the spinal cord, and in particular, those with parallel transmission (pTx) capabilities. This work presents the design, testing, and validation of a pTx/Rx coil for the human neck and cervical/upper thoracic spinal cord. The pTx portion is composed of eight dipoles to ensure high homogeneity over this large region of the spinal cord. The Rx portion is made up of twenty semiadaptable overlapping loops to produce high signal‐to‐noise ratio (SNR) across the patient population. The coil housing is designed to facilitate patient positioning and comfort, while also being tight fitting to ensure high sensitivity. We demonstrate RF shimming capabilities to optimize B1+ uniformity, power efficiency, and/or specific absorption rate efficiency. B1+ homogeneity, SNR, and g‐factor were evaluated in adult volunteers and demonstrated excellent performance from the occipital lobe down to the T4‐T5 level. We compared the proposed coil with two state‐of‐the‐art head and head/neck coils, confirming its superiority in the cervical and upper thoracic regions of the spinal cord. This coil solution therefore provides a convincing platform for producing the high image quality necessary for clinical and research scanning of the upper spinal cord.

Evaluation of coaxial dipole antennas as transceiver elements of human head array for ultra‐high field MRI at 9.4T

“…16 Because of the simplicity of the design, dipoles can provide a reliable and robust alternative to common surface loops. In the last decade, multiple studies describing the use of dipoles for designing multi-element human head 12,[17][18][19][20][21][22][23][24][25][26] and body [27][28][29][30][31][32][33][34] Tx (or TxRx) arrays have been reported. Because of the sample's size, dipole antennas for human head imaging must be designed significantly shorter than their intrinsic length equal to half of the wavelength, λ/2, for example, 50 cm at 300 MHz (7T) and 37.5 cm at 400 MHz (9.4T).…”

Reliability of task-based fMRI in the dorsal horn of the human spinal cord

“…Compared to the brain, the spinal cord is a more challenging environment for fMRI (Bosma & Stroman, 2014; Cohen-Adad, 2017; Eippert, Kong, Jenkinson, et al, 2017; Giove et al, 2004; Kinany, Pirondini, Micera, et al, 2022) and the number of studies using this technique has increased only slowly at first. However, the continued development and improvement of scanner hardware (Cohen-Adad et al, 2011; Lopez-Rios et al, 2023; Topfer et al, 2016), image acquisition protocols for spinal cord fMRI (Barry et al, 2021; Finsterbusch et al, 2013; Kinany,et al, 2022), shimming procedures (Finsterbusch et al, 2012; Islam et al, 2019; Tsivaka et al, 2023), denoising strategies (Brooks et al, 2008; Kong et al, 2012; Vannesjo et al, 2019) and software tools tailored to preprocessing and analyzing spinal cord data (De Leener et al, 2017, 2018; Rangaprakash & Barry, 2022) have made spinal fMRI more robust, sensitive and accessible, and accordingly has met with growing numbers of spinal fMRI studies more recently (Kinany et al, 2022; Landelle et al, 2021; Powers et al, 2018; Tinnermann et al, 2021).…”