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Ultra-high field MRI at 7T holds great potential but also presents significant challenges, often necessitating extensive calibration times to achieve spatially heterogeneous B1+/ΔB0 profiles. This talk explores the development of novel methodologies to address such challenges in cardiac and spinal cord imaging. It includes the creation of calibration-free parallel transmission techniques to eliminate conventional time-consuming calibration routines and covers broadband excitation to compensate for local ΔB0 variations or chemical shifts. Moreover, the presentation delves into respiration-related ΔB0 variations in mid- to lower spinal cord regions, providing essential insights for advancing spinal cord imaging techniques at ultra-high fields. [mehr]

Abstract: Multi-echo gradient-echo (GRE) sequences are commonly used for anatomical imaging of the spinal cord because they provide excellent contrast between grey matter (GM), white matter (WM), and cerebrospinal fluid (CSF). One of their main limitations is the sensitivity to voluntary and involuntary motion, leading to ghosting artifacts and lower image quality even in compliant subjects. Time-varying B0 fields related to the breathing cycle contribute substantially to the artifact load in the spinal cord. Navigator readouts can be used to measure the intensity of the B0 fluctuations, allowing to demodulate the acquired signal before the image reconstruction. However, the standard navigator processing approach, developed for brain imaging, often fails in the spine, which can even exacerbate the artifacts. Therefore, there is a need for navigator processing specifically tailored to spinal cord imaging. In this study, we explore the effect of optimized processing pipelines for navigator-based correction on the image quality of a multi-echo GRE sequence acquired in the spinal cord at 3T. [mehr]

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Magnetic resonance imaging of the human spinal cord at 7 Tesla offers new opportunities to visualize structures with high spatial resolution and enhanced conspicuity, and to detect functional networks with greater sensitivity. Sub-millimeter in-plane fMRI acquisitions are desirable and achievable, but published studies have had modest temporal resolution (>2 sec). Using a custom-built 7T pTx spine coil, we demonstrate sub-second and sub-millimeter cervical cord fMRI for the first time. Employing a 3D multi-shot sequence with appropriate phase corrections and NORDIC denoising, our data demonstrate temporal signal-to-noise ratios comparable to those of supra-second protocols, and we replicate bilateral functional connectivity patterns previously published in the cord. Realizing sub-second and sub-millimeter spinal cord fMRI opens new avenues of discovery that echo what has been reported through high spatiotemporal resolution brain fMRI. [mehr]

Several Parallel Transmit (pTX), capable coils have become available at 7T in the last few years. With pTx comes the ability to shape the excitation field to our needs. However, while pTx applications have seen great uptake in brain and body imaging, their use for the spinal cord has been limited so far. In this talk, we will demonstrate the feasibility of designing and deploying Universal Pulses for the cervical spinal cord at 7T. We will also show the first results in subject-specific B1+ shimming for the c-spine, using a dedicated Shimming Toolbox developed in our lab. Both approaches allow us to improve the signal homogeneity and thus deliver better image contrast for high-field spinal cord imaging. Finally, we will demonstrate the utility of the Shimming Toolbox for dynamic B0 field corrections in the cervical spine at clinical field strengths. [mehr]