MRI at 7 tesla and above: Demonstrated and potential capabilities

Abstract

With more than 40 installed MR systems worldwide operating at 7 Tesla or higher, ultra-high-field (UHF) imaging has been established as a platform for clinically oriented research in recent years. Along with technical developments that, in part, have also been successfully transferred to lower field strengths, MR imaging and spectroscopy at UHF have demonstrated capabilities and potentials for clinical diagnostics in a variety of studies. In terms of applications, this overview article focuses on already achieved advantages for in vivo imaging, i.e., in imaging the brain and joints of the musculoskeletal system, but also considers developments in body imaging, which is particularly challenging. Furthermore, new applications for clinical diagnostics such as X-nuclei imaging and spectroscopy, which only really become feasible at ultra-high magnetic fields, will be presented.

Skin sodium measured with 23Na MRI at 7.0 T

“…The 23 Na RF coil provides improved sensitivity within a range of 1 cm from its surface versus a volume RF coil which facilitates high in-plane spatial resolution imaging of human skin. Intra-subject variability of human skin sodium content in the volunteer population was <10.3%.…”

“…We have developed 23 Na-MRI as a method to non-invasively study the Na + skin depot in normal and hypertensive humans (12,13). We calibrated the method with human tissue that was then ashed and measured with atomic absorption spectrometry (12).…”

“…Realizing the intrinsic sensitivity gain at higher magnetic field strengths (15)(16)(17)(18)(19)(20)(21)(22)(23)(24), 23 Na MRI at B 0 =7.0 T is conceptually appealing to enhance spatial resolution. We reasoned that at 7.0 T, the capabilities to assess Na+ in skin would provide more precision in estimating skin Na + content.…”

“…We reasoned that at 7.0 T, the capabilities to assess Na+ in skin would provide more precision in estimating skin Na + content. For this reason this study examines the feasibility of high in-plane spatial resolution 23 Na MRI in skin at 7.0 T using clinically acceptable acquisition times. To meet this goal we propose a local two-element transceiver RF surface coil that is customized for skin imaging at 7.0 T. Phantom experiments are performed to carefully assess the transmission field performance of the proposed transceiver RF coil an to examine the sensitivity of the proposed 7.0 T configuration versus a 3.0 T setup.…”

“…Transverse slices of the calf were imaged with 23 Na MRI using a high in-plane resolution of (0.9 x 0.9) mm 2 . Skin Na + content was determined using external agarose standards covering a physiological-range of Na + concentrations.…”