MRI with ultrahigh field strength and high-performance gradients: challenges and opportunities for clinical neuroimaging at 7 T and beyond

Abstract

Research in ultrahigh magnetic field strength combined with ultrahigh and ultrafast gradient technology has provided enormous gains in sensitivity, resolution, and contrast for neuroimaging. This article provides an overview of the technical advantages and challenges of performing clinical neuroimaging studies at ultrahigh magnetic field strength combined with ultrahigh and ultrafast gradient technology. Emerging clinical applications of 7-T MRI and state-of-the-art gradient systems equipped with up to 300 mT/m gradient strength are reviewed, and the impact and benefits of such advances to anatomical, structural and functional MRI are discussed in a variety of neurological conditions. Finally, an outlook and future directions for ultrahigh field MRI combined with ultrahigh and ultrafast gradient technology in neuroimaging are examined.

Iron-Based Magnetic Nanosystems for Diagnostic Imaging and Drug Delivery: Towards Transformative Biomedical Applications

“…The threshold for renal clearance is a particle diameter of about 5.5 nm [ 133 ], depending on the chemical structure of the nanoparticle. Larger nanoparticles can be excreted by means of hepatobiliary elimination via bile ducts and intestines [ 145 , 146 ]. Nanoparticles that are being taken up by Kupffer cells undergo long-time retention and slow degradation.…”

“…There is agreement in the field that we are one to two decades away from the onset of ultra-high field MRI beyond 10 T in the clinic [ 146 ]. This field strength will be required for truly contrast-free MRI imaging of most diseases.…”

Impact of Magnetic Field Inhomogeneity on the Quality of Magnetic Resonance Images and Compensation Techniques: A Review

“…These effects can be especially pronounced at magnetic fields of 7 T and higher. 16 Geometric distortion occurs when there is a frequency shift of the NMR signal due to the in-plane local gradient. 17 Geometrical distortions in EPI are prominent in the phase encoding direction due to the substantially smaller sampling rate.…”

Heterogeneous Iron Oxide/Dysprosium Oxide Nanoparticles Target Liver for Precise Magnetic Resonance Imaging of Liver Fibrosis

“…In contrast, MRI has an advantage of diagnosing liver fibrosis with reasonable accuracy. , MRI can sensitively detect anatomical and histological alterations in liver tissues, such as the formation of inflammation, an increase of the extracellular matrix consisting of fibril-forming collagens, and changes in Kupffer cells. , These alterations allow us to obtain the spatial/temporal resolution to distinguish the progress of liver fibrosis. , The spatial/temporal resolution of MRI is inextricably tethered to the static magnetic field strength, and the signal improves with the increase of the magnetic field strength of the imaging system. − Utilizing higher static magnetic field strength overcomes the limitations to improve the signal-to-noise ratio (SNR). Furthermore, the tissue relaxation property also changes along with increased SNR, where longer T 1 relaxation times offer better SNR (applicable for time-of-flight, magnetic resonance angiography, and arterial spin labeling) and shorter T 2 relaxation times provide greater image contrast (applicable for susceptibility-weighted imaging and for detecting functional activation by blood oxygenation level dependent functional MRI) . Therefore, the ultrahigh magnetic field alters sensitivity and improves the spatial resolution to the sub-millimeter level, allowing new structural and functional information and, thus, broadening the impact on clinical research.…”

“…Furthermore, the tissue relaxation property also changes along with increased SNR, where longer T 1 relaxation times offer better SNR (applicable for time-of-flight, magnetic resonance angiography, and arterial spin labeling) and shorter T 2 relaxation times provide greater image contrast (applicable for susceptibilityweighted imaging and for detecting functional activation by blood oxygenation level dependent functional MRI). 26 Therefore, the ultrahigh magnetic field alters sensitivity and improves the spatial resolution to the sub-millimeter level, allowing new structural and functional information and, thus, broadening the impact on clinical research. The progression from conventional MRI (up to 3.0 T) to UHFMRI usually requires a potent contrast agent (CA) to increase the MR signal in ultrahighfield scanners to ensure the highest signal-to-noise ratio.…”