The way back and ahead: MR physics at ultra-high field

An MRI scanner is a device celebrating the great advances of modern physics. The basic concepts needed for understanding ultra-high field MRI have matured over the ages and in this way conquered our scientific hearts and minds. As the effects of magnetic fields are often not linear, the next step we make in increasing the magnetic field strength of MRI scanners may be a leap. In MRI, signal-to-noise ratio (SNR) increases supralinearly with field strength. In addition, the relaxation rates are field strength dependent. In general, the increase in SNR is used to increase the spatial resolution in images. It is well established at 7T to accelerate the acquisition of these large-matrix data via parallel imaging (PI), through GRAPPA or SENSE reconstruction. Further acceleration through compressed sensing (CS)-based acceleration has also been applied at 7T. The benefits of ultra-high fields extend further to improved susceptibility contrast and spectral resolution.