Make MRI Coils Digital and Programmable to Advance Ultra-High-Field Brain MRI

Abstract The overarching goal of the proposal is to bring the RF technology of MRI from the analog to the digital age. By doing so, we aim to address several fundamental challenges and create new capabilities at ultra-high field ( ~- 7T). 7T MRI recently gained FDA approval for clinical use in brain and extremities. The FDA found that 7T "allows for better visualization of smaller structures and subtle pathologies that may improve disease diagnosis". Further, 7T MRI opens the doors for non-proton X-nuclei spectroscopy and imaging that has great untapped clinical potentials for imaging of brain metabolism with applications in brain aging and in several major neurological diseases including dementia and cancer. Despite this monumental advance, 7T MRI still faces numerous challenges; chief among them is the transmit RF system for exciting signals. RF engineering at 7T is fundamentally challenged by the worsening RF heating and field inhomogeneity caused by the shorter wavelength. Existing solutions often prolong the scan time and are prohibitively expensive. We have recently pioneered the Any-nucleus Distributed Active Programmable Transmit (ADAPT) coil, that can be digitally programmed to transmit waveforms without relying on resonant circuits. This is accomplished by integrating fast switches into the structure of the coil and digitally controlling the switches to directly generate the RF waveform in the time domain. The ADAPT coil offers several breakthroughs for 7T MRI. It can be digitally programmed to excite any nucleus and even multiple nuclei simultaneously. The ADAPT coil eliminates the need for the expensive traditional RF amplifier by converting direct current power into RF magnetic fields with frequencies chosen by digital control signals sent to the switches. By eliminating the need of resonant circuits, the ADAPT coil will reduce or even eliminate various couplings, allowing flexible coil circuit layout to improve B1 + homogeneity and reduce local SAR We propose to develop a plug-and-play ADAPT coil system for ultra-high field MRI. To evaluate and disseminate the technology broadly, we are collaborating with several ultra-high field MRI sites and major MRI vendors to test its applications in aging and neurological diseases. A successful outcome will address several fundamental challenges and create new imaging capabilities, which will improve 7T MRI as a whole and broaden its scientific and clinical impact.