A Portable, Liquid-Helium-Free 1-T/560-mm RT bore Point-of-Care MRI Magnet: Prototype Demonstration

Project Summary Magnetic resonance imaging (MRI) is a widely used medical diagnostic tool. Nearly 50% of MR scans are of the head to diagnose ailments, injuries, and diseases including: 1) stroke; 2) other cerebrovascular conditions (e.g., aneurysm and atherosclerosis); 3) brain injury (concussion, TBI, hematoma); 4) tumors; 5) neurodegenerative disorders (e.g., multiple sclerosis, Alzheimer’s, epilepsy; 6) headache; 7) infections (e.g., meningitis). Standard MRI scanners, installed in special MRI rooms, operate with fields of ≥1.5 T. However, <<1 T scanners have been finding some niche applications in bedside and intrasurgical and interventional situations. Although some of these scanners are compact, and may be “portable,” they have a serious limitation of relying on permanent magnets and therefore suffer from low image quality. For example, Hyperfine, with the 0.064-T permanent magnet, markets a portable MRI system for patients in the hospital bed, which allows for critical decision-making in some clinical settings, but its images would never be considered to be of general diagnostic quality. In this project we introduce, for the first time, a portable superconducting 1.0-T head-dedicated MRI magnet, a field that yields proven diagnostic image quality. With the proposed innovative magnet technology incorporated, we believe that this superconducting head MRI will revolutionize point-of-care diagnostics, e.g., in triaging traumatic brain and other injuries at sports events, concerts, disasters, battlefields, and Hospital at Home. The specific aim of this 5-year project is to develop and demonstrate a portable head-imaging MRI magnet system. During operation, our proposed MgB2 superconducting 1.0 T magnet will be free from an external power supply and a refrigeration system. We will use off-the-shelf devices in a separate rack for MRI electronics; and use a custom designed head gradient coil cooled by a closed-loop water-to-air heat exchanger to dispense with a power-consuming water chiller. For our proposed portable 1.0-T MRI unit, we plan to use a detachable “cryocirculator” that circulates cold working fluid, and most importantly for portability, that can be readily coupled to or decoupled from the magnet system, in contrast to a conventional cryocooler that is mechanically attached to the magnet system. Another unique feature of our system is a volume of solid cryogen, e.g. solid neon, in the cold chamber that adds enough thermal mass to the magnet, enabling it to maintain its field over a period of, for this system, ≥8 hours, plenty enough for this portable MRI system, uncoupled from its cryocirculator, to perform its mission before it needs recooling.