2020/04/27 by Clarissa Cooley, Patrick C. McDaniel, Cooley, Clarissa Z. +21 · 3 citations
Medicine · Physics and Astronomy · #Advanced MRI Techniques and Applications #Atomic and Subatomic Physics Research #Radiation Therapy and Dosimetry
paper · pdf · doi:10.48550/arxiv.2004.13183
Access to and availability of MRI scanners is typically limited by their\ncost, siting and infrastructure requirements. This precludes MRI diagnostics,\nthe reference standard for neurological assessment, in patients who cannot be\ntransported to specialized scanner suites. This includes patients who are\ncritically ill and unstable, and patients located in low-resource settings. The\nscanner design presented here aims to extend the reach of MRI by substantially\nreducing these limitations. Our goal is to shift the cost-benefit calculation\nfor MRI toward more frequent and varied use, including improved accessibility\nworldwide and point of care operation. Here, we describe a portable brain MRI\nscanner using a compact, lightweight permanent magnet, with a built-in readout\nfield gradient. Our low-field (80 mT) Halbach cylinder design of rare-earth\npermanent magnets results in a 122 kg magnet with minimal stray-field,\nrequiring neither cryogenics nor external power. The built-in magnetic field\ngradient reduces reliance on high-power gradient drivers, which not only lowers\noverall system power and cooling requirements, but also reduces acoustic noise.\nImperfections in the encoding fields are mitigated with a generalized iterative\nimage reconstruction technique, that uses prior characterization of the field\npatterns. Our system was validated using T1, T2 and proton density weighted in\nvivo brain images with a spatial resolution of 2.2 x 1.3 x 6.8 mm3.\n