Low‐Field MRI of Stroke: Challenges and Opportunities

Abstract

Stroke is a leading cause of death and disability worldwide. The reasons for increased stroke burden in developing countries are inadequately controlled risk factors resulting from poor public awareness and inadequate infrastructure. Computed tomography and MRI are common neuroimaging modalities used to assess stroke with diffusion-weighted MRI, in particular, being the recommended choice for acute stroke imaging. However, access to these imaging modalities is primarily restricted to major cities and high-income groups. In the case of stroke, the time-window of treatment to limit the damage is of a few hours and needs a point-of-care diagnosis. A low-cost MR system typically achieved at the ultra-lowand very-low-field would meet the need for a geographically accessible and portable solution. We review studies focused on accessible stroke imaging and recent developments in MR methodologies, including hardware, to image at low fields. We hypothesize that in the absence of a formal, rapid stroke triaging system, the value of timely on-site delivery of the scanner to the stroke patient can be significant. To this end, we discuss multiple recent hardware and methods developments in the low-field regime. Our review suggests a compelling need to explore further the trade-offs between high signal, contrast, and accessibility at low fields in low-income communities.

Use of Portable Imaging Modalities in Patients With Neurologic Disorders: A Case-Based Discussion

“…More recently, portable MRI machines have also become available which allow for higher quality images when compared with CT studies [ 8 , 9 ]. The current slate of portable MRI machines uses lower magnetic fields which allow them to move into the clinical environment with ease.…”

“…The current slate of portable MRI machines uses lower magnetic fields which allow them to move into the clinical environment with ease. They are safe for use without having to remove rooms of all magnetic objects and do not interfere with ICU room monitoring devices [ 8 , 9 ]. In our case, the portable MRI field strength was 64 mT.…”

On Health Care Disparities and (J)MRI

“…First, make the scanners less expensive. 1 There is often a bias toward what is new and shiny, 2 and perhaps our field is more enamored of this than most. Second, is to make the cost of operation and siting cheaper.…”

Characterization of displacement forces and image artifacts in the presence of passive medical implants in low-field (<100 mT) permanent magnet-based MRI systems, and comparisons with clinical MRI systems

“…These factors limit its use to late in the healthcare cycle, and its siting to major hospitals. As a result it plays little role in screening in the developed world, and it is estimated that worldwide ~ 70% of the population has zero access to an MRI scan [6,7]. Within the past five years there has been a strong push, academically and commercially, to address this issue by developing lowfield (less than100 mT) MRI systems that have been designed for use in the intensive care unit (ICU) [8,9], for pediatric imaging in developing countries [10,11] and as point-of-care devices [12].…”