
Promise of portable MRI
Although they can’t compete with their larger siblings in terms of image quality, small, portable MRI scanners that operate at very low magnetic fields are finding niches where their benefits shine.
In emergency medicine the majority of magnetic resonance imaging (MRI) examinations are for neuroimaging.10 This is a critical determinant of stroke care and is vital for detecting the presence of intracerebral hemorrhage.11 Traditionally, the patient is rushed to a centralized dedicated radiology suite for scanning.11,12 However, this is resource expensive because conventional MRI systems operate at high magnetic field strengths, of 1.5–3T, which require dedicated hospital infrastructure and highly trained technicians, as well as stringent safety protocols.11 High-field MRI scanners are also expensive to purchase (approximately $1 million per tesla) and to maintain.13 Aside from the delay, transporting patients is also not without risks, such as the possibility of increased intracranial pressure and cardiovascular instability, not to mention an increased chance of problems with intravenous lines and monitoring equipment during patient transport.11,12 Having an immobile centralized MRI suite also results in bottlenecks in the provision of care.12 Thus, the advent of small, portable, low-cost MRI is a potential game changer, particularly for resource-constrained healthcare settings as it is significantly less expensive and can be used directly at the point of care.12
Albeit in preliminary studies, the clinical and the practical utility of low-field, portable MRI as a neuroimaging solution has already been demonstrated at the bedsides of intensive care patients.11,14 Portable MRI has been shown to achieve consistent stroke volumes across portable MRI sequences and conventional high-field MRI studies, setting the stage for use in resource-limited contexts.12 Portable MRI was also effectively integrated into the clinical workflow, demonstrating that in practice it can provide timely diagnostic neuroimaging at the bedside.11 Portable MRI also has promise in tracking dynamic changes in stroke pathology over time.11
The major cost saver with portable MRI scanners is they operate at low magnetic field strengths, thus avoiding the considerable purchase and maintenance costs of superconducting magnets. They are also cryogen-free, which simplifies the maintenance.13 Portable MRI would thus be of particular benefit to health systems in more resource-restricted settings. For example, one specific use-case could be for monitoring the treatment of pediatric hydrocephalus in sub-Saharan Africa.10 In these settings outcomes could be improved with better detection of time-critical pathologies at the point of care.10
The other major advantage of portable MRI is in the name, it’s mobile. It can be used at the point of care, eliminating the need to transport patients to an MRI suite. By using MRI at the point of care neurological emergencies that are not as accurately characterized by computed tomography, like increased intracranial pressure could be better identified.10
As portable MRI uses a low magnetic field strength, it’s more compatible with ferromagnetic materials, so life-support and other medical equipment can remain in the room with the patient.11 Portable MRI may prove to be useful to install at large public gatherings, or in rural clinicals and frail-care or assisted-living facilities.13
The scanner design of the portable MRI systems also offers a possibility of scanning patient populations who are difficult to scan with high-field systems. For example, patients on life support who cannot safely be brought into an MRI suite.13 Very large size patients who cannot fit comfortably in MRI scanners may be a niche use for portable MRI. Another potential use is in the assessment of hypoxic ischemia in newborns.13
The low magnetic field strength also means portable MRI has fewer susceptibility artifacts and has a greater flexibility in design than large high-field scanners.11
Although unable to produce images comparable in quality to those of conventional high-field MRI, the emergence of small, portable, cryogen-free, low-field MRI scanners that are easy to use and allow for rapid patient throughput, with minimal power requirements at relatively low cost has the potential to have profound effects on healthcare, particularly in resource-limited or remote settings.13 The work however is just beginning in identifying where portable MRI would be best employed and in validating its usefulness in clinical trials.
References
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- Survivorship and quality of life research. American Cancer Society, 2019. (Accessed July 2022, at https://www.cancer.org/research/population-science/cancer-prevention-and-survivorship-research-team/cancer-survivorship-and-qol-research.html.)
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- Committee opinion no. 625: management of women with dense breasts diagnosed by mammography. Obstet Gynecol 2015;125:750-1.
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- Mazurek MH, Cahn BA, Yuen MM, Prabhat AM, Chavva IR, Shah JT, Crawford AL, Welch EB, Rothberg J, Sacolick L, Poole M, Wira C, Matouk CC, Ward A, Timario N, Leasure A, Beekman R, Peng TJ, Witsch J, Antonios JP, Falcone GJ, Gobeske KT, Petersen N, Schindler J, Sansing L, Gilmore EJ, Hwang DY, Kim JA, Malhotra A, Sze G, Rosen MS, Kimberly WT, Sheth KN. Portable, bedside, low-field magnetic resonance imaging for evaluation of intracerebral hemorrhage. Nat Commun 2021;12:5119.
- Yuen MM, Prabhat AM, Mazurek MH, Chavva IR, Crawford A, Cahn BA, Beekman R, Kim JA, Gobeske KT, Petersen NH, Falcone GJ, Gilmore EJ, Hwang DY, Jasne AS, Amin H, Sharma R, Matouk C, Ward A, Schindler J, Sansing L, de Havenon A, Aydin A, Wira C, Sze G, Rosen MS, Kimberly WT, Sheth KN. Portable, low-field magnetic resonance imaging enables highly accessible and dynamic bedside evaluation of ischemic stroke. Sci Adv 2022;8:eabm3952.
- Basser P. Detection of stroke by portable, low-field MRI: A milestone in medical imaging. Sci Adv 2022;8:eabp9307.
- Prabhat AM, Crawford AL, Mazurek MH, Yuen MM, Chavva IR, Ward A, Hofmann WV, Jr., Timario N, Qualls SR, Helland J, Wira C, Sze G, Rosen MS, Kimberly WT, Sheth KN. Methodology for low-field, portable magnetic resonance neuroimaging at the bedside. Front Neurol 2021;12:760321.