Feasibility of ultra-low-field MRI scans on neuro-intensive care unit and stroke-unit

Feasibility of ultra-low-field MRI scans on neuro-intensive care unit and stroke-unit | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Feasibility of ultra-low-field MRI scans on neuro-intensive care unit and stroke-unit Dimah Hasan, Julian Sauer, Annika Rieder, Clara Heller, Konstantin Ueffing, and 8 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8013346/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Purpose: MRI diagnostics for patients with neurological pathologies and advanced monitoring or intensive care therapy are crucial to guide therapy. We aimed to examine the safety of ultra-low-field (ULF; 0.064 T) portable magnetic resonance imaging (pMRI) for stroke-unit and neuro-intensive care patients. Methods: This was a retrospective analysis of a tertiary hospital with neuro-intensive care and stroke-unit between May and August 2025. 93 patients received 95 scans for different pathologies: ischemic stroke (78%), hemorrhagic stroke (15%), meningoencephalitis/encephalitis 2%) and other conditions (5%). A total of 24 scans (25%) were performed on intubated patients (Study Group 1, n =24 scan). This group was compared to scans performed on non-intubated but surveilled patients (Study Group 2, n =71 scan) in a univariate analysis assessing the completion of ULF-pMRI scans. Image quality was assessed by two trained neuroradiologists using the five-point Likert scale. Results: ULF-pMRI scans were successfully completed in all intubated patients (100%) and in 87.3% of non-intubated/ventilated patients (p = 0.063), with sufficient image quality in 91.7% and 88.6%, respectively (p = 0.582). Patient repositioning was required in 33.3% vs. 21.1% (p = 0.175). No procedure-related complications occurred. Conclusion: ULF-pMRI is feasible in critically ill patients in neuro-intensive care who demand prolonged surveillance. ULF-pMRI safety neuro-intensive stroke-unit safety image quality Figures Figure 1 Figure 2 Figure 3 Figure 4 Introduction Neuro-imaging has become inevitable to assess neurological pathologies in current neuro-intensive care with MRI outperforming CT for assessing parenchymal lesions and subtle parenchymal changes. While high-field MRI with 1.5 Tesla and 3 Tesla is established in many modern neuro-intensive care centers, ultra-low field portable MRI (ULF-pMRI) with 0.064 Tesla has emerged in recent years as bedside scan to assess intracranial pathologies. Advantages of ULF-pMRI for critically ill patients are the capability of scanning the patient without transport to a stationary highfield MRI scanner and the very low magnetic field allowing for scans regardless of many implants or magnetizable monitoring devices. The integration of such technology into current practice promises to optimize healthcare resources due to the practicability and comparability low purchase and maintenance costs. In one of the first single-center experiences, Kuoy et al. showed, 23 ICU ULF-pMRI scans with three (13%) scans demonstrating infarctions not appreciable in CT scans. [ 1 ] In a large cohort multicenter study with patients on Extracorporeal Membrane Oxygenation (ECMO), ULF-pMRI was found to be feasible across different ECMO cannulation strategies in specially trained intensive care units. [ 2 ] Turpin et al. showed an adequate feasibility of ULF-pMRI in n = 19 patients with laboratory-confirmed severe acute respiratory syndrome coronavirus 2 infection. [ 3 ] Limitations and challenges of stroke patients and neurologically critical ill patients are reduced mobility, impaired communication, and altered levels of consciousness. In these patients, rapid imaging is essential for urgent clinical decision-making, yet conventional MRI systems often fail to meet this need due to their lack of portability and complex infrastructure demands. This study aims to evaluate the feasibility of ULF-pMRI for patients treated on stroke-unit and neuro-intensive care unit. Methods Study Design and Participants: This was a single-center retrospective analysis conducted at a a tertiary university hospital ( Institution information removed for blinded review) , based on ULF-pMRI imaging with clinical indication. We included all patients who underwent a low-field portable MRI examination (0.064 T, Hyperfine MRI device) between May 2025 and August 2025 in the neurological stroke unit or intensive care unit as part of routine clinical care for various indications. Patients also underwent additional imaging during their hospital stay, such as conventional CT or MRI, depending on the clinical condition and imaging indications. ULF-pMRI and scan protocol : The 0.064 T Swoop® Portable MR Imaging System (Hyperfine, Inc., Guilford, CT, USA; hardware version 1.7; software version 8.7commercial) was used for all patients reported in this study. The scanner weighs 606 kg, has a high of 150 cm and a diameter of 97 cm, with a patient accessible bore measuring 61 cm in width and 31.5 cm in height. For operation, the scanner is plugged into a standard electrical outlet. The patients are pulled from their bed into the scanner after removing the headboard of the patients’ bed. (Figure 1) The scanner performs a positioning test and confirms or declines correct patient positioning. In case of inadequate patient positioning, the patient can be pulled further into the undetachable head coil. In some scenarios, an adequate patient position is not reachable due to patient characteristics like very short neck or clinical settings like material in head/neck region. In these scenarios the scanner allows for continuing to scan regardless of patient positioning. The scanner was operated by a neuroradiological resident or attending physician with further support of clinical staff (nurse or neurological physician). The protocol used for all patients was the standard scan protocol provided by Hyperfine: Axial FLAIR (3D inversion-recovery turbo spin echo, acquisition time = 7 min 50 s, resolution = 1.7 × 1.7 × 5 mm, TE/TR/TI = 170/3000/1290 ms, receiver bandwidth = 64 kHz, echo train length = 68, excitation/refocusing/inversion flip angles = 90°/180°/180°) and axial diffusion-weighted imaging and Apparent Diffusion Coefficient (ADC) Maps (3D turbo spin echo, acquisition time = 8 min 40 s, resolution = 2.4 × 2.4 × 6 mm, TE/TR = 62/850 ms, receiver bandwidth = 52 kHz, echo train length = 44, excitation/refocusing flip angles = 90°/180°). Axial T1-weighted imaging (3D turbo spin echo, acquisition time = 4 min, resolution = 1.6 × 1.6× 5 mm, TE/TR /TI= 5.4/880/322 ms, receiver bandwidth = 64 kHz, echo train length = 32, excitation/refocusing flip angles = 90°/180°). Axial FAST T2-weighted imaging (3D turbo spin echo, acquisition time = 2 min 10 s, resolution = 1.6 × 1.6 × 5 mm, TE/TR = 195/2000 ms, receiver bandwidth = 64 kHz, echo train length = 80, excitation/refocusing flip angles = 90°/180°). Patients were divided into two study groups based on respiratory status at the time of the scan: Intubated/ventilated, including all patients receiving invasive mechanical ventilation via endotracheal or tracheostomy tube; and Not intubated/ventilated, including patients breathing spontaneously without invasive airway support. Study endpoints: Study endpoints were examination feasibility according to I) successful scan completion II) any complication of scanning or transporting and III) diagnostic imaging quality with proper patient positioning. Subjective perception of imaging quality in relation to artifacts and structure visibility was assessed by two neuroradiologists (reader 1 with 13 years and reader 2 with 11 years practice) using the five-point Likert Scale ranging from 1 ("non-diagnostic") to 5 ("excellent").[4] Likert scale points 1 and 2 were deemed not sufficient in diagnostic image quality. Consent reading was performed in cases of discrepancies. To assess sensitivity detection of pathology in ULF-pMRI, the pMRI-scans were compared to standard clinical imaging of the clinical work-up routine (notably high-field MRI for ischemic strokes etc. and CT for intracranial bleeding). Reading of ULF-pMRI images was blinded to the standard clinical imaging results. Ethics approval and consent to participate: Human ethics approval was granted by the local research ethics committee. The study was conducted in accordance with the Declaration of Helsinki; written informed consent was waived by the ethics committee due to the retrospective nature of the study design. The study followed the STROBE reporting criteria. The study was conducted according to the STROBE criteria. Statistics: Data are shown as number of events and percentage (n, %) and median with interquartile range (IQR) after testing for normal distribution with the Kolmogorov–Smirnov test or Shapiro-Wilk Test. Further analysis was conducted with the Mann-Whitney-U-Test or χ2 test and Fisher’s exact test to compare groups, as appropriate. The overall subjective image quality given by both readers was compared using the Wilcoxon signed-rank test, whereas the McNemar test was used to compare the individual Likert values between readers. All tests were two-sided and a p-value of <0.05 considered statistically significant. Multiple testing was corrected with Benjamini-Hochberg corrections. Statistical analyses were performed with SPSS Statistics (29.0; IBM, Armonk, NY). In cases of Missing data, we adjusted the denominator and delineated these adjustments in the footnotes accompanying the tables. All values refer to the scan rather than the patient, except for age and BMI. Results We scanned 92 patients (age: median, IQR: 69 years, IQR 59–81), who were in average normally weighted (Body Mass Index: median, IQR: 20–28). For them, 95 scans were conducted for different neurological diagnoses, including ischemic stroke (74 scans, 78%), hemorrhagic stroke (14 scans, 15%), meningoencephalitis/encephalitis (2 scans, 2%), status epilepticus (3 scans, 3%), and others (2 scans, 2%). Almost half of the scans (47 scans, 49.5%) were performed on head and neck implant or medical device patients, including gastric tubes, central venous lines, ventricular drainages, nasal oxygen cannulas, and Redon drainage systems. A total of 24 scans (25%) were performed on intubated patients, defined as study group 1. This group was compared to scans performed on not-intubated patients (study group 2, n=71 scan 75%) in a univariate analysis. Study population characteristics, as well as the main study outcome, are summarized in Table 1. MRI scans were successfully completed in all intubated (100%) and 87.3% of the not intubated patients (p = 0.063). For eight patients (11.2 %), the scan had to be terminated because of patient-related reasons such as backache, breathlessness, or restlessness, and in two reasons it was not at data analysis possible to determine the reason. Overall, no complications related to the scans were observed. In particular, there was no event of material dislocation in the head and neck region such as central venous lines or gastric tubes during patient positioning and scan time. Sufficient diagnostic image quality was reached in 87.5% and 88.6%, respectively (p = 0.582). Patient repositioning was required in 33.3% vs. 21.1% (p = 0.175). Sufficient patient position as indicated by the MRI scanner was reached in 79.2% vs. 93% (p = 0.070). Adequate image quality in cases with suboptimal positioning was obtained in 3 of 5 intubated patients (60%), but in none of 5 patients without sufficient final position in group 2. Pathology detected on ULF-pMRI corresponded with findings on reference imaging in 87.5% and 81.2% of the cases (p=0.248). The reference imaging was performed during the same hospital stay within 1-3 days of the ULF-pMRI scan. Table 1 : Characteristics of Patients examined with ultra-low field portable MRI, study groups based on state of intubation/ventilation Intubated/ventilated (n = 24) Not intubated/ventilated (n =71) p-value Patient Characteristics Age [years], median (IQR) 66 (52-72) 72 (61-83) 0.061 Body Mass Index, median (IQR) 26 (13,50-28,50) 24 (20-26) 0.196 Male, n (%) 17 (70.8) 40 (56.3) 0.156 Material in head/neck area Gastric tube, n % 18 (75.0) 14 (19.7) <0.001* Central venous line, n % 15 (62.5) 4 (5.6) <0.001* Ventricular drainage, n % 2 (8.3) 0 (0.0) 0.062 Oxygen nasal cannula, n % 0 (0.0) 17 (23.9) 0.004 Redon drainage system, n % 0 (0.0) 2 (2.8) … Indication for MR scan Ischemic Stroke, n (%) ICH, n (%) Epileptic seizure, n (%) Hypoxic brain injury, n (%) Meningo-/encephalitis, n (%) Others, n (%) 14 (58.3) 60 (84.5) 0.001* 4 (16.7) 10 (14.1) 3 (12.5) 0 (0.0) 1 (4.2) 0 (0.0) 2 (8.3) 0 (0.0) 0 (0.0) 1 (1.4) Scan completed, n % 24 (100) 62 (87.3) 0.063 Repositioning required, n % 8 (33.3) 15 (21.1) 0.175 Sufficient Endposition , n % 19 (79.2) 66 (93.0) 0.070 Sufficient image quality, n% 21 (87.5) 62 (87.3) 0.582 Adequate image quality in cases with suboptimal positioning, n% 3 (60) 0 (0) Pathology correlated in high-field MRI or CT scan during same hospital admission 21 (87.5) 56 (81.2) 0.248 Correlation of hemorrhagic transformation or hematoma in stroke patients, n % 3/10 5/19 0.245 In intubated patients, the pathology could be reliably correlated with the appropriate reference imaging modality in 21 cases (87.5%). (Figure 2,3,4) The few missed findings by portable MRI were confined to an isolated small supratentorial infarct (<5 mm in diameter) and brainstem infarcts (2 of 4 infratentorial cases). In the group of not intubated patients, pathology was correlated in a smaller proportion of cases (81.2%). In the rest of the 15 cases, pathology was not reliably identified. In 8 of these cases, assessment was not possible due to artifacts that impaired image quality; 6 of these patients had supratentorial infarcts and 1 patient had an intracerebral hemorrhage. In the other 7 patients, the pathology was not visible despite good image quality. Among these, 3 patients had small supratentorial infarcts, 2 had infratentorial brainstem infarcts, and 3 patients had intracerebral hemorrhages in the acute or early subacute phase. Discussion Our results demonstrate that portable MRI scans are feasible in stroke-unit and neurointensive care patients. Notably, all scans were completed for all intubated and mechanically ventilated patients. In 19 cases of intubated patients (79.2%), sufficient final positioning was achieved, although interim adjustments of patient position were required in 8 cases (33.3%). Patient positioning of intubated patients in a conventional MRI scanner is generally considered difficult. Despite these challenges, sufficient image quality was achieved in 21 cases (87.5%), a rate comparable to other neuroimaging modalities used in intubated patients. [5, 6] Adequate image quality despite suboptimal positioning was obtained in 3 of 5 intubated patients (60%), which represents a favorable rate in this small cohort. In the other 2 patients, however, suboptimal positioning led to numerous artifacts with a marked reduction in image quality, particularly in the infratentorial region. In the setting of non-intubated stroke patients, adequate end positioning was achieved in a higher proportion of cases (up to 93%) compared with intubated patients, although this difference did not reach statistical significance (p = 0.070). Repositioning was required in only a small proportion of patients—15 patients (21.1%). There are many possible reasons for this difference, given that the two groups were heterogeneous. The intubated patients had higher proportion of materials such as gastric tubes, central venous lines, and ventricular drains, which can make positioning in the scanner somewhat more difficult. This difference may also be explained by body weight, as the median BMI was higher in the intubated group, and by the fact that most non-intubated patients were mostly able to cooperate during the examination. However, due to various reasons, such as back pain or dyspnea, some non-intubated patients were unable to cooperate and had to terminate the examination prematurely. Overall, the scan could be completed in 62 of 71 patients (87.3%). This result is consistent with prior MRI studies in stroke patients of Hand et al. (2005), who reported that up to 85% of admitted acute stroke patients could undergo MRI with medical instability being the predominant barrier to successful scanning.[7] Furthermore, adequate image quality was achieved in the same proportion (87.3%). The reasons for suboptimal image quality were insufficient patient positioning in all 5 cases, without adequate final positioning, which—unlike in the intubated patient group—was not adequately assessable in any case. In addition, motion artifacts occurred in 4 further patients, which is expected in individuals with neurological deficits. Not only was image quality high in both groups, but diagnostic reliability was also high, with slightly better results in the intubated patients, although without statistical significance. These findings are consistent with those of Sorby-Adams et al., who reported a sensitivity of approximately 90% for ultra-low-field MRI, and somewhat higher than those of von Danwitz et al., who found a sensitivity of about 72%. [7, 8] The more favorable outcome in intubated patients was likely due to motion artifact in the non-intubated group, secondary to restlessness or early termination in a few cases. However, in seven patients pathology was not detectable despite good image quality. These were predominantly small infarcts (<5 mm) or infratentorial lesions and, therefore, are not surprisingly more frequent in non-intubated stroke patients. These results agree with those of von Danwitz et al., who also reported similar deficits in the detection of small infarcts.[7, 8] Overall, our results confirm the diagnostic potential of ultra-low-field MRI while also underscoring the limitations in detecting very small infarcts. The current sample size is still too small to define a threshold for infarct size detectable by portable MRI. Notably, we were able to identify punctate infarcts smaller than 6 mm in some cases, in both supratentorial and infratentorial locations, indicating that even very small lesions can be visualized. Nevertheless, in our cohort some larger infratentorial infarcts, particularly in the ADC map, could not be adequately correlated, which may indicate an additional limitation of ultra-low-field MRI. However, the number of such cases was too small to allow a clear definition of sensitivity in infratentorial infarcts, especially brainstem infarcts. Further studies with larger cohorts are needed to clarify the limits of stroke detection. Another limitation concerns hemorrhagic transformation in ischemic infarcts or intracerebral hemorrhage, which occurred in 29 cases, but only 8 of intracerebral hemorrhage were reliably correlated on portable MRI. A major reason for this limitation is the absence of T2*-weighted imaging in the device protocol, leaving us reliant on native T1 sequences, which play only a limited role in detecting hemorrhagic transformation in infarct areas or acute intracerebral hemorrhage. Our findings therefore differ from those of Mazurek et al., who reported higher detection rates of intracerebral hemorrhage using portable low-field MRI. [9, 10] This discrepancy may be explained by the fact that we also included hemorrhagic transformations within infarct areas, which are already hyperintense on FLAIR. In some cases of intracerebral hemorrhage, the bleedings were small and in a stage where they could not be reliably distinguished from surrounding edema on T1 or T2 sequences. Addressing this limitation should be a priority for future studies with larger patient cohorts. Importantly, no complications occurred during the examinations. In particular, no cases of implant dislocation in the head or neck region were observed, including devices such as extra-ventricular drains after burhole trepanation or Redon drainage systems after thrombendarteriectomy. This is particularly remarkable given the device’s limited opening and the rigid, non-removable head shell, both of which could represent potential challenges during patient positioning. Notably, even a patient with a decompressive hemicraniectomy for malignant left hemispheric media infarction was examined without difficulties, indicating that this condition does not restrict the applicability of portable MRI. These findings support the conclusion that portable MRI can be safely applied in patients, even under challenging conditions such as intubation and mechanical ventilation. This observation is consistent with previous reports demonstrating the safety and feasibility of portable MRI in critically ill populations thereby corroborating our results.[3, 11-13] Conclusion Ultra-low field portable MRI can be performed safely and with high diagnostic yield in both intubated/ventilated and not intubated/ventilated patients treated on stroke unit and neuro-intensive care units. Scan completion and image quality were consistently high in this study, the need for repositioning was limited, and diagnostic findings showed strong concordance with reference imaging. These results support the use of portable MRI as a feasible neuroimaging option for critically ill patients. The limitations of ULF-pMRI especially concerning the detection of small infarcts or intracranial hemorrhage need further assessment. Statements and Declarations Competing Interests: The authors have no competing interests to declare . Funding: This research was not funded by external sources. 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Hand, P.J., et al., Magnetic resonance brain imaging in patients with acute stroke: feasibility and patient related difficulties. J Neurol Neurosurg Psychiatry, 2005. 76(11): p. 1525-7. von Danwitz, N.M., et al., Portable ultra-low-field MRI in acute stroke care: A pilot study. Eur Stroke J, 2025: p. 23969873251344761. Mazurek, M.H., et al., Portable, bedside, low-field magnetic resonance imaging for evaluation of intracerebral hemorrhage. Nat Commun, 2021. 12(1): p. 5119. Mazurek, M.H., et al., Detection of Intracerebral Hemorrhage Using Low-Field, Portable Magnetic Resonance Imaging in Patients With Stroke. Stroke, 2023. 54(11): p. 2832-2841. Islam, O., A.W. Lin, and A. Bharatha, Potential application of ultra-low field portable MRI in the ICU to improve CT and MRI access in Canadian hospitals: a multi-center retrospective analysis. Front Neurol, 2023. 14: p. 1220091. Sheth, K.N., et al., Assessment of Brain Injury Using Portable, Low-Field Magnetic Resonance Imaging at the Bedside of Critically Ill Patients. JAMA Neurol, 2020. 78(1): p. 41-7. Sheth, K.N., et al., Bedside detection of intracranial midline shift using portable magnetic resonance imaging. Sci Rep, 2022. 12(1): p. 67. Additional Declarations No competing interests reported. Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. 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08:02:40","extension":"xml","order_by":11,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":50423,"visible":true,"origin":"","legend":"","description":"","filename":"57650bd33e254fdc9740963a62412ac11structuring.xml","url":"https://assets-eu.researchsquare.com/files/rs-8013346/v1/1b61d048bbaf4bd00b0037ce.xml"},{"id":97122782,"identity":"138e8b47-f6b8-4736-99dc-a846c10ce613","added_by":"auto","created_at":"2025-12-01 08:02:40","extension":"html","order_by":12,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":56887,"visible":true,"origin":"","legend":"","description":"","filename":"earlyproof.html","url":"https://assets-eu.researchsquare.com/files/rs-8013346/v1/c86151c907731b3c8022676d.html"},{"id":97122774,"identity":"f8b1d33e-5551-4a53-a8f3-8feeec150f37","added_by":"auto","created_at":"2025-12-01 08:02:40","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":471979,"visible":true,"origin":"","legend":"\u003cp\u003ePatient positioning for portable SWOOP MRI in the intensive care unit. After removal of the bed’s headboard, patients were directly transferred from their bed into the scanner.\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-8013346/v1/3a52e5e006c2f901f0ec2ebb.png"},{"id":97122773,"identity":"fa2bebf8-2f68-48da-a3d3-d7cdb7107b59","added_by":"auto","created_at":"2025-12-01 08:02:40","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":278293,"visible":true,"origin":"","legend":"\u003cp\u003e54-year-old male patient with a left-sided basal ganglia infarction, demonstrated on 1.5-Tesla MRI (Magnetom). Images A–D show conventional sequences in the following order: FLAIR, DWI, ADC map, and T2*-weighted imaging. Images E–H show corresponding SWOOP ULF MRI sequences: FLAIR, DWI, ADC map, and T1-weighted imaging. The subacute infarct is visible as hyperintensity on FLAIR with a corresponding diffusion restriction (arrows). In D(T2*), a microbleed is noted (arrow), without correlation in the other sequences or in the SWOOP images.\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-8013346/v1/0f614b559e3fbf1ce6306c50.png"},{"id":97122776,"identity":"393abbec-80f4-4399-820d-8094e0d9eca1","added_by":"auto","created_at":"2025-12-01 08:02:40","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":330136,"visible":true,"origin":"","legend":"\u003cp\u003e84-year-old male patient with cerebellar infarction involving the right tonsil (arrows). The lesion appears hyperintense on FLAIR with corresponding diffusion restriction. Findings are shown on 1.5-Tesla MRI (top row) and SWOOP ULF MRI (bottom row).\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-8013346/v1/a7696df2bd35e5b6f88af04b.png"},{"id":97122780,"identity":"87ed5adb-5837-42b3-b326-f6dcda1fd9f4","added_by":"auto","created_at":"2025-12-01 08:02:40","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":337199,"visible":true,"origin":"","legend":"\u003cp\u003e47-year-old patient after recanalization of a basilar artery occlusion. SWOOP ULF-MRI- images acquired on day 1 after recanalization (A–E) demonstrate diffuse FLAIR hyperintensity in the pons (A) with corresponding signal increase on DWI (B) and partially relative signal decrease on the ADC map (C, arrow: the exact extent is uncertain), consistent with acute infarction. Additionally, an inhomogeneity is noted in the right paramedian pons on FLAIR (A, black arrowhead) without a correlation on T1 (D) or T2 (E). A follow-up CT performed 2 hours later revealed a small hemorrhage at this location. Subsequent 1.5-Tesla MRI performed the following day (G–H) clearly delineates the infarct extent (arrows), with progression of hemorrhage seen on T2* imaging (J, arrow).\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-8013346/v1/b40dac899ea3877f50dd9524.png"},{"id":97145153,"identity":"abe5dad6-4b8d-46ed-9218-f6dbbe51544e","added_by":"auto","created_at":"2025-12-01 10:13:12","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2242933,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8013346/v1/62462ea1-cad2-4590-a90b-50fb3be14c66.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Feasibility of ultra-low-field MRI scans on neuro-intensive care unit and stroke-unit","fulltext":[{"header":"Introduction","content":"\u003cp\u003eNeuro-imaging has become inevitable to assess neurological pathologies in current neuro-intensive care with MRI outperforming CT for assessing parenchymal lesions and subtle parenchymal changes. While high-field MRI with 1.5 Tesla and 3 Tesla is established in many modern neuro-intensive care centers, ultra-low field portable MRI (ULF-pMRI) with 0.064 Tesla has emerged in recent years as bedside scan to assess intracranial pathologies.\u003c/p\u003e\u003cp\u003eAdvantages of ULF-pMRI for critically ill patients are the capability of scanning the patient without transport to a stationary highfield MRI scanner and the very low magnetic field allowing for scans regardless of many implants or magnetizable monitoring devices. The integration of such technology into current practice promises to optimize healthcare resources due to the practicability and comparability low purchase and maintenance costs. In one of the first single-center experiences, Kuoy et al. showed, 23 ICU ULF-pMRI scans with three (13%) scans demonstrating infarctions not appreciable in CT scans. [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]\u003c/p\u003e\u003cp\u003eIn a large cohort multicenter study with patients on Extracorporeal Membrane Oxygenation (ECMO), ULF-pMRI was found to be feasible across different ECMO cannulation strategies in specially trained intensive care units. [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e] Turpin et al. showed an adequate feasibility of ULF-pMRI in n\u0026thinsp;=\u0026thinsp;19 patients with laboratory-confirmed severe acute respiratory syndrome coronavirus 2 infection. [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e] Limitations and challenges of stroke patients and neurologically critical ill patients are reduced mobility, impaired communication, and altered levels of consciousness. In these patients, rapid imaging is essential for urgent clinical decision-making, yet conventional MRI systems often fail to meet this need due to their lack of portability and complex infrastructure demands.\u003c/p\u003e\u003cp\u003eThis study aims to evaluate the feasibility of ULF-pMRI for patients treated on stroke-unit and neuro-intensive care unit.\u003c/p\u003e"},{"header":"Methods","content":"\u003cp\u003e\u003cstrong\u003eStudy Design and Participants:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis was a single-center retrospective analysis conducted at a a tertiary university hospital (\u003cu\u003eInstitution information removed for blinded review)\u003c/u\u003e, based on ULF-pMRI imaging with clinical indication.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eWe included all patients who underwent a low-field portable MRI examination (0.064 T, Hyperfine MRI device) between May 2025 and August 2025 in the neurological stroke unit or intensive care unit as part of routine clinical care for various indications. Patients also underwent additional imaging during their hospital stay, such as conventional CT or MRI, depending on the clinical condition and imaging indications.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eULF-pMRI and scan protocol\u003c/strong\u003e:\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe 0.064 T Swoop® Portable MR Imaging System (Hyperfine, Inc., Guilford, CT, USA; hardware version 1.7; software version 8.7commercial) was used for all patients reported in this study.\u003c/p\u003e\n\u003cp\u003eThe scanner weighs 606 kg, has a high of 150 cm and a diameter of 97 cm, with a patient accessible bore measuring 61 cm in width and 31.5 cm in height. For operation, the scanner is plugged into a standard electrical outlet. The patients are pulled from their bed into the scanner after removing the headboard of the patients’ bed. (Figure 1) The scanner performs a positioning test and confirms or declines correct patient positioning. In case of inadequate patient positioning, the patient can be pulled further into the undetachable head coil. In some scenarios, an adequate patient position is not reachable due to patient characteristics like very short neck or clinical settings like material in head/neck region. In these scenarios the scanner allows for continuing to scan regardless of patient positioning. The scanner was operated by a neuroradiological resident or attending physician with further support of clinical staff (nurse or neurological physician). The protocol used for all patients was the standard scan protocol provided by Hyperfine:\u003c/p\u003e\n\u003cp\u003eAxial FLAIR (3D inversion-recovery turbo spin echo, acquisition time = 7 min 50 s, resolution = 1.7 × 1.7 × 5 mm, TE/TR/TI = 170/3000/1290 ms, receiver bandwidth = 64 kHz, echo train length = 68, excitation/refocusing/inversion flip angles = 90°/180°/180°) and axial diffusion-weighted imaging and Apparent Diffusion Coefficient (ADC) Maps (3D turbo spin echo, acquisition time = 8 min 40 s, resolution = 2.4 × 2.4 × 6 mm, TE/TR = 62/850 ms, receiver bandwidth = 52 kHz, echo train length = 44, excitation/refocusing flip angles = 90°/180°). Axial T1-weighted imaging (3D turbo spin echo, acquisition time = 4 min, resolution = 1.6 × 1.6× 5 mm, TE/TR /TI= 5.4/880/322 ms, receiver bandwidth = 64 kHz, echo train length = 32, excitation/refocusing flip angles = 90°/180°). Axial FAST T2-weighted imaging (3D turbo spin echo, acquisition time = 2 min 10 s, resolution = 1.6 × 1.6 × 5 mm, TE/TR = 195/2000 ms, receiver bandwidth = 64 kHz, echo train length = 80, excitation/refocusing flip angles = 90°/180°).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003ePatients were divided into two study groups based on respiratory status at the time of the scan:\u003c/p\u003e\n\u003col\u003e\n \u003cli\u003e\u003cstrong\u003eIntubated/ventilated,\u003c/strong\u003e including all patients receiving invasive mechanical ventilation via endotracheal or tracheostomy tube; and\u003c/li\u003e\n \u003cli\u003e\u003cstrong\u003eNot intubated/ventilated,\u003c/strong\u003e including patients breathing spontaneously without invasive airway support.\u003c/li\u003e\n\u003c/ol\u003e\n\u003cp\u003e\u003cstrong\u003eStudy endpoints:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eStudy endpoints were examination feasibility according to I) successful scan completion II) any complication of scanning or transporting and III) diagnostic imaging quality with proper patient positioning. Subjective perception of imaging quality in relation to artifacts and structure visibility was assessed by two neuroradiologists (reader 1 with 13 years and reader 2 with 11 years practice) using the five-point Likert Scale ranging from 1 (\"non-diagnostic\") to 5 (\"excellent\").[4] Likert scale points 1 and 2\u0026nbsp;\u003c/p\u003e\n\u003cp\u003ewere deemed not sufficient in diagnostic image quality. Consent reading was performed in cases of discrepancies.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eTo assess sensitivity detection of pathology in ULF-pMRI, the pMRI-scans were compared to standard clinical imaging of the clinical work-up routine (notably high-field MRI for ischemic strokes etc. and CT for intracranial bleeding). Reading of ULF-pMRI images was blinded to the standard clinical imaging results.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthics approval and consent to participate:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eHuman ethics approval was granted by the local research ethics committee. The study was conducted in accordance with the Declaration of Helsinki; written informed consent was waived by the ethics committee due to the retrospective nature of the study design. The study followed the STROBE reporting criteria. The study was conducted according to the STROBE criteria.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eStatistics:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eData are shown as number of events and percentage (n, %) and median with interquartile range (IQR) after testing for normal distribution with the Kolmogorov–Smirnov test or Shapiro-Wilk Test. Further analysis was conducted with the Mann-Whitney-U-Test or χ2 test and Fisher’s exact test to compare groups, as appropriate. The overall subjective image quality given by both readers was compared using the Wilcoxon signed-rank test, whereas the McNemar test was used to compare the individual Likert values between readers.\u003c/p\u003e\n\u003cp\u003eAll tests were two-sided and a p-value of \u0026lt;0.05 considered statistically significant. Multiple testing was corrected with Benjamini-Hochberg corrections. Statistical analyses were performed with SPSS Statistics (29.0; IBM, Armonk, NY). In cases of Missing data, we adjusted the denominator and delineated these adjustments in the footnotes accompanying the tables.\u003c/p\u003e\n\u003cp\u003eAll values refer to the scan rather than the patient, except for age and BMI.\u003c/p\u003e"},{"header":"Results","content":"\u003cp\u003eWe scanned 92 patients (age: median, IQR: 69 years, IQR 59\u0026ndash;81), who were in average normally weighted (Body Mass Index: median, IQR: 20\u0026ndash;28). For them, 95 scans were conducted for different neurological diagnoses, including ischemic stroke (74 scans, 78%), hemorrhagic stroke (14 scans, 15%), meningoencephalitis/encephalitis (2 scans, 2%), status epilepticus (3 scans, 3%), and others (2 scans, 2%). Almost half of the scans (47 scans, 49.5%) were performed on head and neck implant or medical device patients, including gastric tubes, central venous lines, ventricular drainages, nasal oxygen cannulas, and Redon drainage systems.\u003c/p\u003e\n\u003cp\u003eA total of 24 scans (25%) were performed on intubated patients, defined as study group 1. This group was compared to scans performed on not-intubated patients (study group 2, n=71 scan 75%) in a univariate analysis. Study population characteristics, as well as the main study outcome, are summarized in Table 1.\u003c/p\u003e\n\u003cp\u003eMRI scans were successfully completed in all intubated (100%) and 87.3% of the not intubated patients (p = 0.063). For eight patients (11.2 %), the scan had to be terminated because of patient-related reasons such as backache, breathlessness, or restlessness, and in two reasons it was not at data analysis possible to determine the reason.\u003c/p\u003e\n\u003cp\u003eOverall, no complications related to the scans were observed. In particular, there was no event of material dislocation in the head and neck region such as central venous lines or gastric tubes during patient positioning and scan time. Sufficient diagnostic image quality was reached in 87.5% and 88.6%, respectively (p = 0.582).\u003c/p\u003e\n\u003cp\u003ePatient repositioning was required in 33.3% vs. 21.1% (p = 0.175). Sufficient patient position as indicated by the MRI scanner was reached in 79.2% vs. 93% (p = 0.070). Adequate image quality in cases with suboptimal positioning was obtained in 3 of 5 intubated patients (60%), but in none of 5 patients without sufficient final position in group 2.\u003c/p\u003e\n\u003cp\u003ePathology detected on ULF-pMRI corresponded with findings on reference imaging in 87.5% and 81.2% of the cases (p=0.248). The reference imaging was performed during the same hospital stay within 1-3 days of the ULF-pMRI scan.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable\u0026nbsp;\u003c/strong\u003e\u003cstrong\u003e1\u003c/strong\u003e\u003cstrong\u003e: Characteristics of Patients examined with ultra-low field portable MRI, study groups based on state of intubation/ventilation\u003c/strong\u003e\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"605\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 229px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 142px;\"\u003e\n \u003cp\u003eIntubated/ventilated\u003c/p\u003e\n \u003cp\u003e(n = 24)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 141px;\"\u003e\n \u003cp\u003eNot intubated/ventilated\u003c/p\u003e\n \u003cp\u003e(n =71)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 93px;\"\u003e\n \u003cp\u003ep-value\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"4\" style=\"width: 605px;\"\u003e\n \u003cp\u003ePatient Characteristics\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 229px;\"\u003e\n \u003cp\u003eAge [years], median (IQR)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 142px;\"\u003e\n \u003cp\u003e66 (52-72)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 141px;\"\u003e\n \u003cp\u003e72 (61-83)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 93px;\"\u003e\n \u003cp\u003e\u0026nbsp;0.061\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 229px;\"\u003e\n \u003cp\u003eBody Mass Index, median (IQR)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 142px;\"\u003e\n \u003cp\u003e26 (13,50-28,50)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 141px;\"\u003e\n \u003cp\u003e24 (20-26)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 93px;\"\u003e\n \u003cp\u003e\u0026nbsp;0.196\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 229px;\"\u003e\n \u003cp\u003eMale, n (%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 142px;\"\u003e\n \u003cp\u003e17 (70.8)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 141px;\"\u003e\n \u003cp\u003e40 (56.3)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 93px;\"\u003e\n \u003cp\u003e\u0026nbsp;0.156\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"4\" style=\"width: 605px;\"\u003e\n \u003cp\u003eMaterial in head/neck area\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 229px;\"\u003e\n \u003cp\u003eGastric tube, n %\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 142px;\"\u003e\n \u003cp\u003e18 (75.0)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 141px;\"\u003e\n \u003cp\u003e14 (19.7)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 93px;\"\u003e\n \u003cp\u003e\u0026lt;0.001*\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 229px;\"\u003e\n \u003cp\u003eCentral venous line, n %\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 142px;\"\u003e\n \u003cp\u003e15 (62.5)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 141px;\"\u003e\n \u003cp\u003e4 (5.6)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 93px;\"\u003e\n \u003cp\u003e\u0026lt;0.001*\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 229px;\"\u003e\n \u003cp\u003eVentricular drainage, n %\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 142px;\"\u003e\n \u003cp\u003e2 (8.3)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 141px;\"\u003e\n \u003cp\u003e0 (0.0)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 93px;\"\u003e\n \u003cp\u003e\u0026nbsp;0.062\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 229px;\"\u003e\n \u003cp\u003eOxygen nasal cannula, n %\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 142px;\"\u003e\n \u003cp\u003e0 (0.0)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 141px;\"\u003e\n \u003cp\u003e17 (23.9)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 93px;\"\u003e\n \u003cp\u003e\u0026nbsp;0.004\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 229px;\"\u003e\n \u003cp\u003eRedon drainage system, n %\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 142px;\"\u003e\n \u003cp\u003e0 (0.0)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 141px;\"\u003e\n \u003cp\u003e2 (2.8)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 93px;\"\u003e\n \u003cp\u003e\u0026hellip;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"4\" style=\"width: 605px;\"\u003e\n \u003cp\u003eIndication for MR scan\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"6\" style=\"width: 229px;\"\u003e\n \u003cp\u003eIschemic Stroke, n (%)\u0026nbsp;\u003c/p\u003e\n \u003cp\u003eICH, n (%)\u0026nbsp;\u003c/p\u003e\n \u003cp\u003eEpileptic seizure, n (%)\u003c/p\u003e\n \u003cp\u003eHypoxic brain injury, n (%)\u0026nbsp;\u003c/p\u003e\n \u003cp\u003eMeningo-/encephalitis, n (%)\u003c/p\u003e\n \u003cp\u003eOthers, n (%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 142px;\"\u003e\n \u003cp\u003e14 (58.3)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 141px;\"\u003e\n \u003cp\u003e60 (84.5)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd rowspan=\"6\" style=\"width: 93px;\"\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; 0.001*\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 142px;\"\u003e\n \u003cp\u003e4 (16.7)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 141px;\"\u003e\n \u003cp\u003e10 (14.1)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 142px;\"\u003e\n \u003cp\u003e3 (12.5)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 141px;\"\u003e\n \u003cp\u003e0 (0.0)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 142px;\"\u003e\n \u003cp\u003e1 (4.2)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 141px;\"\u003e\n \u003cp\u003e0 (0.0)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 142px;\"\u003e\n \u003cp\u003e2 (8.3)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 141px;\"\u003e\n \u003cp\u003e0 (0.0)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 142px;\"\u003e\n \u003cp\u003e0 (0.0)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 141px;\"\u003e\n \u003cp\u003e1 (1.4)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 229px;\"\u003e\n \u003cp\u003eScan completed, n %\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 142px;\"\u003e\n \u003cp\u003e24 (100)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 141px;\"\u003e\n \u003cp\u003e62 (87.3)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 93px;\"\u003e\n \u003cp\u003e\u0026nbsp; 0.063\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 229px;\"\u003e\n \u003cp\u003eRepositioning required, n %\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 142px;\"\u003e\n \u003cp\u003e8 (33.3)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 141px;\"\u003e\n \u003cp\u003e15 (21.1)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 93px;\"\u003e\n \u003cp\u003e\u0026nbsp; 0.175\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 229px;\"\u003e\n \u003cp\u003eSufficient Endposition , n %\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 142px;\"\u003e\n \u003cp\u003e19 (79.2)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 141px;\"\u003e\n \u003cp\u003e66 (93.0)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 93px;\"\u003e\n \u003cp\u003e\u0026nbsp; 0.070\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 229px;\"\u003e\n \u003cp\u003eSufficient image quality, n%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 142px;\"\u003e\n \u003cp\u003e21 (87.5)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 141px;\"\u003e\n \u003cp\u003e62 (87.3)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 93px;\"\u003e\n \u003cp\u003e\u0026nbsp;0.582\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 229px;\"\u003e\n \u003cp\u003eAdequate image quality in cases with suboptimal positioning, n%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 142px;\"\u003e\n \u003cp\u003e3 (60)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 141px;\"\u003e\n \u003cp\u003e0 (0)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 93px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 229px;\"\u003e\n \u003cp\u003ePathology correlated in high-field MRI or CT scan during same hospital admission\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 142px;\"\u003e\n \u003cp\u003e21 (87.5)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 141px;\"\u003e\n \u003cp\u003e56 (81.2)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 93px;\"\u003e\n \u003cp\u003e\u0026nbsp; 0.248\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 229px;\"\u003e\n \u003cp\u003eCorrelation of hemorrhagic transformation or hematoma in stroke patients, n %\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 142px;\"\u003e\n \u003cp\u003e3/10\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 141px;\"\u003e\n \u003cp\u003e5/19\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 93px;\"\u003e\n \u003cp\u003e\u0026nbsp;0.245\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003eIn intubated patients, the pathology could be reliably correlated with the appropriate reference imaging modality in 21 cases (87.5%). (Figure 2,3,4) The few missed findings by portable MRI were confined to an isolated small supratentorial infarct (\u0026lt;5 mm in diameter) and brainstem infarcts (2 of 4 infratentorial cases).\u003c/p\u003e\n\u003cp\u003eIn the group of not intubated patients, pathology was correlated in a smaller proportion of cases (81.2%). In the rest of the 15 cases, pathology was not reliably identified. In 8 of these cases, assessment was not possible due to artifacts that impaired image quality; 6 of these patients had supratentorial infarcts and 1 patient had an intracerebral hemorrhage. In the other 7 patients, the pathology was not visible despite good image quality. Among these, 3 patients had small supratentorial infarcts, 2 had infratentorial brainstem infarcts, and 3 patients had intracerebral hemorrhages in the acute or early subacute phase.\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eOur results demonstrate that portable MRI scans are feasible in stroke-unit and neurointensive care patients.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eNotably, all scans were completed for all intubated and mechanically ventilated patients. In 19 cases of intubated patients (79.2%), sufficient final positioning was achieved, although interim adjustments of patient position were required in 8 cases (33.3%). Patient positioning of intubated patients in a conventional MRI scanner is generally considered difficult. Despite these challenges, sufficient image quality was achieved in 21 cases (87.5%), a rate comparable to other neuroimaging modalities used in intubated patients. [5, 6] Adequate image quality despite suboptimal positioning was obtained in 3 of 5 intubated patients (60%), which represents a favorable rate in this small cohort. In the other 2 patients, however, suboptimal positioning led to numerous artifacts with a marked reduction in image quality, particularly in the infratentorial region.\u003c/p\u003e\n\u003cp\u003eIn the setting of non-intubated stroke patients, adequate end positioning was achieved in a higher proportion of cases (up to 93%) compared with intubated patients, although this difference did not reach statistical significance (p = 0.070). Repositioning was required in only a small proportion of patients—15 patients (21.1%). There are many possible reasons for this difference, given that the two groups were heterogeneous. The intubated patients had higher proportion of materials such as gastric tubes, central venous lines, and ventricular drains, which can make positioning in the scanner somewhat more difficult. This difference may also be explained by body weight, as the median BMI was higher in the intubated group, and by the fact that most non-intubated patients were mostly able to cooperate during the examination. However, due to various reasons, such as back pain or dyspnea, some non-intubated patients were unable to cooperate and had to terminate the examination prematurely. Overall, the scan could be completed in 62 of 71 patients (87.3%). This result is consistent with prior MRI studies in stroke patients of Hand et al. (2005), who reported that up to 85% of admitted acute stroke patients could undergo MRI with medical instability being the predominant barrier to successful scanning.[7]\u003c/p\u003e\n\u003cp\u003eFurthermore, adequate image quality was achieved in the same proportion (87.3%). The reasons for suboptimal image quality were insufficient patient positioning in all 5 cases, without adequate final positioning, which—unlike in the intubated patient group—was not adequately assessable in any case. In addition, motion artifacts occurred in 4 further patients, which is expected in individuals with neurological deficits.\u003c/p\u003e\n\u003cp\u003eNot only was image quality high in both groups, but diagnostic reliability was also high, with slightly better results in the intubated patients, although without statistical significance. These findings are consistent with those of Sorby-Adams et al., who reported a sensitivity of approximately 90% for ultra-low-field MRI, and somewhat higher than those of von Danwitz et al., who found a sensitivity of about 72%. [7, 8]\u0026nbsp;The more favorable outcome in intubated patients was likely due to motion artifact in the non-intubated group, secondary to restlessness or early termination in a few cases. However, in seven patients pathology was not detectable despite good image quality. These were predominantly small infarcts (\u0026lt;5 mm) or infratentorial lesions and, therefore, are not surprisingly more frequent in non-intubated stroke patients. These results agree with those of von Danwitz et al., who also reported similar deficits in the detection of small infarcts.[7, 8]\u0026nbsp;Overall, our results confirm the diagnostic potential of ultra-low-field MRI while also underscoring the limitations in detecting very small infarcts.\u003c/p\u003e\n\u003cp\u003eThe current sample size is still too small to define a threshold for infarct size detectable by portable MRI. Notably, we were able to identify punctate infarcts smaller than 6 mm in some cases, in both supratentorial and infratentorial locations, indicating that even very small lesions can be visualized. Nevertheless, in our cohort some larger infratentorial infarcts, particularly in the ADC map, could not be adequately correlated, which may indicate an additional limitation of ultra-low-field MRI. However, the number of such cases was too small to allow a clear definition of sensitivity in infratentorial infarcts, especially brainstem infarcts. Further studies with larger cohorts are needed to clarify the limits of stroke detection.\u003c/p\u003e\n\u003cp\u003eAnother limitation concerns hemorrhagic transformation in ischemic infarcts or intracerebral hemorrhage, which occurred in 29 cases, but only 8 of intracerebral hemorrhage were reliably correlated on portable MRI. A major reason for this limitation is the absence of T2*-weighted imaging in the device protocol, leaving us reliant on native T1 sequences, which play only a limited role in detecting hemorrhagic transformation in infarct areas or acute intracerebral hemorrhage. Our findings therefore differ from those of Mazurek et al., who reported higher detection rates of intracerebral hemorrhage using portable low-field MRI. [9, 10]\u003c/p\u003e\n\u003cp\u003eThis discrepancy may be explained by the fact that we also included hemorrhagic transformations within infarct areas, which are already hyperintense on FLAIR. In some cases of intracerebral hemorrhage, the bleedings were small and in a stage where they could not be reliably distinguished from surrounding edema on T1 or T2 sequences. Addressing this limitation should be a priority for future studies with larger patient cohorts.\u003c/p\u003e\n\u003cp\u003eImportantly, no complications occurred during the examinations. In particular, no cases of implant dislocation in the head or neck region were observed, including devices such as extra-ventricular drains after burhole trepanation or Redon drainage systems after thrombendarteriectomy. This is particularly remarkable given the device’s limited opening and the rigid, non-removable head shell, both of which could represent potential challenges during patient positioning. Notably, even a patient with a decompressive hemicraniectomy for malignant left hemispheric media infarction was examined without difficulties, indicating that this condition does not restrict the applicability of portable MRI. These findings support the conclusion that portable MRI can be safely applied in patients, even under challenging conditions such as intubation and mechanical ventilation. This observation is consistent with previous reports demonstrating the safety and feasibility of portable MRI in critically ill populations thereby corroborating our results.[3, 11-13]\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eUltra-low field portable MRI can be performed safely and with high diagnostic yield in both intubated/ventilated and not intubated/ventilated patients treated on stroke unit and neuro-intensive care units. Scan completion and image quality were consistently high in this study, the need for repositioning was limited, and diagnostic findings showed strong concordance with reference imaging. These results support the use of portable MRI as a feasible neuroimaging option for critically ill patients. The limitations of ULF-pMRI especially concerning the detection of small infarcts or intracranial hemorrhage need further assessment.\u003c/p\u003e"},{"header":"Statements and Declarations","content":"\u003cp\u003eCompeting Interests: The authors have no competing interests to declare\u003cstrong\u003e.\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eFunding: This research was not funded by external sources.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eKuoy, E., et al., Point-of-Care Brain MRI: Preliminary Results from a Single-Center Retrospective Study. Radiology, 2022. 305(3): p. 666-671.\u003c/li\u003e\n\u003cli\u003eCho, S.M., et al., Clinical Use of Bedside Portable Ultra-Low-Field Brain Magnetic Resonance Imaging in Patients on Extracorporeal Membrane Oxygenation: Results From the Multicenter SAFE MRI ECMO Study. Circulation, 2024. 150(24): p. 1955-1965.\u003c/li\u003e\n\u003cli\u003eTurpin, J., et al., Portable Magnetic Resonance Imaging for ICU Patients. Crit Care Explor, 2020. 2(12): p. e0306.\u003c/li\u003e\n\u003cli\u003eLikert, R., A technique for the measurement of attitudes. Archives of psychology, 1932.\u003c/li\u003e\n\u003cli\u003eUcisik-Keser, F.E., et al., Impact of airway management strategies on magnetic resonance image quality. Br J Anaesth, 2016. 117 Suppl 1: p. i97-i102.\u003c/li\u003e\n\u003cli\u003eWadod, M.A., O.M. Aboelazm, and M.M. El Rawas, Effect of Laryngeal Mask Airway on Image Quality in Pediatric Patients Undergoing Brain Magnetic Resonance Imaging: A Randomized Controlled Trial. Anesth Pain Med, 2023. 13(2): p. e129532.\u003c/li\u003e\n\u003cli\u003eHand, P.J., et al., Magnetic resonance brain imaging in patients with acute stroke: feasibility and patient related difficulties. J Neurol Neurosurg Psychiatry, 2005. 76(11): p. 1525-7.\u003c/li\u003e\n\u003cli\u003evon Danwitz, N.M., et al., Portable ultra-low-field MRI in acute stroke care: A pilot study. Eur Stroke J, 2025: p. 23969873251344761.\u003c/li\u003e\n\u003cli\u003eMazurek, M.H., et al., Portable, bedside, low-field magnetic resonance imaging for evaluation of intracerebral hemorrhage. Nat Commun, 2021. 12(1): p. 5119.\u003c/li\u003e\n\u003cli\u003eMazurek, M.H., et al., Detection of Intracerebral Hemorrhage Using Low-Field, Portable Magnetic Resonance Imaging in Patients With Stroke. Stroke, 2023. 54(11): p. 2832-2841.\u003c/li\u003e\n\u003cli\u003eIslam, O., A.W. Lin, and A. Bharatha, Potential application of ultra-low field portable MRI in the ICU to improve CT and MRI access in Canadian hospitals: a multi-center retrospective analysis. Front Neurol, 2023. 14: p. 1220091.\u003c/li\u003e\n\u003cli\u003eSheth, K.N., et al., Assessment of Brain Injury Using Portable, Low-Field Magnetic Resonance Imaging at the Bedside of Critically Ill Patients. JAMA Neurol, 2020. 78(1): p. 41-7.\u003c/li\u003e\n\u003cli\u003eSheth, K.N., et al., Bedside detection of intracranial midline shift using portable magnetic resonance imaging. Sci Rep, 2022. 12(1): p. 67.\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"ULF-pMRI, safety, neuro-intensive, stroke-unit, safety, image quality","lastPublishedDoi":"10.21203/rs.3.rs-8013346/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8013346/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e\u003cstrong\u003ePurpose:\u003c/strong\u003e MRI diagnostics for patients with neurological pathologies and advanced monitoring or intensive care therapy are crucial to guide therapy. We aimed to examine the safety of ultra-low-field (ULF; 0.064 T) portable magnetic resonance imaging (pMRI) for stroke-unit and neuro-intensive care patients.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eMethods:\u003c/strong\u003e This was a retrospective analysis of a tertiary hospital with neuro-intensive care and stroke-unit between May and August 2025. 93 patients received 95 scans for different pathologies: ischemic stroke (78%), hemorrhagic stroke (15%), meningoencephalitis/encephalitis 2%) and other conditions (5%). A total of 24 scans (25%) were performed on intubated patients (Study Group 1, n =24 scan). This group was compared to scans performed on non-intubated but surveilled patients (Study Group 2, n =71 scan) in a univariate analysis assessing the completion of ULF-pMRI scans. Image quality was assessed by two trained neuroradiologists using the five-point Likert scale.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eResults:\u003c/strong\u003e ULF-pMRI scans were successfully completed in all intubated patients (100%) and in 87.3% of non-intubated/ventilated patients (p = 0.063), with sufficient image quality in 91.7% and 88.6%, respectively (p = 0.582). Patient repositioning was required in 33.3% vs. 21.1% (p = 0.175). No procedure-related complications occurred.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConclusion:\u003c/strong\u003e ULF-pMRI is feasible in critically ill patients in neuro-intensive care who demand prolonged surveillance.\u003c/p\u003e","manuscriptTitle":"Feasibility of ultra-low-field MRI scans on neuro-intensive care unit and stroke-unit","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-12-01 08:02:35","doi":"10.21203/rs.3.rs-8013346/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"2fd798bb-2439-45a9-9dcb-f056733cd280","owner":[],"postedDate":"December 1st, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2026-05-15T14:25:39+00:00","versionOfRecord":[],"versionCreatedAt":"2025-12-01 08:02:35","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8013346","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8013346","identity":"rs-8013346","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}