Accelerated multislice MRI with patterned excitation.

PURPOSE: Accelerate multislice 2D MRI by using RF pulses that simultaneously act on different slices to combine contrast preparation and image acquisition. THEORY AND METHODS: MRI applications often require the use of multiple RF pulses to generate desired contrast and prepare the signal for readout. Examples are the use of inversion prepulses to generate T1 contrast, or the use of spin-echo preparations to generate T2 or diffusion contrast. In multislice MRI, this separation of contrast preparation and readout can render scans time-inefficient and lengthy. We introduce a class of pulse sequences that overcomes this inefficiency by combining contrast preparation and signal readout. This is accomplished by using RF pulses that manipulate the magnetization of multiple slices simultaneously and a gradient crusher scheme that selects a target slice for readout. RESULTS: Feasibility of the method was demonstrated for spin echo-based measurement of water diffusion and tissue pulsation in human brain at 3 T. Increases in time-efficiency and reductions in scan time were highly dependent on specific implementation and reached as high as 25% and 53%, respectively. CONCLUSION: A novel approach to multislice MRI is demonstrated that reduces scan time for specific applications.

Single-level laminoplasty approach to selective dorsal rhizotomy with conus localization by rapid spine MRI.

INTRODUCTION: While selective dorsal rhizotomy (SDR) was originally described as a multilevel approach, single-level approaches are now popularized. Conus localization is beneficial for operative planning in single-level selective dorsal rhizotomy. Our approach to SDR involves minimal exposure for a single-level laminoplasty, preserving one attached interspinous ligament. Pre-operative conus localization is required for this tailored approach to determine the laminoplasty level and dictate rostral or caudal division of the superior spinus ligament. While rapid MRI sequences have been popularized for pediatric cranial imaging, its utility for spinal imagining is less well-described, and specific application for conus localization has not been reported. OBJECTIVE: Illustrate that rapid MRI without sedation is sufficient to identify conus level for tailored single-level laminoplasty SDR. MATERIAL AND METHODS: Patients undergoing SDR from 2014 to 2022 at one institution were reviewed for type of pre-operative MRI (rapid vs full), conus level, procedural time for MRI, and radiology report. The typical rapid MRI has four sequences utilizing single-shot technique (scout, sagittal T2, axial T2, and axial T1) that typically take less than 1 min each of acquisition time, with non-single-shot sequences added periodically in cooperative patients. To include time for patient positioning, pre-scan shimming, procedural incidentals, and other patient-specific variations, MRI procedure length was recorded as documented in the electronic medical record. RESULTS: N = 100 patients had documentation of an MRI for pre-operative imaging. Seventy-nine of these had a rapid MRI, and 21 required a full MRI with anesthesia for their treatment plan. Mean total procedure time for rapid MRI was 21.5 min (median 17). Mean procedure time for MRI under general anesthesia was 91.2 min (median 94). Of patients with rapid MRI imaging, 2/79 had an ambiguous conus level (1 from motion artifact, 1 from spinal hardware) vs 1/21 with a full MRI under anesthesia (due to spinal hardware). CONCLUSION: Rapid spinal MRI without sedation can be used for conus localization in a pediatric population. This may be routinely used as pre-operative imaging for a single-level approach to selective dorsal rhizotomy, without sedation or intubation procedures.

Generating spiral gradient waveforms with a compact frequency spectrum.

PURPOSE: To generate efficient gradient waveforms for spiral MRI which mitigate the high-frequency attenuation inherent in gradient systems. THEORY AND METHODS: Spiral MRI has many clinical advantages, including high temporal and SNR efficiency. One of the challenges for robust spiral MRI is a high sensitivity to imperfections in the gradient system, which requires some form of correction in order to map data correctly in k-space. A previous numerical algorithm for generating spiral gradient waveforms was modified to reduce its high-frequency content with minimal increase in waveform duration. RESULTS: Examples are shown of compact frequency gradient waveforms. Software implementing the algorithm is made available. CONCLUSION: An algorithm to produce gradient waveforms with a compact frequency spectrum is described. This algorithm results in greatly reduced overall error and better compatibility with gradient systems than the original algorithm from which it was derived.

Magnetic resonance parameter mapping using model-guided self-supervised deep learning.

PURPOSE: To develop a model-guided self-supervised deep learning MRI reconstruction framework called reference-free latent map extraction (RELAX) for rapid quantitative MR parameter mapping. METHODS: Two physical models are incorporated for network training in RELAX, including the inherent MR imaging model and a quantitative model that is used to fit parameters in quantitative MRI. By enforcing these physical model constraints, RELAX eliminates the need for full sampled reference data sets that are required in standard supervised learning. Meanwhile, RELAX also enables direct reconstruction of corresponding MR parameter maps from undersampled k-space. Generic sparsity constraints used in conventional iterative reconstruction, such as the total variation constraint, can be additionally included in the RELAX framework to improve reconstruction quality. The performance of RELAX was tested for accelerated T1 and T2 mapping in both simulated and actually acquired MRI data sets and was compared with supervised learning and conventional constrained reconstruction for suppressing noise and/or undersampling-induced artifacts. RESULTS: In the simulated data sets, RELAX generated good T1 /T2 maps in the presence of noise and/or undersampling artifacts, comparable to artifact/noise-free ground truth. The inclusion of a spatial total variation constraint helps improve image quality. For the in vivo T1 /T2 mapping data sets, RELAX achieved superior reconstruction quality compared with conventional iterative reconstruction, and similar reconstruction performance to supervised deep learning reconstruction. CONCLUSION: This work has demonstrated the initial feasibility of rapid quantitative MR parameter mapping based on self-supervised deep learning. The RELAX framework may also be further extended to other quantitative MRI applications by incorporating corresponding quantitative imaging models.

Improving the image quality of 3D FLAIR with a spiral MRI technique.

PURPOSE: Fluid-attenuated inversion recovery (FLAIR) nulls the CSF signal and is widely used in neuro MRI exams. A 3D scan can provide high SNR, contiguous coverage, and reduced sensitivity to through-plane CSF flow. In this work, a 3D spiral FLAIR technique is proposed to improve the image quality of conventional 3D Cartesian FLAIR. METHODS: The 3D spiral FLAIR sequence incorporated a spiral-in/out readout to preserve higher scan efficiency and eliminate off resonance-induced artifacts observed with a commonly implemented spiral-out readout, a compensation approach to minimize phase errors due to the concomitant fields accompanying the spiral gradient, and an adapted variable flip angle scheme to preserve scan efficiency and maintain a long and stable echo train. 3D Cartesian and spiral FLAIR (~6 min each) were acquired on a 3 Tesla scanner from 6 subjects (age range: 31-64 years; mean: 39.5). Two neuroradiologists rated the images in a blinded fashion on a 5-point scale. The noise performance was assessed quantitatively. RESULTS: Compared to 3D Cartesian FLAIR, 3D spiral FLAIR exhibits greater reduction of artifacts from CSF, especially anterior to the brain stem (rated better in 4 cases), artifacts attributed to blood/flow in the deep brain (better or much better in all 6 cases), and superior overall image quality (much better in 5 cases) despite residual susceptibility artifacts near the nasal cavity. Quantitative assessment demonstrates ~1.5× higher average SNR than Cartesian data. CONCLUSION: 3D spiral FLAIR achieves higher SNR, reduced CSF, and blood/flow artifacts, providing an alternative to 3D Cartesian FLAIR for neurological exams.

Rapid Knee MRI Acquisition and Analysis Techniques for Imaging Osteoarthritis.

Osteoarthritis (OA) of the knee is a major source of disability that has no known treatment or cure. Morphological and compositional MRI is commonly used for assessing the bone and soft tissues in the knee to enhance the understanding of OA pathophysiology. However, it is challenging to extend these imaging methods and their subsequent analysis techniques to study large population cohorts due to slow and inefficient imaging acquisition and postprocessing tools. This can create a bottleneck in assessing early OA changes and evaluating the responses of novel therapeutics. The purpose of this review article is to highlight recent developments in tools for enhancing the efficiency of knee MRI methods useful to study OA. Advances in efficient MRI data acquisition and reconstruction tools for morphological and compositional imaging, efficient automated image analysis tools, and hardware improvements to further drive efficient imaging are discussed in this review. For each topic, we discuss the current challenges as well as potential future opportunities to alleviate these challenges. LEVEL OF EVIDENCE: 5 TECHNICAL EFFICACY STAGE: 3.

Rapid brain MRI protocols reduce head computerized tomography use in the pediatric emergency department.

BACKGROUND: Rapid magnetic resonance imaging (MRI) protocols may be effective in the emergency department (ED) to evaluate nontraumatic neurologic complaints. We evaluate neuroimaging (rapid MRI [rMRI]), head computerized tomography [HCT], and full MRI) use following widespread implementation of rMRI protocols in a pediatric emergency department (ED). METHODS: We conducted a retrospective study in a tertiary care pediatric ED of encounters with neuroimaging during two 9-month periods: one prior to (control period) and one after generalized availability of 4 rMRI protocols (rMRI period). The primary outcome was differences in neuroimaging rates between the two periods. Secondary outcomes included ED process measures, unsuccessful imaging, and undetected pathology, with full MRI within 14 days as the reference standard. RESULTS: There were 1052 encounters with neuroimaging during the control and 1308 during the rMRI periods. Differences in neuroimaging between periods were 27.7% for rMRI (95% CI, 24.4, 31.0), - 21.5% for HCT (95% CI, - 25.5, - 17.5), and - 6.2% for full MRI (95% CI, - 9.3, - 3.1%.) Time to imaging (182 [IQR 138-255] versus 86 [IQR 52-137] minutes) as well as ED length of stay (396 [IQR 304-484] versus 257 [IQR 196-334] minutes) was longer for rMRI versus HCT (p < 0.01). Between the control and rMRI periods, there were differences in types of neuroimaging performed for patients with altered mental status, headache, seizure, shunt dysfunction, stroke, syncope, trauma, vomiting, infection, and other neurologic complaints (p < 0.05). rMRI studies were unsuccessful in 3.6% of studies versus 0.0% of HCTs (p < 0.01). The 22 unsuccessful rMRI studies were unsuccessful due to artifacts from dental hardware (n = 2) and patient motion (n = 20). None of the rMRI studies with full MRI follow-up imaging had undetected pathology; the false negative rate for the HCT exams was as high as 25%. CONCLUSIONS: After routine ED use of 4 rMRI protocols, there was a more than 20% decrease in HCT use without missed diagnoses. Time to neuroimaging and length of stay were longer for rMRI than HCT, with higher rates of unsuccessful imaging. Despite these limitations, rMRI may be an alternative to HCT for nontraumatic complaints in the ED.

Utility of image fusion software in identifying shunt malfunction.

PURPOSE: Pediatric shunt malfunction occurs frequently and is important to recognize due to the high associated morbidity and mortality. Although neuroimaging plays a crucial role in the diagnosis, it remains imperfect. We sought to identify the effect of image fusion software in predicting shunt malfunction. METHODS: A total of 248 rapid shunt series brain MRIs performed between 2013 and 2017 were compared with prior neuroimaging for changes in ventricular size by two methods: radiology report and Brainlab fusion. Shunt malfunction was defined by an operative report confirming malfunction within 72 h of neuroimaging. The two methods were compared by logistic regression models, with sensitivity and specificity subsequently calculated. RESULTS: Shunt malfunction was identified in 40 cases (16.1%). Imaging report demonstrated a lower Akaike information criterion than the Brainlab fusion and is therefore a better fitting model. While sensitivity is similar for the two models, 0.94 (0.90 to 0.97, 95% CI) for imaging report, and 0.95 (0.91 to 0.98, 95% CI) for Brainlab, the specificity was significantly different, 0.50 (0.37 to 0.63, 95% CI) and 0.33 (0.24 to 0.44, 95% CI) respectively. CONCLUSIONS: Our data indicate that an increased ability to detect subtle changes in ventricular size does not translate to improved accuracy, but instead leads to decreased specificity, and therefore an overdiagnosis of shunt malfunction in children with normally functioning shunts. While imaging continues to play a prominent role in the identification of shunt malfunction, neurosurgical clinical evaluation remains crucial to the final diagnosis.

Rapid MRI evaluation of acute intracranial hemorrhage in pediatric head trauma.

INTRODUCTION: Rapid MRI with ultrafast T2 sequences can be performed without sedation and is often used in place of computed tomography (CT) to evaluate pediatric patients for indications such as hydrocephalus. This study investigated the sensitivity of rapid magnetic resonance imaging (MRI) for detection and follow-up of acute intracranial hemorrhage in comparison to CT, which is commonly the first-line imaging. METHODS: Patients presenting to a pediatric hospital with acute intracranial hemorrhage on CT and follow-up rapid MRI within 48 h were included. Rapid MRI studies consisted of three plane ultrafast T2 sequences either with or without axial gradient echo (GRE) sequences. Identification of hemorrhage on rapid MRI was assessed by readers both blinded and unblinded to prior CT results. RESULTS: One hundred two acute hemorrhages in 61 patients were identified by CT. Rapid MRI detection of subdural and epidural hemorrhages was modest in the absence of prior CT for comparison (sensitivity 61-74 %), but increased with review of the prior CT (sensitivity 80-86 %). Hemorrhage size was a significant predictor of detection (p < 0.0001). Three plane fast T2 images alone without GRE sequences were poor at detecting subarachnoid hemorrhage (sensitivity 10-25 %); rapid MRI with GRE sequences identified the majority of subarachnoid hemorrhage (sensitivity 71-93 %). GRE modestly increased detection of other extra-axial hemorrhages. CONCLUSIONS: Rapid MRI with GRE sequences is sensitive for most acute intracranial hemorrhages only when a prior CT is available for review. Rapid MRI is not adequate to replace CT in initial evaluation of intracranial hemorrhages but may be helpful in follow-up of known hemorrhages.

Comparison of non-sedated brain MRI and CT for the detection of acute traumatic injury in children 6 years of age or less.

CT is considered the first-line study for acute intracranial injury in children because of its availability, detection of acute hemorrhage, and lack of sedation. An MRI study with rapidly acquired sequences can obviate the need for sedation and radiation. We compared the detection rate of rapid non-sedated brain MRI to CT for traumatic head injury in young children. We reviewed a series of children 6 years of age or less who presented to our ED during a 5-year period with head trauma and received a non-sedated brain MRI and CT within 24 h of injury. Most MRI studies were limited to triplane T2 and susceptibility sequences. Two neuroradiologists reviewed the MRIs and CTs and assessed the following findings: fracture, epidural hematoma (EDH)/subdural hematoma (SDH), subarachnoid hemorrhage (SAH), intraventricular hemorrhage (IVH), and parenchymal injury. Thirty of 33 patients had radiologically identified traumatic injuries. There was an overall agreement of 82 % between the two modalities. Skull fracture was the only injury subtype which had a statistically significant difference in detection between CT and MRI (p = 0.0001), with MRI missing 14 of 21 fractures detected on CT. While not statistically significant, MRI had a higher detection rate of EDH/SDH (p = 0.34), SAH (p = 0.07), and parenchymal injuries (p = 0.50). Non-sedated MRI has similar detection rates to CT for intracranial injury in young children presenting with acute head trauma and may be an alternative to CT in select patients.

Calibrationless parallel imaging reconstruction based on structured low-rank matrix completion.

PURPOSE: A calibrationless parallel imaging reconstruction method, termed simultaneous autocalibrating and k-space estimation (SAKE), is presented. It is a data-driven, coil-by-coil reconstruction method that does not require a separate calibration step for estimating coil sensitivity information. METHODS: In SAKE, an undersampled, multichannel dataset is structured into a single data matrix. The reconstruction is then formulated as a structured low-rank matrix completion problem. An iterative solution that implements a projection-onto-sets algorithm with singular value thresholding is described. RESULTS: Reconstruction results are demonstrated for retrospectively and prospectively undersampled, multichannel Cartesian data having no calibration signals. Additionally, non-Cartesian data reconstruction is presented. Finally, improved image quality is demonstrated by combining SAKE with wavelet-based compressed sensing. CONCLUSION: Because estimation of coil sensitivity information is not needed, the proposed method could potentially benefit MR applications where acquiring accurate calibration data is limiting or not possible at all.

Rapid brain MRI for image-guided ventricular catheter placement in pediatric patients: protocol and preliminary clinical outcomes.

OBJECTIVE: Neuronavigation is a useful adjunct for catheter placement during neurosurgical procedures for hydrocephalus or ventricular access. MRI protocols for navigation are lengthy and require sedation for young children. CT involves ionizing radiation. In this study, the authors introduce the clinical application of a 1-minute rapid MRI sequence that does not require sedation in young children and report their preliminary clinical experience using this technique in their pediatric population. METHODS: All patients who underwent ventricular catheter placement at a children's hospital using a rapid noncontrast MRI protocol, standard MRI, or head CT from July 2021 to August 2023 were included. Type of procedure, etiology of hydrocephalus, ventricle configuration and size, morphology of ventricles, need for adjunctive intraoperative ultrasound, duration of procedure, accuracy of catheter placement, and need for proximal revision within 90 days were retrospectively recorded and compared across imaging modalities. RESULTS: Sixty-eight patients underwent 83 procedures: 21 underwent CT navigation, 29 standard MRI, and 33 rapid MRI. Patients who received standard MRI more often had tumor etiology, while those who underwent CT and rapid MRI had posthemorrhagic etiology (χ2 = 13.04, p = 0.042). Intraoperative ultrasound was required for 1 patient in the standard MRI group and 1 patient in the CT group. There was no difference in procedure time across groups (p = 0.831). On multivariable analysis, procedure time differed by procedure type, where external ventricular drain placement and proximal revision were faster (p < 0.001 and p < 0.028, respectively). Proximal revision due to obstruction within 90 days occurred in 3 cases (in the same patient with complex loculated hydrocephalus) in the rapid MRI group and 2 cases in the CT group. CONCLUSIONS: Although this study was not powered for statistical inference, the authors report on the clinical use of a 1-minute rapid MRI sequence for neuronavigation in hydrocephalus or ventricular access surgery. There were no instances in which intraoperative ultrasound was required as an adjunct for procedures navigated with rapid MRI, and intraoperative time did not differ from that of standard navigation protocols.

Effectiveness and Predictors of Poor Prognosis Following Intravenous Thrombolysis in Patients with Wake-Up Ischemic Stroke Guided by Rapid MRI.

PURPOSE: Our aim was to investigate the effectiveness and predictors of poor prognosis in WUIS patients who received alteplase thrombolysis under the guidance of diffusion-weighted imaging (DWI)-T2-weighted imaging (T2WI) mismatch. PATIENTS AND METHODS: We recruited patients within 4.5 h of acute ischemic stroke (AIS) and WUIS patients with uncertain onset times from two stroke centers. To evaluate effectiveness, we compared National Institutes of Health Stroke Scale (NIHSS) scores between the two groups at admission and at 24 h, 3 days, and 1 week thereafter. We also compared the two groups with respect to the modified Rankin Scale (mRS) score at 90 days after thrombolysis. The WUIS patients were divided into a favorable prognosis group (mRS score: 0-1 points) and a poor prognosis group (mRS score ≥2 points). Data were compared between the two subgroups to identify factors that influence poor prognoses. The receiver operating characteristic (ROC) curve was used to evaluate the predictive value of factors related to poor prognosis. RESULTS: A total of 114 patients with WUIS and 316 patients with AIS were enrolled in the study. There were no significant differences between the two groups in terms of NIHSS or 90-day mRS scores (p > 0.05). Baseline NIHSS score (odds ratio [OR] = 1.490, 95% confidence interval [CI] 1.248-1.779, p < 0.001) and atrial fibrillation (OR = 3.825, 95% CI 1.218-12.016, p = 0.022) were identified as independent predictors of poor prognosis following thrombolysis in WUIS patients. The combined ROC diagnosis of these two variables had an area under the curve of 0.850. CONCLUSION: The DWI-T2WI sequence is an effective method to guide intravenous thrombolytic therapy for WUIS. Baseline NIHSS score and atrial fibrillation were identified as independent predictors of poor prognosis following thrombolysis in WUIS patients.

Rapid Brain MRI Use in a Pediatric Emergency Department.

Investigators from the University of Pittsburgh (Department of Emergency Medicine and Division of Pediatric Radiology) and Feinberg School of Medicine (Division of Emergency Medicine) studied the rates of neuroimaging (rapid brain MRI [rMRI], head CT [HCT], and full MRI) before and after implementation of four rapid MRI protocols in their ED.

National Imaging Trends in Pediatric Traumatic Brain Injury and Hydrocephalus.

OBJECTIVE: Reduction in use of computed tomography (CT) in favor of rapid-sequence magnetic resonance imaging (MRI) to decrease pediatric radiation exposure has varied across institutions in the United States. The aims of this study were to understand national trends in CT and rapid-sequence MRI usage and identify variables affecting imaging practices and obstacles to CT reduction. METHODS: This was a retrospective review of deidentified discharge data for children with hydrocephalus and traumatic brain injury (TBI) in the Healthcare Cost and Utilization Project Kids' Inpatient Database in 2000, 2003, 2006, 2009, 2012, and 2016. Utilization of MRI without contrast and CT was extracted using International Classification of Diseases, Ninth Revision, and International Classification of Diseases, Tenth Revision, codes. Hospital region and age cohorts were extracted and used to categorize data. χ2 tests and logistic regression were used for analysis. RESULTS: Hospitalizations utilizing CT decreased (P < 0.05) and hospitalizations utilizing MRI increased (P < 0.05) overall in both diagnosis groups throughout the years analyzed. However, there was significant regional variation in imaging. The Northeast had higher CT rates (P < 0.05) and the South had lower CT rates in patients with hydrocephalus and TBI (P < 0.05). No regional variation was found for rates of MRI use in patients with TBI. CONCLUSIONS: Nationwide, the average number of discharges after hospitalizations utilizing CT in patients with hydrocephalus and TBI has decreased, while discharges after hospitalizations utilizing MRI as an alternative imaging modality have increased. Despite successful overall CT reduction, significant regional variation exists within this trend showing inconsistent reduction of CT use.

Development of ultrafast UTE imaging for granular systems.

Ultrashort echo time (UTE) imaging is commonly used in medical MRI to image 'solid' types of tissue; to date it has not been widely used in engineering or materials science, in part due to the relatively long imaging times required. Here we show how the acquisition time for UTE can be reduced to enable a preliminary study of a fluidized bed, a type of reactor commonly used throughout industry containing short T2∗ material and requiring fast imaging. We demonstrate UTE imaging of particles with a T2∗ of only 185µs, and an image acquisition time of only 25ms. The images are obtained using compressed sensing (CS) and by exploiting the Hermitian symmetry of k-space, to increase the resolution beyond that predicted by the Nyquist theorem. The technique is demonstrated by obtaining one- and two-dimensional images of bubbles rising in a model fluidized bed reactor.

Gastric emptying and duodenal motility upon intake of a liquid meal with monosodium glutamate in healthy subjects.

Glutamate is thought to serve as a special signal for gut functions. We investigated the effects of monosodium l-glutamate (MSG) on gastric emptying and duodenal motility. Ten healthy male volunteers underwent rapid magnetic resonance imaging (MRI) of the abdomen. Coronal images were successively acquired after ingestion of liquid meal (200 kcal in 200 mL: 9 g protein, 28.4 g carbohydrate, 5.6 g fat, 370 mg Na(+)) with and without 0.5% MSG. During the acquisition of MRI, participants breathed freely. In all participants, the gastric residual volume gradually decreased to 80.1 ± 14.2% without MSG and to 75.9 ± 14.3% with MSG after 60 min (P = 0.45 between the groups, n = 10). In two of 10 participants, gastric emptying slowed down significantly, whereas in the remaining eight participants, gastric residual volume decreased to 84.0 ± 13.1% without MSG, and to 73.0 ± 14.6% with MSG after 60 min (P = 0.015, n = 8). There was no difference in the shape of the stomach between groups. In four of the eight participants responding positively to MSG, the duodenum wall was sufficiently identified to quantify the motions. The inclusion of MSG enhanced duodenal motility, judging from changes in (1) the magnitude of the duodenal area, (2) the center of gravity, and (3) the mean velocity of the wall motions. The third parameter most significantly indicated the excitatory effect of l-glutamate on duodenum motility (~ three- to sevenfold increase during 60 min, P < 0.05, n = 4). These results suggest that MSG accelerates gastric emptying by facilitating duodenal motility, at least in subjects with positive responses to MSG.

Rapid Short MRI Sequence Useful in Eliminating Stroke Mimics Among Acute Stroke Patients Considered for Intravenous Thrombolysis.

BACKGROUND: Acute stroke teams are challenged by IV-tPA decision making in patients with acute neurological symptoms when the diagnosis is unclear. The purpose of this study was to evaluate the ability of the rapid Brain Attack Team (BAT) MRI in selecting patients for IV-tPA administration who present acutely to the emergency room with stroke-like symptoms and an unclear diagnosis. METHODS: Consecutive patients were identified who presented within 4.5 hours of onset of stroke-like symptoms and considered for treatment with IV-tPA. When the diagnosis was not clear, a 9-minute BAT MRI was obtained. Stroke risk factors and NIH stroke scale obtained on presentation were compared between patients in whom BAT MRI was obtained and those in whom BAT MRI was not obtained. Similarly, comparisons were made between patients in whom BAT MRI detected abnormalities and those in whom BAT MRI did not detect abnormalities. BAT MRIs were analyzed to determine if radiological findings impacted clinical management and discharge diagnosis. RESULTS: In a 30-month period, 432 patients presenting with acute stroke-like symptoms were identified. Of these patients, 82 received BAT MRI. Patients receiving BAT MRI were younger, more likely to be smokers, and less likely to be selected for IV-tPA administration compared to those in whom a more definitive diagnosis of stroke precluded a BAT MRI. Of the 82 BAT MRIs, 25 were read as positive for acute ischemia. The patients with acute ischemia on BAT MRI were older, more likely to be males, have a history of hypercholesterolemia and atrial fibrillation, and more likely to be selected for IV-tPA administration compared to those with a negative BAT MRI. Of the 57 BAT MRIs read as negative for acute ischemia or hemorrhage, discharge diagnoses included TIA, MRI negative stroke, conversion/functional disorder, and multiple other illnesses. CONCLUSION: In patients with acute stroke-like symptoms, BAT MRI may be used to confirm acute ischemic stroke, exclude stroke mimics, and assess candidacy for IV-tPA.