Keywords: Stroke, Perfusion, Stroke, DSC MRI, Ischemia, Blood Flow Quantification, Deep Learning

Motivation: To assess the ability of quantitative transport mapping (QTM) to estimate blood flow in stroke from DSC MRI through a deep learning model.

Goal(s): To use an automated deep learning based method to measure blood flow in stroke using DSC MRI.

Approach: A deep learning network (QTMnet) is trained on synthetic MR data generated using realistic vascular models to learn the mapping between DSC MR data and underlying tissue blood flow.

Results: QTMnet demonstrates decreased perfusion in ischemic lesion compared to contralateral healthy tissue (p=0.0006), similar to results using traditional modeling. QTMnet performed well without needing to select an appropriate AIF or regularization.

Impact: QTMnet may identify hypoperfused tissue following stroke in an automated manner. Accurate blood flow estimation may assist in determining whether reperfusion therapy is beneficial.

Keywords: Stroke, Vessels

Motivation: Identifying the culprit plaque among the plaques in stroke patients is important. Previous studies were based on 2D sequences, 3D HRMR-VWI is a novel imaging examination to evaluate  vessel wall.

Goal(s): To establish a high performance model to identify the culprit plaques in stroke patients.

Approach: We used traditional method and five different radiomics methods to identify the culprit plaques in stroke patients based on 3D HRMR-VWI.

Results: In traditional information, intraplaque hemorrhage is an independent predictor for culprit plaques, the efficacy of radiomics is much higher than traditional model, the extreme gradient boosting method showed the best performance in radiomics models.

Impact: Our study established an accurate method to identify the culprit plaques in stroke patients, to help clinicians make a more precise treatment plan, it will improve the prognosis and prevent the recurrence in stroke patients.

Keywords: Stroke, Ischemia

Motivation: Timely diagnosis of patient with acute neurologic symptom is critical. Detecting small lesions on DWI can be challenging and experience plays a significant role, especially when motion artifacts affect image quality.

Goal(s): Our goal was to shorten acquisition time and provide highly sensitive images of small lesions, particularly for emergency clinicians unfamiliar with DWI.

Approach: We included 80 patients, comparing quantitative and qualitative analyses between conventional and deep-learning DWI. We assessed diagnostic performance among experienced neuroradiologists and primary care physician.

Results: Results showed similar image quality between two sequences, but deep-learning DWI exhibited superior lesion conspicuity. Diagnostic accuracy remained consistent between the two.

Impact: Deep-learning DWI offers comparable image quality with significant shorter acquisition time. It also enhances detection of tiny brain lesion, providing diagnostic confidence to less experienced clinicians in emergency situation.

Keywords: Stroke, Segmentation

Motivation: Arterial spin labeling (ASL) has shown comparable results with dynamic susceptibility contrast magnetic resonance imaging in evaluating hypoperfused lesions in patients with acute ischemic stroke (AIS). However, the precise delineation of penumbra in ASL is still challenging. 

Goal(s): To develop a deep learning (DL) model based on ASL to identify eligible candidates for endovascular treatment in AIS patients. 

Approach: A multi-task DL model was proposed for simultaneous segmentations of penumbra and infarct by combining cerebral blood flow and DWI images.

Results: The multi-task segmentation performed well, which is comparable to the results achieved by radiologists.

Impact: The proposed approach performed well for the segmentation of penumbra and infarct, which could provide a promising approach for assisting decision-making for endovascular treatment in patients with acute ischemic stroke.

Keywords: Stroke, High-Field MRI, Spectroscopy, Metabolites, Stem Cell Therapy, Neuroinflammation, Preclinical

Motivation: A leading cause of death and disability, stroke is treated foremost by restoring blood flow, but follow-up therapies that focus on ischemic tissue recovery are critical as is the evaluation of therapeutic efficacy.

Goal(s): This work administers extracellular vesicles (EV) derived from human mesenchymal cells (hMSC) to salvage tissue while monitoring recovery and metabolic changes longitudinally using ultra-high field MRI/S.

Approach: T₂-W MRI,²³Na-CSI, and ¹H-MRS were used to quantify lesion reduction, sodium homeostasis and energetic remodeling. 

Results: Upon EV treatment, sodium (and to a lesser extent proton) lesions were reduced by day 3, while lactate, creatine and NAA were stabilized compared to control.

Impact: Combined sodium MRI and proton MRS provide a more sensitive and early quantitative metric to evaluate the efficacy of stem cell-derived therapy following ischemia and longitudinal metabolic, ionic and functional recovery. Such methods can evaluate other treatments against different pathologies.

Keywords: Stroke, Oxygenation, Oxygen Extraction fraction, DWI reversal, infarct reversal, ischemic stroke

Motivation: In patients with ischemic stroke, ischemic tissue reversal after reperfusion therapy has been studied structurally, but metabolic changes have not been widely researched.

Goal(s): Assess the ability of a recently developed algorithm to quantify oxygen extraction fraction in ischemic tissue that reverses and what does not reverse.

Approach: Using multi-echo gradient images, oxygen extraction fraction and magnetic susceptibility maps were generated for 26 ischemic stroke patients. Values were extracted respectively at 24 to 72 hours in the ischemic tissue that reversed and tissue that did not.

Results: Significant differences in oxygen extraction were observed in tissue that reversed versus tissue that did not.

Impact: Differentiating oxygen extraction fraction values in ischemic tissue at an early stage of ischemic stroke can potentially inform neuroprotection strategies for clinicians to reduce post-reperfusion secondary injury. 

Keywords: Stroke, Perfusion, sCoV

Motivation: There is little understanding of how arterial transit artefacts (ATA) on ASL-MRI, which indicate regions of haemodynamic compromise, change in patients with carotid artery stenosis following optimised medical therapy versus surgical revascularisation.

Goal(s): To assess treatment effects using visually rated ATA severity and a spatial coefficient of variance before and after optimised medical therapy versus additional surgical revascularisation.

Approach: We visually rated ATAs using an established four-point grading system and computed the spatial coefficient of variance in corresponding regions.

Results: Both methods demonstrated only surgical revascularisation led to significant improvements in haemodynamics 1-month post-treatment, solely within the ipsilateral middle cerebral artery cortical territory.

Impact: A robust method of quantifying early haemodynamic treatment effects could be used to identify who truly benefits from surgical revascularisation in the long-term. Future work will correlate these measures to long-term clinical outcomes.

Keywords: Stroke, Stroke

Motivation: Iron deposition is associated with brain injury. Exploring alterations of iron deposition in cerebral regions caused by cerebral artery stenosis may help to predict degree of brain injury.

Goal(s): This study aimed to quantify iron alterations in both cortex and deep GM nuclei in patients with long-term unilateral MCA severe stenosis.

Approach: Using structural imaging and QSM, we employed automatic brain regional susceptibility analysis.

Results: We found that patients had higher susceptibility in ipsilateral CN, PU, GP, and transverse temporal gyrus than contralateral side, and patient group had higher susceptibility in PU, GP, TH, middle frontal gyrus, and transvers temporal gyrus than HCs.

Impact: By brain regional susceptibility analysis, this study demonstrated abnormal iron accumulation in deep GM nuclei, middle frontal gyrus, and transvers temporal gyrus after chronic MCA severe stenosis. Therefore, iron deposition may be a potential biomarker for evaluating long-term cerebral ischemia.

Keywords: Stroke, Stroke

Motivation: To explore synthetic MRI's potential for improved stroke lesion characterization and metabolic activity prediction.

Goal(s): To Enhance stroke lesion visualization and to estimate regional metabolism via quantitative relaxation values in synthetic MRI.

Approach: 10 stroke patients underwent integrated PET/MR scanning. We compared tissue contrast in synthetic tailored contrast-enhanced composite images with conventional T2 FLAIR. Relaxometry values were used to build predictive models for PET SUV.

Results: Composite images significantly improved stroke lesion visibility compared to traditional methods. Relaxometry values successfully predicted metabolic activity within the lesion.

Impact: This study demonstrates the potential of synthetic MRI in stroke patients, offering improved 

Keywords: Stroke, Neuro

Motivation: To apply the Precise IQ Engine (PIQE), a new high-resolution MR reconstruction technique, for Flow Sensitive Black Blood (FSBB) imaging.

Goal(s): To evaluate the usefulness of PIQE comparing the super-resolution FSBB images reconstructed from low-resolution FSBB images with short acquisition time using PIQE, low-resolution FSBB images, and high-resolution FSBB images.

Approach: On three FSBB images, cerebral microbleed (CMB) was identified and image quality was assessed for 121 patients who underwent FSBB images for CMB detection.

Results: PIQE made CMBs, blurred due to low resolution, clearly visible. PIQE-FSBB has image quality comparable to high-resolution FSBB even with shorter scan time.

Impact: PIQE, a technique that reconstructs high-resolution images from low-resolution images, was applied for FSBB imaging. The super-resolution FSBB reconstructed from low-resolution FSBB with short acquisition time had good quality, and was comparable to high-resolution FSBB for cerebral microbleeds detection.

Keywords: Stroke, Perfusion, ASL

Motivation: Clinical usefulness of multi-delay (MD) as well as long label duration (LD) pseudo-continuous arterial spin labelling (pCASL) have been suggested. However, MD-pCASL scheme including long LD has not been established.

Goal(s): Long LD combined MD-pCASL scheme was assessed in terms of quantification. The possibility of scan acceleration was also studied.

Approach: MD-pCASL with maximum LD 3 sec for 11 (3min 13sec) and 5 delays (1min 38sec) were assessed, and compared to a scheme with maximum LD 2 sec.

Results: Reasonable quantitative values were obtained by both LD 3 sec schemes, while providing higher SNR.

Impact: The potential of a MD-ASL scheme with long label duration has been demonstrated in terms of improved SNR, reasonable quantitative parameters, and acceleration of scan time. Advantages of the scheme are especially expected for neurovascular applications.

Keywords: Stroke, Stroke, ultrafast MRI, emergency, inpatient, msEPI, compressed sensing, MRA

Motivation: MRI is more sensitive than CT for diagnosing ischemic stroke, yet its use in the acute setting is limited by acquisition time.

Goal(s): To determine the diagnostic performance of an ultrafast 3T brain MRI/head MRA protocol compared to a standard-of-care reference protocol for evaluation of acute ischemic stroke.

Approach: Two raters evaluated diagnostic quality and presence of acute and chronic intracranial findings in 12 inpatients imaged with ultrafast and reference protocols. 

Results: Both raters found the ultrafast protocol was of diagnostic quality. Acute infarction, significant vascular findings, and most chronic findings were equally identified on both ultrafast and reference protocols. 

Impact: The 3.5-minute ultrafast MR/MRA protocol may improve time to diagnosis and intervention in acute stroke without sacrificing diagnostic quality. It may improve patient throughout and triage in inpatient and emergency settings without compromising diagnosis or patient safety. 

Keywords: Stroke, fMRI (resting state)

Motivation: Post-stroke apathy (PSA) is a highly heterogeneous disorder, which presents obstacles to the effective diagnosis and treatment.

Goal(s): We intended to identify distinct subtypes of PSA and revealed the underlying neurological substrates of PSA heterogeneity.  

Approach: By comparison between stroke patients and normal controls, abnormal alterations of resting-state functional connectivity (RSFC) were determined and correlated with apathy syndrome. PSA subtypes were identified based on the significant canonical correlates using hierarchical clustering.

Results: The best clustering scheme was four clusters and we observed significant group differences in graph theoretic metrics.

Impact: Various subtypes displayed distinct characteristics in terms of RSFC and graph theoretic metrics. Our study emphasizes the importance of RSFC of neural network in the evaluation of PSA heterogeneity and provides new insights for future research and therapeutic targets.

Keywords: Stroke, Stroke, Rehabilitation, DTI

Motivation: To study the impact of closed-loop brain stimulation in neuroplasticity in stroke rehabilitation.

Goal(s): In this study we investigate with fMRI and diffusion tensor MR imaging the neural correlates with closed loop brain stimulation in stroke.

Approach: fMRI and DTI for six subjects was taken in a pilot case-control study.

Results: fMRI and DTI both showed higher cortical activity and increase in FA values for ipsilesional CST in cohort of patients with TMS-robotic intervention than the control group.

Impact: A brain stimulation system integrated with an exoskeleton, providing a real-time bidirectional feedback mechanism for patients, has been shown to actively involve patients in their rehabilitation journey. 

Keywords: Stroke, Stroke, Reflexology, real-time, sensory, connectivity

Motivation: To characterize the biological substrates and mechanisms of reflexology.

Goal(s): (1) To characterize the somatotopic relationship between cortical activity and sensory stimulation of reflex areas. (2) To assess possible therapeutic effects of reflexology.

Approach: Real-time task-based and resting-state fMRI in 4 controls and 4 adults with stroke using multi-band multi-echo EPI.

Results: Deactivation of a bilateral network in superior-temporal gyrus, postcentral gyrus and insular cortex (depending on reflex area) in healthy controls and unilateral deactivation, which differed between left and right foot, in patients with stroke. Sensorimotor function in the hemiplegic hand improved (3 patients) and two-point discrimination increased (2 patients) after reflexology.

Impact: This preliminary real-time fMRI study demonstrates the potential to change the reflexologist’s technique application to focus on particular reflex areas for optimizing treatment results and to establish a neurobiological basis for predicting treatment outcomes in patients with neurological disorders.

Keywords: Stroke, Diffusion/other diffusion imaging techniques

Motivation: Post-stroke basal ganglia aphasia is common in clinical practice, and it is necessary to explain the causes of aphasia after basal ganglia infarction from imaging perspectives.

Goal(s): To obtain white matter fiber bundles associated with the occurrence of basal ganglia aphasia.

Approach: To apply DSI studio and use deterministic fiber-tracking algorithm to reconstruct language-related fiber bundles and measurequantitative anisotropy (QA) of each white matter tracts.

Results: The damage to language related white matter fiber bundles such as corpus callosum fibers may be related to the occurrence of basal ganglia aphasia after stroke.

Impact: By studying the integrity of white matter fiber bundles of basal ganglia aphasia after stroke, it provides an auxiliary role for clinical analysis of its pathogenesis.