Keywords: Stroke, Brain, Cerebral ischemia, NODDI, Vic, ODI

Motivation: It is currently unclear whether neurite orientation dispersion and density imaging (NODDI) can reflect the microstructure in early cerebral hypoperfusion.

Goal(s):   Therefore, this study aims to detect the cerebral microstructure using NODDI in rabbits’ cerebral ischemia model.

Approach:   The orientation dispersion index (ODI) and intracellular volume fraction (Vic) were calculated for comparing among groups, including pre-operative and post-operative of rabbit models, and control group. 

Results: The results showed that Vic of bilateral cerebral hemispheres in post-operative state was higher than that of pre-operative and control groups (all P < 0.05). NODDI could be used to reflect the mild injury in early cerebral ischemia.

Impact:   Early recognition of injury in brain tissue microstructure in patients with cerebral ischemia is helpful to guide clinical treatment, and NODDI will be able to identify early brain injury.

Keywords: Stroke, Diffusion/other diffusion imaging techniques

Motivation: Conventional low-resolution 2D DWI has limited diagnosis accuracy in stroke patients.

Goal(s): Our goal was to apply high-resolution 3D DWI in stroke patients and assess its diagnostic capabilities compared to low-resolution 2D DWI.

Approach: We employed simultaneous multislab imaging for 3D diffusion signal sampling, utilizing opposite phase encoding polarity for distortion correction and CPEN for boundary artifact correction. We conducted examinations on 15 acute stroke patients.

Results: The utilization of high-resolution 3D DWI with isotropic resolution significantly enhances image quality in terms of clarity, distortion levels, and clinical value, surpassing traditional 2D DWI.

Impact: High-resolution isotropic 3D DWI, using simultaneous multislab acquisitions, may help in the identification of small brain lesions that may be challenging to detect using low-resolution 2D DWI.

Keywords: Stroke, Stroke, chemical exchange saturation transfer,reperfusion, prognosis

Motivation: Amide proton transfer (APT) imaging can clarify the metabolic microenvironment after ischemia. Few clinical studies to date have examined its use in ischemic tissue after reperfusion therapy, where the pH may return to normal physiological level.

Goal(s): We used a numerical fitting of extrapolated semi-solid magnetization transfer reference (NEMR) method, which has been introduced to improve the detection of ischemia, to assess the tissue microenvironment after reperfusion therapy. 

Approach: Prospectively, case-control study

Results: We found both APT signal and mismatch pattern between APT and DWI (APT<DWI) could reflect tissue-level reperfusion status and provide complementary information to perfusion imaging for predicting 90-day neurological outcomes.

Impact: We demonstrated the utility of APT signal and mismatch pattern between APT and DWI (APT<DWI) as effective biomarkers to characterize the tissue microenvironment and predict 90-day functional outcomes after reperfusion in patients with ischemic stroke.

Keywords: Stroke, Traumatic brain injury

Motivation: This work is to identify d ²³Na (sodium) as a biomarker for early brain injuries (EBI) after subarachnoid hemorrhage (SAH).

Goal(s): This research utilizes a novel head-implanted coil to measure ¹H and ²³Na whole-brain MRI for characterization of EBI.

Approach: We achieved acquisition of ¹H for anatomical templates and ²³Na MRI images at an impressive spatial resolution of 300x300x500 µm.

Results:  We surprisingly observed that the ²³Na signal precedes the appearance of conventional ¹H diffusion-weighted signal after SAH-related brain injury. Also, a concentration gradient distribution of ²³Na mapping within the EBI regions demonstrated a finer granularity not typically depicted by conventional ¹H MRI.

Impact:  This work revealed the distinct ²³Na dynamics for EBI detection and highlighted the critical usage of a multi-modal platform to specify the EBI after SAH.

Keywords: Stroke, Inflammation

Motivation: Aiming to bridge the diagnostic gap in predicting perioperative ischemic lesions post-CAS, crucial for preempting recurrent strokes.

Goal(s): To pinpoint predictive markers on DWI for new ischemic brain lesions within 3 days post-CAS.

Approach: Employed a retrospective analysis of preoperative PET/MR imaging in 47 CAS patients, correlating with postoperative DWI outcomes.

Results: Identification of high PET SUVmax, SCAIL scores, and complex plaques as significant predictors of new ischemic lesions, offering a strategic tool for early high-risk patient detection.

Impact: This study aids clinicians in stratifying stroke risk, influencing patient management and treatment tailoring. It opens avenues for precision medicine in stroke prevention and underscores the need for advanced imaging in preoperative assessments.

Keywords: Stroke, Quantitative Imaging, microstructure\stroke

Motivation: Plaque inflammation is the main cause of plaque instability; thus, a convenient and noninvasive method of evaluating intracranial plaque inflammation is needed.

Goal(s): Noninvasive CDT DCE-MRI enables evaluating the inflammation of MCA culprit plaques in patients with IS.

Approach:  We compared the CDT DCE-MRI parameters of MCA culprit plaques between patients with acute and non-acute ischemic stroke (IS) and assessed the correlations between these parameters and stroke time.

Results: K^trans of the CDT DCE-MRI was higher in patients with acute IS than in patients with non-acute IS. K^trans was significantly negatively correlated with stroke time.

Impact: K^trans allows non-invasively distinguishing responses to MCA plaque inflammation between patients with acute and non-acute IS. CDT DCE-MRI may be a promising noninvasive tool for accurately assessing large intracranial arterial plaque inflammation.

Keywords: Stroke, Neurofluids, Perfusion, Reproducibility

Motivation: We investigated the reproducibility of cerebral blood flow (CBF) measurement techniques with phase contrast (PC) and arterial spin labeling (ASL) MRI  given their importance in diagnosing cerebrovascular diseases.

Goal(s): Demonstrate the reproducibility of phase contrast and arterial spin labeling MRI techniques for measuring CBF.

Approach: We used comparative analysis of CBF measurements using phase contrast and arterial spin labeling pre- and post- diamox vasodilation test, measured twice by a week apart.

Results: Strong interclass correlation across modalities and sessions, indicating strong reproducibility for both techniques.

Impact: We conclude that PC- and ASL- MRI measurements are in good agreement and have strong inter-session reproducibility in measuring CBF before and after vasodilation.

Keywords: Stroke, Quantitative Imaging, 4D flow MRI、Hemodynamics

Motivation: The change of hemodynamics in patients with symptomatic cerebral ischemia are not clear.

Goal(s): This study aims to explore the difference of hemodynamic characteristics in non-stenotic middle cerebral artery (MCA) between healthy subjects and cerebral ischemia patients.

Approach: The multiple hemodynamic parameters in the proximal, curved  and distal segments of MCA were quantitatively analyzed in these two groups  by using 4D flow MRI.

Results: The results showed that the peak blood flow velocity was lower and the circumferential WSS reduced in MCA, the energy loss impaired in the M1 segment of MCA  when compared cerebral ischemia patients with healthy subjects.

Impact: This study was based on 4D flow MRI to explore the hemodynamic characteristics of cerebral ischemia in non-stenosis MCA, which is helpful to reveal the mechanism of cryptogenic stroke and provides a possibility for future prediction of stroke risk.  

Keywords: Stroke, Vessels, lenticulostriate artery;perfusion

Motivation: Due to the limitations of standard imaging tools, few studies have directly reserched infarct lesion or its corresponding arteries to predict prognosis. Now, the morphology of lenticulostriate artery can be seen via VWI¹, and perfusion of infarct lesion can be determined via PWI²

Goal(s): To evaluate the effect of LSA features and quantitative perfusion on SSI prognosis

Approach: The patients were categorized into groups with poor and good prognoses based on the modified Rankin scale (mRS) score. Each group's LSA morphological parameters and perfusion status were compared.

Results: Poorer results are correlated with shorter LSA and lower rCBF

Impact: The prognosis of the SSI can be assessed by analyzing the morphology of the LSA and the subacute perfusion. Our findings provide evidence in support of early therapy intervention.

Keywords: Stroke, Brain

Motivation: Determination of a non-invasive imaging biomarker for outcome following ischemic stroke.

Goal(s): To investigate whether cerebral blood flow from arterial spin labeling can be used as an imaging biomarker for assessment of clinical outcome following stroke with mechanical thrombectomy. 

Approach: Prospective study with pseudo-continuous arterial spin labeling acquired few days after mechanical thrombectomy, combined with outcome evaluation few days and 3-months post-stroke.

Results: Percent cerebral blood flow difference (i.e., between infarct masks in relation to the mirrored mask in the unaffected hemisphere), pre-stroke modified Rankin Scale, and infarct volume were associated with functional independence (i.e., modified Rankin Scale 0-2 at 3-months post-stroke).

Impact: Percent cerebral blood flow difference from the infarct territory may predict functional independence in patients with ischemic stroke and mechanical thrombectomy. Thus, this quantitative parameter may be used as an early non-invasive imaging biomarker to predict clinical outcome.

Keywords: Stroke, Arterial spin labelling

Motivation: Cerebral perfusion-weighted imaging (PWI) can be used to characterize differences in hemodynamic characteristics between transient ischemic attack (TIA) and stroke populations, but little is known about the differences between DSC and ASL.

Goal(s): this study to investigate the differential hemodynamic characteristics of the corresponding regions of the middle cerebral artery (MCA) in patients with ischemic stroke and TIA, and to establish a prediction model for ischemic stroke.

Approach: Dynamic Susceptibility Contrast (DSC) and Arterial Spin Labeling (ASL)

Results: The results indicate that Hyperhomocysteinemia and DSC-2500msASL mismatch can be used to identify patients with TIA and stroke.

Impact: We found that differences in blood perfusion in stroke and TIA patients, especially DSC-2500msASL mismatch may be a biological marker of stroke, which provides a scientific basis for screening high-risk TIA patients and early clinical intervention.

Keywords: Stroke, Stroke

Motivation: Stroke patients commonly face challenges during clinical magnetic resonance imaging (MRI) examinations due to loss of consciousness and involuntary movements. This study aims to address these challenges using a self-developed ultra-fast, multiple overlapping-echo detachment (MOLED) quantitative magnetic resonance technology.

Goal(s): Through this technology, we seek to quantitatively detect potential damage to the motor-related normal-appearing corticospinal tract (NA-CST) following stroke.

Approach: Total  79 patients underwent routine scan and MOLED. A deep learning network was utilized for quantitative image reconstruction.

Results: MOLED T2 imaging showed high accuracy and repeatability, was unaffected by head motion, correlated with motor dysfunction severity, and predicted motor impairment post-stroke.

Impact: The MOLED technique quickly and accurately quantifies imaging in stroke patients with involuntary movements and helps monitor post-stroke motor impairment progression.

Keywords: Stroke, Stroke, MRSI

Motivation: Elucidating the time-dependent pathological evolution of infarction is essential for the effective management of stroke.

Goal(s): Our goal was to investigate the influence of vascular characteristics on neurometabolites changes within lesions at different times post stroke.

Approach: 3D ¹H-MRSI scanning using SPICE technology (scan time: 8 minutes, resolution: 2 × 3 × 3 mm³, FOV: 240 × 240 × 72 mm³) was performed on 74 acute stroke patients. The neurometabolites maps were compared with a statistical atlas of cerebral artery.

Results: We showed the vessel distributions were related to the neurometabolites changes following ischemic stroke, collectively improving the prediction of stroke symptom onset.

Impact: Using fast high-resolution 1H-MRSI together with cerebral artery atlas, our study showed that the interdependence between vessel distribution and neurometabolites changes in ischemic stroke. The finding may help find useful biomarkers for modeling stroke lesion evolution and symptom onset prediction.

Keywords: Stroke, Neuroscience, cerebral blood flow; gray matter volume; gray matter asymmetry; high-risk non-disabling ischemic cerebrovascular events;

Motivation: Patients with high-risk non-disabling ischemic cerebrovascular events (HR-NICE) are recommended as the key population for stroke prevention. However, the functional impairment and underlying neural mechanisms are rarely investigated in this cohort.

Goal(s): We attempt to confirm the neural and cognitive impairment and explain the mechanism of cognitive impairment in aspects of both hypoperfusion and cortical abnormality in HR-NICE patients.

Approach: Cerebral blood flow, grey matter volume and asymmetry were calculated based on MR perfusion and anatomical data.

Results: Hypoperfusion and cortical abnormality are significant in HR-NICE patients, these neural impairments are robustly correlated with cognitive decline.

Impact: Our study confirmed the existence of early neural damage in HR-NICE patients, which is reflected in multiple aspects of hypoperfusion, grey matter atrophy and decreased asymmetry. These abnormalities collectively contribute to cognitive decline, especially in patients with left involvement.

Keywords: Stroke, Stroke

Motivation: Understanding metabolic changes in diaschisis is essential for stroke rehabilitation.

Goal(s): Our goal was to investigate the neurometabolite alterations in the disconnected white matter (WM) tracts and the downstream cortical gray matter (GM) regions, and their associations in early stroke outcome.

Approach: 3D ¹H-MRSI scanning using SPICE technology (scan time: 8 minutes, resolution: 2×3×3 mm³, FOV: 240×240×72 mm³) was performed on 105 acute ischemic stroke patients.

Results: Our findings reveal a trend for decreased cortical GM NAA as the WM NAA in the diaschitic hemisphere decreases, both associated with early stroke outcome.

Impact: Using 3D high-resolution ¹H-MRSI, we found a potential involvement of neuronal mitochondria metabolism in the metabolic changes observed in diaschisis from stroke. It may offer valuable prognostic biomarkers in stroke patients management.

Keywords: Stroke, Arterial spin labelling

Motivation: Accurate quantification of cerebral perfusion in Moyamoya disease using ASL is challenging.

Goal(s): To investigate the effect of long LD in hybrid multi-delay PCASL of time-encoded and variable TR schemes.

Approach: Patients with Moyamoya disease were scanned with hybrid schemes with respectively 12 delays obtained with LD of 2s (LD2s) and 9 delays obtained with LD of 3s (LD3s). 

Results: The tSNR of LD3s was significantly higher than that of LD2s, especially in the regions with prolonged ATT. CBF measured by both methods showed a strong correlation, but the differences in CBF became larger for longer ATT.

Impact: The use of a long LD of 3s for hybrid multi-delay PCASL provides higher SNR compared to that of 2s, and may be useful for assessing cerebral perfusion with prolonged ATT as often seen in Moyamoya disease.