Keywords: Blood Vessels, Brain

Motivation: Recent developments enabled to measure brain tissue strain as induced by arterial pulsations in detail. This opens the opportunity to study how these strains are affected by the brain’s macroscopic environment and its local microstructure.

Goal(s): To explore to what extent the strain principal strain directions can be explained by both global boundary conditions and local tissue microstructure.

Approach: Systolic 3D strain measurements of the brain were compared with a brain model and DTI measurements.

Results: The first principal strain showed good agreement with the brain model and consistent spatial patterns were observed in comparisons between third principal strain and DTI data.

Impact: Our results help confirm previous ideas on how the brain swells during cerebral arterial pulsations while also providing a first view into the relationship between the direction of the Poisson effect and brain microstructure, opening up avenues for further research.

Keywords: Blood Vessels, Susceptibility, echo combination, multi-echo

Motivation: Scan times for multi-echo T₂^*w sequences are too long at 1.5T.

Goal(s): Shorten scan times by reducing the number of echoes needed for a specific contrast.

Approach: During this ISMRM, we introduced a novel echo combination method that increases contrast over the standard Root Sum-of-Squares (RSOS) technique. We applied this method to 7 and 6 echo 3D SPGR protocols and compared the results to a 9 echo protocol that used RSOS.

Results: Contrast was comparable or better in the 6 and 7 echo protocols using our technique, compared to the 9 echo protocol with RSOS, resulting in a scan time reduction of 23-26%.

Impact: Our echo combination technique allows fewer echoes in multi-echo T₂^*w imaging to match the contrast of higher echo protocols resulting in a 23-26% scan time reduction. This alleviates one of the primary concerns clinicians have using T₂^*w imaging at 1.5T.

Keywords: Blood Vessels, Perfusion, Small vessel disease

Motivation: Largely unidentified pathophysiological mechanisms in cerebral small vessel disease (cSVD) hamper treatment development. One of the potentially affected functions is cerebral blood flow (CBF) autoregulation.

Goal(s): Establish whether brain tissue perfusion is (in)dependent of macrovascular blood supply in cSVD patients.

Approach: The relationship between internal carotid artery blood flow (blood supply), measured with phase-contrast MRI, and gray matter CBF (CBF_GM), measured with arterial spin labeling, was determined separately for cSVD patients (n=41) and controls (n=18).

Results: A significant, positive relationship between CBF_GM and blood supply was found in cSVD patients, but not in controls, suggesting impaired autoregulation in cSVD.

Impact: We revealed a positive relationship between internal carotid artery blood supply and the cerebral blood flow in gray matter in cerebral small vessel disease patients, but not in controls, which could indicate compromised autoregulatory capacity.

Keywords: Blood Vessels, Blood vessels, 4D Flow

Motivation: To investigate the relationship between the enhancement of intracranial cystic aneurysm walls and aneurysm morphology and hemodynamics. 

Goal(s): The study aimed to identify new imaging indicators for intracranial aneurysm enhancement.

Approach: We conducted a retrospective collection of magnetic resonance images of aneurysm cases and grouped them based on aneurysm wall enhancement grades. Then the differences in morphological and hemodynamic parameters between groups were compared.

Results: The study found that the maximum flow rate at the aneurysm neck and the ratio of the aneurysm neck to the maximum flow rate of the parent artery were statistically significant.

Impact: This study investigated the hemodynamic relationship between aneurysms and the parent artery, and its potential impact on aneurysm wall enhancement. These results could offer valuable insights into the connection between aneurysm wall enhancement and hemodynamics.

Keywords: Blood Vessels, Animals, The glymphatic system

Motivation: The pathogenesis of hypertensive cerebral edema remains elusive

Goal(s): To visualize and evaluate the transport function of the glymphatic system in the spontaneously hypertensive rats (SHR).

Approach: We used the dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) and immunofluorescence analysis

Results: And we found that there was a significant change in the transport function of the glymphatic system and a decrease in the expression of aquaporin-4 (AQP4) around blood vessels. 

Impact: The combination of DCE-MRI and immunofluorescenc analysis can facilitate further exploration of mechanisms underlying brain edema in the spontaneously hypertensive animal models, thus aiding in the study of the glymphatic system.

Keywords: Blood Vessels, Diffusion Tensor Imaging, cerebral small vessel disease; glymphatic clearance function; ALPS index; SVD score

Motivation: The pathogenesis of cerebral small vessel disease (SVD) is unclear, which may be related to glymphatic clearance.

Goal(s): To assess the association between glymphatic clearance function and the extent of cerebral damage in SVD, along with the effects on cognitive function.

Approach: We derived the ALPS index from DTI data to evaluate lymphatic function, and we utilized MR imaging to determine the SVD score as a measure of cognitive function.

Results: We found a significantly decrease in ALPS index in SVD patients compared to healthy controls, and a significantly negative correlation between the ALPS index in the left hemisphere and SVD severity.

Impact: Glymphatic clearance dysfunction may be present in patients with SVD and may be associated with decreased cognitive function.

Keywords: Blood Vessels, Velocity & Flow

Motivation: The hemodynamic changes after superficial temporal artery-middle cerebral artery (STA-MCA) bypass in patients with Moyamoya disease (MMD) remain unclear. 4D flow is expected to provide more information about the hemodynamic parameters of patients with MMD before and after surgery.

Goal(s): To clarify the hemodynamics by comparing flow parameters obtained by 4D flow magnetic resonance imaging (MRI).

Approach: Patients with MMD were prospectively recruited for 4D flow magnetic resonance scanning before and after bypass surgery.

Results: After bypass surgery, the contralateral internal carotid artery blood flow decreased and cerebral blood flow was redistributed.

Impact: The results indicate that 4D flow MRI is a feasible, noninvasive alternative for evaluating bypass grafts in the early postoperative period. These flow parameter values may help improve the way patients are evaluated after bypass surgery.

Keywords: Blood Vessels, Brain, 7T-CEST

Motivation: The incidence of middle cerebral arterial (MCA) stenosis increases yearly, molecular biomarkers for this condition are needed. Amide proton transfer imaging is a potential imaging marker. 

Goal(s): To investigate the APT changes in MCA stenosis patients.

Approach: We quantitatively evaluated both the affected and healthy middle cerebral arterial blood-supplying brain regions in eight patients with unilateral middle cerebral arterial stenosis using CEST-APT at 7T. 

Results: The CEST values of the affected MCA-supplied brain regions were higher than those of the healthy MCA-supplied brain regions, suggesting metabolic alterations in patients with MCA stenosis.

Impact: CEST values for vascularized brain regions can be quantitatively measured using 7T-CEST and can provide new markers for mechanistic and intervention studies in patients with MCA stenosis. This can contribute to a better understanding of the pathogenesis of MCA stenosis.

Keywords: Blood Vessels, fMRI (resting state), cerebrovascular reactivity

Motivation: Mapping of cerebrovascular reactivity (CVR) using resting-state BOLD fMRI (RS-fMRI) was raised in 2017 and 2021 with verification using the moyamoya disease (MD). But pathological hemodynamics of MD was missing by RS-fMRI.

Goal(s): Arterial stealing phenomenon can be demonstrated by carbogen-based fMRI (CO2-CVR), but not by RS-fMRI.

Approach: Both RS-CVR and CO2-CVR using a 3T MR and an automatic delivery system of carbogens were acquired for eleven subjects and ten patients with MD. Bland-Altman plots was applied for both RS-CVR and CO2-CVR.

Results: By using CO2-CVR, unique negative CVR of MD verified the arterial stealing phenomenon which was missed by RS-CVR.

Impact: Arterial stealing phenomenon of moyamoya disease/syndrome can be demonstrated as negative cerebrovascular reactivity by carbogen-based fMRI (CO2-CVR), but not by resting-state fMRI (RS-CVR).

Keywords: Vascular, Stroke

Motivation: Stroke is major global cause of death. However markers of recovery are still lacking. 

Goal(s): Vasculature affects shear waves propagation acting as a scattering source, ultimately affecting waves dispersion properties measurable with MRE.

Approach: In this study we use multi frequency MRE to find the fingerprint of vascular remodelling after stroke in the dispersion properties of waves, and explored the temporal profile of vascular and tissue remodelling and its relashionship with recovery.

Results: We show for the first time in-vivo that MRE senses tissue integrity as well as vascular organization. We show that such parameters have a good prognostic value.

Impact:   We show that MRE could disentangle tissue constitutive properties and vasculature, and thereby could provide new insights in the understanding of tissue plasticity after stroke and potentially constitute a relevant marker in the context of stroke therapy.

Keywords: Blood Vessels, White Matter

Motivation:  Cardiovascular disease (CVD) is closely related to cerebrovascular injury. However, even when the ejection fraction (EF) is normal, the cardiac microvascular system may still be abnormal.

Goal(s): Explore the relationship between CVD with preserved EF and cerebrovascular injury.

Approach: The heart and brain MRI of the participants were scanned with 3.0T MRI scanner. Different cardiac ejection parameters and high signal images of white matter were obtained.

Results: Patients with CVD, when EF is normal, are still associated with WMH and are still a risk factor for brain injury.

Impact: t is crucial to pay early attention to the early indicators of cerebrovascular abnormalities in patients with heart failure, as timely intervention is essential for reducing the risk of stroke.

Keywords: Blood Vessels, Blood vessels, Microvasculature mapping, vascular abnormalities

Motivation: There is limited understanding of microvascular alterations in neurovascular diseases such as multiple sclerosis (MS) and Parkinson’s disease (PD) using in vivo imaging techniques.

Goal(s): To detect microvascular abnormalities using the novel imaging technique MICRO (Microvascular In-vivo Contrast Revealed Origins).

Approach: MICRO imaging involves high resolution susceptibility weighted imaging (SWI) acquired in the presence of ultrasmall superparamagnetic iron oxides (USPIO). 

Results: As compared to non-contrast conventional vascular imaging, MICRO drastically improves the detection of microvascular abnormalities that can help in identifying the most vulnerable structures in vascular etiology of MS and PD.

Impact: This multicentre study demonstrates that MICRO imaging has the potential to comprehensively study vascular pathology something that is often ignored in evaluating neurodegenerative diseases. 

Keywords: Blood Vessels, Velocity & Flow, ASL

Motivation: Hemodynamic information in the posterior circulation of Moyamoya disease (MMD) patient is crucial and may hint collateral flow.

Goal(s): To assess feasibility of hemodynamic quantification for the posterior circulation of MMD patients based on ASL dynamic MRA.

Approach: The model-free aBF quantification method based on ASL dynamic MRA,  CFD simulation and 3D phase contrast (PC) were compared in the posterior circulation and the circle of Willis.

Results: As compared to CFD, aBF demonstrated better an agreement with PC results and had the potential for quantifying distal vessels. However, its accuracy may be influenced by the choice of AIF.

Impact: This study provides preliminary evidence regarding the feasibility of using ASL dynamic MRA to quantify the flow hemodynamics in Moyamoya disease patients.

Keywords: Blood Vessels, Blood vessels, BOLD dynamic susceptibility contrast

Motivation: Heterogenous BOLD responses are expected across brain regions due to different baseline blood volumes. However, there are very few experimental data to show regional differences of ΔR₂^*.

Goal(s): To determine regional ΔR₂^* by graded hypoxia and to elucidate field dependency of regional ΔR₂^* to transient hypoxic stimuli.

Approach: Three hypoxic conditions (90%N₂, 95%N₂, 100%N₂) were administered to anesthetized mice in two different magnetic field strengths of 9.4T and 15.2T.

Results: The peak ΔR₂^* map revealed heterogenous BOLD responses across regions. Field-dependent ΔR₂^* ratio to 15.2T to 9.4T is close to the ratio of the magnetic field strengths.

Impact: We quantitatively determined regional BOLD responses in whole brain to hypoxia, which is dependent on baseline blood volume. Our result can serve as reference data for normalizing sensitivity of BOLD responses evoked by neuronal activity or vascular stimuli across regions.

Keywords: Blood Vessels, fMRI (task based), Neurovascular coupling

Motivation: We aimed to unravel the intricate relationship between neuronal metrics and vascularization in human visual cortex, addressing the need for a deeper understanding of these factors' impact on fMRI data.

Goal(s): Our study sought to determine if differences exist in pRF sizes between micro- and macro-vascular compartments and the influence of extra- and intra-vascular effects.

Approach: We obtained pRF estimates across cortical depth using different fMRI scan sequences (SE/GE) at varying field strengths (7T/3T).

Results: While our findings confirmed typical pRF size trends and vascularization-dependent amplitude effects across cortical depth, we did not find that vascularization or magnetic field strength affected pRF sizes.

Impact: This study's findings challenge the conventional understanding of how vascularization affects neuronal metrics in functional brain imaging. The research underscores the complexity of neurovascular interactions and their implications for the interpretation of fMRI data.

Keywords: Blood Vessels, Alzheimer's Disease, White Matter; Velocity & Flow

Motivation: This study is driven by the need to understand the intricate relationship between cerebrovascular disease (CVD) and Alzheimer's disease (AD) pathology.

Goal(s): In this study, we aim to investigate the correlations between CVD markers, AD biomarkers and white matter (WM) microstructure.

Approach: To achieve these goals, we used 4D flow MRI and neurite orientation dispersion and density imaging (NODDI) and utilized statistical models to examine the relationships between vascular flow and WM neurite density index. 

Results: Our results identified significant correlations between AD biomarkers, WM integrity and cerebrovascular flow in specific vessels. 

Impact: Our findings motivate further investigations into the intricate relationship between cerebrovascular disease and Alzheimer's disease (AD) pathology. Better understanding of this relationship may improve early AD detection and therapeutic strategies.