Keywords: Blood Vessels, Tumor, dark-blood DCE

Motivation: Scans with dark-blood contrast can improve the conspicuity of small metastases in contrast-enhanced brain examinations and may be useful for vessel-wall imaging.

Goal(s): To describe a novel sequence, called echo-uT1RESS, that overcomes the limitations of the frequently utilized T1 SPACE sequence. 

Approach: The proposed stack-of-stars echo-uT1RESS sequence applies saturation-recovery preparation followed by 3D PSIF readout. Due to radial k-space acquisition, scans are motion-insensitive and can be acquired during free breathing. Dynamic contrast-enhanced images can be obtained through GRASP reconstruction.

Results: Evaluation in a small patient cohort demonstrated high conspicuity of enhancing lesions and vessel walls with reduced motion artifacts compared to conventional sequences.

Impact: The described radial echo-uT1RESS sequence offers improved lesion-to-background and dark-blood contrast. The sequence may help to increase the sensitivity for detecting small metastases and may find application in vessel-wall imaging. It is also compatible with dynamic imaging using GRASP reconstruction.

Keywords: Blood Vessels, Image Reconstruction, Cerebral arteriovenous malformations . Digital Subtraction Angiography. Magnetic resonance angiography . Nidus segmentation . Nidus volume

Motivation: Quantitative nidus volume measurement of cerebral arteriovenous malformation（CAVM）is of great important for the CAVM treatment management.

Goal(s): This study aims to investigate non-invasive nidus volume measurement of CAVM with silent MRA and explore the difference between silent MRA and TOF-MRA.

Approach: Nidus volume was measured by silent MRA, TOF-MRA, and digital subtraction angiography（DSA）. Nidus volume measured by DSA was regarded as golden standard.

Results: Silent MRA can accurately measure the nidus volume of CAVM. There is a significant difference in nidus volume measurement between silent MRA and TOF-MRA, silent MRA also has advantage for CAVM patients treated by embolization.

Impact: As a non-invasive and contrast agent-free MRA imaging technology, silent MRA can be used as an effective and accurate imaging tool for nidus volume measurement and as a follow-up tool for nidus volume change evaluation after surgery, embolization, and radiotherapy.

Keywords: Blood Vessels, Vessels

Motivation: 7T TOF MRA detects the lenticulostriate arteries (LSA), which perfuse important subcortical structures and are implicated in the pathogenesis of cerebral small vessel disease (SVD).

Goal(s): This study aimed to automatically segment LSAs from 7T TOF MRA for SVD patients, to facilitate studies of the arterial pathology of SVD.

Approach: We applied a state-of-the-art deep learning model “DS6” and a classical multi-scale Frangi filter pipeline to 7T contrast-enhanced TOF MRA scans from 8 SVD patients for LSA segmentation.

Results: Both approaches showed comparable and satisfactory performance with mean test dice score=0.74. DS6 was more robust but less sensitive to lower-intensity arteries.

Impact: We present an automatic pipeline for 3D segmentation of the lenticulstriate arteries (LSAs) from 7T TOF MRA. This will enable clinical studies to characterise LSA morphology in cerebral small vessel disease which will open new avenues to understand its pathophysiology.

Keywords: Blood Vessels, Stroke, swI, T2 GRE

Motivation: Our study's aim is to aid radiologists in selecting the most appropriate MRI brain sequence, enhancing diagnostic accuracy.

Goal(s): We aimed to compare the effectiveness of SWI and GRE MRI sequences in detecting brain conditions like hemorrhages, calcifications, and vascular malformations

Approach: We conducted an observational study, analyzing patient data using SWI and GRE sequences on the same patient. Our approach focused on data analysis and assessing image quality.

Results: SWI is our preference for its sensitivity and reliability, but we recognize GRE's value when CT is already available. GRE efficiently distinguishes brain features, particularly beneficial for uncooperative patients.

Impact: Our study's results hold far-reaching implications. Healthcare professionals can benefit by using more accurate MRI-sequence, enabling better patient care. Researchers may explore novel avenues, enhancing scientific understanding, which is invaluable for medical progress.

Keywords: Blood Vessels, Velocity & Flow, Neuro, Hypoxia, Oxygenation, Cerebrovascular Reactivity

Motivation: The cerebrovascular response to mild hypoxia has not been well-characterized, but hypoxic cerebrovascular reactivity (CVR) may be an important metric that could complement hypercapnic CVR in clinical applications, giving distinct information about cerebrovascular health. 

Goal(s): We aimed to increase reliability of hypoxic CVR and modulate the effects of concurrent CO₂ changes.

Approach: Using phase-contrast MRI, we measured cerebral blood flow during baseline, hypoxic, and hypercapnic respiratory states, induced with a computer-controlled gas blender. We used hypercapnic CVR to implement a simple correction for changes in P_ETCO₂ that occurred during hypoxia.

Results: While substantial inter-subject variability remained, P_ETCO₂ correction reduced variability and improved reliability.

Impact: Minimizing and correcting for concurrent changes in PETCO2 during a mild inhaled hypoxic stimulus improves the reliability of hypoxic cerebrovascular reactivity, but normal inter-subject variability and the utility of hypoxic cerebrovascular reactivity in clinical populations have yet to be determined.

Keywords: Blood Vessels, Image Reconstruction

Motivation: ASL-based time-resolved 4D MRA potentially suffers from temporal blurring when accelerating image acquisition by exploiting temporal correlations.

Goal(s): To develop a robust 4D MRA reconstruction framework that enables a very high acceleration rate while preserving good temporal fidelity. 

Approach: We developed a fast low-rank subspace high-resolution 4D MRA (Flash-4D-MRA) that combines SOS golden-angle radial sampling with joint subtraction-based self-calibrated low-rank subspace and magnitude-subtraction sparsity constraint to achieve an ultra-high temporal resolution. Each 4D MRA data was reconstructed with four high acceleration rates.

Results: Dynamic MRA images were successfully reconstructed using Flash-4D-MRA with higher acceleration rates without compromising temporal fidelity.    

Impact: Flash-4D-MRA allows for the delineation of cerebral dynamic flow with good image quality and temporal fidelity at an ultra-high temporal resolution, which could be a potentially useful non-contrast 4D MRA technique in clinical applications to characterize fast-flow events. 

Keywords: Blood Vessels, Blood vessels, 4D flow MRI，compressed sensing，venous sinus

Motivation: Due to the small diameter of intracranial-venous sinus, higher spatial resolution is required when using 4D-flow MRI to observe hemodynamics, which greatly prolongs scan time.

Goal(s): Accelerating 4D-flow MRI of intracranial-venous sinus with compressed sensing (CS), and comparing the performance of CS acceleration factors (AFs). 

Approach: The 4D-flow hemodynamic  of straight sinus, superior sagittal sinus and transverse sinus with different AFs (SENSE4, CS4, CS6, CS8, and CS10) were compared in 8 healthy volunteers. 

Results: Compared to the reference (SENSE4) scan, the hemodynamic for the straight sinus, several parameters were underestimated by CS6-CS10，while for the other sinuses obtained by CS4-CS10 showed no significant difference.

Impact: 4D flow MRI with acceleration by compressed sensing can be used as a efficient method to evaluate venous sinus hemodynamics in routine clinical practice.

Keywords: Blood Vessels, Blood vessels, Vessel Wall Imaging, Accelerated Acquisition, Compressed Sensing

Motivation: Clinical VWI scans demand high spatial resolutions, which lead to extended acquisition times, potentially causing limited field-of-view (FOV), motion artifacts, and patient burden.

Goal(s): We evaluated FDA-approved acceleration methods for 3D T1w SPACE to develop optimized protocols for clinical VWI studies.

Approach: Compressed Sensing (CS) and CAIPI acceleration techniques optimized to reduce scan times and provide whole-head coverage were compared against our current GRAPPA accelerated limited-FOV clinical protocol.

Results: The whole-head FOV combined with CS yielded image quality comparable to our current clinical protocol but with almost half the scan time, promising significant reductions in lengthy clinical VWI protocols and patient burden.

Impact: Compressed Sensing enabled increased FOV imaging with substantially reduced scan times without significant loss of image quality compared to CAIPI and standard-of-care GRAPPA-accelerated techniques for a clinical T1-weighted vessel wall imaging protocol.  

Keywords: Blood Vessels, Blood vessels

Motivation: Intracranial vessels undergo age-related changes with increased risk of vascular pathologies such as atherosclerosis, or intracranial aneurysms. The occurrence probability of these pathologies could be indicated based on an altered vascular geometry.

Goal(s): The application of a geometric analysis to the vascular system of healthy volunteers of two age groups to study age-related changes in the geometry of intracranial arteries.

Approach: The analysis involved labeled centerline determination of intracranial arteries and calculating geometric parameters.

Results: Our study provided quantitative insights into age-related changes in intracranial artery geometry. Future research with larger, diverse samples can enhance the understanding and enable ML-based analyses.

Impact: The objective was to examine age-related changes in women of intracranial arteries by performing a geometric analysis on healthy volunteers. The quantitative evaluation enhances the comprehension of how intracranial artery geometry evolves with age.

Keywords: Blood Vessels, Aging, Cerebral Small Vessel Disease

Motivation: Tracking hippocampal radiomic changes over time may provide a biomarker to monitor disease progression and treatment response in cerebral small vessel disease (CSVD). Extending proven hippocampal radiomic methods from AD research to the study of CSVD represents a promising approach worthy of further investigation.

Goal(s): To develop a radiomics model based on 3D-T1WI images to improve the diagnosis of CSVD with cognitive impairment.

Approach: LASSO regression was used for feature selection and model construction

Results: The model attained an accuracy of 0.781, AUC of 0.818, sensitivity of 0.538, and specificity of 0.947 in distinguishing group 2 from NCs in the test sets.

Impact: Overall, our findings support the potential for hippocampal textural features to serve as neuroimaging biomarkers of CSVD, providing a useful tool to aid clinical decision-making in precision medicine. 

Keywords: Blood Vessels, Arterial spin labelling

Motivation: Vertebrobasilar dolichoectasia (VBD) poses a risk to cerebral blood flow and can lead to ischemic strokes. Understanding its impact on blood flow and identifying predictive factors are crucial.

Goal(s): This study aims to assess differences in CBF and other parameters between VBD patients and controls. We also investigate the influence of extracranial blood flow and predict PCI risk factors.

Approach: 32 VBD patients and 32 controls underwent Multi-delay-ASL and Doppler ultrasound. We analyzed CBF, aCBV, ATT, and blood flow velocities.

Results: VBD patients exhibited lower CBF and aCBV in both circulations and longer ATT. Bilateral occipital and cerebellar ATTs predicted PCI.

Impact: This study enhances our understanding of VBD's impact on cerebral blood flow and identifies predictors of posterior circulation ischemia. It underscores the importance of maintaining extracranial blood flow, aiding in early detection and prevention of ischemic strokes in VBD patients.

Keywords: Blood Vessels, Blood vessels

Motivation: Intracranial vessels exhibit significant variations stemming from anatomical distinctions and pathological conditions; therefore, automated vessel labeling is challenging.

Goal(s): We aimed to investigate the performance of automated intracranial vessel labeling for multiple cerebrovascular conditions, including normal structure, severe stenosis, occlusion, aging, and calcification.

Approach: We developed an automated vessel labeling model solely based on the dataset with normal structures (202 real cases) and evaluated its labeling performance in different cerebrovascular conditions (50 real and 200 simulated cases).

Results: The proposed model showed high generalization across cerebrovascular conditions with an average labeling accuracy of 0.82, which could facilitate future quantitative analysis of vessel anomalies.

Impact: This study contributes to the application of automated intracranial vessel labeling in different cerebrovascular conditions and offers insights into the model applications in future quantitative analysis for the diagnosis and treatment of vessel anomalies.

Keywords: Blood Vessels, Arterial spin labelling, ultra-high field, reproducibility

Motivation: To develop and optimize multi-delay pCASL at ultra-high field 5T MR system and further assess the reproducibility of this technique for the quantifications of cerebral perfusion.

Goal(s): Develop a whole-brain multi-delay pCASL imaging protocol with good reproducibility at 5T MRI.

Approach: Optimize labeling gradient parameters for the field inhomogeneities, scan 8 healthy volunteers and test the reproducibility of cerebral blood flow(CBF) and arterial transit time(ATT).

Results: We first achieved whole-brain multi-delay pCASL imaging at ultra-high field with prolonged post-labeling delays. CBF showed excellent reproducibility in all brain regions, especially in subcortical region. ATT showed excellent reproducibility in anterior brain regions.

Impact: Our findings enable a reliable quantitative analysis of whole-brain perfusion from multi-delay pCASL at ultra-high field with good reproducibility, offering a promising advancement in the effective and accurate diagnosis for neurological diseases.

Keywords: Blood Vessels, Neuroinflammation

Motivation: Previous studies have not developed a high-resolution wall imaging scoring system for TA patients with intracranial vascular involvement  to explore its relationship with intracranial lesions.

Goal(s): Develop a HR-VWI score to demonstrate the relationship between the score and incidence of intracranial lesions.

Approach: Integrated the degree of luminal stenosis, the pattern and degree of vessel wall enhancement and the number of affected vessels on HR-VWI into a HR-VWI score.

Results: TA patients with intracranial lesions had higher HR-VWI scores and HR-VWI scores performed well in distinguishing TA patients with intracranial lesions from those without intracranial lesions. 

Impact: HR-VWI is a powerful tool for physicians to visualize the condition of vessels by showing the various changes in the vesseel walls  and a more reliable method of diagnosing intracranial arterial stenosis than TOF-MRA.

Keywords: Data Processing, Quantitative Imaging, SNR, ASL, Brain

Motivation: SNR is a key image quality metric; however estimating it can be difficult when using more complex image acquisition and reconstruction techniques.

Goal(s): Demonstrate the validity of the pseudoreplica method as an accurate SNR estimation tool and show potential for its translation into clinical scanning protocols.

Approach: We quantified SNR using our pseudoreplica method implementation in MATLAB in a prostate phantom, as well as in a brain ASL dataset of healthy volunteers.

Results: SNR values obtained with the pseudoreplica method in the prostate phantom and in-vivo brain ASL dataset had good agreement with the multiple and dual acquisition SNR quantification methods.

Impact: We have demonstrated the reliability and accuracy of our pseudoreplica SNR quantification implementation in ASL. Integrating this method into the scanner's pipeline would allow for real-time assessment of image quality and further optimization of new MR sequences and reconstruction methods.

Keywords: Data Processing, Perfusion, ASL

Motivation: VE-DASL is promising in achieving fast vascular territory mapping by using short labeling duration and post-labeling delay, but the accuracy is limited, especially in the border zones.

Goal(s): To achieve a robust vascular territories separation using VE-DASL.

Approach: We adopted optimal encoding scheme and simulated the signal for each territory. The voxels that best matched the simulated signal were identified and their signal was used as the reference. The vascular territories were obtained using matrix inversion or correlation analysis.

Results: The proposed method achieved results comparable to VEASL and demonstrated the capability to differentiate the four vascular territories.

Impact: We improved VE-DASL by using OES and the proposed vessel-decoding method. This approach enabled us to achieve results comparable to VEASL while offering the potential for extension to more complex vascular scenarios.