Image-Quality Assessment of 3D Intracranial Vessel Wall MRI Using DANTE or DANTE-CAIPI for Blood Suppression and Imaging Acceleration

An extended phase graph-based framework for DANTE-SPACE simulations including physiological, temporal, and spatial variations

PURPOSE

The delay alternating with nutation for tailored excitation (DANTE)-sampling perfection with application-optimized contrasts (SPACE) sequence facilitates 3D intracranial vessel wall imaging with simultaneous suppression of blood and CSF. However, the achieved image contrast depends closely on the selected sequence parameters, and the clinical use of the sequence is limited in vivo by observed signal variations in the vessel wall, CSF, and blood. This paper introduces a comprehensive DANTE-SPACE simulation framework, with the aim of providing a better understanding of the underlying contrast mechanisms and facilitating improved parameter selection and contrast optimization.

METHODS

An extended phase graph formalism was developed for efficient spin ensemble simulation of the DANTE-SPACE sequence. Physiological processes such as pulsatile flow velocity variation, varying flow directions, intravoxel velocity variation, diffusion, andB 1 + $$ {\mathrm{B}}_1^{+} $$ effects were included in the framework to represent the mechanisms behind the achieved signal levels accurately.

RESULTS

Intravoxel velocity variation improved temporal stability and robustness against small velocity changes. Time-varying pulsatile velocity variation affected CSF simulations, introducing periods of near-zero velocity and partial rephasing. Inclusion of diffusion effects was found to substantially reduce the CSF signal. Blood flow trajectory variations had minor effects, butB 1 + $$ {\mathrm{B}}_1^{+} $$ differences along the trajectory reduced DANTE efficiency in low-B 1 + $$ {\mathrm{B}}_1^{+} $$ areas. Introducing low-velocity pulsatility of both CSF and vessel wall helped explain the in vivo observed signal heterogeneity in both tissue types.

CONCLUSION

The presented simulation framework facilitates a more comprehensive optimization of DANTE-SPACE sequence parameters. Furthermore, the simulation framework helps to explain observed contrasts in acquired data.

Usefulness of Different Imaging Methods in the Diagnosis of Cerebral Vasculopathy

Assessment of cerebral vasculopathies is challenging and requires understanding the utility of different imaging methods. Various techniques are available to image the vessel lumen, each with unique advantages and disadvantages. Bolus-based CT and MR angiography requires careful timing of a contrast bolus to provide optimal luminal enhancement. Non-contrast MRA techniques do not require a contrast agent and can provide images with little venous contamination. Digital subtraction angiography remains the gold standard but is invasive, while VW-MRI provides a non-invasive way of assessing vessel wall pathology. Conventional brain MRI has high sensitivity in the diagnosis of vasculitis but findings are nonspecific.

Primary Large Vessel Vasculitis: Takayasu Arteritis and Giant Cell Arteritis

Takayasu arteritis (TA) and Giant cell arteritis (GCA) are large vessel vasculitides, with TA targeting the aorta and its branches, and GCA targeting both large and medium-sized arteries. Early diagnosis of TA and GCA are of great importance, since delayed, inappropriate or no treatment can result in severe and permanent complications. Imaging plays a central role in establishing diagnosis, targeting lesions for confirmational diagnostic biopsy, specifically for GCA, and longitudinal disease evolution. In this article, we discuss imaging diagnosis of large artery vasculitis and the value of different imaging modalities.

Association of intravascular enhancement sign detected on high-resolution vessel wall imaging with ischaemic events in middle cerebral artery occlusion

PURPOSE

Patients with intracranial artery occlusion have high rates of ischaemic events and recurrence. Early identification of patients with high-risk factors is therefore beneficial for prevention. Here we assessed the association between the intravascular enhancement sign (IVES) on high-resolution vessel wall imaging (HR-VWI) and acute ischaemic stroke (AIS) in a population with middle cerebral artery (MCA) occlusion.

METHOD

We retrospectively analysed the records of 106 patients with 111 MCA occlusions, including 60 with and 51 without AIS, who had undergone HR-VWI and computed tomography angiography (CTA) examinations from November 2016 to February 2023. Numbers of IVES vessels were counted and compared to the CTA findings. Statistical analyses of demographic and medical data were also performed.

RESULTS

Occurrence rates and numbers of IVES vessels were significantly higher in the AIS than the non-AIS group (P < 0.05), and most vessels were detected on CTA. Numbers of vessels positively correlated with AIS occurrence (rho = 0.664; P < 0.0001). A multivariable ordinal logistic regression model adjusted for age, degree of wall enhancement, hypertension, and heart status identified the number of IVES vessels as an independent predictor for AIS (odds ratio = 1.6; 95% CI, 1.3-1.9; P < 0.0001).

CONCLUSION

Number of IVES vessels is an independent risk factor for AIS events, and may represent poor cerebral blood flow status and collateral compensation level. It thus provides cerebral haemodynamic information for patients with MCA occlusion for clinical use.

Vessel Wall Imaging in Cryptogenic Stroke

Cryptogenic strokes are symptomatic cerebral ischemic infarcts without a clear etiology identified following standard diagnostic evaluation and currently account for 10% to 40% of stroke cases. Continued research is needed to identify and bridge gaps in knowledge of this stroke grouping. Vessel wall imaging has increasingly shown its utility in the diagnosis and characterization of various vasculopathies. Initial promising evidence suggests rational use of vessel wall imaging in stroke workup may unravel pathologies that otherwise would have been occult and further improve our understanding of underlying disease processes that can translate into improved patient outcomes and secondary stroke prevention.

High-resolution vessel wall magnetic resonance imaging in intracranial vasculopathies: an experience from eastern India

OBJECTIVE

To evaluate the role of high-resolution intracranial vessel wall imaging (HR-IVWI) in differentiation of various intracranial vasculopathies in addition to luminal and clinical imaging in the largest cohort of Indian stroke patients.

METHODS

A single-center, cross-sectional study was undertaken recruiting consecutive stroke or TIA patients presenting within a month of onset, with luminal irregularity/narrowing upstream from the stroke territory. The patients were initially classified into TOAST and Chinese ischemic stroke sub-classification (CISS) on the basis of clinical and luminal characteristics and reclassified again following incorporation of HR-IVWI findings.

RESULTS

In our cohort of 150 patients, additional use of HR-IVWI led to a 10.7 and 14% change in initial TOAST and CISS classification respectively (p < 0.001). In TOAST classification, 12 "undetermined aetiology" were reclassified into intracranial atherosclerotic disease (ICAD), 1 "undetermined aetiology" into CNS angiitis and 1 "undetermined aetiology" into arterial dissection. Similarly, in CISS 19 "undetermined aetiology" was reclassified into 16 large artery atherosclerosis (LAA) and 3 "other aetiology" consisting of one CNS angiitis, Moyamoya disease (MMD) and arterial dissection each. Two initial classification of MMD by CISS and TOAST were changed into ICAD. The observed change in diagnosis following incorporation of HR-IVWI was proportionately highest in ICAD (LAA) subgroup (TOAST-9.3%, CISS-12%).

CONCLUSION

Adjunctive use of HR-IVWI, to clinical and luminal assessment, can significantly improve diagnostic accuracy during evaluation of intracranial vasculopathies, with its greatest utility in diagnosing in ICAD, CNS angiitis and dissection.

ADVANCES IN KNOWLEDGE

HR-IVWI allows clearer etiological distinction of intracranial vasculopathies having therapeutic and prognostic implications.

Advanced cross-sectional imaging of cerebral aneurysms

While the rupture rate of cerebral aneurysms is only 1% per year, ruptured aneurysms are associated with significant morbidity and mortality, while aneurysm treatments have their own associated risk of morbidity and mortality. Conventional markers for aneurysm rupture include patient-specific and aneurysm-specific characteristics, with the development of scoring systems to better assess rupture risk. These scores, however, rely heavily on aneurysm size, and their accuracy in assessing risk in smaller aneurysms is limited. While the individual risk of rupture of small aneurysms is low, due to their sheer number, the largest proportion of ruptured aneurysms are small aneurysms. Conventional imaging techniques are valuable in characterizing aneurysm morphology; however, advanced imaging techniques assessing the presence of inflammatory changes within the aneurysm wall, hemodynamic characteristics of blood flow within aneurysm sacs, and imaging visualization of irregular aneurysm wall motion have been used to further determine aneurysm instability that otherwise cannot be characterized by conventional imaging techniques. The current manuscript reviews conventional imaging techniques and their value and limitations in cerebral aneurysm characterization, and evaluates the applications, value and limitations of advanced aneurysm imaging and post-processing techniques including intracranial vessel wall MRA, 4D-flow, 4D-CTA, and computational fluid dynamic simulations.

Improved Blood Suppression of Motion-Sensitized Driven Equilibrium in High-Resolution Whole-Brain Vessel Wall Imaging: Comparison of Contrast-Enhanced 3D T1-Weighted FSE with Motion-Sensitized Driven Equilibrium and Delay Alternating with Nutation for Tailored Excitation

BACKGROUND AND PURPOSE

High-resolution vessel wall MR imaging is prone to slow-flow artifacts, particularly when gadolinium shortens the T1 relaxation time of blood. This study aimed to determine the optimal preparation pulses for contrast-enhanced high-resolution vessel wall MR imaging.

MATERIALS AND METHODS

Fifty patients who underwent both motion-sensitized driven equilibrium and delay alternating with nutation for tailored excitation (DANTE) preparation pulses with contrast-enhanced 3D-T1-FSE were retrospectively included. Qualitative analysis was performed using a 4-grade visual scoring system for black-blood performance in the small-sized intracranial vessels, overall image quality, severity of artifacts, and the degree of blood suppression in all cortical veins as well as transverse sinuses. Quantitative analysis of the M1 segment of the MCA was also performed.

RESULTS

The qualitative analysis revealed that motion-sensitized driven equilibrium demonstrated a significantly higher black-blood score than DANTE in contrast-enhanced 3D-T1-FSE of the A3 segment (3.90 versus 3.58, P < .001); M3 (3.72 versus 3.26, P = .004); P2 to P3 (3.86 versus 3.64, P = .017); the internal cerebral vein (3.72 versus 2.32, P < .001); and overall cortical veins (3.30 versus 2.74, P < .001); and transverse sinuses (2.82 versus 2.38, P < .001). SNR_lumen, contrast-to noise ratio_wall-lumen, and SNR_wall in the M1 vessel were not significantly different between the 2 preparation pulses (all, P > .05).

CONCLUSIONS

Motion-sensitized driven equilibrium demonstrated improved blood suppression on contrast-enhanced 3D-T1-FSE in the small intracranial arteries and veins compared with DANTE. Motion-sensitized driven equilibrium is a useful preparation pulse for high-resolution vessel wall MR imaging to decrease venous contamination and suppress slow-flow artifacts when using contrast enhancement.