Hyperintense Vessels on T2-PROPELLER-FLAIR in Patients with Acute MCA Stroke: Prediction of Arterial Stenosis and Perfusion Abnormality

Continuum topological derivative - a novel application tool for denoising CT and MRI medical images

BACKGROUND

CT and MRI modalities are important diagnostics tools for exploring the anatomical and tissue properties, respectively of the human beings. Several advancements like HRCT, FLAIR and Propeller have advantages in diagnosing the diseases very accurately, but still have enough space for improvements due to the presence of inherent and instrument noises. In the case of CT and MRI, the quantum mottle and the Gaussian and Rayleigh noises, respectively are still present in their advanced modalities of imaging. This paper addresses the denoising problem with continuum topological derivative technique and proved its trustworthiness based on the comparative study with other traditional filtration methods such as spatial, adaptive, frequency and transformation techniques using measures like visual inspection and performance metrics.

METHODS

This research study focuses on identifying a novel method for denoising by testing different filters on HRCT (High-Resolution Computed Tomography) and MR (Magnetic Resonance) images. The images were acquired from the Image Art Radiological Scan Centre using the SOMATOM CT and SIGNA Explorer (operating at 1.5 Tesla) machines. To compare the performance of the proposed CTD (Continuum Topological Derivative) method, various filters were tested on both HRCT and MR images. The filters tested for comparison were Gaussian (2D convolution operator), Wiener (deconvolution operator), Laplacian and Laplacian diagonal (2nd order partial differential operator), Average, Minimum, and Median (ordinary spatial operators), PMAD (Anisotropic diffusion operator), Kuan (statistical operator), Frost (exponential convolution operator), and HAAR Wavelet (time-frequency operator). The purpose of the study was to evaluate the effectiveness of the CTD method in removing noise compared to the other filters. The performance metrics were analyzed to assess the diligence of noise removal achieved by the CTD method. The primary outcome of the study was the removal of quantum mottle noise in HRCT images, while the secondary outcome focused on removing Gaussian (foreground) and Rayleigh (background) noise in MR images. The study aimed to observe the dynamics of noise removal by examining the values of the performance metrics. In summary, this study aimed to assess the denoising ability of various filters in HRCT and MR images, with the CTD method being the proposed approach. The study evaluated the performance of each filter using specific metrics and compared the results to determine the effectiveness of the CTD method in removing noise from the images.

RESULTS

Based on the calculated performance metric values, it has been observed that the CTD method successfully removed quantum mottle noise in HRCT images and Gaussian as well as Rayleigh noise in MRI. This can be evidenced by the PSNR (Peak Signal-to-Noise Ratio) metric, which consistently exhibited values ranging from 50 to 65 for all the tested images. Additionally, the CTD method demonstrated remarkably low residual values, typically on the order of e-09, which is a distinctive characteristic across all the images. Furthermore, the performance metrics of the CTD method consistently outperformed those of the other tested methods. Consequently, the results of this study have significant implications for the quality, structural similarity, and contrast of HRCT and MR images, enabling clinicians to obtain finer details for diagnostic purposes.

CONCLUSION

Continuum topological derivative algorithm is found to be constructive in removing prominent noises in both CT and MRI images and can serve as a potential tool for recognition of anatomical details in case of diseased and normal ones. The results obtained from this research work are highly inspiring and offer great promise in obtaining accurate diagnostic information for critical cases such as Thoracic Cavity Carina, Brain SPI Globe Lens 4th Ventricle, Brain-Middle Cerebral Artery, Brain-Middle Cerebral Artery and neoplastic lesions. These findings lay the foundation for implementing the proposed CTD technique in routine clinical diagnosis.

FLAIR vascular hyperintensity combined with asymmetrical prominent veins in acute anterior circulation ischemic stroke: prediction of collateral circulation and clinical outcome

BACKGROUND

To investigate the value of fluid-attenuated inversion recovery vascular hyperintensity (FVH) within asymmetrical prominent veins sign (APVS) on susceptibility-weighted imaging predicting collateral circulation and prognosis in patients with acute anterior circulation ischemic stroke.

METHOD

Patients with severe stenosis or occlusion of ICA or MCA M1, who underwent MRI within 72 h from stroke onset were reviewed. The Alberta Stroke Program Early CT Score was used to evaluate the volume of infarction on DWI, the degree of FVH and APVS. Spearman correlation analysis was used to evaluate the correlation between FVH and APVS. All patients were divided into the good prognosis group and the poor prognosis group according to the score of the modified ranking scale (mRS) 90 days after the stroke. Logistic regression analysis was used to explore the relationship between FVH and APVS and functional prognosis, while receiver operating characteristic (ROC) curves were plotted to assess the value of FVH and APVS in predicting prognosis.

RESULTS

Spearman correlation analysis revealed moderate positive correlations between FVH and APVS (r = 0.586, P < 0.001). The poor prognosis group had a higher rate of a history of atrial fibrillation, a larger cerebral infarction volume, a higher NIHSS score at admission, and a higher FVH and APVS score compared with the good prognosis group (all P < 0.05). A further logistic regression indicated that the NIHSS score, cerebral infarction volume, FVH and APVS were independent risk factors for a poor functional prognosis. In terms of FVH, APVS, alone and their combination for the diagnosis of poor prognosis, the sensitivity, specificity, area under the ROC curve (AUC), and 95% confidence interval (CI) were 86.8%, 83.3%, 0.899 (95% CI 0.830-0.968); 60.5%, 93.7%, 0.818 (95% CI 0.723-0.912); 86.8%, 89.6%, 0.921 (95% CI 0.860-0.981), respectively.

CONCLUSION

The presence of FVH and APVS can provide a comprehensive assessment of collateral circulation from the perspective of veins and arteries, and the correlation between the two is positively correlated. Both of them were independent risk factors for poor prognosis, their combination is complementary and can improve the predictive value.

Individualized interpretation for the clinical significance of fluid-attenuated inversion recovery vessel hyperintensity in ischemic stroke and transient ischemic attack: A systematic narrative review

Fluid-attenuated inversion recovery (FLAIR) vessel hyperintensity（FVH）refers to the hyperintensity corresponding to the arteries in the subarachnoid space. It is caused by critically slowed blood flow and is commonly encountered in patients with large artery steno-occlusions. Quite a few studies have focused on the clinical significance of FLAIR vessel hyperintensity in terms of its relationship to the prognosis of transient ischemic attack (TIA), baseline severity or infarction volume, early neurological deterioration or infarction growth, and functional outcomes in acute ischemic stroke (AIS). However, inconsistent or conflicting findings were common in these studies and caused confusion in the clinical decision-making process guided by this imaging marker. Through reviewing the available studies on the etiologic mechanism of FVH and investigating findings on its clinical significance in AIS and TIA, this review aims to elucidate the key factors for interpreting the clinical significance of FVH individually.

Association of fluid-attenuated inversion recovery vascular hyperintensity with ischaemic events in internal carotid artery or middle cerebral artery occlusion

BACKGROUND AND PURPOSE

Individuals with intracranial artery occlusion have high rates of ischaemic events and recurrence. It has been challenging to identify patients who had high-risk stroke using a simple, valid and non-invasive screening approach. This study aimed to investigate whether fluid-attenuated inversion recovery (FLAIR) vascular hyperintensity (FVH), a specific imaging sign on the FLAIR sequence, could be a predictor of ischaemic events in a population with internal carotid artery (ICA) or middle cerebral artery (MCA) occlusion.

METHODS

We retrospectively analysed 147 patients (mean 60.43±12.83 years) with 149 lesions, including 37 asymptomatic and 112 symptomatic cases of ICA or MCA occlusion. Symptomatic occlusion was considered if ischaemic events were present in the relevant territory within 90 days. FVH Alberta Stroke Program Early Computed Tomography Score (FVH-ASPECTS: 0-7, with 0 indicating absence of FVH and 7 suggesting prominent FVH) and collateral circulation grade were assessed for each participant. Multivariable logistic regression analysis was performed to detect independent markers associated with symptomatic status.

RESULTS

A lower FVH-ASPECTS was associated with a more favourable collateral circulation grade (rho=-0.464, p<0.0001). The FVH-ASPECTS was significantly lower in the asymptomatic occlusion group than in the symptomatic occlusion group (p<0.0001). FVH-ASPECTS (Odd ratio, 2.973; 95% confidence interval, 1.849 to 4.781; p<0.0001) was independently associated with symptomatic status after adjustment for age, sex, lesion location and collateral circulation grade in the multivariate logistic regression. The area under the curve was 0.861 for the use of FVH-ASPECTS to identify symptomatic occlusion.

CONCLUSIONS

The ability to discriminate symptomatic from asymptomatic occlusion suggests that FVH may be a predictor of stroke. As a simple imaging sign, FVH may serve as a surrogate for haemodynamic impairments and can be used to identify high-risk stroke cases early in ICA or MCA occlusion.

Comparison of imaging findings on three-dimensional black-blood enhanced MR imaging between intracranial atherosclerotic occlusion and thrombotic occlusion

PURPOSE

The purpose of this study was to compare the imaging findings on three-dimensional (3D) black-blood (BB) contrast-enhanced MR imaging between intracranial atherosclerotic occlusion (IAO) and thrombotic occlusion (TO) of the middle cerebral artery (MCA) territory.

MATERIALS AND METHODS

From August 2020 to September 2021, we retrospectively reviewed the BB contrast-enhanced MR imaging of patients visiting the emergency room for evaluation of acute ischemic stroke. In total, 77 patients with complete occlusion of the MCA territory on 3D BB contrast-enhanced MR imaging and cerebral angiography were enrolled in this study. We divided the IAO and TO groups according to occlusion causes based on angiography findings.

RESULTS

Of 77 patients, 44 (57.1%) had an IAO in the M1 and M2 and 33 had a TO. Lesion length contrast enhancement (CE) in patients with a TO was significantly longer than that in patients with an IAO (18.95 mm [IQR: 20.91] vs. 7.1 mm [8.92], p <0.001). Overall, 38 (39.4%) patients showed a disconnection of CE on 3D BB contrast-enhanced MR imaging, and 35 showed CE before and after the stenotic or thrombotic lesion. Symptomatic lesions on diffusion-weighted imaging in the TO group were significantly higher than that of the IAO group (97.0% vs, 70.5%, p = 0.003).

CONCLUSION

The long segment CE on 3D BB contrast-enhanced MR imaging was related to TO of MCA. CE before and after a stenotic or thrombotic lesion is a common finding on 3D BB contrast-enhanced MR imaging.

Fluid-Attenuated Inversion Recovery Vascular Hyperintensity in Cerebrovascular Disease: A Review for Radiologists and Clinicians

Neuroradiological methods play important roles in neurology, especially in cerebrovascular diseases. Fluid-attenuated inversion recovery (FLAIR) vascular hyperintensity (FVH) is frequently encountered in patients with acute ischemic stroke and significant intracranial arterial stenosis or occlusion. The mechanisms underlying this phenomenon and the clinical implications of FVH have been a matter of debate. FVH is associated with large-vessel occlusion or severe stenosis, as well as impaired hemodynamics. Possible explanations suggested for its appearance include stationary blood and slow antegrade or retrograde filling of the leptomeningeal collateral circulation. However, the prognostic value of the presence of FVH has been controversial. FVH can also be observed in patients with transient ischemic attack (TIA), which may have different pathomechanisms. Its presence can help clinicians to identify patients who have a higher risk of stroke after TIA. In this review article, we aim to describe the mechanism and influencing factors of FVH, as well as its clinical significance in patients with cerebrovascular disease.

The diagnostic reliability and validity of noninvasive imaging modalities to assess leptomeningeal collateral flow for ischemic stroke patients: A systematic review and meta-analysis

Leptomeningeal collateral flow (LMF) is associated with infarct area and clinical outcome for ischemic stroke patients. Although LMF can be detected by multiple imaging methods, but their diagnostic performance is uncertain.The aim of this study was to evaluate the diagnostic validity or reliability of noninvasive image methods in assessing LMF.Databases included PubMed, Web of Science, Embase, and Cochrane Library.Original observational cohort studies.Ischemic stroke patients.Different noninvasive image methods to assess LMF.Newcastle-Ottawa Scale to evaluate the quality of the studies; forest plot to show pooled results; I2 and Egger test to evaluate the heterogeneity and publication bias.Thirty of the 126 selected studies were eligible. For CT angiography, the interobserver agreement ranged from 0.494 to 0.93 and weighted kappa was 0.888; for patients receiving thrombolysis or endovascular treatment, 0.68 to 0.91; 0.494 to 0.89 for the 2-point system, 0.60 to 0.93 for the 3-point system, 0.68 to 0.87 for the system of >4 points; area under the curve (AUC) was 0.78. For perfusion computed tomography (CTP), the interobserver agreement ranged from 0.724 to 0.872; for patients receiving thrombolysis or endovascular treatment, 0.74 to 0.872; 0.724 for the 2-point system, 0.783 to 0.953 for the 3-point system; the intraobserver agreement was 0.884; AUC was 0.826. For MRI-fluid attenuated inversion recovery (FLAIR), the interobserver agreement ranged from 0.58 to 0.86; for patients receiving thrombolysis or endovascular treatment, 0.75 to 0.86; 0.86 for the two-point system, 0.77 to 0.87 for the system of more than 5 points; AUC was 0.82.No pooled data of CTP and FLAIR. The difference cohort study had difference bias. The unpublished data were not included.CT angiography is a good tool for assessing LMF. CTP shows a good validity and reliability, but its diagnostic value needs more evidence. FLAIR is a good modality to assess LMF. These image methods had better validity and reliability to evaluate LMF of patients receiving thrombolysis or endovascular treatment than all ischemic stroke patients.

Interpretation of fluid-attenuated inversion recovery vascular hyperintensity in stroke

Fluid-attenuation inversion recovery (FLAIR) vascular hyperintensity (FVH) is a common presentation on brain magnetic resonance images of patients with acute ischemic stroke. This sign is known as a sluggish collateral flow. Although FVH represents the large ischemic penumbra and collateral circulation, the clinical significance of FVH has not been established. Varying protocols for FLAIR, treatment differences, and heterogeneity of endpoints across studies have complicated the interpretation of FVH in patients with acute stroke. In this review article, we describe the mechanism of FVH, as well as its association with functional outcome, perfusion-weighted images, and large artery stenosis. In addition, we review the technological variables that affect FVH and discuss the future perspectives.

Topography of the hyperintense vessel sign on fluid-attenuated inversion recovery represents cerebral hemodynamics in middle cerebral artery occlusion: a CT perfusion study

PURPOSE

Whether the topography of fluid-attenuated inversion recovery hyperintense vessel sign (FHVs) can serve as a measure of cerebral hemodynamic stress remains unclear. We hypothesized that FHVs topography represents different cerebral hemodynamic status, as assessed by CT perfusion (CTP).

METHODS

We retrospectively reviewed 75 patients with acute middle cerebral artery (MCA) occlusion who underwent MR imaging and CTP. The FHVs topography included FHVs inside the diffusion-weighted imaging (DWI) lesion (FHVs in-group), FHVs outside the DWI lesion (FHVs out-group), and FHVs distributed inside and outside the DWI lesion (FHVs all-group). FHVs scores were assessed by the Alberta stroke program early computed tomography score (ASPECT) territories. Cerebral hemodynamic status was evaluated by relative (r) CTP parameters. Cerebral hemodynamic status was analyzed with respect to different FHVs topographies and FHVs scores.

RESULTS

Hemodynamic impairment was present in all patients, with the following mean rCTP parameters: rCBF, 0.77 ± 0.23; rCBV, 1.06 ± 0.32; and rMTT, 1.52 ± 0.60. Comparison of the rCTP parameters among the three groups, rCBF and rCBV (rCBF, P < 0.001; rCBV, P < 0.001) in the FHVs out-group and the FHVs all-group (rCBF, P = 0.001; rCBV, P < 0.001), were significantly higher than that in the FHVs in-group. Similarly, CTA collateral grade in the FHVs in-group was significantly lower than those in the FHVs out-group and FHVs all-group (P < 0.001). No significant difference was found in rCTP parameters between different FHVs scores.

CONCLUSION

The different FHVs topographies represented different cerebral hemodynamic status. FHVs topography may serve as a surrogate for patient selection for reperfusion therapy whenever perfusion data are unavailable.

Significance of hyperintense arteries on Gd-enhanced 3D T1W black-blood imaging in acute stroke

OBJECTIVES

To elucidate the pathogenesis of hyperintense arteries on Gd-enhanced 3D T1W BB FSE and their clinical significance in acute middle cerebral artery (MCA) stroke.

METHODS

We retrospectively reviewed 20 patients with MCA infarction. We measured the contrast-to-noise ratio between hyperintense artery and adjacent grey matter on T2-FLAIR and Gd-enhanced 3D T1W BB FSE and compared them by using Student's t test. The agreement of positive hyperintense artery between T2 FLAIR and Gd-enhanced 3D T1WI BB FSE was estimated with intraclass correlation coefficient. Our cohort was dichotomised into two groups depending on hyperintense artery scores, and clinical data were compared between two groups by using Student's t test and chi-square test.

RESULTS

The contrast between hyperintense artery and grey matter on Gd-enhanced 3D T1W BB FSE was significantly higher than that on T2-FLAIR (2.27 ± 1.65 versus 0.94 ± 0.86, p = 0.01). Overall, agreement of hyperintense arteries on T2-FLAIR and Gd-enhanced 3D T1W BB FSE was excellent (ρ = 0.76, p < 0.01). Patients with higher hyperintense artery scores had higher perfusion deficits that those with lower hyperintense artery scores (196.7 ± 41.4 vs 100.1 ± 130.1, p = 0.03).

CONCLUSION

Hyperintense arteries on Gd-enhanced 3D T1W BB FSE in acute MCA stroke may be associated with slow collateral flows. Their territories corresponded to those of FLAIR, but had a better contrast. The patients with hyperintense arteries in a wider territory showed larger perfusion deficit than those with hyperintense arteries in a narrower territory.

KEY POINTS

• Hyperintense arteries on Gd-enhanced 3D T1W BB FSE are slow collateral flows. • Hyperintense arteries on Gd-enhanced 3D T1W BB FSE are well matched with FLAIR hyperintense vessels. • Hyperintense arteries are associated with perfusion deficit in stroke patients.

Significance of Magnetic Resonance Imaging (MRI) T2 Hyperintense Endo-Vessels Sign in Progressive Posterior Circulation Infarction

Background

MRI FLAIR hyperintense vessels sign (FHVs) is a special imaging marker that plays a key role in acute infarction imaging and diagnosis. However, FHVs have not been studied in the context of progressive posterior circulation infarction (PPCI), and little is known about the association of hyperintense endo-vessels sign (HEVs) on transverse section MRI with infarction. Thus, our objective here was to investigate the clinical significance of transverse MRI T2 HEVs in patients with PPCI.

Material/Methods

In this retrospective, case-control study, we enrolled 100 consecutive posterior circulation infarction patients. All the patients underwent head MRI examinations on the onset day and the seventh day after admission. Neurologic deficits of the patients were assessed by the National Institutes of Health Stroke Scale (NIHSS) scores upon admission and after 7 days. Infarction volume on DWI was compared.

Results

HEVs were detected in 25 of 37 patients in the PPCI group (67.6%) and 22 of 63 patients in the NPPCI group (34.9%). Logistic regression analysis showed that the proportion of HEVs in the PPCI group was higher than in the NPPCI group (P=0.007). Among all the patients, HEVs were detected in 15 of 18 patients (83.3%) with occlusion of the vertebral artery or basilar artery, and 17 of 23 (73.9%) showed severe stenosis. The proportion of vertebrobasilar artery occlusions in the PPCI group was higher than in the NPPCI group (P<0.05). MRI DWI showed that 20 patients had cerebellum infarction among 23 vertebral artery HEVs patients, and 14 patients had brainstem infarction among 15 basilar artery HEVs patients. All of the 9 vertebral and basilar artery HEVs patients had brainstem infarction. The increase in NIHSS scores from baseline to 7 days was significantly greater in patients with HEVs than in patients without HEVs in the PPCI group (P=0.002). The expansion of the infarction size from baseline to 7 days was significantly larger in patients with HEVs than in patients without HEVs in the PPCI group (P=0.037).

Conclusions

HEVs are frequently detected in patients with vertebrobasilar artery territory infarction, and they can be considered as a special imaging marker for vertebral artery and basilar artery occlusion and severe stenosis. HEVs can indicate whether or not posterior circulation infarction progresses and they may be an independent risk factor of PPCI.

Hyperintense Vessels, Collateralization, and Functional Outcome in Patients With Stroke Receiving Endovascular Treatment

Background and Purpose—

Fluid-attenuated inversion recovery hyperintense vessels (FHV) are frequently observed on magnetic resonance imaging in acute stroke patients with proximal vessel occlusion. Whether FHV can serve as a surrogate for the collateral status and predict functional outcome of patients is still a matter of debate.

Methods—

Acute ischemic stroke patients with M1-middle cerebral artery occlusion who received magnetic resonance imaging before endovascular treatment in 3 hospitals in Germany between January 2007 and June 2016 were eligible. Quantification of FHV was performed using an FHV–Alberta Stroke Program Early CT Score (ASPECTS) rating system. Functional outcome was evaluated with the modified Rankin Scale 3 months after stroke. Collateral status of patients was graded on baseline angiography using the American Society of Interventional and Therapeutic Neuroradiology grading system. Odds for good outcome (modified Rankin Scale score, 0–2) were determined using logistic regression analyses.

Results—

Overall, 116 patients were analyzed (median age, 74; interquartile range [IQR], 64–79; median National Institutes of Health Stroke Scale, 14; IQR, 10–19). The median FHV-ASPECTS was 2 (IQR, 1–3). Good collateral status (American Society of Interventional and Therapeutic Neuroradiology grade 3–4) on angiography was more frequently observed in patients with FHV-ASPECTS ≤2 (83% versus 57%; P =0.025). Patients with an FHV-ASPECTS ≤2 had a better functional outcome after 3 months (median modified Rankin Scale score, 2; IQR, 0–5), compared with patients with an FHV-ASPECTS >2 (median modified Rankin Scale score, 4; IQR, 3–6; P =0.015). In multiple regression analyses, FHV-ASPECTS ≤2 was independently associated with good functional outcome (adjusted odds ratio, 5.3; 95% confidence interval, 1.5–18.2).

Conclusions—

Low FHV-ASPECTS is associated with both better collateral status and better 3-month functional outcome in acute stroke patients with M1 vessel occlusion.

Fluid-attenuated inversion recovery vascular hyperintensities in predicting cerebral hyperperfusion after intracranial arterial stenting

PURPOSE

No reliable imaging sign predicting cerebral hyperperfusion after intracranial arterial stenting (IAS) had been described in the literature. This study evaluated the effect of fluid-attenuated inversion recovery vascular hyperintensities (FVHs), also called hyperintense vessel sign on T2-weighted fluid-attenuated inversion recovery (T2-FLAIR) MR images, in predicting significant increase in cerebral blood flow (CBF) defined by arterial spin labeling (ASL) after IAS.

METHODS

We reviewed ASL CBF images and T2-FLAIR MR images before (D0), 1 day after (D1), and 3 days after (D3) IAS of 16 patients. T1-weighted MR images were used as cerebral maps for calculating CBF. The changes in CBF values after IAS were calculated in and compared among stenting and nonstenting vascular territories. An increase more than 50% of CBF was considered as hyperperfusion. The effect of FVHs in predicting hyperperfusion was calculated.

RESULTS

The D1 CBF value was significantly higher than the D0 CBF value in stenting vascular, contralateral anterior cerebral artery, contralateral middle cerebral artery, and contralateral posterior cerebral artery (PCA) territories (all P < .05). The D1 and D3 CBF values were significantly higher than the D0 CBF value in overall vascular (P < .001), overall nonstenting vascular (P < .001), and ipsilateral PCA (P < .05) territories. The rate of more than 50% increases in CBF was significantly higher in patients who exhibited asymmetric FVHs than in those who did not exhibit these findings.

CONCLUSION

FVHs could be a critical predictor of a significant increase in CBF after IAS.