Middle cerebral artery (MCA) susceptibility sign at susceptibility-based perfusion MR imaging: clinical importance and comparison with hyperdense MCA sign at CT

Susceptibility weighted imaging for detection of thrombus in acute ischemic stroke: A cross-sectional study

Background and Aims

Susceptibility-weighted imaging (SWI) can help in the diagnosis of thrombus within the vessel in acute ischemic stroke, known as susceptibility vessel sign (SVS), and detection of SVS within the vessel can predict treatment modality and outcome. In this study, the purpose is to correlate the SVS on SWI with different parameters of stroke.

Methods

This prospective cross-sectional study enrolled consecutive stroke patients with vessel occlusion on magnetic resonance angiography (MRA) over 1 year. The relationship between SVS on SWI with risk factors, territory involved, and length of thrombus was correlated with the National Institutes of Health Stroke Scale (NIHSS).

Results

A total of 105 patients were enrolled in this study. Sixty-two percent (66 out of 105) of patients showed SVS on SWI with MRA-positive occlusion. A positive correlation was observed between SVS on SWI and the risk factor (p = 0.003, chi-square test), with 86% of patients with heart disease and 47% with hypertension exhibiting SVS. Additionally, a positive correlation was observed between SVS on SWI and territorial occlusion (p = 0.000, chi-square test). A moderate positive correlation was observed between the NIHSS and thrombus length (p = 0.002, Pearson's correlation coefficient), with a Pearson's coefficient of 0.367.

Conclusions

SWI can be useful in identifying the location of the thrombus, and NIHSS can determine the thrombus length in acute stroke. A higher incidence of SVS can be associated with risk factors, and it also depends upon the site of occlusion of the vessel.

Stent Retriever Deployment Tracing Susceptibility Vessel Sign in the M2 Branch Predicts the Effective First-Pass Reperfusion in Thrombectomy for M1 Occlusion

BACKGROUND AND PURPOSE

Successful first-pass reperfusion is associated with better functional outcomes after mechanical thrombectomy (MT) for acute ischemic stroke, but its treatment strategies remain unclear.

MATERIALS AND METHODS

We retrospectively recruited patients who underwent MT for M1 occlusion between December 2020 and May 2023 at our institution. The locations of susceptibility vessel sign (SVS) on magnetic resonance imaging were classified into M1 only, M1 to single M2 branch, or M1 to both M2 branches. Patients were included in the SVS tracing group when the stent retriever of the first pass covered the entire SVS length. Successful reperfusion was defined as a modified Thrombolysis in Cerebral Infarction scale 2b-3. Any intracranial hemorrhage detected at 24-hour postoperatively was included as a hemorrhagic complication.

RESULTS

The SVS was detected in M1 only, M1 to single M2 branch, and M1 to both M2 branches in 8, 22, and 4 patients, respectively. Among the 34 patients, 27 were included in the SVS-tracing group. Successful first-pass reperfusion was significantly more frequent in the SVS-tracing group compared with the non-SVS tracing group (odds ratio, 14.4; 95% confidence interval, 2.0 - 101; P = 0.007). The procedural time was significantly reduced in the SVS tracing group (median, 29 [interquartile range, 22 - 49] minute vs. 63 [43 - 106] minute; P = 0.043). There was a trend toward less frequent hemorrhagic complications in the SVS tracing group (odds ratio, 0.17; 95% confidence interval, 0.029 - 1.0; P = 0.052).

CONCLUSIONS

This study provides a thrombus imaging-based MT strategy to efficiently achieve first-pass reperfusion in M1 occlusion.

Susceptibility vessel sign, a predictor of long-term outcome in patients with stroke treated with mechanical thrombectomy

BACKGROUND

The absence of the susceptibility vessel sign (SVS) in patients treated with mechanical thrombectomy (MT) is associated with poor radiological and clinical outcomes after 3 months. Underlying conditions, such as cancer, are assumed to influence SVS status and could potentially impact the long-term outcome. We aimed to assess SVS status as an independent predictor of long-term outcomes in MT-treated patients.

METHODS

SVS status was retrospectively determined in consecutive MT-treated patients at a comprehensive stroke center between 2010 and 2018. Predictors of long-term mortality and poor functional outcome (modified Rankin Scale (mRS) ≥3) up to 8 years were identified using multivariable Cox and logistic regression, respectively.

RESULTS

Of the 558 patients included, SVS was absent in 13% (n=71) and present in 87% (n=487) on baseline imaging. Patients without SVS were more likely to have active cancer (P=0.003) and diabetes mellitus (P<0.001) at the time of stroke. The median long-term follow-up time was 1058 days (IQR 533-1671 days). After adjustment for active cancer and diabetes mellitus, among others, the absence of SVS was associated with long-term mortality (adjusted HR (aHR) 2.11, 95% CI 1.35 to 3.29) and poor functional outcome in the long term (adjusted OR (aOR) 2.90, 95% CI 1.29 to 6.55).

CONCLUSION

MT-treated patients without SVS have higher long-term mortality rates and poorer long-term functional outcome. It appears that this association cannot be explained by comorbidities alone, and further studies are warranted.

Automated Intracranial Clot Detection: A Promising Tool for Vascular Occlusion Detection in Non-Enhanced CT

(1) Background: to test the diagnostic performance of a fully convolutional neural network-based software prototype for clot detection in intracranial arteries using non-enhanced computed tomography (NECT) imaging data. (2) Methods: we retrospectively identified 85 patients with stroke imaging and one intracranial vessel occlusion. An automated clot detection prototype computed clot location, clot length, and clot volume in NECT scans. Clot detection rates were compared to the visual assessment of the hyperdense artery sign by two neuroradiologists. CT angiography (CTA) was used as the ground truth. Additionally, NIHSS, ASPECTS, type of therapy, and TOAST were registered to assess the relationship between clinical parameters, image results, and chosen therapy. (3) Results: the overall detection rate of the software was 66%, while the human readers had lower rates of 46% and 24%, respectively. Clot detection rates of the automated software were best in the proximal middle cerebral artery (MCA) and the intracranial carotid artery (ICA) with 88-92% followed by the more distal MCA and basilar artery with 67-69%. There was a high correlation between greater clot length and interventional thrombectomy and between smaller clot length and rather conservative treatment. (4) Conclusions: the automated clot detection prototype has the potential to detect intracranial arterial thromboembolism in NECT images, particularly in the ICA and MCA. Thus, it could support radiologists in emergency settings to speed up the diagnosis of acute ischemic stroke, especially in settings where CTA is not available.

Imaging diagnosis of intracranial atherosclerosis stenosis-related large vessel occlusion before and during endovascular therapy

It is becoming increasingly important to identify the type of stroke, especially the mechanism of occlusion, before and during its treatment. In the case of intracranial atherosclerotic stenosis-related large vessel occlusion, it is necessary to develop a treatment strategy that includes not only mechanical thrombectomy but also adjunctive therapies such as primary or rescue therapy (percutaneous angioplasty, intracranial/carotid stenting, local fibrinolysis) and perioperative antithrombotic therapy. However, in clinical practice we often encounter cases where it is difficult to identify the occlusive mechanism before endovascular treatment because of insufficient information in the minimal circumstances of the hyperacute phase of stroke. Here we focus on the imaging diagnosis before and during treatment of intracranial atherosclerotic stenosis-related large vessel occlusion with in situ thrombotic occlusion as the mechanism of thrombotic occlusion, based on previous reports. We describe the diagnosis of intracranial atherosclerotic stenosis-related large vessel occlusion from the perspectives of "thrombus imaging," "perfusion," and "occlusion margin."

Absence of susceptibility vessel sign and hyperdense vessel sign in patients with cancer-related stroke

Background and aim

Identification of paraneoplastic hypercoagulability in stroke patients helps to guide investigations and prevent stroke recurrence. A previous study demonstrated an association between the absence of the susceptibility vessel sign (SVS) on brain MRI and active cancer in patients treated with mechanical thrombectomy. The present study aimed to confirm this finding and assess an association between the absence of the hyperdense vessel sign (HVS) on head CT and active cancer in all stroke patients.

Methods

SVS and HVS status on baseline imaging were retrospectively assessed in all consecutive stroke patients treated at a comprehensive stroke center between 2015 and 2020. Active cancer, known at the time of stroke or diagnosed within 1 year after stroke (occult cancer), was identified. Adjusted odds ratios (aOR) and their 95% confidence interval (CI) for the association between the thrombus imaging characteristics and cancer were calculated using multivariable logistic regression.

Results

Of the 2,256 patients with thrombus imaging characteristics available at baseline, 161 had an active cancer (7.1%), of which 36 were occult at the time of index stroke (1.6% of the total). The absence of SVS was associated with active cancer (aOR 3.14, 95% CI 1.45-6.80). No significance was reached for the subgroup of occult cancer (aOR 3.20, 95% CI 0.73-13.94). No association was found between the absence of HVS and active cancer (aOR 1.07, 95% CI 0.54-2.11).

Conclusion

The absence of SVS but not HVS could help to identify paraneoplastic hypercoagulability in stroke patients with active cancer and guide patient care.

Deep learning of MRI contrast enhancement for mapping cerebral blood volume from single-modal non-contrast scans of aging and Alzheimer's disease brains

While MRI contrast agents such as those based on Gadolinium are needed for high-resolution mapping of brain metabolism, these contrast agents require intravenous administration, and there are rising concerns over their safety and invasiveness. Furthermore, non-contrast MRI scans are more commonly performed than those with contrast agents and are readily available for analysis in public databases such as the Alzheimer's Disease Neuroimaging Initiative (ADNI). In this article, we hypothesize that a deep learning model, trained using quantitative steady-state contrast-enhanced structural MRI datasets, in mice and humans, can generate contrast-equivalent information from a single non-contrast MRI scan. The model was first trained, optimized, and validated in mice, and was then transferred and adapted to humans. We observe that the model can substitute for Gadolinium-based contrast agents in approximating cerebral blood volume, a quantitative representation of brain activity, at sub-millimeter granularity. Furthermore, we validate the use of our deep-learned prediction maps to identify functional abnormalities in the aging brain using locally obtained MRI scans, and in the brain of patients with Alzheimer's disease using publicly available MRI scans from ADNI. Since it is derived from a commonly-acquired MRI protocol, this framework has the potential for broad clinical utility and can also be applied retrospectively to research scans across a host of neurological/functional diseases.

Factors That Influence Susceptibility Vessel Sign in Patients With Acute Stroke Referred for Mechanical Thrombectomy

Background and Purpose

The presence of a Susceptibility Vessel Sign (SVS) in the acute phase of proximal occlusion ischemic stroke indicates the presence of deoxyhemoglobin in the thrombus. Thrombi composition changes over time. The aim of this study was to investigate whether the absence of SVS is associated with a shorter symptom onset to imaging time.

Methods

We retrospectively analyzed all patients referred for mechanical thrombectomy at Besançon University Hospital between 1 January 2015 and 31 December 2020 for whom readable T2^*-weighted imaging was available. We compared patient characteristics according to the presence or absence of an SVS. We also studied the subgroup for whom the exact symptom onset time was known. We performed a univariate statistical analysis, then a multivariate analysis on the variables that were statistically significant in the univariate analysis.

Results

Of the 389 patients included, 309 (79.4%) were SVS+. We found no significant relationship between SVS– and the time between symptom onset and imaging in the whole cohort. In the multivariate analysis, SVS– was associated with anticoagulant treatment (p < 0.01), and SVS+ with age (p = 0.023) and carotid terminus occlusion (p = 0.042). In the known symptom onset subgroup, SVS– was significantly associated with a shorter symptom onset -imaging time (p < 0.001), and this was confirmed in the multivariate analysis (p = 0.011; OR 0.911; 95% CI [0.844; 0.972]).

Conclusion

In the acute phase of proximal occlusion ischemic stroke, absence of SVS was associated with a shorter symptom onset–imaging time for patients with a known symptom onset time.

High-Resolution Vessel Wall MR Imaging in Diagnosis and Length Measurement of Cerebral Arterial Thrombosis: A Feasibility Study

BACKGROUND

Detecting and measuring intraluminal thrombus has prognostic and therapeutic implications for stroke patients.

PURPOSE

To investigate the feasibility of 3D isotropic high-resolution T1w-CUBE imaging to detect and measure intraluminal thrombus in stroke patients.

STUDY TYPE

Retrospective.

SUBJECTS

A total of 93 patients with acute (N = 39) and subacute (N = 54) stroke.

FIELD STRENGTH/SEQUENCE

A 3.0 T/spin-echo echo-planar diffusion-weighted imaging (DWI), high-resolution T1w-CUBE imaging and 3D flow compensated gradient-echo susceptibility-weighted imaging (SWI).

ASSESSMENT

Data assessment was performed by three neuroradiologists with 11, 13, and 20 years of clinical experience. The accuracy of T1W-CUBE and SWI in diagnosing thrombosis was compared by using digital subtraction angiography (DSA) as the reference. For thrombus length measurement, the image quality of proximal and distal thrombus of T1w-CUBE images was first evaluated with a 4-point rating system. Then, the proximal and distal positions to lesions were determined on T1w-CUBE images and compared with those from DSA acquired during endovascular reperfusion therapy. If comparable both locations were found between CUBE and DSA, CUBE imaging can thus be considered for accurate measurement of thrombus length.

STATISTICAL TESTS

Fleiss' Kappa; the area under the receiver operating characteristic (ROC) curve (AUC); Pearson's chi-squared test with Yates' continuity correction.

RESULTS

Moderate-to-good interobserver agreements were validated with all Kappa coefficients higher than 0.40 in thrombus diagnosis and measurement. CUBE imaging showed higher clinical efficacy than SWI (AUC: 0.966 vs. 0.850) in thrombus diagnosis. Additionally, high quality of CUBE imaging was confirmed with 3 or 4 points rated by all three observers. Compared to intraoperative DSA, T1w CUBE showed consistent proximal and distal positions of thrombi in 16 of the 18 patients, validating the accuracy of T1w-CUBE in measuring thrombus length.

DATA CONCLUSION

T1w-CUBE imaging has potential to facilitate diagnosis and measurement of intraluminal thrombus.

EVIDENCE LEVEL

4 TECHNICAL EFFICACY: Stage 2.

Quantitative time-of-flight MR angiography for simultaneous luminal and hemodynamic evaluation of the intracranial arteries

PURPOSE

To report a quantitative time-of-flight (qTOF) MRA technique for simultaneous luminal and hemodynamic evaluation of the intracranial arteries.

METHODS

Implemented using a thin overlapping slab 3D stack-of-stars based 3-echo FLASH readout, qTOF was tested in a flow phantom and for imaging the intracranial arteries of 10 human subjects at 3 Tesla. Display of the intracranial arteries with qTOF was compared to resolution-matched and scan time-matched standard Cartesian 3D time-of-flight (TOF) MRA, whereas quantification of mean blood flow velocity with qTOF, done using a computer vision-based inter-echo image analysis procedure, was compared to 3D phase contrast MRA. Arterial-to-background contrast-to-noise ratio was measured, and intraclass correlation coefficient was used to evaluate agreement of flow velocities.

RESULTS

For resolution-matched protocols of similar scan time, qTOF portrayed the intracranial arteries with good morphological correlation with standard Cartesian TOF, and both techniques provided superior contrast-to-noise ratio and arterial delineation compared to phase contrast (20.6 ± 3.0 and 37.8 ± 8.7 vs. 11.5 ± 2.2, P < .001, both comparisons). With respect to phase contrast, qTOF showed excellent agreement for measuring mean flow velocity in the flow phantom (intraclass correlation coefficient = 0.981, P < .001) and good agreement in the intracranial arteries (intraclass correlation coefficient = 0.700, P < .001). Stack-of-stars data sampling used with qTOF eliminated oblique in-plane flow misregistration artifacts that were seen with standard Cartesian TOF.

CONCLUSION

qTOF is a new 3D MRA technique for simultaneous luminal and hemodynamic evaluation of the intracranial arteries that provides significantly greater contrast-to-noise ratio efficiency than phase contrast and eliminates misregistration artifacts from oblique in-plane blood flow that occur with standard 3D TOF.

Susceptibility vessel sign as a predictor for recanalization and clinical outcome in acute ischaemic stroke: A systematic review and meta-analysis

OBJECTIVE

To assess the prognostic values of susceptibility vessel sign (SVS) on T2*-weighted MRI using GRE and SWI sequences for recanalization status and clinical outcomes in patients with acute ischaemic stroke undergoing different therapies.

METHODS

Literature search on PubMed, EMBASE databases and other sources from inception up to 01 June 2021 was conducted. 11 studies which reported SVS, recanalization and clinical outcomes were included in qualitative synthesis and meta-analysis.

RESULTS

Pooled analysis demonstrated significant association between good clinical outcome and SVS-positive patients who underwent mechanical thrombectomy (RR = 1.34, 95% CI = 1.07-1.67, p = 0.01), which is in line with higher recanalization rate in SVS-positive patients who were treated with mechanical thrombectomy compared to intravenous thrombolysis only. No statistically significant association was demonstrated between presence of SVS and successful recanalization, likely due to limitations in the recruited studies.

CONCLUSIONS

Presence of SVS in patients with acute ischaemic stroke who underwent mechanical thrombectomy is associated with good clinical outcome. SVS-positive patients treated with mechanical thrombectomy also shows better recanalization rate comparing to intravenous thrombolysis only, although not statistically significant. MRI assessment of the clot content using SVS is useful in selection of reperfusion strategy for acute ischaemic stroke and prognostication.

SWI Susceptibility Vessel Sign in Patients Undergoing Mechanical Thrombectomy for Acute Ischemic Stroke

BACKGROUND AND PURPOSE

The frequency and clinical significance of the susceptibility vessel sign in patients with acute ischemic stroke remains unclear. We aimed to assess its prevalence in patients with acute ischemic stroke undergoing mechanical thrombectomy and to analyze its association with interventional and clinical outcome parameters in that group.

MATERIALS AND METHODS

Six hundred seventy-six patients with acute ischemic stroke and admission MR imaging were reviewed retrospectively. Of those, 577 met the eligibility criteria for further analysis. Imaging was performed using a 1.5T or 3T MR imaging scanner. Associations between baseline variables, interventional and clinical outcome parameters, and susceptibility vessel sign were determined with multivariable logistic regression models. Results are shown as adjusted ORs with 95% CIs.

RESULTS

The susceptibility vessel sign was present in 87.5% (n = 505) of patients and associated with tandem occlusion (adjusted OR, 3.3; 95% CI, 1.1-10.0; P = .032) as well as successful reperfusion, defined as an expanded TICI score of ≥2b (adjusted OR, 2.4; 95% CI, 1.28-4.6; P = .007). The susceptibility vessel sign was independently associated with functional independence (mRS ≤ 2: adjusted OR, 2.1; 95% CI, 1.1-4.0; P = .028) and lower mortality (adjusted OR, 0.4; 95% CI, 0.2-0.7; P = .003) at 90 days, even after adjusting for successful reperfusion. The susceptibility vessel sign did not influence the number of passes performed during mechanical thrombectomy, the first-pass reperfusion, or the risk of peri- or postinterventional complications.

CONCLUSIONS

The susceptibility vessel sign is an MR imaging phenomenon frequently observed in patients with acute ischemic stroke and is associated with successful reperfusion after mechanical thrombectomy. However, superior clinical functional outcome and lower mortality noted in patients showing the susceptibility vessel sign could not be entirely attributed to higher reperfusion rates.

Relation of Pre-Stroke Aspirin Use With Cerebral Infarct Volume and Functional Outcomes

Objective

We investigated (1) the associations of pre‐stroke aspirin use with thrombus burden, infarct volume, hemorrhagic transformation, early neurological deterioration (END), and functional outcome, and (2) whether stroke subtypes modify these associations in first‐ever ischemic stroke.

Methods

This multicenter magnetic resonance imaging (MRI)‐based study included 5,700 consecutive patients with acute first‐ever ischemic stroke, who did not undergo intravenous thrombolysis or endovascular thrombectomy, from May 2011 through February 2014. Propensity score‐based augmented inverse probability weighting was performed to estimate adjusted effects of pre‐stroke aspirin use.

Results

The mean age was 67 years (41% women), and 15.9% (n = 907) were taking aspirin before stroke. Pre‐stroke aspirin use (vs nonuse) was significantly related to a reduced infarct volume (by 30%), particularly in large artery atherosclerosis stroke (by 45%). In cardioembolic stroke, pre‐stroke aspirin use was associated with a ~50% lower incidence of END (adjusted difference = −5.4%, 95% confidence interval [CI] = −8.9 to −1.9). Thus, pre‐stroke aspirin use was associated with ~30% higher likelihood of favorable outcome (3‐month modified Rankin Scale score < 3), particularly in large artery atherosclerosis stroke and cardioembolic stroke (adjusted difference = 7.2%, 95% CI = 1.8 to 12.5 and adjusted difference = 6.4%, 95% CI = 1.7 to 11.1, respectively). Pre‐stroke aspirin use (vs nonuse) was associated with 85% less frequent cerebral thrombus‐related susceptibility vessel sign (SVS) in large artery atherosclerosis stroke (adjusted difference = −1.4%, 95% CI = −2.1 to −0.8, p < 0.001) and was associated with ~40% lower SVS volumes, particularly in cardioembolic stroke (adjusted difference = −0.16 cm³, 95% CI = −0.29 to −0.02, p = 0.03). Moreover, pre‐stroke aspirin use was not significantly associated with hemorrhagic transformation (adjusted difference = −1.1%, p = 0.09).

Interpretation

Pre‐stroke aspirin use associates with improved functional independence in patients with first‐ever ischemic large arterial stroke by reducing infarct volume and/or END, likely by decreasing thrombus burden, without increased risk of hemorrhagic transformation. ANN NEUROL 2021;90:763–776

Acute Ischemic Stroke: MR Imaging-Based Paradigms

Multimodal MR imaging provides valuable information in the management of patients with acute ischemic stroke (AIS), with diagnostic, therapeutic, and prognostic implications. MR imaging plays a critical role in treatment decision making for (1) thrombolytic treatment of AIS patients with unknown symptom-onset and (2) endovascular treatment of patients with large vessel occlusion presenting beyond 6 hours from the symptom onset. MR imaging provides the most accurate information for detection of ischemic brain and is invaluable for differentiating AIS from stroke mimics.

Large vessel cardioembolic stroke and embolic stroke of undetermined source share a common profile of matrix metalloproteinase-9 level and susceptibility vessel sign length

BACKGROUND

Embolic stroke of undetermined source (ESUS) accounts for up to 25% of ischemic strokes. Identification of biomarkers that could improve the prediction of stroke subtype and subsequently of stroke prevention still remains a major issue.

METHODS

The HIBISCUS-STROKE cohort includes ischemic stroke patients with large vessel occlusion treated with mechanical thrombectomy following admission magnetic resonance imaging. Presence and length of susceptibility vessel sign (SVS) were assessed by gradient-recalled echo T2*-weighted imaging. Matrix metalloproteinase-9 (MMP-9) was measured on sera collected at admission. A multiple logistic regression model was performed to detect independent markers distinguishing cardioembolic (CE) from large-artery atherosclerosis (LAA) subtype.

RESULTS

A total of 147 patients were included, of them the etiology was distributed as follows: 86 (58.5%) CE, 26 (17.7%) LAA, and 35 (23.8%) ESUS. The optimal cutoff for differentiating CE from LAA subtype was 14.5 mm for SVS length (sensitivity, 79.7%; specificity, 72.7%) and 1110 ng/ml for admission MMP-9 level (sensitivity, 85.3%; specificity, 52.2%). Multivariate analysis revealed that current smoking (odds ratio [OR] 0.07, 95% confidence interval [CI] 0.01-0.93), tandem occlusion (OR 0.01, 95% CI 0.01-0.21), SVS length (OR 0.78, 95% CI 0.63-0.97), and admission MMP-9 level (OR 0.99, 95% CI 0.99-1.00) were inversely associated with CE subtype. SVS length and MMP-9 level did not differ between ESUS and CE subtypes.

CONCLUSION

SVS length and admission MMP-9 level may improve the prediction of CE subtype whose profile is close to ESUS, thus suggesting a common cardiac embolic source.

Clot Burden Score and Collateral Status and Their Impact on Functional Outcome in Acute Ischemic Stroke

BACKGROUND AND PURPOSE

Collateral status and thrombus length have been independently associated with functional outcome in patients with acute ischemic stroke. It has been suggested that thrombus length would influence functional outcome via interaction with the collateral circulation. We investigated the individual and combined effects of thrombus length assessed by the clot burden score and collateral status assessed by a FLAIR vascular hyperintensity-ASPECTS rating system on functional outcome (mRS).

MATERIALS AND METHODS

Patients with anterior circulation acute ischemic stroke due to large-vessel occlusion from the ASTER and THRACE trials treated with endovascular thrombectomy were pooled. The clot burden score and FLAIR vascular hyperintensity score were determined on MR imaging obtained before endovascular thrombectomy. Favorable outcome was defined as an mRS score of 0-2 at 90 days. Association of the clot burden score and the FLAIR vascular hyperintensity score with favorable outcome (individual effect and interaction) was examined using logistic regression models.

RESULTS

Of the 326 patients treated by endovascular thrombectomy with both the clot burden score and FLAIR vascular hyperintensity assessment, favorable outcome was observed in 165 (51%). The rate of favorable outcome increased with clot burden score (smaller clots) and FLAIR vascular hyperintensity (better collaterals) values. The association between clot burden score and functional outcome was significantly modified by the FLAIR vascular hyperintensity score, and this association was stronger in patients with good collaterals, with an adjusted OR = 6.15 (95% CI, 1.03-36.81).

CONCLUSIONS

The association between the clot burden score and functional outcome varied for different collateral scores. The FLAIR vascular hyperintensity score might be a valuable prognostic factor, especially when contrast-based vascular imaging is not available.

Susceptibility-Weighted Imaging as a Distinctive Imaging Technique for Providing Complementary Information for Precise Diagnosis of Neurologic Disorder

Various sequences have been developed for MRI to aid in the radiologic diagnosis. Among the various MR sequences, susceptibility-weighted imaging (SWI) is a high-spatial-resolution, three-dimensional gradient-echo MR sequence, which is very sensitive in detecting deoxyhemoglobin, ferritin, hemosiderin, and bone minerals through local magnetic field distortion. In this regard, SWI has been used for the diagnosis and treatment of various neurologic disorders, and the improved image quality has enabled to acquire more useful information for radiologists. Here, we explain the principle of various signals on SWI arising in neurological disorders and provide a retrospective review of many cases of clinically or pathologically proven disease or components with distinctive imaging features of various neurological diseases. Additionally, we outline a short and condensed overview of principles of SWI in relation to neurological disorders and describe various cases with characteristic imaging features on SWI. There are many different types diseases involving the brain parenchyma, and they have distinct SWI features. SWI is an effective imaging tool that provides complementary information for the diagnosis of various diseases.

Pre-Therapeutic Factors Predicting for the Necessity of Rescue Treatments in Mechanical Thrombectomy

Objective

Mechanical thrombectomy for acute large vessel occlusion (LVO) is currently widely performed. However, rescue treatment (RT), such as percutaneous transluminal angioplasty (PTA) and stenting, is occasionally required, particularly in the case of atherothrombotic brain infarction (ATBI) or dissection. As RT requires higher levels of therapeutic skills and additional devices, early prediction of its performance and preparation are important. We retrospectively investigated the pre-therapeutic factors for predicting the necessity of RT.

Methods

We reviewed 149 consecutive patients who underwent mechanical thrombectomy for acute LVO between April 2014 and December 2019. Eight patients were excluded because of missing clinical data. RT was performed when severe stenosis was observed in occluded vessels or proximal to them during mechanical thrombectomy. We investigated pre-therapeutic neurological, laboratory, and radiological findings in the 141 remaining patients, and compared them between RT and non-RT groups.

Results

RT was performed on 23 of the 141 patients. We found four pre-therapeutic factors with significantly different rates between RT/non-RT as follows: (1) Atrial fibrillation 8.7%/71.1% (p <0.001), (2) diabetes mellitus 39.1%/19.5% (p = 0.04), (3) susceptibility vessel sign (SVS) by T2-weighted imaging 17.4%/66.1% (p <0.001), and (4) tapered occlusion by magnetic resonance angiography (MRA) 47.8%/11.9% (p <0.001). The plasma level of brain natriuretic peptide (BNP) was also significantly different between the two groups. When the BNP level was less than 70 pg/mL, the sensitivity for being in the RT group was 86.9% and the specificity was 83.5%.

Conclusion

Pre-therapeutic findings, such as diabetes mellitus, tapered occlusion, absence of atrial fibrillation, negative SVS, and BNP level less than 70 pg/mL, are predictors of RT in mechanical thrombectomy.

The impact of FLAIR vascular hyperintensity on clinical severity and outcome : A retrospective study in stroke patients with proximal middle cerebral artery stenosis or occlusion

BACKGROUND

The clinical significance of fluid-attenuated inversion recovery vascular hyperintensity (FVH) has not been clarified. The aim of this study was to clarify the effects of FVH on the clinical severity and long-term prognosis of patients with proximal middle cerebral artery (MCA) occlusion or severe stenosis.

METHOD

Because their clinical and imaging data is not accessible, we excluded the patients being treated with IV thrombolysis or mechanical thrombectomy. Clinical and imaging characteristics were documented in 282 consecutive AIS patients with proximal MCA occlusion or severe stenosis. We assessed clinical severity using the National Institutes of Health Stroke Scale (NIHSS) score and clinical outcomes using mRS scores. The average time interval between symptom onset and imaging was 16-18 h. The FVH score according to FVH-ASPECTS ranged from 0 to 7, based on the numbers of territories where FVH is positive.

RESULTS

FVH was observed in 235 (83.33%) of the AIS patients. The FVH(+) group tended to have more alcoholics (65 [27.66%] vs 6 [12.77%], P = 0.032), a higher NIHSS score on the 7th day (3 [1-6] vs 2 [1-3], P = 0.039), more instances of early neurological deterioration (END) (27 [11.4%] vs 1 [2.12%], P = 0.05), and more patients with MCA occlusion (94 [40.00%] vs 3 [6.38%]). Among the patients with positive FVH, a high FVH score represented severe clinical impairment (higher NIHSS score on admission [P = 0.009] and 7th day since admission [P = 0.02]) and poor clinical outcomes. Spearman's rank correlations showed that FVH scores were positively correlated with NIHSS scores on admission and NIHSS scores on the 7th day (P = 0.039; P = 0.017, respectively).

CONCLUSION

In patients with proximal middle cerebral artery (MCA) occlusion or stenosis ≥ 70%, a high FVH score represented severe clinical impairment and poor clinical outcomes. In acute ischemic stroke (AIS) patients with proximal MCA occlusion, a high FVH score represented favorable clinical outcomes.

Value of thrombus imaging in predicting the outcomes of patients with large-vessel occlusive strokes after endovascular therapy

BACKGROUND

Acute ischemic stroke leads to serious long-term disability and high mortality, especially in patients with large-vessel occlusive strokes. Nowadays, endovascular therapy is considered as an alternative treatment for these patients. Several studies have used thrombus characteristics based on non-contrast computed tomography (NCCT) and computed tomography angiography (CTA) to predict prognosis in ischemic stroke. We conducted a systematic review to identify potential imaging predictive factors for successful recanalization and improved clinical outcome after endovascular therapy in patients with large-vessel occlusion (LVO) in anterior arterial circulation.

METHODS

The PubMed databases were searched for related studies reported between September 18, 2009, and September 18, 2019.

RESULTS

We selected 11 studies on revascularization and 12 studies on clinical outcome. Patients with thrombus of higher Hounsfield unit (HU), shorter length, higher clot burden score, and increased thrombus permeability may achieve higher recanalization and improved clinical outcome, but the matter is still under debate.

CONCLUSION

Imaging of thrombus can be used as an aseessment tool to predict the outcomes and it needs further studies in the future.

Middle cerebral artery thrombus susceptibility-weighted imaging mapping predicts prognosis

Background

Susceptibility weighted imaging and mapping (SWIM) of magnetic resonance imaging (MRI) is used to evaluate cerebral arterial thrombosis. The aim of this research was to assess susceptibility, length, and clot burden score (CBS) of thrombus in the middle cerebral artery (MCA) and their relationship with cerebral infarction and early clinical prognosis in patients with acute or subacute cerebral infarction.

Methods

In total, 56 patients with acute or subacute cerebral infarction (with the time from onset to admission less than 72 h) and only unilateral MCA occlusion were included in the current study. All the patients had the corresponding susceptibility vessel sign (SVS) on susceptibility-weighted imaging (SWI). Parameters including susceptibility, length, and CBS of thrombus were obtained from SWI and SWIM. The differences in susceptibility of different portions of the thrombus were compared with each other by one-way ANOVA test. The relationship between susceptibility and stroke onset time was further analyzed by Spearman correlation analysis, in addition to the relationships between susceptibility, length, CBS, diffusion-weighted imaging-Alberta stroke program early CT score (DWI-ASPECTS), and admission and discharge National Institutes of Health Stroke Scale (NIHSS).

Results

The susceptibility among different portions and different segments of thrombus showed no statistical difference. The susceptibility and length were weakly yet negatively correlated with DWI-ASPECTS (r_s=-0.382, -0.457; P=0.004, 0.000). The susceptibility was weakly yet positively correlated with admission NIHSS and discharged NIHSS (r_s=0.403, 0.430; P=0.002, 0.001). CBS was weakly yet positively correlated with DWI-ASPECTS (r_s=0.349; P=0.008) and weakly yet negatively correlated with admission and discharged NIHSS (r_s=-0.375, -0.335; P=0.004, 0.012).

Conclusions

The susceptibility remained consistent regardless of location, length, and onset time, which indicates that the thrombus composition was similar when detected on SWI less than 72 h from the onset. Susceptibility and CBS may help to predict clinical severity and short-term clinical prognosis to some extent.

Fluid-attenuated inversion recovery vascular hyperintensities in anterior circulation acute ischemic stroke: associations with cortical brain infarct volume and 90-day prognosis

BACKGROUND AND PURPOSE

Fluid-attenuated inversion recovery vascular hyperintensity (FVH) is often observed in conjunction with acute ischemic stroke (AIS) of the carotid system. However, the significance of FVH in patients with AIS has not been fully elucidated. The purpose of this study is to investigate the effects of FVH on the final infarct volume (including cortical and deep brain infarct volume) and on 90-day prognosis in AIS patients.

MATERIAL AND METHODS

We analyzed data of 160 patients who had AIS of anterior circulation. FVH was identified and the cortical brain infarct volume (CBIV) and deep brain infarct volume (DBIV) were calculated. We assessed 90-day clinical outcome using the modified Rankin Scale (mRS).

RESULTS

FVH was identified in 83 of the 160 patients (51.88%). Patients with FVH showed larger CBIV (13.94 ± 25.55 vs. 6.56 ± 13.49 ml; p = 0.025), more frequent intracranial-large artery disease (74.70 vs. 27.27%; p < 0.001), and more severe clinical impairment on admission (NIHSS 7.22 ± 4.01 vs. 5.42 ± 4.52; p = 0.009). Considering the factors influencing prognosis, FVH positivity (OR = 2.12, 95% CI 1.13-3.99; p = 0.02) and NIHSS (at discharge) (OR = 2.14, 95% CI 1.64-2.78; p < 0.001) were independently associated with 90-day clinical outcome of AIS patients.

CONCLUSION

FVH is a more common finding associated with larger CBIV, intracranial-large artery disease, and more severe strokes on admission. In the presence of good collateral circulation, FVH may be a predictor of better outcome in anterior circulation AIS patients at 90 days.

Synergistic role of susceptibility-weighted imaging with diffusion-weighted imaging and magnetic resonance angiography in the evaluation of acute arterial stroke

Objective

This study was performed to investigate whether diffusion-weighted imaging (DWI) and susceptibility-weighted imaging (SWI) are more effective than conventional imaging modalities for evaluation of stroke and selection of candidates for thrombolytic therapy.

Methods

Eighty patients who presented within 12 hours of onset of symptoms of brain ischemia underwent 1.5T magnetic resonance imaging. DWI and SWI were compared with conventional sequences (T1, T2, and fluid-attenuated inversion recovery [FLAIR]) and time-of-flight magnetic resonance angiography (TOF-MRA) to assess factors that affect stroke management and prognosis.

Results

The volume of brain tissue showing hyperintensity was significantly greater than that showing diffusion restriction in patients with a >6-hour symptom onset. The hypointensity sign (susceptibility sign) on SWI showed a sensitivity of 66.7%, specificity of 87.5%, positive predictive value of 88.9, and negative predictive value of 63.6 compared with TOF-MRA. Micro-hemorrhagic foci were significantly associated with 27-mL infarcts on DWI (sensitivity, 71.4%; specificity, 85.0%). Patients with DWI–SWI mismatch showed better responses to thrombolytics. FLAIR–DWI mismatch helped to assess the time of stroke onset.

Conclusion

DWI and SWI should be part of the routine imaging protocol in patients with acute stroke and serve as a decision-making tool for selection of patients for thrombolytic therapy.

Profiling of the Causative Bacteria in Infected Lymphocysts after Lymphadenectomy for Gynecologic Cancer by Pyrosequencing the 16S Ribosomal RNA Gene Using Next-Generation Sequencing Technology

Background

Surgery for gynecologic cancer with lymphadenectomy and pelvic radiotherapy can produce lymphoceles that sometimes complicate with infection, resulting in abscesses. The true pathogenic bacteria of abscesses are not always found because of false-negative results due to administered antibiotics and difficulty with detection, including for anaerobic bacteria. Analyzing bacteria flora by next-generation sequencing (NGS) using 16S ribosomal DNA may reveal the true pathogenic bacteria in abscesses. This is the first report on causative pathogens for infectious lymphocele using this technology.

Methods

The subjects were patients who developed infectious lymphocele after surgery for gynecologic cancer at our hospital from July 2015 to September 2016. NGS analyses of bacterial flora were performed using specimens preserved at -80°C. Two steps of PCR were performed for purified DNA samples to obtain sequence libraries. Processing of sequence data, including operational taxonomic unit (OTU) definition, taxonomy assignment, and an OTU BLAST search were performed. All patients gave written informed consent and the study was approved by the institutional research ethics committee.

Results

Six patients underwent puncture and drainage. The result in most cases indicated a single causative pathogen, including Staphylococcus lugdunensis, Streptococcus dysgalactiae, Streptococcus equinus, Enterococcus saccharolyticus, and Escherichia coli. Conclusions. NGS revealed that the causative bacteria in lymphocele infection are normally a single strain, such as a surface Gram-positive coccus or enteric bacteria. Antibiotics should be chosen as appropriate for elimination of these respective bacteria.

Does Clot Burden Score on Baseline T2*-MRI Impact Clinical Outcome in Acute Ischemic Stroke Treated with Mechanical Thrombectomy?

Background and Purpose

A long clot, defined by a low (0-6) clot burden score (CBS) assessed by T2*-MR sequence, is associated with worse clinical outcome after intravenous thrombolysis (IVT) for acute ischemic stroke than is a small clot (CBS, 7-10). The added benefit of mechanical thrombectomy (MT) might be higher in patients with long clot. The aim of this pre-specified post hoc analysis of the THRombectomie des Artères CErebrales (THRACE) trial was to assess the association between T2*-CBS, successful recanalization and clinical outcome.

Methods

Of 414 patients randomized in the THRACE trial, 281 patients were included in this analysis. Associations between T2*-CBS and clinical outcome on the modified Rankin Scale (mRS) at 3 months were tested.

Results

High T2*-CBS, i.e., small clot, was associated with a shift toward better outcome on the mRS; proportional odds ratio (POR) per point CBS was 1.19 (95% confidence interval [CI], 1.05 to 1.34) in the whole population, 1.34 (95% CI, 1.13 to 1.59) in IVT group, and 1.04 (95% CI, 0.87 to 1.23) in IVTMT group. After adjustment for baseline prognostic variables, the effect of the full scale T2*-CBS was not statistically significant in the whole population and for the IVTMT group but remains significant for the IVT group (POR, 1.32; 95% CI, 1.11 to 1.58).

Conclusions

A small clot, as assessed using T2*-CBS, is associated with improved outcome and may be used as a prognostic marker. Despite the worst outcome with long clot, the relative benefit of MT over IVT seemed to increase with low T2*-CBS and longer clot.

Susceptibility vessel sign on MRI predicts better clinical outcome in patients with anterior circulation acute stroke treated with stent retriever as first-line strategy

BACKGROUND

Susceptibility vessel sign (SVS) can be a useful MRI biomarker of an occlusion but its relationship with clinical outcomes of acute ischemic stroke (AIS) is yet to be fully elucidated.

OBJECTIVE

To investigate SVS in relation to the clinical outcomes after mechanical thrombectomy using a stent retriever (SR) as first-line approach in patients with AIS.

MATERIAL AND METHODS

We included patients with a first-line SR approach for anterior AIS from the the Contact Aspiration vs Stent Retriever for Successful Revascularization (ASTER) and THRombectomie des Artères CErebrales (THRACE) trials when both baseline imaging of SVS and 90-day modified Rankin Scale (mRS) scores were available. Patients were assigned to two groups based on the presence of an SVS (independent core laboratory), and the overall distributions of the mRS score at 90 days (shift analysis) and clinical independence (mRS score ≤2) were compared.

RESULTS

217 patients were included and SVS was diagnosed in 76.0% of cases (n=165, 95% CI 70.4% to 81.7%). After adjustment for potential confounders, SVS+ was significantly associated with 90-day mRS improvement (adjusted common OR=2.75; 95% CI 1.44 to 5.26) and favorable outcome (adjusted common OR=2.76; 95% CI 1.18 to 6.45).

CONCLUSION

Based on results for patients of the ASTER and THRACE trials receiving first-line SR treatment, SVS was associated with lower disability at 3 months. Large prospective studies using MRI-based thrombus evaluation are warranted.

Susceptibility-weighted Imaging in Thrombolytic Therapy of Acute Ischemic Stroke

Objective:

To provide a comprehensive and latest overview of susceptibility-weighted imaging (SWI) in the application of thrombolysis in acute ischemic stroke, and to update the decision-making effect and clinical value of SWI on identifying stroke patients suitable for thrombolytic therapy and possible benefits and risks followed.

Data Sources:

Literatures referred to this review were collected from PubMed, Medline, and EMBASE published till May 2017, using the search terms including susceptibility-weighted imaging, gradient-echo, T2*, thrombolysis, recombinant tissue plasminogen activator (rt-PA), thrombolytic therapy, and stroke.

Study Selection:

Papers in English or with available English abstracts were considered, with no limitation of study design. References were also identified from the bibliographies of identified articles and the authors’ files.

Results:

SWI is of guiding significance for thrombolytic therapy in stroke patients, it can predict the location and length of thrombus and ischemic penumbra. It is worthy of noting that susceptibility vessel sign (SVS) on SWI can be used to predict recanalization after thrombolytic therapy and whether it is better to implement endovascular thrombolectomy in combination or alone. SWI is sensitive in detecting cerebral microbleed (CMB), and CMB might not be a contraindication for thrombolytic therapy, yet CMBs in multiple foci could possibly be related to intracranial hemorrhage (ICH) after thrombolysis. SVS and CMB on SWI sequence are of instructive value in performing antiplatelet therapy after thrombolytic therapy. Cerebral venous change on SWI is related to lower recanalization rate and poor outcome after thrombolysis.

Conclusions:

It seems that SWI can be applied to guide individualized thrombolytic therapies and assist clinicians in making better decisions by weighing benefits and risks. However, there still exist controversies about the relationship between signs on SWI and thrombolytic therapy.

Procedural and clinical outcomes of endovascular recanalization therapy in patients with cancer-related stroke

Objective Embolism due to coagulopathy might be the main pathomechanism underlying cancer-related stroke (CRS). CRS patients with a large artery occlusion could be candidates for endovascular recanalization therapy (ERT), although its procedural and clinical outcomes are not well known. This study aimed to investigate the procedural and clinical outcomes of ERT in CRS patients and the characteristics associated with outcomes compared with those of conventional stroke patients. Methods A registry of consecutive acute ischemic stroke patients who underwent ERT between January 2011 and October 2015 was retrospectively reviewed. CRS patients are described as those who had (a) cryptogenic stroke with advanced or metastatic cancer; (b) no other possible causes of stroke such as cardioembolism (CE) and large artery atherosclerosis (LAA); and (c) elevated D-dimer levels or diffusion-restricted lesions in multiple vascular territories. We compared procedural and clinical outcomes at discharge among CRS, CE, and LAA patients. Results A total of 329 patients were finally enrolled in this study; of these, 19 were CRS patients. The rate of successful recanalization, defined as modified treatment in cerebral infarction grade 2b or 3, was lower in the CRS group than in the LAA and CE groups (63% versus 84% versus 84%, p = .06). CRS subtype was an independent predictor for successful recanalization after ERT in the multivariate analysis (odds ratio, 0.317; 95% confidence interval, 0.116-0.867; p < .001). No significant difference in the rate of good clinical outcomes at discharge was observed among groups. Conclusions Although clinical outcomes at discharge were similar for CE and LAA patients, complete recanalization seemed more difficult to achieve in CRS patients than in conventional stroke patients.

Susceptibility weighted imaging: Clinical applications and future directions

Susceptibility weighted imaging (SWI) is a recently developed magnetic resonance imaging (MRI) technique that is increasingly being used to narrow the differential diagnosis of many neurologic disorders. It exploits the magnetic susceptibility differences of various compounds including deoxygenated blood, blood products, iron and calcium, thus enabling a new source of contrast in MR. In this review, we illustrate its basic clinical applications in neuroimaging. SWI is based on a fully velocity-compensated, high-resolution, three dimensional gradient-echo sequence using magnitude and phase images either separately or in combination with each other, in order to characterize brain tissue. SWI is particularly useful in the setting of trauma and acute neurologic presentations suggestive of stroke, but can also characterize occult low-flow vascular malformations, cerebral microbleeds, intracranial calcifications, neurodegenerative diseases and brain tumors. Furthermore, advanced MRI post-processing technique with quantitative susceptibility mapping, enables detailed anatomical differentiation based on quantification of brain iron from SWI raw data.

Predictors of short-term outcome in patients with acute middle cerebral artery occlusion: unsuitability of fluid-attenuated inversion recovery vascular hyperintensity scores

Fluid-attenuated inversion recovery (FLAIR) vascular hyperintensity (FVH) is used to assess leptomeningeal collateral circulation, but clinical outcomes of patients with FVH can be very different. The aim of the present study was to assess a FVH score and explore its relationship with clinical outcomes. Patients with acute ischemic stroke due to middle cerebral artery M1 occlusion underwent magnetic resonance imaging and were followed up at 10 days (National Institutes of Health Stroke Scale) and 90 days (modified Rankin Scale) to determine short-term clinical outcomes. Effective collateral circulation indirectly improved recovery of neurological function and short-term clinical outcome by extending the size of the pial penumbra and reducing infarct lesions. FVH score showed no correlation with 90-day functional clinical outcome and was not sufficient as an independent predictor of short-term clinical outcome.

Susceptibility vessel sign predicts poor clinical outcome for acute stroke patients untreated by thrombolysis

The location and length of the susceptibility vessel sign (SVS) predicts poor outcome for patients having received reperfusion therapy. The aim of the present study was to assess the predictive value of SVS regarding the clinical outcome for patients untreated with thrombolysis. A retrospective study on acute stroke patients who underwent multimodal magnetic resonance imaging within 3 days from the onset of symptoms was performed. None of the patients had received thrombolysis therapy. The presence, location and length of the SVS were assessed. Uni- and multivariate analyses were used to examine the association between SVS and clinical outcome. A total of 43 SVS+ and 73 SVS- patients were included in the study. A modified Rankin Scale (mRS) of ≤2 at 3 months was determined in 41.9% of patients in the SVS+ group and 79.4% in the SVS- group (P<0.001). Multivariate analysis revealed that the presence of SVS was an independent parameter to predict mRS >2 at 3 months (odds ratio, 3.390; 95% confidence interval, 1.122-10.240; P=0.030). For patients with SVS+ status, the location and length of the SVS were not independent predictors of the clinical outcome. In conclusion, the presence of SVS may predict poor clinical outcome for acute stroke patients untreated with thrombolysis.

The Prevalence of and Factors Related to Vascular Hyperintensity on T1-Weighted Imaging in Acute Ischemic Stroke

BACKGROUND

Thrombus visualization in patients with acute ischemic stroke has been detected and reported using various imaging modalities. T1-weighted imaging (T1-WI) can depict thrombi as hyperintense signals within vessels. Moreover, in addition to thrombi, T1-WI hyperintensities in arteries may suggest arterial dissection. However, the frequency of and factors related to the T1-hyperintense vessel sign (T1-HVS) are not fully known. The aim of this study was to clarify the prevalence of and related factors for the T1-HVS in patients with acute ischemic stroke.

METHODS

From September 2014 through December 2015, consecutive acute ischemic stroke patients who were admitted to our stroke unit within 7 days from symptom onset were retrospectively recruited from the prospective registry. A T1-HVS was defined as the presence of a hyperintense signal, with intensity higher than surrounding brain, within the vessel lumen. Moreover, T1-HVSs were separated into filled T1-HVSs (hyperintensity fills whole vessel lumen) and non-filled T1-HVSs. The frequency of the T1-HVS and the timing of emersion and the relationship between the presence of the T1-HVS and arterial occlusion were assessed.

RESULTS

A total of 399 patients (139 women; median age 73 years; National Institutes of Health Stroke Scale score 3) were enrolled in the present study. Of these, 327 (82%) patients had T1-WI on admission. Two hundred and sixty-seven (67%) subjects had at least one follow-up T1-WI (median 6 days after admission), and 134 (34%) cases had ≥2 follow-up T1-WI examinations. The T1-HVS was observed in 18 patients during admission; therefore, the frequency of the T1-HVS in acute ischemic stroke patients was 4.5% (95% CI 2.5-6.5%). All but one (94%) of the T1-HVSs were first observed on follow-up imaging, and the median number of days from onset to T1-HVS appearance was 9. For patients having initial major artery occlusion and follow-up MRI (n = 95), sensitivity and specificity of the T1-HVS for persistent arterial occlusion on follow-up MR angiography were 22 and 100%, respectively. T1-HVS persisted for a few months and then normalized. Although there were no significant differences between filled and non-filled T1-HVS, more patients with non-filled T1-HVS had arterial dissection (43%) than those with filled T1-HVS (9%, p = 0.245).

CONCLUSION

The T1-HVS was observed in 4.5% of acute ischemic stroke patients. T1-HVSs appeared in the subacute phase in arteries with persistent occlusion and remained for a few months.

Overestimation of Susceptibility Vessel Sign

Background and Purpose—

The extent of blooming artifact may reflect the amount of paramagnetic material. We thus assessed the overestimation ratio of susceptibility vessel sign (SVS) on susceptibility-weighted imaging, defined as the extent of SVS width beyond the lumen and examined its value for predicting the stroke cause in acute ischemic stroke patients.

Methods—

We included consecutive acute ischemic stroke patients with proximal large artery occlusion who underwent both susceptibility-weighted imaging and time-of-flight magnetic resonance angiography within 8 hours poststroke onset. We calculated the length, width, and overestimation ratio of SVS on susceptibility-weighted imaging and then investigated their values for predicting the stroke cause, respectively.

Results—

One-hundred eleven consecutive patients (72 female; mean age, 66.6±13.4 years) were enrolled, among whom 39 (35.1%) were diagnosed with cardiogenic embolism, 43 (38.7%) with large artery atherosclerosis, and 29 (26.1%) with undetermined cause. The presence, length, width, and overestimation ratio of SVS were all independently associated with the cause of cardiogenic embolism after adjusting for baseline National Institute of Health Stroke Scale and infarct volume. After excluded patients with undetermined cause, the sensitivity and specificity of overestimation ratio of SVS for cardiogenic embolism were 0.971 and 0.913; for the length of SVS, they were 0.629 and 0.739; for the width of SVS, they were 0.829 and 0.826, respectively.

Conclusions—

The overestimation ratio of SVS can predict cardiogenic embolism, with both high sensitivity and specificity, which can be helpful for the management of acute ischemic stroke patients in hyperacute stage.

Prediction of Stroke Subtype and Recanalization Using Susceptibility Vessel Sign on Susceptibility-Weighted Magnetic Resonance Imaging

Supplemental Digital Content is available in the text.

Background and Purpose—

The susceptibility vessel sign (SVS) is a hypointense signal visualized because of the susceptibility effect of thrombi, sensitively detected on susceptibility-weighted magnetic resonance imaging. The relationship of SVS parameters with the stroke subtype and recanalization status after endovascular treatment remains uncertain.

Methods—

The data from 89 patients with acute stroke caused by anterior circulation infarcts who underwent susceptibility-weighted magnetic resonance imaging before endovascular treatment were examined. Independent reviewers, blinded to the stroke subtype and recanalization status, measured the SVS diameter, length, and estimated volume. The intra- and interrater agreements of the SVS parameters were assessed.

Results—

The SVS was identified in 78% of the patients. SVS was more commonly associated with cardioembolism than with noncardioembolism (P=0.01). The SVS diameter (P<0.01) and length (P=0.01) were larger in the cardioembolism group. The SVS diameter was larger in the recanalization group (thrombolysis in cerebral infarction ≥2b) than in the nonrecanalization group (P=0.04). Multivariable analysis revealed that the SVS diameter was an independent predictor of cardioembolism (adjusted odds ratio, 1.97; 95% confidence interval, 1.34–2.90; P<0.01). There was no significant association between the SVS volume and the recanalization status (adjusted odds ratio, 1.003; 95% confidence interval, 0.999–1.006; P=0.12). The optimal cutoff value of the SVS diameter for the cardioembolism was 5.5 mm (sensitivity, 45.6%; specificity, 93.8%).

Conclusions—

Increased SVS diameter on susceptibility-weighted magnetic resonance imaging may predict cardioembolism. No clear association was found between SVS volume and endovascular recanalization.

Proximal Bright Vessel Sign on Arterial Spin Labeling Magnetic Resonance Imaging in Acute Cardioembolic Cerebral Infarction

BACKGROUND

The congestion of spin-labeled blood at large-vessel occlusion can present as hyperintense signals on perfusion magnetic resonance imaging with 3-dimensional pseudo-continuous arterial spin labeling (proximal bright vessel sign). The purpose of this study was to clarify the difference between proximal bright vessel sign and susceptibility vessel sign in acute cardioembolic cerebral infarction.

METHODS

Forty-two patients with cardioembolic cerebral infarction in the anterior circulation territory underwent magnetic resonance imaging including diffusion-weighted imaging, 3-dimensional pseudo-continuous arterial spin labeling perfusion magnetic resonance imaging, T2*-weighted imaging, and 3-dimensional time-of-flight magnetic resonance angiography using a 3-T magnetic resonance scanner. Visual assessments of proximal bright vessel sign and the susceptibility vessel sign were performed by consensus of 2 experienced neuroradiologists. The relationship between these signs and the occlusion site of magnetic resonance angiography was also investigated.

RESULTS

Among 42 patients with cardioembolic cerebral infarction, 24 patients showed proximal bright vessel sign (57.1%) and 25 showed susceptibility vessel sign (59.5%). There were 19 cases of proximal bright vessel sign and susceptibility vessel sign-clear, 12 cases of proximal bright vessel sign and susceptibility vessel sign-unclear, and 11 mismatched cases. Four out of 6 patients with proximal bright vessel sign-unclear and susceptibility vessel sign-clear showed distal middle cerebral artery occlusion, and 2 out of 5 patients with proximal bright vessel sign-clear and susceptibility vessel sign-unclear showed no occlusion on magnetic resonance angiography.

CONCLUSIONS

Proximal bright vessel sign is almost compatible with susceptibility vessel sign in patients with cardioembolic cerebral infarction.

Clot Imaging in Large Vessel Occlusion Strokes

Advances in mechanical thrombectomy techniques have resulted in improved, recanalization and functional outcomes in acute stroke, as demonstrated in recent, randomized trials comparing mechanical thrombectomy with thrombolysis. In conjunction with the technological advancements in thrombectomy devices, there has been better appreciation of stricter patient selection criteria for endovascular therapy based on pre-procedural imaging, including clot location, infarct volume, and penumbral territory at risk. Pre-procedural imaging performed to assess suitability for endovascular therapy commonly provides information on clot characteristics, such as clot location, length, density, and susceptibility, which can influence and may predict the efficacy of intravenous and endovascular treatments. The purpose of this review is to evaluate the role of clot imaging in acute large vessel occlusion strokes and discuss the relevance of clot imaging to thrombolytic and endovascular therapy.

Comparison between enhanced susceptibility-weighted angiography and time of flight sequences in the detection of arterial occlusion in acute ischemic stroke

PURPOSE

Optimizing the MRI protocol in acute ischemic stroke remains a challenging issue. In this field, susceptibility-weighted sequences have proved their superiority over T2*. Besides the strengthened susceptibility effect, enhanced susceptibility-weighted angiography (eSWAN) sequence provides also a time-of-flight (TOF) effect, allowing the exploration of the intracranial arterial circulation. The objective of our study was to compare eSWAN and 3D TOF, considered as the reference, in the detection of arterial occlusion in acute stroke.

METHODS

Patients who underwent MRI between March and July 2014 for suspected acute stroke with an acute ischemic lesion on diffusion-weighted imaging (DWI) were prospectively included in this study. eSWAN and TOF images were analyzed under double-blind conditions by a junior radiologist and a senior neuroradiologist for the detection of arterial occlusion. eSWAN images were assessed in order to estimate the inter-observer agreement. After a consensus, eSWAN and TOF data were compared to calculate inter-modality agreement.

RESULTS

Thirty-four patients were included. Inter-observer agreement was excellent (kappa: 0.96) for eSWAN detection of occlusion. After consensus, comparison between TOF and eSWAN showed substantial agreement (kappa: 0.71). eSWAN provided better detection of distal occlusions, but poorer performance for detection of siphon occlusions.

CONCLUSIONS

Shortest echoes eSWAN images enabled detection of arterial occlusion with substantial agreement with TOF images. The susceptibility vessel sign associated with the TOF effect improved the identification of distal occlusions. In acute stroke protocol, eSWAN may represent a valuable alternative to T2* and TOF sequences.

Review of Post Ischemic Stroke Imaging and Its Clinical Relevance

In this day and age, multiple imaging modalities are available to the stroke physician in the post-treatment phase.The practical challenge for physicians who treat stroke is to evaluate the pros and cons of each technique and select the best choice for the situation. The choice of imaging modality remains contentious at best and varies among different institutions and centres. This is no simple task an there are many factors to consider, including the differential diagnosis which need to be evaluated, the availability and reliability of the imaging technique and time and expertise required to perform and interpret the scanning. Other ancillary competing interest also come into play such as the financial cost of the modality, the requirement for patient monitoring during the imaging procedure and patient comfort. In an effort to clear some of the ambiguity surrounding this topic we present some of the current techniques in use and others, which are still in the realm of research and have not yet transitioned into clinical practice.

Understanding the continuum of radionecrosis and vascular disorders in the brain following gamma knife irradiation: An MRI study

PURPOSE

The radiation dose delivered to brain tumors is limited by the possibility to induce vascular damage and necrosis in surrounding healthy tissue. In the present study, we assessed the ability of MRI to monitor the cascade of events occurring in the healthy rat brain after stereotactic radiosurgery, which could be used to optimize the radiation treatment planning.

METHODS

The primary somatosensory forelimb area (S1FL) and the primary motor cortex in the right hemisphere of Fischer rats (n = 6) were irradiated with a single dose of Gamma Knife radiation (Leksell Perfexion, Elekta AG, Stockholm, Sweden). Rats were scanned with a small-animal 7 Tesla MRI scanner before treatment and 16, 21, 54, 82, and 110 days following irradiation. At every imaging session, T₂ -weighted (T₂ w), Gd-DTPA dynamic contrast-enhanced MRI (DCE-MRI), and T2*-weighted ( T2* w) images were acquired to measure changes in fluid content, blood vessel permeability, and structure, respectively. At days 10, 110, and 140, histopathology was performed on brain sections. Locomotion and spatial memory ability were assessed longitudinally by behavioral tests.

RESULTS

No vascular changes were initially observed. After 54 days, a small necrotic volume in the white matter below the S1FL, surrounded by an area presenting significant vascular permeability, was revealed. Between 54 and 110 days, the necrotic volume increased and was accompanied by the formation of a ring-like region, where a mixture of necrosis and permeable blood vessels were observed, as confirmed by histology. Behavioral changes were only observed after day 82.

CONCLUSION

Together, DCE-MRI and T2* w images supported by histology provided a coherent picture of the phenomena involved in the formation of new, leaky blood vessels, which was followed by the detection of radionecrosis in a preclinical model of brain irradiation. Magn Reson Med 78:1420-1431, 2017. © 2016 International Society for Magnetic Resonance in Medicine.