Characteristics of Misclassified CT Perfusion Ischemic Core in Patients with Acute Ischemic Stroke

Background

CT perfusion (CTP) is used to estimate the extent of ischemic core and penumbra in patients with acute ischemic stroke. CTP reliability, however, is limited. This study aims to identify regions misclassified as ischemic core on CTP, using infarct on follow-up noncontrast CT. We aim to assess differences in volumetric and perfusion characteristics in these regions compared to areas that ended up as infarct on follow-up.

Materials and Methods

This study included 35 patients with >100 mm brain coverage CTP. CTP processing was performed using Philips software (IntelliSpace 7.0). Final infarct was automatically segmented on follow-up noncontrast CT and used as reference. CTP and follow-up noncontrast CT image data were registered. This allowed classification of ischemic lesion agreement (core on CTP: rMTT≥145%, aCBV<2.0 ml/100g and infarct on follow-up noncontrast CT) and misclassified ischemic core (core on CTP, not identified on follow-up noncontrast CT) regions. False discovery ratio (FDR), defined as misclassified ischemic core volume divided by total CTP ischemic core volume, was calculated. Absolute and relative CTP parameters (CBV, CBF, and MTT) were calculated for both misclassified CTP ischemic core and ischemic lesion agreement regions and compared using paired rank-sum tests.

Results

Median total CTP ischemic core volume was 49.7ml (IQR:29.9ml-132ml); median misclassified ischemic core volume was 30.4ml (IQR:20.9ml-77.0ml). Median FDR between patients was 62% (IQR:49%-80%). Median relative mean transit time was 243% (IQR:198%-289%) and 342% (IQR:249%-432%) for misclassified and ischemic lesion agreement regions, respectively. Median absolute cerebral blood volume was 1.59 (IQR:1.43–1.79) ml/100g (P<0.01) and 1.38 (IQR:1.15–1.49) ml/100g (P<0.01) for misclassified ischemic core and ischemic lesion agreement, respectively. All CTP parameter values differed significantly.

Conclusion

For all patients a considerable region of the CTP ischemic core is misclassified. CTP parameters significantly differed between ischemic lesion agreement and misclassified CTP ischemic core, suggesting that CTP analysis may benefit from revisions.     

Effect of Extended CT Perfusion Acquisition Time on Ischemic Core and Penumbra Volume Estimation in Patients with Acute Ischemic Stroke due to a Large Vessel Occlusion

Background and Purpose

It has been suggested that CT Perfusion acquisition times <60 seconds are too short to capture the complete in and out-wash of contrast in the tissue, resulting in incomplete time attenuation curves. Yet, these short acquisitions times are not uncommon in clinical practice. The purpose of this study was to investigate the occurrence of time attenuation curve truncation in 48 seconds CT Perfusion acquisition and to quantify its effect on ischemic core and penumbra estimation in patients with acute ischemic stroke due to a proximal intracranial arterial occlusion of the anterior circulation.

Materials and Methods

We analyzed CT Perfusion data with 48 seconds and extended acquisition times, assuring full time attenuation curves, of 36 patients. Time attenuation curves were classified as complete or truncated. Ischemic core and penumbra volumes resulting from both data sets were compared by median paired differences and interquartile ranges. Controlled experiments were performed using a digital CT Perfusion phantom to investigate the effect of time attenuation curve truncation on ischemic core and penumbra estimation.

Results

In 48 seconds acquisition data, truncation was observed in 24 (67%) cases for the time attenuation curves in the ischemic core, in 2 cases for the arterial input function and in 5 cases for the venous output function. Analysis of extended data resulted in smaller ischemic cores and larger penumbras with a median difference of 13.2 (IQR: 4.3–26.0)ml (P<0.001) and; 12.4 (IQR: 4.1–25.7)ml (P<0.001), respectively. The phantom data showed increasing ischemic core overestimation with increasing tissue time attenuation curve truncation.

Conclusions

Truncation is common in patients with large vessel occlusion and results in repartitioning of the area of hypoperfusion into larger ischemic core and smaller penumbra estimations. Phantom experiments confirmed that truncation results in overestimation of the ischemic core.     

Altered Hemodynamic Activity in Conduct Disorder: A Resting-State fMRI Investigation

Background

Youth with conduct disorder (CD) not only inflict serious physical and psychological harm on others, but are also at greatly increased risk of sustaining injuries, developing depression or substance abuse, and engaging in criminal behaviors. The underlying neurobiological basis of CD remains unclear.

Objective

The present study investigated whether participants with CD have altered hemodynamic activity under resting-state conditions.

Methods

Eighteen medication-naïve boys with CD and 18 age- and sex- matched typically developing (TD) controls underwent functional magnetic resonance imaging (MRI) scans in the resting state. The amplitude of low-frequency fluctuations (ALFF) was measured and compared between the CD and TD groups.

Results

Compared with the TD participants, the CD participants showed lower ALFF in the bilateral amygdala/parahippocampus, right lingual gyrus, left cuneus and right insula. Higher ALFF was observed in the right fusiform gyrus and right thalamus in the CD participants compared to the TD group.

Conclusions

Youth with CD displayed widespread functional abnormalities in emotion-related and visual cortical regions in the resting state. These results suggest that deficits in the intrinsic activity of resting state networks may contribute to the etiology of CD.     

Altered Spontaneous Brain Activity in Patients with Acute Spinal Cord Injury Revealed by Resting-State Functional MRI

Background

Previous neuroimaging studies have provided evidence of structural and functional reorganization of brain in patients with chronic spinal cord injury (SCI). However, it remains unknown whether the spontaneous brain activity changes in acute SCI. In this study, we investigated intrinsic brain activity in acute SCI patients using a regional homogeneity (ReHo) analysis based on resting-state functional magnetic resonance imaging.

Methods

A total of 15 patients with acute SCI and 16 healthy controls participated in the study. The ReHo value was used to evaluate spontaneous brain activity, and voxel-wise comparisons of ReHo were performed to identify brain regions with altered spontaneous brain activity between groups. We also assessed the associations between ReHo and the clinical scores in brain regions showing changed spontaneous brain activity.

Results

Compared with the controls, the acute SCI patients showed decreased ReHo in the bilateral primary motor cortex/primary somatosensory cortex, bilateral supplementary motor area/dorsal lateral prefrontal cortex, right inferior frontal gyrus, bilateral dorsal anterior cingulate cortex and bilateral caudate; and increased ReHo in bilateral precuneus, the left inferior parietal lobe, the left brainstem/hippocampus, the left cingulate motor area, bilateral insula, bilateral thalamus and bilateral cerebellum. The average ReHo values of the left thalamus and right insula were negatively correlated with the international standards for the neurological classification of spinal cord injury motor scores.

Conclusion

Our findings indicate that acute distant neuronal damage has an immediate impact on spontaneous brain activity. In acute SCI patients, the ReHo was prominently altered in brain regions involved in motor execution and cognitive control, default mode network, and which are associated with sensorimotor compensatory reorganization. Abnormal ReHo values in the left thalamus and right insula could serve as potential biomarkers for assessment of neuronal damage and the prediction of clinical outcomes in acute SCI.     

Altered Network Topologies and Hub Organization in Adults with Autism: A Resting-State fMRI Study

Recent functional magnetic resonance imaging (fMRI) studies on autism spectrum condition (ASC) have identified dysfunctions in specific brain networks involved in social and non-social cognition that persist into adulthood. Although increasing numbers of fMRI studies have revealed atypical functional connectivity in the adult ASC brain, such functional alterations at the network level have not yet been fully characterized within the recently developed graph-theoretical framework. Here, we applied a graph-theoretical analysis to resting-state fMRI data acquired from 46 adults with ASC and 46 age- and gender-matched controls, to investigate the topological properties and organization of autistic brain network. Analyses of global metrics revealed that, relative to the controls, participants with ASC exhibited significant decreases in clustering coefficient and characteristic path length, indicating a shift towards randomized organization. Furthermore, analyses of local metrics revealed a significantly altered organization of the hub nodes in ASC, as shown by analyses of hub disruption indices using multiple local metrics and by a loss of “hubness” in several nodes (e.g., the bilateral superior temporal sulcus, right dorsolateral prefrontal cortex, and precuneus) that are critical for social and non-social cognitive functions. In particular, local metrics of the anterior cingulate cortex consistently showed significant negative correlations with the Autism-Spectrum Quotient score. Our results demonstrate altered patterns of global and local topological properties that may underlie impaired social and non-social cognition in ASC.     

Plasma D-Dimer Levels Are Associated with Stroke Subtypes and Infarction Volume in Patients with Acute Ischemic Stroke

Background

It has been suggested that modestly elevated circulating D-dimer values may be associated with acute ischemic stroke (AIS). Thus, the purpose of this study was to investigate the association between plasma D -dimer level at admission and AIS in Chinese population.

Methods

In a prospective observational study, plasma D-dimer levels were measured using a particle-enhanced, immunoturbidimetric assay on admission in 240 Chinese patients with AIS. The National Institutes of Health Stroke Scale (NIHSS) score was assessed on admission blinded to D-dimer levels.

Results

Plasma median D-dimer levels were significantly (P = 0.000) higher in AIS patients as compared to healthy controls (0.88; interquartiler range [IQR], 0.28–2.11 mg/L and 0.31; IQR, 0.17–0.74 mg/L). D-dimer levels increased with increasing severity of stroke as defined by the NIHSS score(r = 0.179, p = 0.005) and infarct volume(r = 0.425, p = 0.000). Those positive trends still existed even after correcting for possible confounding factors (P = 0.012, 0.000; respectively). Based on the Receiver operating characteristic (ROC) curve, the optimal cut-off value of plasma D-dimer levels as an indicator for diagnosis of cardioembolic strokes was projected to be 0.91 mg/L, which yielded a sensitivity of 83.7% and a specificity of 81.5%, the area under the curve was 0.862(95% confidence interval [CI], 0.811–0.912).

Conclusion

We had shown that plasma D-dimer levels increased with increasing severity of stroke as defined by the NIHSS score and infarct volume. These associations were independent other possible variables. In addition, cardioembolic strokes can be distinguished from other stroke etiologies by measuring plasma D-dimer levels very early (0–48hours from stroke symptom onset).     

Altered Fronto-Striatal and Fronto-Cerebellar Circuits in Heroin-Dependent Individuals: A Resting-State fMRI Study

Background

The formation of compulsive pattern of drug use is related to abnormal regional neural activity and functional reorganization in the heroin addicts’ brain, but the relationship between heroin-use-induced disrupted local neural activity and its functional organization pattern in resting-state is unknown.

Methodology/Principal Findings

With fMRI data acquired during resting state from 17 male heroin dependent individuals (HD) and 15 matched normal controls (NC), we analyzed the changes of amplitude of low frequency fluctuation (ALFF) in brain areas, and its relationship with history of heroin use. Then we investigated the addiction related alteration in functional connectivity of the brain regions with changed ALFF using seed-based correlation analysis. Compared with NC, the ALFF of HD was obviously decreased in the right caudate, right dorsal anterior cingulate cortex (dACC), right superior medial frontal cortex and increased in the bilateral cerebellum, left superior temporal gyrus and left superior occipital gyrus. Of the six regions, only the ALFF value of right caudate had a negative correlation with heroin use. Setting the six regions as “seeds”, we found the functional connectivity between the right caudate and dorsolateral prefrontal cortex (dlPFC) was reduced but that between the right caudate and cerebellum was enhanced. Besides, an abnormal lateral PFC-dACC connection was also observed in HD.

Conclusions

The observations of dysfunction of fronto-striatal and fronto-cerebellar circuit in HD implicate an altered balance between local neuronal assemblies activity and their integrated network organization pattern which may be involved in the process from voluntary to habitual and compulsive drug use.     

Ischemic Stroke in Critically Ill Patients with Malignancy

Background

Cerebrovascular diseases are a frequent cause of neurological symptoms in patients with cancer. The clinical characteristics of ischemic stroke (IS) in patients with cancer have been reported in several studies; however, limited data are available regarding critically ill patients with cancer who develop IS during their stay in the intensive care unit (ICU).

Methods

All consecutive patients who underwent brain magnetic resonance imaging (MRI) for suspicion of IS with acute abnormal neurologic symptoms or who developed signs of IS while in the ICU were retrospectively evaluated. We compared the clinical characteristics and diffusion-weighted imaging (DWI) lesion patterns between patients finally diagnosed as having or not having IS.

Results

Over the study period, a total of 88 patients underwent brain MRI for suspicion of IS, with altered mental status in 55 (63%), hemiparesis in 28 (32%), and seizure in 20 (23%). A total of 43 (49%) patients were ultimately diagnosed with IS. Multiple DWI lesions (41%) were more common than single lesions (8%). The etiologies of IS were not determined in the majority of patients (n = 27, 63%). In the remaining 16 (37%) patients, the most common aetiology of IS was cardioembolism (n = 8), followed by large-vessel atherosclerosis (n = 3) and small-vessel occlusion (n = 2). However, brain metastases were newly diagnosed in only 7 (8%) patients. Univariate comparison of the baseline characteristics between patients with or without IS did not reveal any significant differences in sex, malignancy type, recent chemotherapy, vascular risk factors, or serum D-dimer levels at the time of suspicion of IS. Thrombotic events were more common in the IS group than in the non-IS group (P = 0.028). However, patients who were ultimately diagnosed with IS had more hemiparesis symptoms at the time of suspicion of IS (P = 0.001). This association was significant even after adjusting for potentially confounding factors (adjusted odds ratio 5.339; 95% confidence interval, 1.521–19.163).

Conclusions

IS developed during ICU stays in critically ill patients with cancer have particular features that may be associated with cancer-related mechanism.     

Altered Regional Homogeneity in Pediatric Bipolar Disorder during Manic State: A Resting-State fMRI Study

Pediatric bipolar disorder (PBD) is a severely debilitating illness, which is characterized by episodes of mania and depression separated by periods of remission. Previous fMRI studies investigating PBD were mainly task-related. However, little is known about the abnormalities in PBD, especially during resting state. Resting state brain activity measured by fMRI might help to explore neurobiological biomarkers of the disorder. Methods: Regional homogeneity (ReHo) was examined with resting-state fMRI (RS-fMRI) on 15 patients with PBD in manic state, with 15 age-and sex-matched healthy youth subjects as controls. Results: Compared with the healthy controls, the patients with PBD showed altered ReHo in the cortical and subcortical structures. The ReHo measurement of the PBD group was negatively correlated with the score of Young Mania Rating Scale (YMRS) in the superior frontal gyrus. Positive correlations between the ReHo measurement and the score of YMRS were found in the hippocampus and the anterior cingulate cortex in the PBD group. Conclusions: Altered regional brain activity is present in patients with PBD during manic state. This study presents new evidence for abnormal ventral-affective and dorsal-cognitive circuits in PBD during resting state and may add fresh insights into the pathophysiological mechanisms underlying PBD.     

急性缺血性脑卒中动脉内溶栓治疗

目的:探讨急性缺血性脑卒中动脉内溶栓治疗。方法:随机选取411例急性缺血性脑卒中患者,男238例,女173例,平均为(64±11)岁,发病距接受治疗的时间为2～24小时,视闭塞血管部位,采取超选择性接触性溶栓。尿激酶用微量泵以1万单位/min持续泵入,总量为80～130万单位。在泵入尿激酶的过程中,通过导引导管造影,了解闭塞血管再通情况。结果:颈内动脉系统血管闭塞192例,椎-基底动脉系统闭塞68例。脑血管造影未见明显异常78例。颈内动脉闭塞再通27例。大脑中动脉闭塞再通52例。大脑中动脉分支闭塞再通41例。椎-基底动脉系统闭塞再通47例。有35例因明显的血管狭窄而给予球囊扩张、支架置入术。临床症状完全恢复正常或有明显好转的247例。为60.01%。结论:我们认为动脉内接触性溶栓治疗急性脑梗塞还是很值得进行的。随着溶栓经验的积累,溶栓药的开发,脑保护剂的应用,总有效率会不断提高。     

Stroke Code Improves Intravenous Thrombolysis Administration in Acute Ischemic Stroke

Background and Purpose

Timely intravenous (IV) thrombolysis for acute ischemic stroke is associated with better clinical outcomes. Acute stroke care implemented with “Stroke Code” (SC) may increase IV tissue plasminogen activator (tPA) administration. The present study aimed to investigate the impact of SC on thrombolysis.

Methods

The study period was divided into the “pre-SC era” (January 2006 to July 2010) and “SC era” (August 2010 to July 2013). Demographics, critical times (stroke symptom onset, presentation to the emergency department, neuroimaging, thrombolysis), stroke severity, and clinical outcomes were recorded and compared between the two eras.

Results

During the study period, 5957 patients with acute ischemic stroke were admitted; of these, 1301 (21.8%) arrived at the emergency department within 3 h of stroke onset and 307 (5.2%) received IV-tPA. The number and frequency of IV-tPA treatments for patients with an onset-to-door time of <3 h increased from the pre-SC era (n = 91, 13.9%) to the SC era (n = 216, 33.3%) (P<0.001). SC also improved the efficiency of IV-tPA administration; the median door-to-needle time decreased (88 to 51 min, P<0.001) and the percentage of door-to-needle times ≤60 min increased (14.3% to 71.3%, P<0.001). The SC era group tended to have more patients with good outcome (modified Rankin Scale ≤2) at discharge (49.5 vs. 39.6%, P = 0.11), with no difference in symptomatic hemorrhage events or in-hospital mortality.

Conclusion

The SC protocol increases the percentage of acute ischemic stroke patients receiving IV-tPA and decreases door-to-needle time.     

Clues to Occult Cancer in Patients with Ischemic Stroke

Background

We hypothesized that hidden malignancy could be detected in patients with cryptogenic stroke without active cancer when they showed the distinctive characteristics of cancer-related stroke.

Methods and Findings

Among 2,562 consecutive patients with acute ischemic stroke, patients with cryptogenic stroke were analyzed and categorized into two groups according to the presence of active cancer: cryptogenic stroke with active cancer (cancer-related stroke, CA-stroke) group and without active cancer (CR-stroke) group. Patients with active lung cancer without stroke were also recruited for comparison purposes (CA-control). Clinical factors, lesion patterns on diffusion-weighted MRI (DWI), and laboratory findings were analyzed among groups. A total of 348 patients with cryptogenic stroke were enrolled in this study. Among them, 71 (20.4%) patients had active cancer at the time of stroke. The D-dimer levels were significantly higher in patients with CA-stroke than those with CR-stroke or CA-control (both p<0.001). Regarding lesion patterns, patients with CA-stroke mostly had multiple lesions in multiple vascular territories, while more than 80% of patients with CR-stroke had single/multiple lesions in a single vascular territory (P<0.001). D-dimer levels (OR 1.11 per 1 µg/mL increase; 95% CI 1.06–1.15; P<0.001) and DWI lesion patterns (OR 7.13; 95% CI 3.42–14.87; P<0.001) were independently associated with CA-stroke. Workup for hidden malignancy was performed during hospitalization in 10 patients who showed elevated D-dimer levels and multiple infarcts involving multiple vascular territories but had no known cancer, and it revealed hidden malignancies in all the patients.

Conclusion

Patients with CA-stroke have distinctive D-dimer levels and lesion patterns. These characteristics can serve as clues to occult cancer in patients with cryptogenic stroke.     

Serum YKL-40 Levels Correlate with Infarct Volume,Stroke Severity,and Functional Outcome in Acute Ischemic Stroke Patients

Background and Purpose

YKL-40 is associated with various neurological disorders. However, circulatory YKL-40 levels early after onset of acute ischemic stroke (AIS) have not been systematically assessed. We aimed to identify the temporal changes and clinical usefulness of measuring serum YKL-40 immediately following AIS.

Methods

Serum YKL-40 and C-reactive protein (CRP) levels were monitored over time in AIS patients (n = 105) and compared with those of stroke-free controls (n = 34). Infarct volume and stroke severity (National Institutes of Health Stroke Scale; NIHSS) were measured within 48 hours of symptom onset, and functional outcome (modified Rankin Scale; mRS) was measured 3 months after AIS.

Results

Within 12 hours of symptom onset, levels of YKL-40 (251 vs. 41 ng/mL) and CRP (1.50 vs. 0.96 µg/mL) were elevated in AIS patients compared to controls. The power of YKL-40 for discriminating AIS patients from controls was superior to that of CRP (area under the curve 0.84 vs. 0.64) and YKL-40 (r = 0.26, P<0.001) but not CRP levels were correlated with mRS. On day 2 of admission (D2), YKL-40 levels correlated with infarct volume and NIHSS. High YKL-40 levels predicted poor functional outcome (odds ratio 5.73, P = 0.03). YKL-40 levels peaked on D2 and declined on D3, whereas CRP levels were highest on D3.

Conclusions

Our results demonstrate serial changes in serum YKL-40 levels immediately following AIS and provide the first evidence that it is a valid indicator of AIS extent and an early predictor of functional outcome.     

Dual-Phase CT Collateral Score: A Predictor of Clinical Outcome in Patients with Acute Ischemic Stroke

Background and Purpose

The presence of good collaterals on CT angiography (CTA) is a well-known predictor for favorable outcome in acute ischemic stroke. Recently, multiphase CT has been introduced as a more accurate method in assessing collaterals. The aim of this study was to assess the ability of dual-phase CT to evaluate collateral status and predict clinical outcome.

Methods

Forty-three patients who underwent both dual-phase CT and transfemoral cerebral angiography (TFCA) for occluded intracranial internal carotid artery (ICA) and/or middle cerebral artery (M1 segment) were recruited from a prospectively collected database. The collateral status on dual-phase CT was graded by using a 4-point scale: grade 0 = no collaterals; 1 = some collaterals with persistence of some defects; 2 = slow but complete collaterals; and 3 = fast and complete collaterals. Univariate and multivariate analysis were performed to define the independent predictors for favorable outcome at 3 months.

Results

Dual-phase CT collateral status (ρ = 0.744) showed higher correlation with TFCA collateral status than CTA collateral status (ρ = 0.596) and substantial interobserver agreement (weighted κ = 0.776). In the univariate analysis, age, history of hypertension, collateral scores on CTA, dual-phase CT, and TFCA, occlusion in intracranial ICA, final infarct volume, and symptomatic hemorrhage were significantly associated with outcome. Among them, only the dual-phase CT collateral score was an independent predictor for favorable outcome (OR = 26.342 (2.788–248.864); P = 0.004) in the multivariate analysis.

Conclusions

The collateral status on dual-phase CT can be a useful predictor for clinical outcome in acute stroke patients, especially when advanced CT techniques are not available in emergent situations.     

Penumbra Pattern Assessment in Acute Stroke Patients: Comparison of Quantitative and Non-Quantitative Methods in Whole Brain CT Perfusion

Background And Purpose

While penumbra assessment has become an important part of the clinical decision making for acute stroke patients, there is a lack of studies measuring the reliability and reproducibility of defined assessment techniques in the clinical setting. Our aim was to determine reliability and reproducibility of different types of three-dimensional penumbra assessment methods in stroke patients who underwent whole brain CT perfusion imaging (WB-CTP).

Materials And Methods

We included 29 patients with a confirmed MCA infarction who underwent initial WB-CTP with a scan coverage of 100 mm in the z-axis. Two blinded and experienced readers assessed the flow-volume-mismatch twice and in two quantitative ways: Performing a volumetric mismatch analysis using OsiriX imaging software (MM_VOL) and visual estimation of mismatch (MM_EST). Complementarily, the semiquantitative Alberta Stroke Programme Early CT Score for CT perfusion was used to define mismatch (MM_ASPECTS). A favorable penumbral pattern was defined by a mismatch of ≥30% in combination with a cerebral blood flow deficit of ≤90 ml and an MM_ASPECTS score of ≥1, respectively. Inter- and intrareader agreement was determined by Kappa-values and ICCs.

Results

Overall, MM_VOL showed considerably higher inter-/intrareader agreement (ICCs: 0.751/0.843) compared to MM_EST (0.292/0.749). In the subgroup of large (≥50 mL) perfusion deficits, inter- and intrareader agreement of MM_VOL was excellent (ICCs: 0.961/0.942), while MM_EST interreader agreement was poor (0.415) and intrareader agreement was good (0.919). With respect to penumbra classification, MM_VOL showed the highest agreement (interreader agreement: 25 agreements/4 non-agreements/κ: 0.595; intrareader agreement 27/2/0.833), followed by MM_EST (22/7/0.471; 23/6/0.577), and MM_ASPECTS (18/11/0.133; 21/8/0.340).

Conclusion

The evaluated approach of volumetric mismatch assessment is superior to pure visual and ASPECTS penumbra pattern assessment in WB-CTP and helps to precisely judge the extent of 3-dimensional mismatch in acute stroke patients.     

Automated Segmentation and Quantification of White Matter Hyperintensities in Acute Ischemic Stroke Patients with Cerebral Infarction

White matter hyperintensities (WMHs) of presumed vascular origin are common in ageing population, especially in patients with acute cerebral infarction and the volume has been reported to be associated with mental impairment and the risk of hemorrhage from antithrombotic agents. WMHs delineation can be computerized to minimize human bias. However, the presence of cerebral infarcts greatly degrades the accuracy of WMHs detection and thus limits the application of computerized delineation to patients with acute cerebral infarction. We propose a computer-assisted segmentation method to depict WMHs in the presence of cerebral infarcts in combined T1-weighted, fluid attenuation inversion recovery, and diffusion-weighted magnetic resonance imaging (MRI). The proposed method detects WMHs by empirical threshold and atlas information, with subtraction of white matter voxels affected by acute infarction. The method was derived using MRI from 25 hemispheres with WMHs only and 13 hemispheres with both WMHs and cerebral infarcts. Similarity index (SI) and correlation were utilized to assess the agreement between the new automated method and a gold standard visually guided semi-automated method done by an expert rater. The proposed WMHs segmentation approach produced average SI, sensitivity and specificity of 83.142±11.742, 84.154±16.086 and 99.988±0.029% with WMHs only and of 68.826±14.036, 74.381±18.473 and 99.956±0.054% with both WMHs and cerebral infarcts in the derivation cohort. The performance of the proposed method with an external validation cohort was also highly consistent with that of the experienced rater.     

Development and Validation of Intracranial Thrombus Segmentation on CT Angiography in Patients with Acute Ischemic Stroke

Background and Purpose

Thrombus characterization is increasingly considered important in predicting treatment success for patients with acute ischemic stroke. The lack of intensity contrast between thrombus and surrounding tissue in CT images makes manual delineation a difficult and time consuming task. Our aim was to develop an automated method for thrombus measurement on CT angiography and validate it against manual delineation.

Materials and Methods

Automated thrombus segmentation was achieved using image intensity and a vascular shape prior derived from the segmentation of the contralateral artery. In 53 patients with acute ischemic stroke due to proximal intracranial arterial occlusion, automated length and volume measurements were performed. Accuracy was assessed by comparison with inter-observer variation of manual delineations using intraclass correlation coefficients and Bland–Altman analyses.

Results

The automated method successfully segmented the thrombus for all 53 patients. The intraclass correlation of automated and manual length and volume measurements were 0.89 and 0.84. Bland-Altman analyses yielded a bias (limits of agreement) of −0.4 (−8.8, 7.7) mm and 8 (−126, 141) mm³ for length and volume, respectively. This was comparable to the best interobserver agreement, with an intraclass correlation coefficients of 0.90 and 0.85 and a bias (limits of agreement) of −0.1 (−11.2, 10.9) mm and −17 (−216, 185) mm³.

Conclusions

The method facilitates automated thrombus segmentation for accurate length and volume measurements, is relatively fast and requires minimal user input, while being insensitive to high hematocrit levels and vascular calcifications. Furthermore, it has the potential to assess thrombus characteristics of low-density thrombi.