Mechanical Thrombectomy Up to 24 Hours in Large Vessel Occlusions and Infarct Velocity Assessment.

Background We retrospectively compared early- (<6 hours) versus late- (6-24 hours) presenting patients using perfusion-weighted imaging selection and evaluated clinical/radiographic outcomes. Methods and Results Large vessel occlusion patients treated with mechanical thrombectomy from August 2017 to July 2020 within 24 hours of onset were retrieved from a single-center database. Perfusion-weighted imaging was analyzed by automated software and final infarct volume was measured semi-automatically within 14 days. The primary end point was good outcome (modified Rankin Scale 0-2 at 90 days). Secondary end points were excellent outcome (modified Rankin Scale 0-1 at 90 days), symptomatic intracranial hemorrhage, and death. Clinical characteristics/radiological values including hypoperfusion volume and infarct growth velocity (baseline volume/onset-to-image time) were compared between the groups. Of 1294 patients, 118 patients were included. The median age was 74 years, baseline National Institutes of Health Stroke Scale score was 14, and core volume was 13 mL. The late-presenting group had more female patients (67% versus 31%, respectively; P=0.001). No statistically significant differences were seen in good outcome (42% versus 53%, respectively; P=0.30), excellent outcome (26% versus 32%, respectively; P=0.51), symptomatic intracranial hemorrhage (6.5% versus 4.6%, respectively; P=0.74), and death (3.2% versus 5.7%, respectively; P=0.58) between the groups. The late-presenting group had more atherothrombotic cerebral infarction (19% versus 6%, respectively; P=0.03), smaller hypoperfusion volume (median: 77 versus 133 mL, respectively; P=0.04), and slower infarct growth velocity (median: 0.6 versus 5.1 mL/h, respectively; P=0.03). Conclusions Patients with early- and late-time windows treated with mechanical thrombectomy by automated perfusion-weighted imaging selection have similar outcomes, comparable with those in randomized trials, but different in infarct growth velocities. Registration URL: https://www.clinicaltrials.gov; Unique identifier: NCT02251665.

Value of the Barthel scale in prognostic prediction for patients with cerebral infarction.

BACKGROUND: This study aims to evaluate the ADL(activity of daily living) of patients with acute cerebral infarction through BI scoring, in order to observe its predictive value in the prognosis of these patients. METHODS: According to the inclusion and exclusion criteria, patients with acute anterior circulation cerebral infarction were included in the present study. Then, the BI scoring was analyzed through five grades, in order to further investigate the dose-response relationship between BI scoring and mortality risk in patients with cerebral infarction. The receiver operating characteristic (ROC) curves for BI-scored patients were drawn, and the predictive authenticity of the Barthel scale in prognostic prediction for patients with cerebral infarction was estimated. RESULTS: The difference in BI scores between the survival group and death group were statistically significant (t = 10.029, P < 0.05), in which the score was lower in the death group than in the survival group. According to the linear trend ×2-test, the decrease in BI score indicates an increase in mortality risk in patients with cerebral infarction. The area under the curve (AUC) of the ROC curve was 0.794 with a P-value of < 0.05. CONCLUSION: BI scoring is a highly valuable scoring system for the prognostic prediction of patients with acute cerebral infarction.

Assessment of cerebral infarction after transient cerebral ischemic attack by ABCD2 score combined with the position of intracranial vascular stenosis.

This study aims to investigate the value of the ABCD score combined with the position of the offending vessel stenosis in predicting the risk of transient ischemic attack (TIA) to develop into cerebral infarction.The ABCD score and head magnetic resonance imaging + magnetic resonance angiography (MRA) results of 192 patients with TIA were retrospectively analyzed. With the 7th day as the endpoint time, these patients were divided into 3 groups, according to ABCD scores: low-risk group (n = 105), moderate-risk group (n = 60), and high-risk group (n = 27). Blood vessels were screened using head MRA results, and patients were accordingly divided into 2 groups: proximal vascular stenosis group (n = 71) and nonproximal vascular stenosis group (n = 171). Then, the association of the position of the intracranial vascular stenosis and ABCD score with short-term prognosis was analyzed.Based on the ABCD score, the incidence of cerebral infarction after 1 week was significantly higher in the high-risk group (85.7%) than in the moderate-risk group (16.7%) and low-risk group (1.9%), and the differences were statistically significant (P < .05). When the ABCD score was ≥4 points, the incidence of cerebral infarction after 1 week was significantly higher in the proximal vascular stenosis group (59.1%) than in the nonproximal vascular stenosis group (30.8%), and the difference was statistically significant (P < .05). When the ABCD score was <4 points, the incidence of cerebral infarction after 1 week in the proximal stenosis group (2%) was not significantly different from that in the nonproximal stenosis group (1.9%, P > .05).The ABCD score combined with proximal offending vessel stenosis can improve the short-term prediction of cerebral infarction in patients with TIA.

Assessment of Percheron infarction in images and clinical findings.

OBJECTIVE: To assess the imaging and clinical features of patients with an artery of Percheron infarction comprehensively. METHODS: Of 6539 patients with a first-ever stroke, 18 patients with a Percheron infarction were enrolled, and their images and clinical data were retrospectively investigated. RESULTS: All patients underwent neurological intensive care unit (NICU) management. The initial symptom of a Percheron infarction included dizziness, transient blurred vision, double vision, barylalia, cerebellar ataxia, drowsiness, and a coma. Subsequent symptoms differed for the three subtypes of Percheron infarction, and the three subtypes are bilateral paramedian thalamic infarction with midbrain involvement, bilateral paramedian thalamic infarction without midbrain involvement, and bilateral paramedian and anterior thalamic infarction without midbrain involvement. Between favorable and unfavorable outcomes, there was no significant difference in the following patient characteristics including current smoking, hypertension, diabetes, hyperlipidemia, hyperhomocysteinemia, heart disease, time from stroke onset to medical care, and Glasgow Coma Scale score at admission (P>0.05), but there were significant differences in both the National Institute of Health stroke scale (NIHSS) and Acute Physiology and Chronic Health Evaluation II (APACHE II) score at admission (P<0.05). If the midbrain or larger infarct volume was involved or hemorrhagic transformation occurred, outcomes of a Percheron infarction were frequently unfavorable. CONCLUSION: The clinical presentation of patients with a Percheron infarction is variable; early recognition, image performance, NICU management, NIHSS, and APACHE II score would help in diagnosis, evaluation, and treatment.

[Disorder of Gastric Myoelectric Activity in Patients with Cerebral Infarction:Electrogastrographic Assessment].

In this study, gastric myoelectric activity in patients with acute cerebral infarction was investigated using electrogastrography. The patients were divided into four groups; those with mild brainstem infarction(group A, n=13, men:8, women:5, 75±2 years old), severe brainstem infarction(group B, n=6, men:4, women:2, 79±4 years old), mild non-brainstem infarction(group C, n=14, men:7, women:7, 76±3 years old), and severe non-brainstem infarction(group D, n=9, men:3, women:6, 87±2 years old). In group B, the% ratio of normogastria(2.4-3.6 cycles per minute)was significantly lower in the fasting period. The dominant power(DP)significantly increased after the meal in group C, but did not in group A, compared to before the meal. The DP increased in all patients in group C after the meal, whereas it increased in only five of ten patients in group A. The possibility of gastric dysfunction should be considered in patients with brainstem infarction.

Motor Recovery Prediction With Clinical Assessment and Local Diffusion Homogeneity After Acute Subcortical Infarction.

BACKGROUND AND PURPOSE: Initial clinical assessment or conventional diffusion tensor imaging parameters alone do not reliably predict poststroke recovery of motor function. Recently, local diffusion homogeneity (LDH) has been proposed to represent the local coherence of water molecule diffusion and can serve as a complementary marker for investigating white matter alterations of the brain. We aimed to determine whether a combination of initial clinical assessment and LDH could predict motor recovery after acute subcortical infarction. METHODS: Standard upper extremity Fugl-Meyer assessment and diffusion tensor imaging were performed 1, 4, and 12 weeks after onset in 50 patients with subcortical infarction. Proportional recovery model residuals were used to assign patients to proportional recovery and poor recovery groups. Tract-based spatial statistics analysis was used to compare diffusion differences between proportional and poor recovery outcomes. Multivariate logistic regression model was used to identify the predictors of motor improvement within 12 weeks after stroke. RESULTS: The poor recovery group had lower LDH than the proportional recovery group, mainly in the ipsilesional corticospinal tract in the superior corona radiate and posterior limb of internal capsule 1 week after stroke (P<0.005; family-wise error corrected). Multivariate logistic regression analysis indicated that both initial Fugl-Meyer assessment and LDH in the ipsilesional corticospinal tract in the superior corona radiate and posterior limb of internal capsule were predictors of motor improvement within 12 weeks after stroke (G=47.22; P<0.001). Leave-one-out cross-validation confirmed a positive predictive value of 0.818, a negative predictive value of 0.833, and an accuracy of 0.824 (P<0.00 001; permutation test). CONCLUSIONS: These results suggest that a combination of clinical assessment and LDH in the ipsilesional corticospinal tract in the acute phase can accurately predict resolution of upper limb impairment within 12 weeks after subcortical infarction.

Quantitative assessment of hyperacute cerebral infarction with intravoxel incoherent motion MR imaging: Initial experience in a canine stroke model.

PURPOSE: To evaluate the feasibility of intravoxel incoherent motion (IVIM) for the measurement of diffusion and perfusion parameters in hyperacute strokes. MATERIALS AND METHODS: An embolic ischemic model was established with an autologous thrombus in 20 beagles. IVIM imaging was performed on a 3.0 Tesla platform at 4.5 h and 6 h after embolization. Ten b values from 0 to 900 s/mm2 were fitted with a bi-exponential model to extract perfusion fraction f, diffusion coefficient D, and pseudo-diffusion coefficient D*. Additionally, the apparent diffusion coefficient (ADC) was calculated using the mono-exponential model with all the b values. Statistical analysis was performed using the pairwise Student's t test and Pearson's correlation test. RESULTS: A significant decrease in f and D was observed in the ischemic area when compared with those in the contralateral side at 4.5 h and 6 h after embolization (P < 0.01 for all). No significant difference was observed in D* between the two sides at either time point (P = 0.086 and 0.336, respectively). In the stroke area, f at 6 h was significantly lower than that at 4.5 h (P = 0.016). A significantly positive correlation was detected between ADC and D in both stroke and contralateral sides at 4.5 h and 6 h (P < 0.001 for both). Significant correlation between ADC and f was only observed in the contralateral side at 4.5 h and 6 h (P = 0.019 and 0.021, respectively). CONCLUSION: IVIM imaging could simultaneously evaluate the diffusion and microvascular perfusion characteristics in hyperacute strokes. LEVEL OF EVIDENCE: 2 Technical Efficacy: Stage 1 J. MAGN. RESON. IMAGING 2017;46:550-556.

Longitudinal Assessment of Motor Recovery of Contralateral Hand after Basal Ganglia Infarction Using Functional Magnetic Resonance Imaging.

We used functional fMRI to study the brain activation during active finger movements at different time points during the recovery phase following basal ganglia infarction. Four hemiplegic patients with basal ganglia infarction were serially evaluated at different time points spanning the acute and chronic phase using fMRI. To evaluate motor recovery, the patients were asked to perform functional tasks arranged in a block design manner with their hand. On follow-up (chronic phase), three patients achieved significant recovery of motor function of affected limbs. Activation of bilateral sensorimotor cortex (SMC) was observed in two of these patients, while activation of cerebellum was observed in all patients. No remarkable recovery of motor function was noted in one patient with left basal ganglia infarction. In this patient, the activation domain was located in SMC of both sides in acute phase and in ipsilateral SMC in chronic phase. Contralateral SMC appears to be involved in the functional rehabilitation following basal ganglia infarction. The cerebellum may act as an intermediary during functional recovery following basal ganglia infarction. The activation domain associated with active finger movement may be bilateral in acute phase; one patient was ipsilateral in the chronic stage.

Negative Word Production in Adults With Right Hemisphere Brain Damage: Effects of Implicit Assessment and Contextual Bias.

PURPOSE: Both theory and evidence suggest that unilateral right hemisphere brain damage (RHD) should impair the processing of negative emotions. Typical metalinguistic assessments, however, may obscure processing strengths. This study investigated whether adults with RHD would produce proportionately fewer negative emotion words than control participants in an implicit assessment task and whether a negatively toned contextual bias would enhance performance. METHODS: Eleven participants with RHD and 10 control participants without brain damage watched a video in 2 parts and described each segment. Between segments, participants evaluated the emotion conveyed by sentences designed to induce the negative bias. RESULTS: The primary outcome measure, percentage of negative emotion words in video descriptions, did not differ between groups. After the contextual bias, this measure significantly increased for both groups, whereas production of motion words, a control variable, remained constant. CONCLUSIONS: Findings are consistent with a view that attributes some deficient RHD performances to the nature and/or demands of explicit metalinguistic assessment tasks. These results call for modulation of prevailing hypotheses that attribute negative emotion processing as an undifferentiated whole solely to the right cerebral hemisphere. The results also further substantiate the rationale of an experimental treatment that exploits contextual bias and priming for individuals with RHD.

Comparisons of Predictive Equations for Resting Energy Expenditure in Patients with Cerebral Infarct during Acute Care.

BACKGROUND: Estimation of resting energy expenditure (REE) is essential in planning nutrition support. Several equations are used for this estimation in the clinical setting. The purpose of this study was to compare the predictive accuracy of existing equations for REE in patients with cerebral infarct during acute care. METHODS: We assessed the Harris-Benedict, Mifflin, Owen, Japanese simplified, Wang, and Cunningham equations. The Owen and Japanese simplified equations use sex and weight as explanatory variables, the Harris-Benedict and Mifflin equations include sex, weight, age, and height, and the Wang and Cunningham equations use fat-free mass (FFM) measured using bioelectrical impedance technology. Actual REE values were measured by indirect calorimetry on days 2 and 7 and were then averaged. Applying analysis of variance, predictive accuracy was assessed by comparing the predicted and actual values. RESULTS: A total of 30 patients were analyzed. Actual REE values ranged from 796 to 1637 kcal (mean, 1109). The standard deviation of these values was the smallest with the Harris-Benedict equation (99), followed by the Cunningham (165), and Wang (181) equations. The Mifflin equation underestimated REE in females, whereas the Owen and Japanese simplified equations tended to overestimate it. CONCLUSIONS: Based on our results, the Harris-Benedict equation provides the most accurate prediction of REE. In addition, the Cunningham and Wang equations may be useful in long-term care settings involving patients at risk of malnutrition resulting in uneven loss of FFM relative to weight.

Strategies of collateral blood flow assessment in ischemic stroke: prediction of the follow-up infarct volume in conventional and dynamic CTA.

BACKGROUND AND PURPOSE: Collateral blood flow is an important prognostic marker in the acute stroke situation but approaches for assessment vary widely. Our aim was to compare strategies of collateral blood flow assessment in dynamic and conventional CTA in their ability to predict the follow-up infarction volume. MATERIALS AND METHODS: We retrospectively included all patients with an M1 occlusion from an existing cohort of 1912 consecutive patients who underwent initial multimodal stroke CT and follow-up MR imaging or nonenhanced CT. Collateralization was assessed in both conventional CT angiography and dynamic CT angiography by using 3 different collateral grading scores and segmentation of the volume of hypoattenuation. Arterial, arteriovenous, and venous phases were reconstructed for dynamic CT angiography, and all collateral scores and the volume of hypoattenuation were individually assessed for all phases. Different grading systems were compared by using the Bayesian information criterion calculated for multivariate regression analyses (Bayesian information criterion difference = 2-6, "positive"; Bayesian information criterion difference = 6-10, "strong"; Bayesian information criterion difference = >10, "very strong"). RESULTS: One hundred thirty-six patients (mean age, 70.4 years; male sex, 41.2%) were included. In the multivariate analysis, models containing the volume of hypoattenuation showed a significantly better model fit than models containing any of the 3 collateral grading scores in conventional CT angiography (Bayesian information criterion difference = >10) and dynamic CT angiography (Bayesian information criterion difference = >10). All grading systems showed the best model fit in the arteriovenous phase. For the volume of hypoattenuation, model fit was significantly higher for models containing the volume of hypoattenuation as assessed in the arteriovenous phase of dynamic CT angiography compared with the venous phase (Bayesian information criterion difference = 6.2) and the arterial phase of dynamic CT angiography (Bayesian information criterion difference = >10) and in comparison with conventional CT angiography (Bayesian information criterion difference = >10). CONCLUSIONS: The use of dynamic CT angiography within the arteriovenous phase by using quantification of the volume of hypoattenuation is the superior technique for assessment of collateralization among the tested approaches.

ANTONIA perfusion and stroke. A software tool for the multi-purpose analysis of MR perfusion-weighted datasets and quantitative ischemic stroke assessment.

OBJECTIVES: The objective of this work is to present the software tool ANTONIA, which has been developed to facilitate a quantitative analysis of perfusion-weighted MRI (PWI) datasets in general as well as the subsequent multi-parametric analysis of additional datasets for the specific purpose of acute ischemic stroke patient dataset evaluation. METHODS: Three different methods for the analysis of DSC or DCE PWI datasets are currently implemented in ANTONIA, which can be case-specifically selected based on the study protocol. These methods comprise a curve fitting method as well as a deconvolution-based and deconvolution-free method integrating a previously defined arterial input function. The perfusion analysis is extended for the purpose of acute ischemic stroke analysis by additional methods that enable an automatic atlas-based selection of the arterial input function, an analysis of the perfusion-diffusion and DWI-FLAIR mismatch as well as segmentation-based volumetric analyses. RESULTS: For reliability evaluation, the described software tool was used by two observers for quantitative analysis of 15 datasets from acute ischemic stroke patients to extract the acute lesion core volume, FLAIR ratio, perfusion-diffusion mismatch volume with manually as well as automatically selected arterial input functions, and follow-up lesion volume. The results of this evaluation revealed that the described software tool leads to highly reproducible results for all parameters if the automatic arterial input function selection method is used. CONCLUSION: Due to the broad selection of processing methods that are available in the software tool, ANTONIA is especially helpful to support image-based perfusion and acute ischemic stroke research projects.

Behavioral and histopathological assessment of adult ischemic rat brains after intracerebral transplantation of NSI-566RSC cell lines.

Stroke is a major cause of death and disability, with very limited treatment option. Cell-based therapies have emerged as potential treatments for stroke. Indeed, studies have shown that transplantation of neural stem cells (NSCs) exerts functional benefits in stroke models. However, graft survival and integration with the host remain pressing concerns with cell-based treatments. The current study set out to investigate those very issues using a human NSC line, NSI-566RSC, in a rat model of ischemic stroke induced by transient occlusion of the middle cerebral artery. Seven days after stroke surgery, those animals that showed significant motor and neurological impairments were randomly assigned to receive NSI-566RSC intracerebral transplants at two sites within the striatum at three different doses: group A (0 cells/µl), group B (5,000 cells/µl), group C (10,000 cells/µl), and group D (20,000 cells/µl). Weekly behavioral tests, starting at seven days and continued up to 8 weeks after transplantation, revealed dose-dependent recovery from both motor and neurological deficits in transplanted stroke animals. Eight weeks after cell transplantation, immunohistochemical investigations via hematoxylin and eosin staining revealed infarct size was similar across all groups. To identify the cell graft, and estimate volume, immunohistochemistry was performed using two human-specific antibodies: one to detect all human nuclei (HuNu), and another to detect human neuron-specific enolase (hNSE). Surviving cell grafts were confirmed in 10/10 animals of group B, 9/10 group C, and 9/10 in group D. hNSE and HuNu staining revealed similar graft volume estimates in transplanted stroke animals. hNSE-immunoreactive fibers were also present within the corpus callosum, coursing in parallel with host tracts, suggesting a propensity to follow established neuroanatomical features. Despite absence of reduction in infarct volume, NSI-566RSC transplantation produced behavioral improvements possibly via robust engraftment and neuronal differentiation, supporting the use of this NSC line for stroke therapy.

Assessment of baseline hemodynamic parameters within infarct progression areas in acute stroke patients using perfusion-weighted MRI.

INTRODUCTION: The value of perfusion MRI for identifying the tissue at risk has been questioned. Our objective was to assess baseline perfusion-weighted imaging parameters within infarct progression areas. METHODS: Patients with anterior circulation stroke without early reperfusion were included from a prospective MRI database. Sequential MRI examinations were performed on admission, 2-3 h (H2), 2-3 days (D2), and between 15 and 30 days after the initial MRI. Maps of baseline time-to-peak (TTP), mean transit time (MTT), cerebral blood volume (CBV), and cerebral blood flow (CBF) were calculated. Lesion extension areas were defined as pixels showing de novo lesions between each MRI and were generated by subtracting successive lesion masks: V(0), baseline diffusion-weighted imaging (DWI) lesion; V(1), lesion extension between baseline and H2 DWI; V(2), lesion extension from H2 to D2 DWI; and V(3), lesion extension from D2 DWI to final FLAIR. Repeated measures analysis was used to compare hemodynamic parameters within the baseline diffusion lesion and subsequent lesion extension areas. RESULTS: Thirty-two patients were included. Baseline perfusion parameters were significantly more impaired within the acute DWI lesion compared to lesion extension areas (TTP, p < 0.0001; MTT, p < 0.0001; CBF p < 0.0001; CBV, p < 0.0001). A significant decrease in MTT (p = 0.01) and TTP (p = 0.01) was found within successive lesion growth areas. CONCLUSION: A decreasing gradient of severity for TTP and MTT was observed within successive infarct growth areas.

Metabolic impact of shivering during therapeutic temperature modulation: the Bedside Shivering Assessment Scale.

BACKGROUND AND PURPOSE: Therapeutic temperature modulation is widely used in neurocritical care but commonly causes shivering, which can hamper the cooling process and result in increases in systemic metabolism. We sought to validate a grading scale to assist in the monitoring and control of shivering. METHODS: A simple 4-point Bedside Shivering Assessment Scale was validated against continuous assessments of resting energy expenditure, oxygen consumption, and carbon dioxide production as measured by indirect calorimetry. Therapeutic temperature modulation for fever control or the induction of hypothermia was achieved with the use of a surface or endovascular device. Expected energy expenditure was calculated using the Harris-Benedict equation. A hypermetabolic index was calculated from the ratio of resting of energy expenditure to energy expenditure. RESULTS: Fifty consecutive cerebrovascular patients underwent indirect calorimetry between January 2006 and June 2007. Fifty-six percent were women, and mean age 63+/-16 years. The majority underwent fever control (n=40 [80%]) with a surface cooling device (n=44 [87%]) and had signs of shivering (Bedside Shivering Assessment Scale >0, 64% [n=34 of 50]). Low serum magnesium was independently associated with the presence of shivering (Bedside Shivering Assessment Scale >0; OR, 6.8; 95% CI, 1.7 to 28.0; P=0.01). The Bedside Shivering Assessment Scale was independently associated with the hypermetabolic index (W=16.3, P<0.001), oxygen consumption (W=26.3, P<0.001), resting energy expenditure (W=27.2, P<0.001), and carbon dioxide production (W=18.2, P<0.001) with a high level of interobserver reliability (kappa(w)=0.84, 95% CI, 0.81 to 0.86). CONCLUSIONS: The Bedside Shivering Assessment Scale is a simple and reliable tool for evaluating the metabolic stress of shivering.

Accuracy and anatomical coverage of perfusion CT assessment of the blood-brain barrier permeability: one bolus versus two boluses.

PURPOSE: To assess whether blood-brain barrier permeability (BBBP) values, extracted with the Patlak model from the second perfusion CT (PCT) contrast bolus, are significantly lower than the values extracted from the first bolus in the same patient. MATERIALS AND METHODS: 125 consecutive patients (29 with acute hemispheric stroke and 96 without stroke) who underwent a PCT study using a prolonged acquisition time up to 3 min were retrospectively identified. The Patlak model was applied to calculate the rate of contrast leakage out of the vascular compartment. Patlak plots were created from the arterial and parenchymal time enhancement curves obtained in multiple regions of interest drawn in ischemic brain tissue and in nonischemic brain tissue. The slope of a regression line fit to the Patlak plot was used as an indicator of BBBP. Square roots of the mean squared errors and correlation coefficients were used to describe the quality of the linear regression model. This was performed separately for the first and the second PCT bolus. Results from the first and the second bolus were compared in terms of BBBP values and the quality of the linear model fitted to the Patlak plot, using generalized estimating equations with robust variance estimation. RESULTS: BBBP values from the second bolus were not lower than BBBP values from the first bolus in either nonischemic brain tissue [estimated mean with 95% confidence interval: 1.42 (1.10-1.82) ml x 100 g(-1) x min(-1) for the first bolus versus 1.64 (1.31-2.05) ml x 100 g(-1) x min(-1) for the second bolus, p = 1.00] or in ischemic tissue [1.04 (0.97-1.12) ml x 100 g(-1) x min(-1) for the first bolus versus 1.19 (1.11-1.28) ml x 100 g(-1)min(-1) for the second bolus, p = 0.79]. Compared to regression models from the first bolus, the Patlak regression models obtained from the second bolus were of similar or slightly better quality. This was true both in nonischemic and ischemic brain tissue. CONCLUSION: The contrast material from the first bolus of contrast for PCT does not negatively influence measurements of BBBP values from the second bolus. The second bolus can thus be used to increase anatomical coverage of BBBP assessment using PCT.

Dynamic perfusion CT assessment of the blood-brain barrier permeability: first pass versus delayed acquisition.

BACKGROUND AND PURPOSE: The Patlak model has been applied to first-pass perfusion CT (PCT) data to extract information on blood-brain barrier permeability (BBBP) to predict hemorrhagic transformation in patients with acute stroke. However, the Patlak model was originally described for the delayed steady-state phase of contrast circulation. The goal of this study was to assess whether the first pass or the delayed phase of a contrast bolus injection better respects the assumptions of the Patlak model for the assessment of BBBP in patients with acute stroke by using PCT. MATERIALS AND METHODS: We retrospectively identified 125 consecutive patients (29 with acute hemispheric stroke and 96 without) who underwent a PCT study by using a prolonged acquisition time up to 3 minutes. The Patlak model was applied to calculate BBBP in ischemic and nonischemic brain tissue. Linear regression of the Patlak plot was performed separately for the first pass and for the delayed phase of the contrast bolus injection. Patlak linear regression models for the first pass and the delayed phase were compared in terms of their respective square root mean squared errors (square root MSE) and correlation coefficients (R) by using generalized estimating equations with robust variance estimation. RESULTS: BBBP values calculated from the first pass were significantly higher than those from the delayed phase, both in nonischemic brain tissue (2.81 mL x 100 g(-1) x min(-1) for the first pass versus 1.05 mL x 100 g(-1) x min(-1) for the delayed phase, P < .001) and in ischemic tissue (7.63 mL x 100 g(-1) x min(-1) for the first pass versus 1.31 mL x 100 g(-1) x min(-1) for the delayed phase, P < .001). Compared with regression models from the first pass, Patlak regression models obtained from the delayed data were of better quality, showing significantly lower square root MSE and higher R. CONCLUSION: Only the delayed phase of PCT acquisition respects the assumptions of linearity of the Patlak model in patients with and without stroke.

Temporal MRI assessment of intracerebral hemorrhage in rats.

BACKGROUND AND PURPOSE: MRI was used to evaluate the effects of experimental intracerebral hemorrhage (ICH) on brain tissue injury and recovery. METHODS: Primary ICH was induced in rats (n=6) by direct infusion of autologous blood into the striatum. The evolution of ICH damage was assessed by MRI estimates of T(2) and T(1sat) relaxation times, cerebral blood flow, vascular permeability, and susceptibility-weighted imaging before surgery (baseline) and at 2 hours and 1, 7, and 14 days post-ICH. Behavioral testing was done before and at 1, 7, and 14 days post-ICH. Animals were euthanized for histology at 14 days. RESULTS: The MRI appearance of the hemorrhage and surrounding regions changed in a consistent manner over time. Two primary regions of interest were identified based on T(2) values. These included a core, corresponding to the bulk of the hemorrhage, and an adjacent rim; both varied with time. The core was associated with significantly lower cerebral blood flow values at all post-ICH time points, whereas cerebral blood flow varied in the rim. Increases in vascular permeability were noted at 1, 7, and 14 days. Changes in T(1sat) were similar to those of T(2). MRI and histological estimates of tissue loss were well correlated and showed approximately 9% hemispheric tissue loss. CONCLUSIONS: Although the cerebral blood flow changes observed with this ICH model may not exactly mimic the clinical situation, our results suggest that the evolution of ICH injury can be accurately characterized with MRI. These methods may be useful to evaluate therapeutic interventions after experimental ICH and eventually in humans.

Rapid assessment of perfusion-diffusion mismatch.

BACKGROUND AND PURPOSE: For MR perfusion-diffusion (PWI-DWI) mismatch to become routine in thrombolysis patient selection, rapid and reliable assessment tools are required. We examined interrater variability in PWI/DWI volume measurements and developed a rapid assessment tool based on the Alberta Stroke Program Early CT Scores (ASPECTS) system. METHODS: DWI and PWI were performed in 35 patients with stroke <6 hours after symptom onset. DWI lesion and PWI (time to peak) volumes were measured with planimetric techniques by 4 raters and the 95% limits of agreement calculated. ASPECT scores were assessed separately by 4 investigators (2 experienced and 2 inexperienced) for DWI (MR DWI scores) and PWI (MR time to peak scores). MR mismatch scores were calculated as MR DWI-MR time to peak scores. RESULTS: Interobserver variability was much greater for PWI (95% limit of agreement=+/-72.3 mL) than for DWI (95% limit of agreement=+/-12.6 mL). A semiautomated PWI volume (time to peak+2 s) was therefore used to calculate mismatch volume. MR mismatch scores >or=2 predicted 20% PWI-DWI mismatch by volume with mean 78% sensitivity (range, 72% to 84%) and 88% specificity (range, 83% to 90%). There was excellent agreement on mismatch classification using MR mismatch scores between experienced raters (weighted kappa scores of 0.94) with agreement in 34 of 35 cases. Agreement was less consistent between inexperienced raters (weighted kappa=0.49, 28 of 35 cases). CONCLUSIONS: Variability in planimetric mismatch measurements arises primarily from differences in PWI volume assessment. High specificity and interrater reliability may make MR mismatch scores an ideal rapid screening tool for potential thrombolysis patients.