Exploring Reperfusion Following Endovascular Thrombectomy.

Background and Purpose- Cerebral perfusion in acute ischemic stroke patients is often assessed before endovascular thrombectomy (EVT), but rarely after. Perfusion data obtained following EVT may provide additional prognostic information. We developed a tool to quantitatively derive perfusion measurements from digital subtraction angiography (DSA) data and examined perfusion in patients following EVT.

Lower Blood Pressure Is Not Associated With Decreased Arterial Spin Labeling Estimates of Perfusion in Intracerebral Hemorrhage.

Background Subacute ischemic lesions in intracerebral hemorrhage ( ICH ) have been hypothesized to result from hypoperfusion. Although studies of cerebral blood flow ( CBF ) indicate modest hypoperfusion in ICH , these investigations have been limited to early time points. Arterial spin labeling ( ASL ), a magnetic resonance imaging technique, can be used to measure CBF without a contrast agent.

Aggressive blood pressure reduction is not associated with decreased perfusion in leukoaraiosis regions in acute intracerebral hemorrhage patients.

Leukoaraiosis regions may be more vulnerable to decreases in cerebral perfusion. We aimed to assess perfusion in leukoaraiosis regions in acute intracerebral hemorrhage (ICH) patients. We tested the hypothesis that aggressive acute BP reduction in ICH patients is associated with hypoperfusion in areas of leukoaraiosis.

Early hematoma retraction in intracerebral hemorrhage is uncommon and does not predict outcome.

Background: Clot retraction in intracerebral hemorrhage (ICH) has been described and postulated to be related to effective hemostasis and perihematoma edema (PHE) formation. The incidence and quantitative extent of hematoma retraction (HR) is unknown. Our aim was to determine the incidence of HR between baseline and time of admission.

Magnitude of Hematoma Volume Measurement Error in Intracerebral Hemorrhage.

Background And Purpose: Limiting intracerebral hemorrhage (ICH) and intraventricular hemorrhage (IVH) expansion is a common target for acute ICH studies and, therefore, accurate measurement of hematoma volumes is required. We investigated the amount of hematoma volume difference between computed tomography scans that can be considered as measurement error.

Methods: Five raters performed baseline (<6 hours) and 24-hour total hematoma (ICH+IVH) computer-assisted volumetric analysis from 40 selected ICH patients from the Predicting Hematoma Growth and Outcome in Intracerebral Hemorrhage Using Contrast Bolus CT (PREDICT) study cohort twice.

Perihematomal Edema Is Greater in the Presence of a Spot Sign but Does Not Predict Intracerebral Hematoma Expansion.

Background And Purpose: Perihematomal edema volume may be related to intracerebral hemorrhage (ICH) volume at baseline and, consequently, with hematoma expansion. However, the relationship between perihematomal edema and hematoma expansion has not been well established. We aimed to investigate the relationship among baseline perihematomal edema, the computed tomographic angiography spot sign, hematoma expansion, and clinical outcome in patients with acute ICH.

Ischemia in intracerebral hemorrhage is associated with leukoaraiosis and hematoma volume, not blood pressure reduction.

Background And Purpose: Diffusion-weighted imaging (DWI) lesions have been identified both inside and outside the perihematoma region. We tested the hypotheses that larger hematoma volumes and blood pressure reduction are associated with DWI lesions.

Methods: Hematoma and perihematoma edema volumes were measured using planimetric techniques in 117 intracerebral hemorrhage (ICH) patients who underwent DWI.

National Institutes of Health Stroke Scale score is an unreliable predictor of perfusion deficits in acute stroke.

Background: Perfusion-weighted magnetic resonance imaging is not routinely used to investigate stroke/transient ischemic attack. Many clinicians use perfusion-weighted magnetic resonance imaging selectively in patients with more severe neurological deficits, but optimal selection criteria have never been identified.

Aims And/or Hypothesis: We tested the hypothesis that a National Institutes of Health Stroke Scale score threshold can be used to predict the presence of perfusion-weighted magnetic resonance imaging deficits in patients with acute ischemic stroke/transient ischemic attack.

Blood-brain barrier compromise does not predict perihematoma edema growth in intracerebral hemorrhage.

Background And Purpose: There are limited data on the extent of blood-brain barrier (BBB) compromise in acute intracerebral hemorrhage patients. We tested the hypotheses that BBB compromise measured with permeability-surface area product (PS) is increased in the perihematoma region and predicts perihematoma edema growth in acute intracerebral hemorrhage patients.

Methods: Patients were randomized within 24 hours of symptom onset to a systolic blood pressure (SBP) treatment of <150 (n=26) or <180 mm Hg (n=27).

Planimetric hematoma measurement in patients with intraventricular hemorrhage: is total volume a preferred target for reliable analysis?

Background And Purpose: Reliable quantification of both intracerebral hemorrhage and intraventricular hemorrhage (IVH) volume is important for hemostatic trials. We evaluated the reliability of computer-assisted planimetric volume measurements of IVH.

Methods: Computer-assisted planimetry was used to quantify IVH volume.

Prediction of haematoma growth and outcome in patients with intracerebral haemorrhage using the CT-angiography spot sign (PREDICT): a prospective observational study.

Background: In patients with intracerebral haemorrhage (ICH), early haemorrhage expansion affects clinical outcome. Haemostatic treatment reduces haematoma expansion, but fails to improve clinical outcomes in many patients. Proper selection of patients at high risk for haematoma expansion seems crucial to improve outcomes.

Quantomo: validation of a computer-assisted methodology for the volumetric analysis of intracerebral haemorrhage.

Background: Volume measurements of intracerebral haemorrhage are prognostically important and are increasingly used in clinical trials to measure the effects of potential interventions. The purpose of this work is to establish the reliability of haematoma volume measurements obtained using a computer-assisted method called Quantomo (for quantitative tomography) and the ABC/2 method. Hypothesis Quantomo reliably detects smaller changes in intracerebral haemorrhage volume as compared with the ABC/2 method because computer-assisted volume measurements are tailored to measure the geometry of individual haematoma volumes whereas the ABC/2 method approximates all haematoma volumes as ellipsoids.

Perfusion parameters derived from bolus-tracking perfusion imaging are immune to tracer recirculation.

Purpose: To investigate the impact of tracer recirculation on estimates of cerebral blood flow (CBF), cerebral blood volume (CBV), and mean transit time (MTT).

Materials And Methods: The theoretical model used to derive CBF, CBV, and MTT was examined. CBF and CBV estimates with and without tracer recirculation were compared in computer simulations to examine the effects of tracer recirculation.

Reliability of measuring lesion volumes in transient ischemic attack and minor stroke.

Background And Purpose: Lesion volume measurements in disabling ischemic stroke have excellent reliability, but it is not clear whether this is also true for small lesions. We assessed the reliability of measuring baseline and follow-up lesion volumes in transient ischemic attack and minor stroke.

Methods: Patients who presented with a transient ischemic attack or minor stroke (NIHSS < or = 3) who had brain MRI within 24 hours from symptom onset and at 30-day follow-up and had an acute lesion on baseline MRI were included.

Atlas-based topographical scoring for magnetic resonance imaging of acute stroke.

Background And Purpose: The Alberta Stroke Program Early CT Score (ASPECTS), a 10-point scale, is a clinical tool for assessment of early ischemic changes after stroke based on the location and extent of a visible stroke lesion. It has been extended for use with MR diffusion-weighted imaging. The purpose of this work was to automate a MR topographical score (MR-TS) using a digital atlas to develop an objective tool for large-scale analyses and possibly reduce interrater variability and slice orientation differences.

Defining the CT angiography 'spot sign' in primary intracerebral hemorrhage.

Purpose: The computed tomogram angiography (CTA) 'spot sign' describes foci of intralesional enhancement associated with hematoma expansion in primary intracerebral hemorrhage patients. A consistent radiological definition is required for two proposed recombinant Factor VIIa trials planning patient dichotomization according to 'spot sign' presence or absence. We propose radiological criteria for diagnosis of the CTA 'spot sign' and describe different morphological patterns.

Normal magnetic resonance perfusion-weighted imaging in lacunar infarcts predicts a low risk of early deterioration.

Background: Current clinical tools to identify lacunar infarct patients at risk of deterioration are inadequate, and imaging techniques to predict fluctuation and deterioration would be of value. We sought to determine the occurrence of MRI perfusion-weighted imaging (PWI) abnormalities in lacunes, and whether they help predict clinical and radiological outcome.

Methods: Patients with lacunar stroke or TIA were selected from a prospective MR imaging study.

Cerebral blood flow estimation in vivo using local tissue reference functions.

Purpose: To evaluate the use of bolus signals obtained from tissue as reference functions (or local reference functions [LRFs]) rather than arterial input functions (AIFs) when deriving cross-calibrated cerebral blood flow (CBF(CC)) estimates via deconvolution.

Materials And Methods: AIF and white matter (WM) LRF CBF(CC) maps (cross-calibrated so that normal WM was 23.7 mL/minute/100 g) derived using singular value decomposition (SVD) were examined in 28 ischemic stroke patients.

Identifying lesion growth with MR imaging in acute ischemic stroke.

Purpose: To determine whether different MR diffusion- and perfusion-weighted imaging (DWI and PWI) parameters are important in distinguishing lesion growth from the acute lesion and from oligemia.

Materials And Methods: MR DWI and PWI were acquired from thirteen patients. We defined three regions: (i) LESION - intersection of acute and final lesions, (ii) GROWTH - portion of final lesion not part of acute lesion, and (iii) OLIGEMIA - region of perfusion abnormality not part of either the acute or final lesions.

Recurrent events in transient ischemic attack and minor stroke: what events are happening and to which patients?

Background And Purpose: The risk of a recurrent stroke after transient ischemic attack (TIA) or minor stroke is high. Clinical trials are needed to assess acute treatment options in these patients. We sought to evaluate the type of recurrent events and to identify which subsets of patients are at risk for recurrent events.

Robust dynamic susceptibility contrast MR perfusion using 4D nonlinear noise filters.

Purpose: To investigate if 4D (simultaneous space and time) nonlinear filtering techniques can produce more robust cerebral blood flow (CBF) estimates by reducing noise in acquired dynamic susceptibility contrast (DSC) MR perfusion data.

Materials And Methods: A digital anthropomorphic brain perfusion phantom was constructed to analyze filter performance by: 1) deriving anthropomorphic tissue volume fractions from a human subject and 2) simulating DSC-MR perfusion signals for voxels with mixed tissue for various signal-to-noise ratios (SNRs). DSC-MR data for 11 acute ischemic stroke patients were also acquired at 3T.

MRI of ischemic stroke in canines: applications for monitoring intraarterial thrombolysis.

Purpose: To describe a canine embolic stroke model that is appropriate for endovascular procedure evaluations and develop local cerebral blood flow (CBF) maps to monitor the progression of stroke and thrombolysis. In the future, MR may displace X-ray imaging in some endovascular procedures, such as intraarterial (IA) thrombolysis for stroke therapy, due to increased monitoring capabilities. For MR to attain its full potential in endovascular therapy, the development of appropriate disease models and monitoring techniques is essential.

Improved dynamic susceptibility contrast (DSC)-MR perfusion estimates by motion correction.

Purpose: To investigate the effect of patient motion on quantitative cerebral blood flow (CBF) maps in ischemic stroke patients and to evaluate the efficacy of a motion-correction scheme.

Materials And Methods: Perfusion data from 25 ischemic stroke patients were selected for analysis. Two motion profiles were applied to a digital anthropomorphic brain phantom to estimate accuracy.