Increased cortical capillary transit time heterogeneity in Alzheimer's disease: a DSC-MRI perfusion study.

Alzheimer's disease (AD) is characterized by the accumulation of hyperphosphorylated tau and neurotoxic Aβ in the brain parenchyma. Hypoxia caused by microvascular changes and disturbed capillary flows could stimulate this build-up of AD-specific proteins in the brain. In this study, we compared cerebral microcirculation in a cohort of AD and mild cognitive impairment (MCI) patients with that of age-matched controls, all without a history of diabetes or of hypertension for more than 2 years, using dynamic susceptibility contrast magnetic resonance imaging (DSC-MRI).

Cerebral blood flow, blood volume, and mean transit time responses to propofol and indomethacin in peritumor and contralateral brain regions: perioperative perfusion-weighted magnetic resonance imaging in patients with brain tumors.

Background: The regional cerebral blood flow (CBF) response to propofol and indomethacin may be abnormal in patients with brain tumors. First, the authors tested the hypothesis that during propofol anesthesia alone and combined with indomethacin, changes in CBF, cerebral blood volume (CBV), and plasma mean transit time (MTT) differ in the peritumoral tissue compared with the contralateral normal brain region. Second, the authors tested the hypothesis that CBF and CBV are reduced and MTT is prolonged, in both regions during propofol anesthesia and indomethacin administration compared with propofol alone.

Interrater agreement for final infarct MRI lesion delineation.

Background And Purpose: Lesion volume measured on follow-up magnetic resonance imaging (MRI) is commonly used as an outcome parameter in clinical stroke trials. However, few studies have evaluated the optimal sequence choice and the interrater reliability of this outcome measure. The objective of this study was to quantify the geometric interrater agreement for lesion delineation of chronic infarcts on T2-weighted and fluid-attenuated inverse recovery (FLAIR) MRI.

Feasibility and logistics of MRI before thrombolytic treatment.

Objectives: The study analyzes feasibility and time-delays in Magnetic resonance imaging (MRI) based thrombolysis and estimate the impact of MRI on individual tissue plasminogen activator (rtPA) treatment.

Materials And Methods: Feasibility of MRI and time logistics were prospectively recorded in patients referred with presumed acute stroke over a 2 year time period. Door-to-needle-times (DNT) were compared with those of patients treated with rtPA after conventional CT during the same time period, and to published open label studies.

MRI detection of early blood-brain barrier disruption: parenchymal enhancement predicts focal hemorrhagic transformation after thrombolysis.

Background And Purpose: Blood-brain barrier disruption may be a predictor of hemorrhagic transformation (HT) in ischemic stroke. We hypothesize that parenchymal enhancement (PE) on postcontrast T1-weighted MRI predicts and localizes subsequent HT.

Methods: In a prospective study, 33 tPA-treated stroke patients were imaged by perfusion-weighted imaging, T1 and FLAIR before thrombolytic therapy and after 2 and 24 hours.

[Imaging of the pathophysiology in acute stroke].

Recent developments in neuroimaging have changed the diagnostic aspect of acute stroke and improved our understanding of stroke pathophysiology. Both diffusion weighted MR imaging and CT are capable of detecting the infarcted volume damaged by cytotoxic edema. However, within six hours of stroke onset, DWI has both higher sensitivity and specificity than CT.

[Diagnostic imaging in dementia evaluation].

Introduction: The aim of the study was to evaluate the changes in diagnoses and treatment by structural scanning in dementia evaluation.

Material And Methods: 336 elderly, consecutively evaluated patients from two university memory clinics (mean age 75 y, mean MMSE 21.7), were retrospectively diagnosed without and with inclusion of scan results.

Ischemic injury detected by diffusion imaging 11 minutes after stroke.

A 78-year-old woman suffered a stroke inside a magnetic resonance scanner while being imaged because of a brief transient ischemic attack 2 hours earlier. Diffusion-weighted images obtained 11 minutes after stroke showed tissue injury not found on initial images. The data show early, abrupt diffusion changes in hypoperfused tissue, adding to our understanding of the progression of microstructural abnormalities in the hyperacute phase of stroke.

Do indomethacin and propofol cause cerebral ischemic damage? Diffusion-weighted magnetic resonance imaging in patients undergoing craniotomy for brain tumors.

Background: Diffusion-weighted magnetic resonance imaging was used to determine whether indomethacin and propofol induce cerebral ischemic damage in patients undergoing craniotomy for cerebral tumors. As a secondary aim, the authors investigated whether low jugular bulb oxygen saturation values were associated with brain parenchymal damage as evaluated by diffusion-weighted imaging.

Methods: Nine patients subjected to craniotomy for supratentorial brain tumors in propofol-fentanyl anesthesia were studied.

Sensory perception in complete spinal cord injury.

Objectives: To describe sensations evoked by painful or repetitive stimulation below injury level in patients with a clinically complete (American Spinal Injury Association, ASIA Grade A) spinal cord injury (SCI).

Material And Methods: Twenty-four patients (11 with central neuropathic pain and 13 without pain) with a traumatic SCI above the tenth thoracic vertebra were examined using quantitative sensory testing, MR imaging, and somatosensory evoked potentials (SEP).

Results: Painful (pressure, pinch, heat or cold) or repetitive (pinprick) stimuli elicited vague localized sensations in 12 patients (50%).

MRI in chronic spinal cord injury patients with and without central pain.

Background: Central pain following spinal cord injury (SCI) is common and thought to be related to lesion of the spinothalamic pathways.

Objective: To examine additional mechanisms of SCI pain.

Methods: Twenty-three SCI patients with traumatic lesions above T10 (14 with central neuropathic pain and 9 without pain) underwent MRI examination.

Final infarct size after acute stroke: prediction with flow heterogeneity.

Purpose: To compare acute measurements of flow heterogeneity (FH) and mean transit time (MTT) with follow-up data to determine which method yields better predictive measures of final infarct volumes.

Materials And Methods: Twenty-three patients with symptoms of stroke underwent magnetic resonance (MR) imaging during the acute stage, and the tissue at risk was estimated from MTT maps and maps generated by means of detecting abnormal FH. Final infarct volumes were calculated from T2-weighted follow-up MR image measurement.

Blood flow and ischemia within traumatic cerebral contusions.

Objective: To provide evidence of irreversible ischemia in cerebral contusions among patients with severe traumatic brain injuries and to clarify the potential viability of tissue in the pericontusional zone, quantitative regional cerebral blood flow (rCBF) measurements obtained with the xenon-enhanced computed tomographic method were correlated with the areas of contusions, by using image fusion.

Methods: rCBF measurements obtained during the acute phase (mean, 2 d after injury; range, 0-10 d) were statistically correlated with the extent of tissue necrosis identified as focal atrophy on late follow-up computed tomographic scans (mean time after the xenon-enhanced computed tomographic cerebral blood flow investigation, 265 d; range, 30-1047 d).

Results: Seventeen patients exhibited 26 traumatic contusions.

Time evolution of cerebral perfusion and apparent diffusion coefficient measured by magnetic resonance imaging in a porcine stroke model.

Purpose: To demonstrate the feasibility of sequential diffusion-weighted (DW) and perfusion-weighted (PW) magnetic resonance imaging (MRI) of a recently developed porcine stroke model and to evaluate the evolution of cerebral perfusion and the apparent diffusion coefficient (ADC) over time. Materials and Methods In five pigs, DW imaging (DWI) and PW imaging (PWI) was carried out for 7 hours after stroke onset, starting 1 hour after middle cerebral artery occlusion (MCAO).

Results: The DWI lesion volume increased significantly with time, and final DWI lesion volume correlated well with lesion area on histological sections (r = 0.

Correlation between diffusion- and perfusion-weighted MRI and neurological deficit measured by the Scandinavian Stroke Scale and Barthel Index in hyperacute subcortical stroke (< or = 6 hours).

Objective: We used combined diffusion-weighted (DWI) and perfusion-weighted (PWI) MRI to characterize hyperacute infarctions within 6 h of symptom onset with special reference to subcortical infarctions, and investigated the relation between perfusion-diffusion mismatch volume and functional outcome.

Material And Methods: Twenty-two patients presenting with symptoms of acute stroke underwent DWI and PWI within 6 h of symptom onset, and follow-up MRI 30 days later. Twelve of these had a subcortical infarction on acute DWI.

Prediction of tissue survival after middle cerebral artery occlusion based on changes in the apparent diffusion of water.

Object: In this study the authors tested the hypothesis that the estimate of the apparent diffusion coefficient (ADC) of water is a reliable pathophysiological index of the viability of ischemic brain tissue.

Methods: Cerebral blood flow (CBF) and the cerebral metabolic rates of oxygen and glucose (CMRO2 and CMRglc, respectively) were measured using positron emission tomography (PET) scanning before and after permanent middle cerebral artery occlusion (MCAO) or reperfusion in pigs. The ADC value, which was measured using diffusion-weighted magnetic resonance (DW MR) imaging was compared with physiological variables obtained by PET scanning and with histological findings.

Viability thresholds of ischemic penumbra of hyperacute stroke defined by perfusion-weighted MRI and apparent diffusion coefficient.

Background And Purpose: The penumbra of ischemic stroke consists of hypoperfused, but not irreversibly damaged, tissue surrounding the ischemic core. The purpose of this study was to determine viability thresholds in the ischemic penumbra, defined as the perfusion/diffusion mismatch in hyperacute stroke, by the use of diffusion- and perfusion-weighted MRI (DWI and PWI, respectively).

Methods: DWI and PWI were performed in 11 patients View Article and Find Full Text PDF

[MR scanning in acute apoplexy].

MR is increasingly used as a diagnostic tool in stroke management, especially since new and acute treatments are now available. This article describes the new MR sequences used in the scanning of stroke patients. A scanning protocol is suggested and our preliminary experiences with acute MR scanning of stroke patients are presented.

Relationship between residual cerebral blood flow and oxygen metabolism as predictive of ischemic tissue viability: sequential multitracer positron emission tomography scanning of middle cerebral artery occlusion during the critical first 6 hours after stroke in pigs.

Object: The authors tested the hypothesis that oxygen metabolism is the key factor linking the long-term viability of ischemic brain tissue to the magnitude of residual blood flow during the first 6 hours following a stroke.

Methods: Eleven anesthetized pigs underwent a series of positron emission tomography studies to measure cerebral blood flow (CBF) and metabolism before and for 7 hours after the animals were subjected to permanent middle cerebral artery (MCA) occlusion. The extent of collateral blood supply was assessed using angiography.

Cerebral blood flow and blood volume measured by magnetic resonance imaging bolus tracking after acute stroke in pigs: comparison with [(15)O]H(2)O positron emission tomography.

Background And Purpose: Early and accurate assessments of cerebral ischemia allow therapy to be tailored to individual stroke patients. We examined the feasibility of using a novel method for measuring cerebral blood flow (CBF) of ischemic tissue based on MRI after middle cerebral artery occlusion (MCAO). Moreover, the regional correlations between CBF and cerebral blood volume (CBV) were investigated in the regions with acute ischemic stroke.

Combined diffusion-weighted and perfusion-weighted flow heterogeneity magnetic resonance imaging in acute stroke.

Background And Purpose: The heterogeneity of microvascular flows is known to be an important determinant of the efficacy of oxygen delivery to tissue. Studies in animals have demonstrated decreased flow heterogeneity (FH) in states of decreased perfusion pressure. The purpose of the present study was to assess microvascular FH changes in acute stroke with use of a novel perfusion-weighted MRI technique and to evaluate the ability of combined diffusion-weighted MRI and FH measurements to predict final infarct size.

Xenon CT cerebral blood flow in patients with head injury: influence of pulmonary trauma on the input function.

The noninvasive xenon-enhanced CT (Xe CT) cerebral blood flow (CBF) method has been used in patients with severe traumatic brain injury (TBI) to identify the blood-flow thresholds for the development of irreversible ischaemia or infarction following severe TBI. Quantitative regional CBF (rCBF) estimates are based on the assumption of identity between the end-tidal xenon concentration curve, used as the input function, and the arterial xenon concentration curve, being the true input function to the brain. Accordingly, rCBF data addressing the issue of ischaemia should be viewed in relation to possible deviations between the end-tidal and arterial xenon concentration curves.

Cerebral blood flow in volunteers measured by PET and Xe CT/CBF. A comparison.

Aim of this study was to compare two quantitative CBF methods. Seven young, healthy volunteers were studied with PET (15-0 labelled water) and afterwards with Xe CT/CBF (30% xenon in oxygen, 3 minutes wash-in, 5 minutes washout protocol). Xe CT/CBF showed greater differences between high and low flow areas than PET CBF.

The influence of the input function on quantitative rCBF by the Xe/CT method.

Measurements of rCBF by the Xe/CT method are based on the assumption of identity between the end-tidal xenon curve which is applied as input function, and the arterial xenon curve being the true input function to the brain. In this study corresponding end-tidal and arterial xenon curves were measured in an experimental animal model (part 1) and in 5 patients with traumatic brain injury (part 2) and used for rCBF calculation. In both studies rCBF was underestimated by using the end-tidal xenon concentration curve as brain input function.