Flow territory mapping of the cerebral arteries with regional perfusion MRI.

Background And Purpose: Conventional contrast-enhanced angiography is the gold standard for visualization of the vascular tree supplied by the major cerebral arteries and assessment of collateral flow. Thus far, however, no methods are available to assess the actual flow territories of the individual cerebral arteries. In the present study, we evaluate a noninvasive arterial spin labeling MRI method for selective mapping of the flow territories of the left and right internal carotid arteries and posterior circulation (basilar artery and vertebral arteries).

Diffusion-weighted magnetic resonance imaging and identification of the epileptogenic tuber in patients with tuberous sclerosis.

Background: Patients with tuberous sclerosis complex and drug-resistant epilepsy may be considered candidates for epilepsy surgery. This demands the unambiguous demonstration of the epileptogenicity of one of the tubers.

Objective: To test whether diffusion-weighted magnetic resonance imaging enables differentiation of epileptogenic tubers from inert ones.

Hemodynamic compensation via an excimer laser-assisted, high-flow bypass before and after therapeutic occlusion of the internal carotid artery.

Objective: High-flow, extracranial-intracranial (EC-IC) bypass operations are performed to prevent strokes among patients with giant aneurysms who cannot tolerate internal carotid artery (ICA) occlusion. However, the volume flow through the bypass, compared with preoperative ICA flow, has not been evaluated for any type of bypass. We describe a prospective case study that tested the ability of the high-flow EC-IC bypass to replace the volume flow of the ipsilateral ICA after deliberate ICA occlusion.

Prevalence and volume of internal border zone lesions in patients with impaired cerebral carbon dioxide vasomotor reactivity: a follow-up study.

Background: The precise etiology of border zone infarcts is controversial. Hemodynamic impairment due to obstructive disease of the internal carotid artery (ICA) is suggested as a cause of border zone infarcts.

Objective: To investigate changes in prevalence and volume of ischemic border zone lesions over time in patients with occlusive disease of the ICA after 1 year of follow-up.

Model of the human vasculature for studying the influence of contrast injection speed on cerebral perfusion MRI.

Simulations of dynamic susceptibility contrast (DSC) MRI are frequently performed by assuming a certain shape for the input function and the microvascular response function. However, to investigate the influence of parameters that will affect the shape of the input function, a more complex model of the human vasculature is required. In this study, a model of the human vasculature is proposed that consists of a network of vascular operators based on physiological data typical of a 35-year-old male subject.

Probability of regaining dexterity in the flaccid upper limb: impact of severity of paresis and time since onset in acute stroke.

Background And Purpose: To improve the accuracy of early postonset prediction of motor recovery in the flaccid hemiplegic arm, the effects of change in motor function over time on the accuracy of prediction were evaluated, and a prediction model for the probability of regaining dexterity at 6 months was developed.

Methods: In 102 stroke patients, dexterity and paresis were measured with the Action Research Arm Test, Motricity Index, and Fugl-Meyer motor evaluation. For model development, 23 candidate determinants were selected.

Measurements of cerebral perfusion and arterial hemodynamics during visual stimulation using TURBO-TILT.

Estimation of cerebral blood flow (CBF) in functional perfusion imaging could benefit from a method capable of separating effects of arterial arrival time and trailing edge. To accomplish this, the transfer insensitive labeling technique (TILT) was combined with a train of 13 consecutive acquisitions, called TURBO-TILT. Visual activation maps obtained at 13 postlabeling delay times (TI) showed a spatial shift from regions surrounding the arterial vasculature at short TI to brain parenchyma at longer delay times.

Effect of carotid endarterectomy on primary collateral blood flow in patients with severe carotid artery lesions.

Background And Purpose: In patients with severe obstruction of the internal carotid artery (ICA), it is recognized that the preoperative failure to visualize collaterals of the circle of Willis increases the risk of hemispheric ischemia before, during, and after carotid endarterectomy (CEA). The purpose of the present study was to assess the effect of CEA on the anatomy and function of the circle of Willis.

Methods: Time-of-flight and phase-contrast MR angiography were used to study changes in vessel diameter and collateral flow of the circle of Willis in 48 patients with 70% to 99% ICA stenosis before and after CEA.

Measuring the arterial input function with gradient echo sequences.

The measurement of the arterial input function by use of gradient echo sequences was investigated by in vitro and in vivo experiments. First, calibration curves representing the influence of the concentration of Gd-DTPA on both the phase and the amplitude of the MR signal were measured in human blood by means of a slow-infusion experiment. The results showed a linear increase in the phase velocity and a quadratic increase in DeltaR(*) (2) as a function of the Gd-DTPA concentration.

Cognitive impairment is related to cerebral lactate in patients with carotid artery occlusion and ipsilateral transient ischemic attacks.

Background And Purpose: Patients with carotid artery occlusion (CAO) and ipsilateral transient ischemic attack (TIA) can have lasting cognitive impairment, despite the recovery of focal neurological deficits. We sought to assess whether cognitive impairment in these patients is associated with hemodynamic compromise and/or impaired cerebral metabolism.

Methods: In 39 consecutive patients with a TIA associated with an angiographically proven occlusion of the carotid artery, we examined (1) cognitive functioning, (2) cerebrovascular reserve capacity of the middle cerebral artery ipsilateral to the CAO as measured by transcranial Doppler ultrasound, and (3) metabolic ratios as measured by 1H-MR spectroscopy in the centrum semiovale ipsilateral to the symptomatic CAO.

1H magnetic resonance spectroscopy in human hydrocephalus.

Purpose: To evaluate cerebral metabolism in clinical hydrocephalus with (1)H magnetic resonance spectroscopy (MRS).

Materials And Methods: In 24 children and adults with progressive, arrested, or normal pressure hydrocephalus, long-echo time (1)H MR spectra were acquired from periventricular white matter and intraventricular cerebrospinal fluid (CSF). Metabolite ratios, and the presence of lactate, were compared with 38 age-matched controls.

Association between impaired carbon dioxide reactivity and ischemic lesions in arterial border zone territories in patients with unilateral internal carotid artery occlusion.

Context: Ischemic lesions in patients with internal carotid artery (ICA) steno-occlusive disease can be categorized on the basis of their location and presumed cause: external border zone infarcts, internal border zone infarcts, cortical infarcts, lacunar infarcts, and periventricular lesions.

Objective: To evaluate the association between the prevalence and size of ischemic lesions and cerebral vasomotor reactivity in patients with unilateral occlusion of the ICA.

Design: Cross-sectional study.

Magnetic resonance angiography of collateral compensation in asymptomatic and symptomatic internal carotid artery stenosis.

Objective: In patients with stenosis of the internal carotid artery (ICA), the presence of collateral circulatory pathways may be crucial to maintain cerebral perfusion pressure, metabolism, and function. The purpose of the present study was to determine whether patients with asymptomatic stenosis of the ICA have a better collateral ability of the circle of Willis when compared with patients with symptomatic ICA stenosis.

Method: Magnetic resonance angiography consisting of the circle of Willis was performed in 19 patients with severe asymptomatic ICA stenosis and in 21 patients with severe symptomatic ICA stenosis prior to carotid endarterectomy and in 53 control subjects.

Proximal and distal hyperattenuating middle cerebral artery signs at CT: different prognostic implications.

Purpose: To determine whether a proximal (M1-segment) or distal (M2- and/or M3-segment) hyperattenuating middle cerebral artery (MCA) sign in patients with ischemic infarction in the territory of the MCA indicates a worse short-term prognosis than that in patients without a hyperattenuating MCA sign.

Materials And Methods: We retrospectively reviewed the records of 352 patients who were diagnosed with ischemic brain infarction in the territory of the MCA. Of these patients, 186 patients met our final criteria and were included in this study.

Hemodynamic and metabolic changes in transient ischemic attack patients: a magnetic resonance angiography and (1)H-magnetic resonance spectroscopy study performed within 3 days of onset of a transient ischemic attack.

Background And Purpose: We investigated whether patients with transient ischemic attack (TIA) have systemic low flow to the brain or an abnormal intracranial flow distribution caused by an abnormal anatomy of the circle of Willis. Furthermore, we investigated whether metabolic changes were present in the brain.

Methods: Forty-four patients with clinically diagnosed TIA were prospectively included in our study.