Journal of neuroimaging : official journal of the American Society of Neuroimaging
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Comparative Study
In vitro validation of color velocity imaging and spectral Doppler for velocity determination.
Color velocity imaging (CVI) is a new non-Doppler ultrasound technique for vascular color flow imaging. Using information contained in the two-dimensional B-mode, gray-scale image to determine velocity, CVI offers potential advantages over Doppler color flow imaging methods. In order to be used clinically, velocity determination with CVI must be validated by other current methods. ⋯ At all string speeds tested, the averaged estimated and the actual velocities for both methods were within the 95% confidence estimates. The range for the CVI 95% confidence limits from the regression line varied from +/-1.07 cm/sec at the lowest speed of 10 cm/sec (11.6%) to +/-7.72 cm/sec at 200 cm/sec (3.87%). Based on in vitro testing, CVI is as accurate as Doppler spectral analysis for the estimation of flow velocity.
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Magnetic resonance imaging (MRI) findings in a group of 60 ambulatory elderly individuals (average age, 75.8 yr) were characterized as normal (grade 0), periventricular changes only (grade 1 ). small punctate lesions (grade 2), and confluent or large (> 2 mm) punctate lesions (grade 3). Patients were characterized by stroke risk factors, cardiolipin antibodies, coagulation factors (fibrinogen and plasminogen activator inhibitor-1 ). and Doppler ultrasound findings in the carotid and middle cerebral arteries. ⋯ There was no significant association between variables and MRI grade. These findings suggest that ischemia is not a major cause of MRI signal abnormalities in neurologically asymptomatic elderly individuals.
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Tha pathophysiology of brain injury in patients undergoing cardiopulmonary bypass remains unclear despite several decades of inquiry. The advent of noninvasive high-resolution brain and cerebrovascular imaging by magnetic resonance, computed tomography, and pulsed Doppler ultrasonography now permits in vivo assessment of pathophysiological mechanisms. Neuroradiographic and carotid duplex studies were performed in patients who developed neurological deficits following cardiopulmonary bypass. ⋯ Watershed injury was the predominant finding in a single patient, while findings consistent with global anoxia were present in another patient. Carotid atheroemboli were excluded as a possible source of embolism in 11 patients whose carotid duplex studies were unremarkable preoperatively as well as in 3 further patients whose neuroradiographic findings did not correspond with their moderate carotid disease. It is concluded that infarction due to noncarotid embolism is the primary pathophysiology of neurological deterioration following cardiopulmonary bypass.
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Atrial fibrillation and congestive heart failure are risk factors for ischemic stroke usually attributed to cardiac embolism. To define potential alternative mechanisms, patients with atrial fibrillation and congestive heart failure were investigated by transcranial Doppler. Middle cerebral artery (MCA) blood flow velocities were analyzed in neurologically asymptomatic patients with nonvalvular (n = 10) and valvular (n = 13) atrial fibrillation, patients in normal sinus rhythm with congestive heart failure (n = 13), and control subjects (n = 11). ⋯ Peak, mean, and diastolic MCA velocities in patients with atrial fibrillation and those with congestive heart failure were significantly less than those in control subjects. Patients with nonvalvular atrial fibrillation had a higher pulsatility index compared to each of the other three groups. These findings demonstrate substantial nonemboligenic alterations of the intracranial circulation associated with atrial fibrillation and congestive heart failure, and also provide an intracranial hemodynamic profile that may distinguish valvular from nonvalvular atrial fibrillation.
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Comparative Study
Medial temporal atrophy as a magnetic resonance imaging marker for Alzheimer's disease.
Medial temporal lobe atrophy (MTLA) on brain magnetic resonance imaging (MRI) may help differentiate Alzheimer's disease (AD) from multiinfarct dementia (MID) and other dementias. MTLA was seen in 6 of 11 patients with clinically diagnosed AD, 16 of 20 with mixed dementia (with both AD and MID), 1 of 5 with psychiatric disease, and in none of 32 with MID or 8 with other dementias (p less than 0.0001). Increased patchy periventricular signal, or "unidentified bright objects" were seen in 2 of 11 patients with AD, 10 of 20 patients with AD and MID, and 26 of 32 patients with MID. A larger series with autopsy correlation may verify that MTLA is a reasonably specific marker for AD, and unidentified bright objects are a sensitive, but not specific, marker for vascular dementias.