Journal of neuroimaging : official journal of the American Society of Neuroimaging
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The pathophysiology of arterial air embolism inducing brain injuries remains unclear. Previous experiments demonstrated the usefulness of computed tomography (CT) in the detection of air emboli in canine brain. This canine study investigates CT's ability to detect small air bubbles and to determine the kinetics of air elimination from cerebral arteries and its relationship with clinical, electroencephalographic (EEG), and histological manifestations. ⋯ Air clearance time significantly depends on intracerebral air volume (r2 = 0.86, p = 0.04) and on the number of bubbles (r2 = 0.71, p = 0.03), whereas half-life of air elimination does not. No relationship was found between injected air dose, air clearance time, intracerebral volume of air, and clinical, EEG, and histological findings. The data indicate that CT accurately detects small air bubbles in the early course of cerebral air embolism, that air elimination from cerebral arteries follows a first-order compartment model, and that early CT findings do not correlate with clinical, EEG, and histological manifestations.
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The progression of subclavian arterial stenosis and the subsequent formation of collateral pathways serve to alter the pressure gradients in subclavian steal syndrome, altering ipsilateral vertebral artery flow from its normal state to "latent," "transient," and "continuous" steals. A similar altered flow in the carotid arteries can be observed with stenosis of the proximal common or innominate artery. A 59-year-old man was seen in the vascular laboratory for evaluation of symptomatic peripheral arterial disease. ⋯ Further cerebral vascular evaluation displayed a continuous right subclavian steal and a latent steal in the right internal carotid artery. Transcranial Doppler examination displayed "transient" steal in the terminal right internal carotid artery. Combining duplex and transcranial Doppler evaluations allows sequential evaluation of the progression of arterial disease and its effect on the flow patterns in the cerebral vasculature.
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Case Reports
Localized in vivo 1H magnetic resonance spectroscopy and in vitro analyses of heterogeneous brain tumors.
Results of magnetic resonance spectroscopic (MRS) studies of the chemical patterns in brain tumors have been inconsistent. Actual biochemical correlations are needed. In 2 patients with heterogeneous intracranial tumors, in vivo 1H MRS and in vitro biochemical analyses were correlated. ⋯ Creatine was diffusely decreased while lactate was elevated in all regions of both tumors. Furthermore, the increase in the choline peak on 1H MRS appeared to be due to increases in water-soluble choline compounds. This study illustrates the value of small localized voxels for differentiating regional chemical differences in tumors.