PubMed · 7535943
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A K Vine. 1994. Retinal vasculitis.. https://doi.org/10.1055/s-2008-1041095
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For flow imaging applications, radial-line k-space acquisition methods offer advantages over conventional 2DFT methods. Specifically, radial-line acquisition methods mitigate artifacts resulting from pulsatile flow while offering a potential reduction in scan times. In this paper, radial-line and 2DFT acquisitions are compared in a two-dimensional time-of-flight angiography sequence. The twisting radial-line (TwiRL) trajectory, a variant of 2D projection reconstruction, is used to represent the family of radial-line trajectories. In both phantom and in vivo studies, the TwiRL images demonstrate improved vessel depiction including a more uniform signal intensity and better delineation of the vasculature in comparison with images obtained via the 2DFT method.
BACKGROUND AND PURPOSE: Among the pathogenetic causes of subcortical hemispheric infarcts are small-vessel disease, thromboembolic occlusions of small arteries, and hemodynamic compromise in low-flow conditions. A topographic classification of these infarcts based on CT and MRI can be misleading. METHODS: We evaluated 30 consecutive patients with presumed supratentorial low-flow infarcts. CT was available in all cases, with additional MRI in 14 patients. In all cases the occlusion pattern of the extracranial and intracranial arterial system was studied in detail with angiography. RESULTS: The dominant lesion patterns seen on CT and MRI were multilocal chainlike lesions in 19 and confluent striated lesions in 8 cases located in the supraventricular and paraventricular deep white matter. In 8 patients subcortical lesions extended into the adjacent cortex. Angiography revealed that extracranial occlusive disease (n = 24) or stenosis of the middle cerebral artery (n = 6) was always accompanied by impairment of the circle of Willis, in either the anterior part (n = 25) and/or the posterior part (n = 16). Moreover, leptomeningeal pathways indicative of vascular hemispheric compromise were identified in 26 cases. In total, 29 of 30 patients displayed a noncompetent circle of Willis. CONCLUSIONS: Low-flow infarcts show typical but not pathognomonic lesion patterns on CT and MRI. Definite diagnosis requires knowledge of the complex vascular compromise of the extracranial and/or intracranial arterial system. A noncompetent circle of Willis should be regarded as the additional predisposing condition in hemispheric low-flow infarcts.
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