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FIG 4. Collaterals (cross-filling and dilution) and late arrival of ICA to the head.
A, Anterioposterior right carotid angiogram, head view, contralateral to left near occlusion shows exuberant cross-filling to left middle cerebral branches and even slightly down the supraclinoid carotid (arrow) to supply the anterior choroidal artery.
B, Lateral left carotid angiogram, late arterial neck and head view, shows delay in ICA filling intracranially, and abrupt dilution contrast in the supraclinoid carotid (arrow) above the origin of a fetal-type posterior cerebral artery. This dilution indirectly demonstrates the excellent collateral already shown in A, not opacified here. It also shows the supraclinoid carotid site of the "watershed" between the right carotid source and the extremely severe left carotid stenosis.
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