Arterial spin-labeling in routine clinical practice, part 3: hyperperfusion patterns

Abstract

Arterial spin-labeled (ASL) perfusion imaging can be implemented successfully into a routine clinical neuroimaging protocol and can accurately demonstrate alterations in brain perfusion. We have observed patterns of focal, regional, and global hyperperfusion in a wide variety of disease processes. The causes of hyperperfusion at clinical ASL have not been previously characterized. Focal lesions such as brain tumors and vascular malformations with increased perfusion can be well depicted by ASL. More global causes of hyperperfusion, including postanoxia vasodilation and hypercapnia, may go undetected on conventional MR images, whereas the regional hyperperfusion, which may occur in reversible encephalopathies and luxury perfusion, has been consistently illustrated on ASL cerebral blood flow maps at our institution.

Fig 1.

Luxury perfusion. Asymmetric intravascular enhancement of the cortical vessels in a large infarcted left MCA territory (ellipse) on the postcontrast T1-weighted images. ASL CBF map demonstrates hyperperfusion in the left caudate, insula, and frontal lobe (arrow). The posterior parietal regions are hypoperfused.

Fig 2.

Reperfusion. An 80-year-old woman presenting with right hemiparesis met the criteria for systemic thrombolytics. ASL CBF map acquired approximately 12 hours after tissue plasminogen activator administration reveals localized hyperperfusion within the left MCA territory (arrow). Perfusion is otherwise preserved throughout the left hemisphere.

Fig 3.

Hyperperfused stroke territory on ASL. A 73-year-old woman with atrial fibrillation and embolic infarcts in the left posterior cerebral artery and posterior watershed territories. Punctate areas of restricted diffusion are seen (left, yellow arrow). ASL map (right) shows gyral hyperperfusion in the left hemisphere (white arrow). Hypoperfusion is also seen in the right posterior watershed territory.

Fig 4.

Hyperperfused seizure territory. A 6-year-old boy with a history of Landau-Kleffner syndrome who presented with complex partial seizures causing paresis of the right face and upper extremity. ASL shows regional hyperperfusion in the left parietal hemisphere associated with the ictal phase of seizure activity (arrows). EEG confirmed almost continuous seizure activity within the left hemisphere. Findings of the diffusion-weighted sequence were normal (not shown). Symptoms improved on antiepileptic medications and a course of intravenous immunoglobulin.

Fig 5.

Hyperperfusion underlying a subdural hematoma. Axial T2-weighted image (left) demonstrates an acute-to-subacute left cerebral convexity hematoma (yellow arrows). Postcontrast image (center) shows compression of underlying vessels (ellipse). ASL CBF map (right) shows intense gyral hyperperfusion in the left parietal and occipital lobes (white arrow).

Fig 6.

A 57-year-old woman with atypical meningioma. An avidly enhancing falcine-based mass is demonstrated on the postgadolinium image (left). ASL map demonstrates ringlike hyperperfusion corresponding to the outer margins of the tumor (right, arrow).

Fig 7.

Hyperperfusion of a glioblastoma multiforme. Axial postgadolinium T1-weighted image demonstrates avid enhancement of a high-grade neoplasm centered in the genu of the corpus callosum. ASL CBF map demonstrates high signal intensity corresponding to increased flow within the periphery of the tumor (arrow).

Fig 8.

Ependymal tumor hyperperfusion. Gadolinium-enhanced spoiled gradient-recalled image shows diffuse enhancement of the ependymal surfaces (yellow arrow). Representative ASL image demonstrates hyperperfusion outlining the right lateral ventricle (white arrow). CSF analysis revealed leptomeningeal seeding of metastatic melanoma.

Fig 9.

ASL hyperperfusion in infiltrative tumor. A 49-year-old woman who presented with seizures had an infiltrative T2 (upper left) hyperintense lesion in the right frontal lobe without significant enhancement on postgadolinium T1-weighted (upper right) imaging (arrowheads). Multivoxel MR spectroscopy (bottom left) reveals an elevated choline/creatine ratio (3:2) consistent with gliomatosis cerebri (yellow arrow). ASL CBF map (bottom right) demonstrates increased signal intensity in the subcortical white matter corresponding to tumor (white arrow).

Fig 10.

Gyral hyperperfusion with venous angioma. A 41-year-old woman being followed for grade III astrocytoma had a resection cavity in the right frontal lobe without significant enhancement or hyperperfusion. Incidentally noted is a venous angioma on the postgadolinium spoiled gradient-recalled sequence (yellow arrow) and bandlike cortical high signal intensity on the ASL map (white arrow).

Fig 11.

Evolution of perfusion changes in PRES in a 31-year-old woman. A, Initial images: high signal intensity on the initial diffusion-weighted image (left) represents T2 shinethrough secondary to edema seen on the apparent diffusion coefficient (ADC) images (center) in the occipital cortices. A corresponding ASL map (right) reveals marked flow asymmetry with hypoperfusion in the left occipital lobe (white arrow). B, At 2-week follow-up, diffusion and ADC images show new posterior restricted diffusion (yellow arrows), and bilateral hyperperfusion is now evident on perfusion images (right, white arrow).

Fig 12.

Cerebral hyperperfusion after carotid endarterectomy (CEA). ASL CBF map obtained 2 days after left CEA for dizziness demonstrates markedly increased flow throughout the left hemisphere (arrows).

Fig 13.

Paradoxical hyperperfusion following diffuse anoxic insult. A 69-year-old woman sustained a 10- to 15-minute period of pulseless electric activity. Diffusion-weighted image reveals multiple infarcts in the bilateral basal ganglia and watershed zones (top). ASL maps (bottom) show global hyperperfusion consistent with postischemic hyperemia.

Fig 14.

Hypercapnia. A 77-year-old patient with severe pulmonary edema (left) and a PCO₂ of 76 mm Hg (normal range, 35–45 mm Hg) at the time of MR imaging. Globally increased gray matter flow is shown on the ASL CBF map (right).