Brain and Vessels

Key images

Findings

50-year-old male presented with progressive speech difficulty and headache that started about 10 hours previously without motor or sensory symptoms, suspicious of stroke.

Virtual monoenergetic images at lower keV may provide better demonstration of hyperdense artery sign indicating thrombus on non-contrast images. After contrast administration, increased attenuation of iodine in vessels is obtained with lower keV virtual monoenergetic images. Iodine density and Z effective images help in diagnosing occluded segment of the vessel by demonstrating lack of iodine.

Axial and sagittal images

Conventional non-contrast axial CT images revealed hyperdense middle cerebral artery on the left and subtle hyperdensity of left internal carotid artery. Hyperdense left carotid artery was more prominent in virtual monoenergetic images at 40 keV. CT angiography revealed typical “flute beak” tapering and complete occlusion of the left internal carotid artery compatible with thrombosed dissection and partial thrombus extending to middle cerebral artery. Iodine density and Z effective images demonstrated narrowing and occlusion of the lumen of left internal carotid artery as well as thrombus extending to left middle cerebral artery. Virtual monoenergetic images at 50 keV provided increased attenuation of vessels. T2-weighted MRI images showed hyperintensity of left internal carotid artery and middle cerebral artery compatible with occlusion.

Discussion

Virtual monoenergetic images at lower keV could be helpful in increasing conspicuity of hyperdense vessels on non-contrast images as a sign of thrombus. After contrast administration, virtual monoenergetic images at lower keV increase vessel attenuation and thus may improve diagnostic performance with lower contrast volumes. Iodine density and Z effective images demonstrate lack of iodine within the lumen and help in diagnosis of vessel occlusion.

Conventional non-contrast CT axial image at 120 kVp: hyperdense and enlarged internal carotid artery (arrow).

Conventional non-contrast CT axial image at 120 kVp: hyperdense middle cerebral artery sign (arrow).

Conventional non-contrast CT axial image at 120 kVp: hyperdense left internal carotid artery intracavernous segment (arrow).

Virtual monoenergetic image at 40 keV: hyperdensity of left internal carotid artery intracavernous segment is more prominent (arrow).

Conventional CT angiography in sagittal reformation: demonstration of the narrowing (arrow) and occlusion of internal carotid artery.

Virtual monoenergetic image at 50 keV, sagittal reformation: better attenuation of internal carotid artery (arrow).

Iodine density sagittal image, sagittal reformation: tapering of the lumen of cervical segment of ICA (arrow).

Z effective image: tapering of the lumen of cervical segment of internal carotid artery color coded in dark blue (blue arrow) and occluded distal segment coded in light blue (white arrow).

CT angiography, axial image: demonstrating in a subtle way the narrowing and thrombus in middle cerebral artery (arrow).

Iodine density axial image: partial thrombus in left middle cerebral artery (arrow).

Z effective image: area of partial thrombus color coded in light blue (arrow).