Quantitative Assessment of External Carotid Artery Territory Supply with Modified Vessel-Encoded Arterial Spin-Labeling

Left: Perfusion territory maps. Images a, b, and c represent the results of 3 scans (right) with different spatial gradient-encoding methods. Image d indicates the integrated results of the perfusion image with encoded vessels. Blood flows contributed by the vessels of the right ICA, left ICA, VAs, and ECA are red, green, blue, and yellow (white arrows), respectively. Center: The histograms (shown in blue) of the calculated tagging efficiencies for each encoding step. Gaussian fits to the peaks in the histograms are red; the center of the Gaussian fits, as the estimated tagging efficiencies for each vessel, are used to reconstruct the modified encoding matrix. The orange arrows originating from the histograms indicate the corresponding labeling vessels whose tagging efficiencies are estimated by the abscissa values of the center of the Gaussian fits (eg, in the first row of the histograms, the center of the Gaussian fit in an abscissa of −1 represents the tagging efficiency of the right ICA, in which the center of the Gaussian fit in nearly an abscissa of 1 represents the tagging efficiency of the left ICA and ECA). Right: The modified tagging geometries. The red and blue lines represent the locations that are marked as contrast (one represents the vessel inverted; the other, the vessel relaxed). A, The right and left ICAs are separated. B, Carotid and vertebral arteries are prominently distinguished. C, The VAs and ECAs are contrasted.

Perfusion territory maps of a healthy subject by using modified VE-ASL. The first row is the perfusion territories of the right ICA (red), left ICA (green), and VAs (blue); the second row is the perfusion territories of intracarotid (gray) and extracarotid (yellow) arteries. Note that the bottom section shows flow in the frontal brain region, which appears to be artifacts caused by magnetic inhomogeneities of B0 or eye motion. In the fourth image from the bottom, there is also a hint of ghosting in the white matter of the right hemisphere, which may be caused by the decoding process.

Sagittal DSA results (left) and vascular territories (right) in a patient undergoing carotid stent placement for right ICA stenosis. A, DSA results of the patient before surgery show that there is collateral flow from the ECA (white arrow). B, Preoperatively, the collateral supply is manifested as the ECA supply to the right ICA territory (red arrow). C, Postoperatively, there is normalization of the right ICA perfusion with a corresponding reduction of collateral supply (red arrow). Hyperperfusion of the right hemisphere after stent placement is also clearly shown.