Bilateral Cerebral Hypoperfusion in Asymptomatic Unilateral Carotid Artery Stenosis: An Arterial Spin Labeling MRI Study

Figure 1. ROI Placement and ASL Perfusion Map in a Control Subject. This figure illustrates the placement of regions of interest (ROIs) on T1-weighted anatomical images and their corresponding arterial spin labeling (ASL) perfusion maps in a control subject. (a) T1-weighted image with ROI placement in the precentral gyrus (frontal cortex) bilaterally, ensuring precise localization in the gray matter, and (b) the corresponding ASL perfusion map with identically positioned ROIs for cerebral blood flow (CBF) quantification. (c) T1-weighted image with ROI placement in the lentiform nucleus bilaterally, and (d) the corresponding ASL perfusion map. (e) T1-weighted image with ROI placement in the insular cortex bilaterally, and (f) the corresponding ASL perfusion map. (g) T1-weighted image with ROI placement in the temporal cortex bilaterally, and (h) the corresponding ASL perfusion map. ROI sizes ranged from 15 to 40 mm2, with elliptical ROIs used in thinner cortical regions and circular ROIs in larger areas. The colored ASL perfusion maps (b,d,f,h) represent quantitatively measured cerebral blood flow (CBF), with warmer colors (red, yellow) corresponding to higher CBF values and cooler colors…

Figure 2. ROI Placement and ASL Perfusion Map in a Patient with Carotid Stenosis. This figure presents ROI placement and ASL perfusion maps in a patient with unilateral carotid stenosis, following the same methodology as in Figure 1. (a) T1-weighted image with ROI placement in the precentral gyrus (frontal cortex) bilaterally, and (b) the corresponding ASL perfusion map with the same ROIs transferred for CBF quantification. (c) T1-weighted image with ROI placement in the lentiform nucleus bilaterally, and (d) the corresponding ASL perfusion map. (e) T1-weighted image with ROI placement in the insular cortex bilaterally, and (f) the corresponding ASL perfusion map. (g) T1-weighted image with ROI placement in the temporal cortex bilaterally, and (h) the corresponding ASL perfusion map. ROI sizes (15–40 mm2) were adjusted according to the anatomical region, with elliptical ROIs applied in thinner cortical regions and circular ROIs in larger areas. The colored ASL perfusion maps (b,d,f,h) represent quantitatively measured cerebral blood flow (CBF), with warmer colors (red, yellow) corresponding to higher CBF values and cooler colors (green, blue) indicating lower values.

Figure 3. The graph displays confidence interval ellipses representing CBF values in the regions that contribute the most to the differentiation between the ipsilateral (2) and contralateral (3) hemispheres in individuals with unilateral stenosis, as well as the control group (1), based on Table 6. These values were obtained in the insular cortex and the frontal cortex–precentral gyrus, which are the first two variables listed in Table 6. The graph shows that CBF values are highest in the control group (1), intermediate in the contralateral hemisphere (3), and lowest in the ipsilateral hemisphere (2) in individuals with unilateral stenosis, and that these groups are clearly separated.

Figure 4. The graph displays confidence interval ellipses representing CBF values in the regions that contribute the most to the differentiation between the ipsilateral (2) and contralateral (3) hemispheres in individuals with unilateral stenosis, as well as the control group (1), based on Table 6. These values were obtained in the insular and temporal cortex, which are the first and third variables listed in Table 6. The graph shows that CBF values are highest in the control group (1), intermediate in the contralateral hemisphere (3), and lowest in the ipsilateral hemisphere (2) in individuals with unilateral stenosis. Furthermore, groups 2 and 3 (ipsilateral and contralateral hemispheres) are closer to each other, whereas the control group is clearly distinct from both.