Figure 4: TOF-MRA axial source image for the right internal carotid (ICA) and external carotid artery (ECA). (a) At the arterial periphery, the signal was darker near the outer wall of ICA than near the inner wall because of the difference in intraluminal saturation. (b) Color displays of the arterial signal intensity showed a clear gradation in the color scale from the arterial center region to the periphery. (c) TOF-MRA SIG showed the regions with high or low SIG values.