Fig 5. Quantification of a diminutive residual carotid bulb lumen. A, Axial CTA source image showing a diminutive right residual carotid bulb lumen (white arrow). B, Axial magnification of the residual carotid bulb lumen with measurement calipers placed at the region of narrowest stenosis (calipers marked [A], showing measurement of 0.10 cm [1.0 mm]). C, Axial magnification of the residual carotid bulb lumen with the AGFA Impax 4.5 VT, showing the cross-sectional 2D area of 0.02 cm² (2.0 mm²). The HUs between the contrast-filled lumen and the surrounding tissues was great enough for the VT to accurately measure the lumen, despite the small lumen size.