Figure 7.

Right lower extremity ischemia with gangrenous toes. (a) MIP and (b) multipath curved planar reformation from lower extremity CT angiogram depict extensive bilateral atherosclerotic disease. Arterial supply to the right lower extremity is severely compromised by 3-cm-long common iliac artery occlusion (1), 2-cm-long high-grade stenosis of the external iliac artery (2), and proximal through midsuperficial femoral artery stenoses (curved arrow with 5-cm-long occlusion) (3). Right posterior tibial artery is occluded at its origin, but is reconstituted by the peroneal artery above the ankle (4), resulting in two-vessel runoff across the ankle. Arterial supply to the left lower extremity is compromised by a 75% stenosis of the proximal common iliac artery (5), greater than 90% stenoses of the external iliac artery (6, 7), 3-cm-long midsuperficial femoral artery occlusion (8), and moderate distal superficial femoral artery stenosis (9). Left anterior tibial artery is occluded 10 cm distal to its origin but is reconstituted by the peroneal artery above the ankle (11) to provide two-vessel runoff across the ankle. Legions obscured on MIP by heavy arterial wall calcifications (1, 2, 5, 6, 7) are not obscured by calcium and better displayed on the multipath curved planar reformation. Because the displayed plane of a curved planar reformation is always through the vessels of interest, the representation of nonvascular structures may not follow standard anatomic relationships. An example of this is the ovoid opacities lateral to the popliteal artery, which represent portions of the lateral femoral condyles and lateral aspect of the tibial plateaus.