Arterial and venous enhancement seen at CTA. The red arrow shows the arteries that run to the periphery without narrowing or obstruction. The blue arrows indicate veins that accompany these arteries. If the enhancement is simply an error caused by differing rate of contrast medium injection and CT scan timing, the superficial and deep veins on the contralateral side would show enhancement; however, in this case, deep veins on the affected side showed earlier enhancement than did those on the healthy side. CTA = computed tomographic angiography.