On plain scan, focal high-low or low-mixed density shadows were seen as spots, clumps or strips with indistinct margins. Among them, high-density shadows are due to focal gliosis, thrombus, calcification, new hemorrhage or slow blood flow within the malformation and iron-containing heme deposits, while low-density shadows are small infarcts or old hemorrhages with limited cerebral atrophy around the lesion, no obvious occupying effect and no peripheral cerebral edema. In some patients, arteriovenous malformations cannot be detected on plain scan, but contrast is injected to reveal the lesion. After contrast injection, the arteriovenous malformations in the brain show mass enhancement, and even tortuous vascular shadows, blood supplying arteries and draining veins are visible.