Background: It is well known that hyperintense vessels (HV) on fluid-attenuated inversion recovery (FLAIR) image suggest slow collateral flow in case of large arterial occlusion. Multiphase CT angiography (CTA) is an imaging technique that provides time-resolved images of pial arteries. We analyzed the correlation of HVs on FLAIR image with collateral vessels on the different phases of multiphase CTA.
Methods: FLAIR images and multiphase CTA was analyzed in 7 patients with proximal MCA occlusion. We counted the number of discrete FLAIR HVs distal to the occlusion site and investigated whether the FLAIR HVs could be seen at the same area in different phases of multiphase CTA.
Results: The mean duration between symptom onset and acquisition of multiphase CTA was 5.6 hours and mean duration between CTA and MRI was 0.6 hour. A total 32 FLAIR HVs were observed in 7 patients. Of these, 13 HVs were observed in the 1st phase CTA, 25 HVs in the 2nd phase, and 26 HVs in the 3rd phase. Six HVs were not observed in all three phases of CTA.
Conclusions: In cases of acute proximal MCA occlusion, the collateral vessels shown as FLAIR HVs are more frequently observed in the late phase of multiphase CTA.
Fig 1. A 74-year-old man with acute occlusion of left middle cerebral artery. FLAIR image (A) shows 3 discrete HVs at left temporoparietal area. These FLAIR HVs are most clearly seen at 3rd phase contrast enhanced CTA (D) B, C: 1st and 2nd phase contrast enhanced CTA