There's a line in my mri results that I can't decipher.

"grossly patent-appearing flow-voids are identified in the visualized portions of the intracranial carotid and vertebrobasilar systems."

if the flow voids are patent, is that a good thing or a bad thing? Is there such a thing as a "good" flow void? I've surfed the web for hours and I can't find any answers...Please help!