Sorry MJ, I’m not knowledgable enough regarding scans of arteries to comment, though I know the vertebral artery doesn’t follow a straight course, at the point you are indicating, it sort of hooks over the C1 bone and up and under the skull.
I notice one appears thicker than the other, though it’s difficult to tell on this scale. I was told it was common to see one vertebral artery thicker than the other too, when I questioned years after my fall, whether I had a ‘partially dissected’ left vertebral artery – so got no closer with that one either (though I had all the heavy bruising signs at the time of the accident!)
What did the radiologists written report of the scan say ? I’d get a copy of the written report, if you haven’t already.
Did you ever get any fundus photo’s done of your eyes because, as Dr Diana says, vascular structure, therefore general artery/vein condition and any associated abnormalities, can be seen more clearly in these vessels, just in case you have an overall blood vessel issue.