From my one ear and 2 back mri's, yes they can go back and forth over the area that requires the scan.  I'm no radiologist, but I'm kinda assuming they do it as to make sure they get as clear a picture as they can. Saves having to recall you back because the pictures were of poor quality or they needed a different view. That would freak you out more or it would freak me out more if i got a recall letter to redo the scans. "What have they found", "why am i getting recalled when Doug from next door never" and so on.

Funnily enough, I over thought this particular thing too.  During each of my scans. Each time my scans came back fine other than a disc bulge.

You'll find yourself doing this a lot with other things. Reading waaay too much into why they're doing what they're doing, why they said what they did and so on. The reality is, they're saying and doing what they do because it's their job.

As for telling you you're fine, I've been told each and every time by the person doing the US scan or the doctor that comes in afterwards everything is fine from the US. The wife was told it looked like breast cancer so they do tell people good or bad. They know what they're looking for.  I had a lump on my arm.  Had an xray. Got told nothing. Had the US and was told on the spot it was a fatty lump. Nowt to worry about.  That was 10 years ago and I'm still here minus the lump that eventually disappeared.