With a lowish psa score like yours and a Gleason sore of 6 I'd be putting off radiation and settling on surveillance with an mri my first thing. MRIs are so informative - an mri showed my lesions and where they were.
Shop around clinics and tell them of your claustrophobia and what options there are. There's all kinds of sedation from light to that heavy where you won't know what planet you're on
I'm sure there'll be one that'll work for you.
I'd be avoiding radiation myself as long as possible as side effects are a roll of a dice. Your doc was right in that sometimes psa levels don't tell all the story so it's always a hard and personal decision on what to do.