Well, determining autism or not is a bit more nebulous than having before and after MRI's.
Given the supreme simplicity of hyperbaric treatment, one has to wonder why it isn't used more broadly. The equipment can't be all that expensive to acquire and operate.
Most likely the cost and the fact it's not proven to be effective. A friend had one session following back surgery that didn't turn out as expected. The cost to him was $145 and they said it could take up to 40 sessions........yea, right.