I'm so sorry you are faced with this.
If my dog was 3 and I was faced with a situation where surgery had a high percentage of being successful and we had a good idea it was not invasive...I'd jump at the clinical study.
That said, this is of course an individual decision and you dont't owe anything to another dog or human.
If my older dog's time was limited, I'd want it to be about spending that time together, treats, short drives, icecream , naps in sunbeams etc ..
I would want it as clinical, strangers, needles/IV, anesthesia, scan, stress and discomfort free as possible.