Total waste of your money. If for example the tumour size is the same, did it grow for a while before going down to the same size? Did it not change? The good folks at Colorado State University (one of the original places doing SRT) told me that it wasn't something they recommended. I just don't know what a rescan would tell them and more importantly, what they would do differently with that data, In the mean time, Buster would have to undergo anaesthesia, a long one again. With acros, I strongly recommend reducing anaesthesia to those medically necessary. I've seen too many have hidden acro heart conditions found during anaesthesia.
I do see that Buster is responding to the SRT and keeping you busy! In a good way. Look how much his dose has gone down.
I'd buy into blood work to make sure his T4 levels are OK, that should be tested every 3 months for a year after SRT as a small % of SRT kitties go hypothyroid after treatment.