Has anyone heard of or had interoperative radiation?

My 63-year old brother finished 37 treatments of radiation, plus chemo for his Stage IV Tongue Cancer. He is six weeks out of treatment and a biopsy recently revealed a cancerous growth beneath his chin. Apparently this proposed procedure is to zap him with radiation during surgery.(I already thought he had his lifetime maximum--but I guess this is very specifically directed.)

I have posted elsewhere in this forum about his unwillingness to seek another opinion. So that is now out of the question.

Can anyone offer me any insight about this treatment? What to expect afterwards, how effective is it?

I am so grateful for all the information this site has provided--I feel as though I know many of you.
God bless.

M.