I tried emailing but you don't list an email address.
This is someone I know, his brother is my best friend. He's "hot crap" and at Mass General, right by you.www.massgeneral.org/radiationoncology/doctors/doctor.aspx?id=16736
As you can see from his resume he is Medical Director, Francis H. Burr Proton Therapy Center
Co-Director, Center for Sarcoma and Connective Tissue Oncology and lists Brachytherapy as one of his interests.
He wouldn't be the guy to treat you given his specialty, but given his role at Mass General, and his expertise in BT he could certainly steer you in the right direction of at least getting an opinion.
I've already put in a call. He's just waiting for an email with your name and situation should you be interested. If you are, ask the mods for my email and email me so I can make the introductions.
You're really going to be fine.