200 million proton beam expansion proton beam therapy system 200 million proton beam expansion proton beam facility construction radiation oncology clinical cal proton beam therapy program mayo clinic proton therapy installation mayo clinic proton therapy installation mayo s proton beam therapy adds to hitachi proton beam therapy coming to mayo clinic s proton therapy project charged particle therapy proton beam centers sprout despite mayo clinic proton beam center proton beam facility construction mayo clinic rochester minnesota 233 million oncology building mayo clinic practical proton therapy proton beam therapy services mayo clinic proton beam center mayo clinic practical proton therapy mayo clinic practical proton therapy proton beam treatment at mayo clinic