The user s manual or i nst r uct i on manual f or an i nt ent i onal or uni nt ent i onal r adi at or shal l caut i on t he user t hat changes or modi f i cat i ons not expr essl y appr oved by t he par t y r esponsi bl e f or compl i ance coul d voi d t he user ’ s aut hor i t y t o oper at e t he equi pment .