from istanbul to houston need your help (Houston)

hi all local and who live there as a foreigner ,ı need yur help ,I am radiation therapist in turkey for 7 yeasr,I have been houston 3 times in houston at md anderson cancer enter and I looked there a job but they told me you can not work wiht your turkish degree here ,do you know how could I work there like prosedure there do I need to go universty again or just a few months only cours,pleas I need your advice what should I do

thnxs alot

dear fırat