a radiologic technologist is someone who has completed a 2 yr program at a school that is approved by the ARRT www.arrt.org
They then sit for the board exam and work as a diagnostic tech or they can specialize in an advanced specialty. Radiation therapy is one of these specialties. It usually involves going back to school for another year in addition to the 2 yrs they've already gone through. radiation therapists work with oncologists and they are the ones that administer radiation treatments to cancer patients. it is a different environment than that of a radiology tech in that rad therapists see the same pt's over a certain period of time, while rad techs see a variety of patients, depending on where they are working. You can also check out www.asrt.org www.radiography.com
for more information. I am applying to a rad tech program myself, if you have more questions, feel free to PM me.