plainly put, it is physics applied to medicine, especially in the areas of medical imaging and radiotherapy. you will see mp's working is dosimetry or in programming algorithms for PET (positron emission topography) scans, MRIs and CTs. they can also train radiology techs, they monitor radiation exposure for health care providers as well as patients and may work with radiologists, oncologists and radiation therapists. i myself work with radiology picture, archiving and collection (PAC) systems. i did my graduate work at UT health science center and got certified in imaging informatics at the veterbi school of engineering at USC (it is an oline program by the way and is under the school of biomedical engineering). you probably have taken at least up to quantum physics and diff eq as well as some c++ classes so you can easily qualify for admission into a program.