Your major won’t impress medical school admissions committees. Students from quantitative fields–math, statistics, and physical sciences–perform best on the MCAT. Look up the data on the AAMC website if you’re that interested. Radiology is a speciality that one picks after medical school, and it is one of the most difficult ones to match into. You need to be interested in medicine in general, first–not be attached to one specific highly selective and difficult specialty–if you plan on a career in medicine. Moreover, medicine is something you learn in medical school (and beyond). Your undergraduate major is largely irrelevant.