After you've interviewed at MOST radiology programs, if you let them know in February that you really want to go there, I bet your odds of matching are 50% or better.
The programs interview 10 applicants for every spot in part because they have to. Remember: most applicants go on 10+ interviews. If the program interviews fewer applicants, they might end up with open spots for the scramble.
Also, most programs go roughly 1/4 to 1/3 of the way down their rank order list before the program fills, so your odds on that basis alone are roughly 25 - 33%. If you let the program know that they're your #1, there's a good chance you'll be ranked in the top 1/4 to 1/3. They don't want to fill their program with folks who would really rather be elsewhere -- spouse lives 10 hours away, applicant hates the city, whatever.
Obviously here I'm talking about MOST programs. As you get into the top 30 and especially into the top 10 in terms of competitiveness, you might tell them they're your #1, they might rank you in their top 1/4 or even 1/5, and you might still not match.
Hope that relieves some anxiety -- unless you absolutely HAVE to go to a UCSF type program.
Good luck!