Most college graduates are 22 years old.
If you go straight to medical school, you will graduate at age 26.
Radiology is a 5 year residency, leaving you at age 31 when you finish.
The majority of residents do a fellowship which the majority are 1 year long, making you 32 years old when you are finally "on your own".
The above scenerio is the "fastest" way to get there. There are plenty of people out there that are older than age 32 when they finish for a number of different reasons.
The length of your career is really up to you. I guess it's conceivable to live frugally, work crazy hours and comfortably retire in 10 years. Most people will likely work between 20 and 30 years.