I will describe how it was when I was a resident.
I spent a little over 3 years in the program.
We rotated through various disciplines: GI (gastrointestinal), cardiovascular, chest (chest x-rays, would now include chest CT scans), pediatrics, mammography, bones, etc.
You would spend your entire day in one particular field of endeavor.
I imagine residency programs are somewhat similar now in that regard.
But add CT and MRI (including MRI of the breast) and PET scanning.
Also interventional radiology.
I think most radiology residency programs are now 4 years.