Long ago I remarked to our Chief Radiologist that I felt guilty "sitting" between cases or injections . . (I do find things to do, but still . . .)
He replied, "As long as you're here when we need you, that's the important thing."
Our IR is HOPPING!!
I work in Cath Lab (totally separate) but I visit there occasionally, to borrow a catheter or ask advice on a technicality. They're ALWAYS busy!! They have only two rooms and 5-6 staff (plus a Radiology Fellow, I believe).
At first, when learning the ropes, you certainly won't be bored.

You'll figure it out (procedures, time management, catch-up projects for down times, etc).