Repeat examinations advised by Radiologists-how much do they contribute to the bulk??

According to a recent article in Radiology. 2007 Mar;242(3):857-64,

From 1997 to mid-2003, MR imaging and CT repeat rates increased (0.71% per year and 1.87% per year respectively). Repeat examinations account for nearly one-third of high-cost radiology examinations and represent an increasing proportion of such examinations. Most repeat examinations are initiated clinically without a recommendation by a radiologist.

Article entitled-

Does radiologist recommendation for follow-up with the same imaging modality contribute substantially to high-cost imaging volume?

Radiology 2007 Mar;242(3):857-64.