Please see the current National Correct Coding Initiative Policy Manual for Medicare Services. I have an extraction from the 2013 edition where it states that CPT codes 76942, 77002, 77003, 77012 and 77021 radiologic guidance are "allowed one unit of service for a single patient encounter regardless of the number of needle placements performed. The unit of service for these codes is the patient encounter, not number of lesions, number of aspirations, number of biopsies, number of injections, or number of localizations."
Awhile back there was discussion as to the implementation of modifier GD to override the MUE's, but our medicare contractor NGS does not recognize this modifier. I'm not sure if ANY contractor recognizes it. Wish this would be addressed again.
As far as the commericial carriers are concerned you'll have to do your research as to how they want or even accept multiple units billed. Depends on the payor.