Hcpcs q code

Can anyone help me understand what the difference is between Q9960 and Q9966 and what CPT procedures would be billed with Q9966

Q9960 is HIGH osmolar contrast, Q9966 is LOW osmolar contrast material.

These are generally used with CTs, but may be used with other exams also.

High osmolar contrast materials are generally not paid separately (definitely not by Medicare), but Low osmolar is paid separately for offices and imaging centers, packaged for hospitals under OPPS.