Bring in a plan from a TPS and a film irradiated to that plan, and compare them using Van Dyk's criteria, the most critical of the tests for an IMRT system because it verifies the patient exposure on a pixel by pixel basis. You can view histograms or pixel images for any of the gradiant/dose combinations.

Van Dyk, J., Barnett, R., Cygler, J, and Shragge, P., "Commissioning and Quality Assurance of Treatment Planning Computers," Int. Journal Radiation Oncology, Biol. Phys., 26, pp 261-273, 1003.