It is recommended that the phantom image evaluation test be performed using films from the box currently being used to produce clinical mammograms. If dedicated boxes of QC films are used for the phantom tests, the chance of detecting problems with the clinically used film is sacrificed.
FDA realizes that, due to differences in emulsion batches, a phantom image test with films from a new box may show variance in optical density and density difference greater than the allowed limits (when measured against the operating level established with films from the previous box). In such a case, facilities are advised to first check the whole imaging chain including the processor performance (facilities may wish to contact their medical physicist for help with this process). If no problems are detected, the facility may assume the change is due to different film emulsion batches. They may then adjust their typical clinical technique factors to meet the phantom optical density requirements.