The term mammographic modality refers to a technology for radiography of the breast. 21 C.F.R. 900.2(z) Examples of long available mammographic modalities are screen-film mammography and xeromammography. An example of a relatively new mammographic modality is full field digital mammography (FFDM). Personnel whose training pertained solely to screen-film mammography would be required to obtain 8 hours of training in FFDM, if they are to begin providing services or interpretations using this modality after April 28, 1999. However, if those personnel gained their experience using investigational FFDM units (units that were used for research purposes before being approved by FDA for commercial distribution), they are considered to have met the 8 hour requirement. New mammographic modality training can be in many forms, including, but not limited to, professional training, special training courses, continuing medical education, and training provided by the manufacturer.