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Principles, technique and equipment

Full field digital mammography (FFDM) offers potential improvements over the limitations of screen film mammography (SFM). While film acts both as the detector and display medium for the breast, a digital technique can separate these two functions with the possibility of maximizing the performance of each independently.

Digital detectors create an electronic image of the structure radiographed as picture elements or pixels. Detectors used are typically amorphous silicon flat panels, charge-coupled devices (CCDs), or amorphous selenium.

The various approaches that have been taken to develop FFDM systems include slot scanning with indirect capture utilizing a moving row of CCDs in order to achieve the full breast coverage, flat panel designs with both direct or indirect image capture and photo-stimulable phosphor plates.

Clinical FFDM

Lewin and colleagues conducted the first blinded prospective study comparing SFM to FFDM. The recall rate for FFDM was less than SFM (P < 0.001), with fewer patients sent to biopsy but with no significant difference in cancer detection. It thus appears from this study that FFDM was more effective for detecting malignancy than SFM, sending fewer women to biopsy for a similar yield of malignancy. Two other trials were also reported on SFM and FFDM in a screening situation. The Oslo I trial did not demonstrate a significant difference in cancer detection and the recall rate was 4.6% for FFDM and 3.5% for SFM. This difference was not significant. A second trial, the Oslo II study, demonstrated that the recall rates were statistically higher for FFDM than SFM. The ACRIN DMIST trial demonstrated a significant difference in favor of a digital technique for women under 50, for women with dense breasts and for premenopausal and perimenopausal women.

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