Assessment of full field digital mammography (FFDM) detected microcalcification is not hindered by low spatial resolution

Background

Full field digital mammography (FFDM) seems set to replace conventional film-screen technique. Concern has been raised over FFDM diminished spatial resolution (5–6 Ip/mm). If valid, this could compromise detection of calcification and diagnosis of ductal carcinoma in situ (DCIS). However, in our centre we were not able to perceive any difference between microfocus magnification and on-screen magnification when assessing microcalcification.

Aim

To evaluate replacement of analogue microfocus technique by on-screen digital magnification for microcalcification, and to analyse the relative importance of spatial resolution versus contrast detail test scores.

Methods

We performed phantom image quality testing on our digital unit (GE 2000D), using the TORMAX and TORMAM phantoms. We subsequently compared these results with average scores for over 90 film-screen mammography systems.

Results

Although our digital unit had a lower spatial resolution (6–7 Ip/mm) than the film-screen systems (up to 15 Ip/mm), both TORMAX and TORMAM scores were superior for digital soft-copy reporting compared to hard-copy reporting, film-screen technique and analogue microfocus magnification.

Conclusion

Despite lower spatial resolution, the superior contrast and image manipulation abilities of FFDM obviate the need for conventional microfocus magnification in the radiographic work up of microcalcifications. Sufficient information is provided on FFDM upon which to base a decision to proceed to diagnostic interventional procedures such as core biopsy or mammotome excision.