Comparison of film screen, computed radiography and direct digital mammography in the Southern Derby screening programme

Introduction

Our screening programme has been fully digital since April 2009 and utilises a combination of computed radiography (CR) (Fuji Profect) and three direct digital mammography (DDM) mammographic systems (Fuji Amulet, GE DS and GE Essential). This study compares the performance of our CR and DDM systems against film screen (FS) mammography in a real-life screening environment.

Methods

Southern Derbyshire screening episodes between April 2007 and April 2010 were interrogated on NBSS using a Crystal report. Recall and cancer detection rates were collected according to mammography type. Data were analysed for significance using the chi-squared test.

Results

A total of 66,989 screening episodes were recorded, 22,039 FS (recall rate 3.23%, cancer detection 8.08/1,000), 30,739 CR (recall rate 2.73%, cancer detection 7.87/1,000) and 14,157 DDM (recall rate 3.87%, cancer detection 9.89/1,000). Recall rates compared with FS were statistically significantly different for CR (P = 0.0007) and DDM (P = 0.0016). Cancer detection rates compared with FS mammography were not significantly different for either CR (P = 0.833) or DDM (P = 0.081), although there was a significant difference found between CR and DDM (P = 0.035).

Conclusions

DDM in our programme has detected an increased number of cancers but at an increased recall rate. CR has detected a similar number of cancers as FS mammography at a lower recall rate and the study supports the use of CR in our programme. As an interim measure in changing to a fully DDM service it has allowed us to spread costs whilst adopting a single digital workflow, which is efficient and safe for our clients.