Impact of the digitalisation of mammography on performance parameters and breast dose in the Flemish Breast Cancer Screening Programme.

OBJECTIVES: To investigate the impact of digitalisation on performance parameters and breast dose of the Flemish Breast Cancer Screening Programme. Both computed (CR) and direct radiography (DR) are compared with screen-film mammography (SFM). METHODS: Data from 975,673 mammographic examinations were collected from units which underwent digitalisation from SFM to CR (41 units) or DR (72 units) in the period 2005-2011. Performance indicators were obtained by consulting the Screening Programme database. Phantom and patient dosimetry data were acquired from the physical technical quality assurance of the programme. RESULTS: Digitalisation induced no significant change in cancer detection rate (CDR), percentage of ductal carcinomas in situ and percentage of breast cancers smaller than 1 cm. A decrease in false-positive results and third readings was observed, which was a time-related observation. After digitalisation, positive predictive value (PPV) increased and recall rates decreased. Compared with SFM, an increase of 30% in mean glandular dose (MGD) was found for CR, while a similar change in the opposite direction was found for DR. CONCLUSIONS: No major differences in performance parameters after digitalisation were found. Transition of SFM to CR resulted in a higher MGD and associated lower detection-over-induction ratio (DIR), while the change to DR induced an improvement of DIR. KEY POINTS: • Performance parameters showed no major differences after digitalisation to CR or DR. • Transition from SFM to CR results in a higher mean glandular dose. • Transition from SFM to DR results in a lower mean glandular dose.

Technical and clinical breast cancer screening performance indicators for computed radiography versus direct digital radiography.

OBJECTIVES: To compare technical and clinical screening performance parameters between computed radiography (CR) and direct digital radiography (DR) systems. METHODS: The number of women screened with CR was 73,008 and with DR 116,945. Technical and patient dose survey data of 25 CR and 37 DR systems were available. Technical performance was expressed by threshold thickness values at the mean glandular dose (MGD) level of routine practice. Clinical indicators included recall rate (RR), cancer detection rate (CDR), percentage of ductal carcinoma in situ (DCIS), percentage of cancers with T-scores smaller than 1 cm and positive predictive value (PPV). RESULTS: Contrast threshold values for the 0.1-mm gold disk were 1.44 µm (SD 0.13 µm) for CR and 1.20 µm (SD 0.13 µm for DR). MGD was 2.16 mGy (SD 0.36 mGy) and 1.35 mGy (SD 0.32 mGy) for CR and DR respectively. We obtained for CR, respectively DR, the following results: RR in the first round of 5.48 % versus 5.61 %; RR in subsequent rounds of 2.52 % versus 2.65 %; CDR of 0.52 % versus 0.53 %; DCIS of 0.08 % versus 0.11 %; a rate of cancers with T-scores smaller than 1 cm of 0.11 % versus 0.11 %; PPV of 18.45 % versus 18.64 %; none of them was significantly different. CONCLUSION: Our screening indicators are reassuring for the use of CR and DR, with CR operating at 60 % higher MGD. KEY POINTS: • Breast cancer screening can employ both computed (CR) and direct digital radiography (DR). • Screening performance parameters for CR and DR technology are not significantly different. • Screening parameters are in accordance with European Guidelines. • Radiation doses employed for CR are generally 60 % greater than for DR.