Compression forces used in the Norwegian Breast Cancer Screening Program.

OBJECTIVE: Compression is used in mammography to reduce breast thickness, which is claimed to improve image quality and reduce radiation dose. In the Norwegian Breast Cancer Screening Program (NBCSP), the recommended range of compression force for full-field digital mammography (FFDM) is 11-18 kg (108-177 N). This is the first study to investigate the compression force used in the programme.

METHODS: The study included information from 17,951 randomly selected females screened with FFDM at 14 breast centres in the NBCSP, during January-March 2014. We investigated the applied compression force on the left breast in craniocaudal and mediolateral oblique views for breast centres, mammography machines within the breast centres and for the radiographers.

RESULTS: The mean compression force for all mammograms in the study was 116 N and ranged from 91 N to 147 N between the breast centres. The variation in compression force was wider between the breast centres than that between mammography machines (range 137-155 N) and radiographers (95-143 N) within one breast centre. Approximately 59% of the mammograms in the study complied with the recommended range of compression force.

CONCLUSION: A wide variation in applied compression force was observed between the breast centres in the NBCSP. This variation indicates a need for evidence-based recommendations for compression force aimed at optimizing the image quality and individualizing breast compression. Advances in knowledge: There was a wide variation in applied compression force between the breast centres in the NBCSP. The variation was wider between the breast centres than that between mammography machines and radiographers within one breast centre.