SIMULATING LOCAL DENSE AREAS USING PMMA TO ASSESS AUTOMATIC EXPOSURE CONTROL IN DIGITAL MAMMOGRAPHY

[Evaluation of AEC Performance for Stability of Image Quality in Local Dense Area in Mammography]

The local dense area (LDA) test is a test for evaluating the stability of image quality published in the EUREF fourth edition-supplements for local high-density areas. In this test, a small PMMA plate imitating LDA is placed on a rectangular PMMA, and the exposure conditions and SNR are evaluated when the thickness is changed. In this study, we replaced the rectangular PMMA with a D-shaped PMMA phantom-like breast. Then, we inserted an implant and a muscle phantom simulating the pectoral muscle and varied the distance from the edge of the chest wall to a small PMMA plate. In most of the tests, the SNR was stable as the thickness of the small PMMA plate increased as the exposure conditions increased. However, the SNR was not stable because the exposure conditions were not appropriate depending on the insertion distance of the muscle phantom and the position of the small PMMA plate.

Performance evaluation of digital breast tomosynthesis systems: physical methods and experimental data

Digital breast tomosynthesis (DBT) has become a well-established breast imaging technique, whose performance has been investigated in many clinical studies, including a number of prospective clinical trials. Results from these studies generally point to non-inferiority in terms of microcalcification detection and superior mass-lesion detection for DBT imaging compared to digital mammography (DM). This modality has become an essential tool in the clinic for assessment and ad-hoc screening but is not yet implemented in most breast screening programmes at a state or national level. While evidence on the clinical utility of DBT has been accumulating, there has also been progress in the development of methods for technical performance assessment and quality control of these imaging systems. DBT is a relatively complicated ‘pseudo-3D’ modality whose technical assessment poses a number of difficulties. This paper reviews methods for the technical performance assessment of DBT devices, starting at the component level in part one and leading up to discussion of system evaluation with physical test objects in part two. We provide some historical and basic theoretical perspective, often starting from methods developed for DM imaging. Data from a multi-vendor comparison are also included, acquired under the medical physics quality control protocol developed by EUREF and currently being consolidated by a European Federation of Organisations for Medical Physics working group. These data and associated methods can serve as a reference for the development of reference data and provide some context for clinical studies.