Realistic compressed breast phantoms for medical physics applications

Anthropomorphic digital breast phantoms are an essential part in the development, simulation, and optimisation of x-ray breast imaging systems. They could be used in many applications, such as running virtual clinical trials or developing dosimetry methods. 3D image modalities, such as breast computed tomography (BCT), provide high resolution images to help produce breast models with realistic internal tissue distribution. However, in order to mimic X-ray imaging procedures such as mammography or digital breast tomosynthesis, the breast model needs to be compressed. In this work, we describe a method to generate compressed breast phantoms using a biomechanical finite element (FE) model from BCT volumes, by simulating physically realistic tissue deformation. Unlike prior literature, we propose a new tissue interpolation methodology which avoids interpolating the deformation fields, resulting in the preservation of the breast tissue amount during the compression process and therefore increasing the accuracy of the deformation. In this study, a total of 88 BCT images were compressed in order to obtain a set of realistic phantoms. The information associated with the phantom (i.e. amount of glandular tissue and adipose tissue and total breast volume) is compared before and after compression (showing a correlation R of 0.99). Also, the same metrics were evaluated between compressed phantoms and Volpara (TM) measurements from breast tomosynthesis images (R=0.81-0.85). Furthermore, we include a 3D surface analysis and describe several medical physics applications in which our phantoms have been used. x-ray dosimetry, scattered radiation estimation or glandular tissue assessment.