Proceedings Article | 19 March 2010
KEYWORDS: Digital breast tomosynthesis, Signal to noise ratio, Sensors, Breast, Polymethylmethacrylate, Breast imaging, Tissues, Control systems, Spherical lenses, Tomography
As a collaborative effort between scientists affiliated with the American Association of Physicists in Medicine
(AAPM) and the European reference center for breast cancer screening and diagnosis (EUREF), the Working Group
on Phantoms for Breast Imaging (WGPBI) aims to develop phantoms and evaluation techniques for 2D & 3D breast
imaging modalities. In the first phase of this collaboration, this project aimed to develop a phantom and associated
procedure for constancy testing of digital breast tomosynthesis (DBT) systems. The procedure involves daily and
weekly components. The daily evaluation is performed on a simple, homogenous PMMA plate of 4 cm thickness. For
the weekly part, a new phantom has been designed consisting of a 45 mm thick homogeneous slab of PMMA with a
set of spherical and rectangular inserts at specific 3D positions, and a thin wire positioned at a small angle to the plane
of the detector. Quality control parameters are extracted from both projection images (if available) and reconstructed
planes. The homogeneous phantom for daily QC allows a trend analysis of homogeneity and the assessment of
detector artifacts. With the proposed phantom concept for weekly QC, the stability of the following parameters can be
evaluated: the propagation and correlation of the noise in plane and across the reconstructed tomographic planes, lag,
signal difference to noise ratio (SDNR) and signal to noise ratio (SNR), the geometry and the motion, effective
thickness of the reconstructed planes, homogeneity, distance accuracy, frequency dependent SNR, and artifacts.
Analysis of the DICOM header provides information on the stability of the automatic exposure control (AEC),
exposure settings, and several system parameters. In an on-going study, the proposed strategy is being applied to five
tomosynthesis systems both in Europe and in the US. In this paper we report on the specifics of the phantom, the QC
procedure, the practicalities of remote data analysis, and the results of the initial trial.
