Evaluation of a photon-counting breast tomosynthesis imaging system

Abstract

Digital breast tomosynthesis promises solutions to many of the problems currently associated with projection mammography, including elimination of artifactual densities due to the superposition of normal tissues and increasing the conspicuity of true lesions that would otherwise be masked by superimposed normal tissue. We have investigated tomosynthesis using 45 photon counting, orientation sensitive, linear detectors which are precisely aligned with the focal spot of the x-ray source. The x-ray source and the digital detectors are scanned in a continuous motion across the object (patient); each linear detector collecting an image at a distinct angle. Simulations of the imaging system were performed to evaluate the effect of: (1) the range of angles over which projection images are acquired; and (2) the number of projection images acquired used in the tomosynthetic reconstruction. Two different simulations were evaluated; the first was a numerical simulation of a tungsten wire; the second consisted of tomosynthetic reconstructions of a cadaveric rabbit, in which the number and/or range of projection angles was varied. We have shown, analytically and through these simulations, that both the use of more projection angles and the use of a larger range of projection angles improve the image quality of tomosynthetic image reconstructions. The use of a photon-counting x-ray detector system allows us to consider image acquisition geometries with a large number of projection angles, as there is no additive detector noise to degrade the projection or reconstructed images. The maximum number of projection angles and the range of projections angles do have upper practical limits; the range of projection angles is determined predominantly by the detector element size.

Task-based assessment of breast tomosynthesis: Effect of acquisition parameters and quantum noisea)

“…This research found an increase in detectability with scan angle for all signal diameters greater than 500 m. Previous research found an improvement in depth resolution with increased scan angle. 15,18,41 Both results are equivalent because greater depth resolution results in higher signal contrast. This can be understood by considering the projections of a tomosynthesis volume acquired with different scan angles.…”

Task-based performance analysis of FBP, SART and ML for digital breast tomosynthesis using signal CNR and Channelised Hotelling Observers

“…The stationary case is the most common, but several prototype DBT systems have been built with a C-arm geometry as well (e.g. Ren et al, 2005;Maidment et al, 2005;Maidment et al, 2006). The present study is, to the best of our knowledge, the first in the DBT literature to present a direct comparison between the stationary and C-arm imaging geometries.…”

“…Such image normalisation is an important research area in itself (Tromans et al, 2008), and is beyond the scope of this paper. Following Zhou et al (2006), we assume attenuation coefficients at 30 keV, which is within the range reported in the literature (Wu et al, 2003;Ren et al, 2005;Bissonnette et al, 2005;Maidment et al, 2005;Maidment et al, 2006). We also assume an ideal photon-counting detector.…”

“…We also assume an ideal photon-counting detector. This is realistic since photoncounting detectors without electronic noise have already been developed for DBT (Maidment et al, 2005;Maidment et al, 2006). Conveniently, this avoids the complications of modelling an energy integrating detector.…”

Musculoskeletal imaging with a prototype photon-counting detector

“…In order to improve contrast at reduced doses, photoncounting detectors have been considered in the search for alternatives to the conventional X-ray detectors used in radiography and CT [3][4][5].…”