A dual-axis tilt acquisition geometry for digital musculoskeletal tomosynthesis

Digital tomosynthesis (DT) is a limited angle tomographic x-ray technique. It is an attractive low-dose alternative to computed tomography (CT) in many imaging applications. However, the DT dataset is incomplete, which leads to out-of-focus artifacts and limited axial resolution. In this paper, a novel dual-axis tilt acquisition geometry is proposed and evaluated. This geometry solves some issues in tomosynthesis with the traditional scanning geometry by scanning the object with a set of perpendicular arcs. In this geometry the acquisition in the additional perpendicular direction is done using a tiltable object supporting platform. The proposed geometry allows for capturing more singularities of the Radon transform, filling the Fourier space with more data and better approximating the Tuy-Smith conditions. In order to evaluate the proposed system, several studies have been carried out. To validate the simulation setup the performance of the traditional scanning geometry has been simulated and compared to known results from the literature. It has also been shown that the possible improvement of the image quality in the traditional geometry is limited. These limitations can be partially overcome by using the proposed dual-axis tilt geometry. The novel geometry is superior and with the same number of projections better reconstructed images can be obtained. All studies have been made using a software tomosynthesis simulator. A micro-CT reconstruction of a bone has been used as a software phantom. Simultaneous algebraic reconstruction has been used to reconstruct simulated projections. As a conclusion, acquiring data outside the standard arc allows for improving performance of musculoskeletal tomosynthesis. With the proposed dual-axis acquisition geometry a performance gain is achieved without an increase in dose and major modifications to the instrumentation of existing tomosynthesis devices.