A Novel Multi-direction Adjustment Strategy for Reducing Ghost Artifact in Body Tomosynthesis

Digital tomosynthesis (DT) reduces tissue overlap and provides tomographic images of high quality with clinically acceptable low radiation dose, it begins to be recognized as an essential diagnostic tool. The scanning direction and model are more flexible in DT. However, scanning parameters of DT are not easy to be determined. In this study, we investigated the effect of dual direction scanning on artifact improvement and the optimization of scanning parameters using the INER Prototype Tomosynthesis scanner. The line-pair shape phantom with 2, 3, 5, 8, 10, 15 mm line widths and 5 mm thickness was used. The projections were acquired with 31 views over a 15° angular range in HF (Head-Foot) direction and RL (Right-left) direction, respectively. 3D images were reconstructed with ML-EM algorithm to evaluate the spread range of ghost artifact with various sweep methods (HF, RL and Dual) and object sizes. Moreover, the projection number ratios (PNR) in dual directions were also evaluated for the influence on artifacts. Under single direction sweep (HF or RL), the spread range was wide when the sweep direction paralleled with the shape direction of object (SDO); the spread range was narrow when the sweep direction is perpendicular to the SDO. The spread range of dual scan was unaffected by the SDO. The PNR in dual directions revealed a similar trend to single direction sweep when the ratio is not equal to one. Based on the above experimental results, we proposed a novel multi-direction adjustment strategy for body tomosynthesis. For the default scanning, the user should choose the isotropic dual direction scan (PNR = 1). After preview, the advanced process can use different PNR depending on the anatomy of interest to improve diagnostic image quality to reduce ghost artifact and distortion.