Geometrical Relationship Estimation Between X-ray Source and Detector for Mobile Tomosynthesis

Mobile X-ray imaging is used in various applications in the clinical field. Tomosynthesis, which enables a tomogram to be reconstructed, can improve the diagnostic ability in comparison to an X-ray radiograph. In mobile X-ray imaging, there are no restrictions on the geometric relationship between the X-ray source and the detector; however, the geometric relationship is an essential factor for image reconstruction. In this study, we propose a novel method of estimating this geometric relationship during tomosynthesis scanning. In the proposed method, a marker panel consisting of a panel and four markers was attached to the detector. The proposed method has three steps for performing mobile tomosynthesis: estimation of the marker positions; estimation of the X-ray source position; and image reconstruction. In this study, we quantitatively evaluated the proposed method in a numerical simulation and examined whether it could be performed under conditions close to a clinical setting. In numerical simulations, the mean marker estimation error was 0.021 mm. The mean X-ray source estimation errors were approximately 3 mm in the xz plane and 12 mm in the y direction. The normalized root mean squared error of the reconstructed image was 10% in numerical simulation and the tomosynthesis image could also be reconstructed in X-ray experiments using the proposed mobile tomosynthesis method. In this study, we proposed a novel method for estimating the geometric relationship between the X-ray source and the detector during tomosynthesis scanning and suggested its clinical usefulness.