A geometrical calibration method by using only two small balls for X-ray intraoral digital tomosynthesis

The X-ray tomosynthesis technique has become a popular clinical imaging in clinical imaging modality, such as the breast and lung tomosynthesis. For high quality image reconstruction, it is essential to know the accurate geometric definitions of the scanning system which are referred to the relative positions between the focal spot of the x-ray tube and the center of the detector. Some methods have reported to measure or calibrate the geometric parameters of the tomosynthesis and CT. However, most of these methods needed complicated calibration phantoms and were not available for real-time calibration during patient scanning. This paper focuses on the geometrical calibration problem for X-ray intraoral digital tomosynthesis where the X-ray tube moves along the straight line or arc, and the flat-panel detector and the object stay static. A new calibration method is presented which only uses two positioning balls at least locating in the plane parallel to the detector. With three preconditions or prior information, all of the X-ray source positions can be calculated. It is easy to use and also suitable for other tomosynthesis applications like breast tomosynthesis. The results of the numerical simulation validate this calibration method.