Geometry calibration between X-ray source and detector for tomosynthesis with a portable X-ray system

Abstract

PurposeTomosynthesis is attracting attention as a low-dose tomography technology compared with X-ray CT. However, conventional tomosynthesis imaging devices are large and stationary. Furthermore, there is a limitation in the working range of the X-ray source during image acquisition. We have previously proposed the use of a portable X-ray device for tomosynthesis that can be used for ward rounds and emergency medicine. The weight of this device can be reduced by using a flat panel detector (FPD), and flexibility is realized by the free placement of the X-ray source and FPD. Tomosynthesis using a portable X-ray device requires calibration of the geometry between the X-ray source and detector at each image acquisition. We propose a method for geometry calibration and demonstrate tomosynthesis image reconstruction by this method.MethodsAn image processing-based calibration method using an asymmetric and multilayered calibration object (AMCO) is presented. Since the AMCO is always attached to the X-ray source housing for geometry calibration, the additional setting of a calibration object or marker around or on the patients is not required. The AMCO’s multilayer structure improves the calibration accuracy, especially in the out-of-plane direction.ResultsTwo experiments were conducted. The first was performed to evaluate the calibration accuracy using an XY positioning stage and a gonio stage. As a result, an accuracy of approximately 1 mm was achieved both in the in-plane and out-of-plane directions. An angular accuracy of approximately was confirmed. The second experiment was conducted to evaluate the reconstructed image using a foot model phantom. Only the sagittal plane could be clearly observed with the proposed method.ConclusionWe proposed a tomosynthesis imaging system using a portable X-ray device. From the experimental results, the proposed method could provide sufficient calibration accuracy and a clear sagittal plane of the reconstructed tomosynthesis image.

Self-Determined Shot Geometry for Open-Configuration Portable X-Ray CT

“…The error for the transverse detector position and the rotation error are comparable to those reported in Ref. [20] and much better than Ref. [12].…”

“…Thus, one may reproject a 3D model of the reference constellation for final optimization. Results show that when this process is performed, the geometric error is satisfactorily low, which is close to the geometric error of tomosynthesis [20].…”

“…However, for the open configuration CT system described here, placing large constellations in every x-ray shot will interfere with the inspection of the region of interest. The closest geometric calibration technique available in literature uses a large cuboid reference constellation for one step of the geometric calibration and depends upon mechanical repeatability thereafter [20]. As a result, it fails to address the requirements for open-configuration portable CT.…”

Geometrical Calibration of a 2.5D Periapical Radiography System

“…However, methods proposed by previous scholars cannot be effectively applied to the 2.5D Periapical Radiography System because of the system's small sensor size and the sensor being too close to the object. Therefore, such previous methods [18][19][20][21][22][23] are unsuitable for the geometric calibration of the proposed system. This study proposes an approach for the geometrical calibration of hardware component positioning that is suitable for digital tomosynthesis using small-area sensors with an extremely short distance between the sensor and object.…”