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A Practical CBCT Calibration Method Using Simplified Phantom
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DOI：10.1109/TIM.2026.3665963.png)
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Abstract
En 中文
This article presents an extended direct linear transform (DLT) method for cone-beam computed tomography (CBCT) calibration with circular trajectory, utilizing a simplified phantom with fiducial markers arranged in a straight line. CBCT is a widely used imaging modality in both clinical and research applications. The calibration is essential for obtaining precise geometric parameters, which are crucial for the high quality of 3-D reconstructed images. However, the accuracy of most phantom-based CBCT calibration methods is highly dependent on the spatial precision of the fiducial markers. Previous calibration phantoms with 3-D fiducial arrangements are specifically fabricated and measured with high-precision standards, which are difficult to achieve. A simple line-beads phantom is cost-effective due to its ease of fabrication and implementation, but it presents new challenges arising from the unknown 3-D positions of the fiducial markers. To address these issues, this study proposed an extended DLT to transform the original nonlinear problem into a linear one solvable by the least-squares method. Then, the inverse of this transform is developed to recover the geometric parameters of the CBCT system and the spatial positions of fiducial markers from the least-squares solution. This calibration framework provides an analytical solution for the full set of geometric parameters of the CBCT system. Both simulation and hardware experimental results demonstrate the effectiveness of this method. Compared to the existing methods, the proposed method demonstrates greater robustness to errors in the extracted centroids of projected fiducial markers, with the resulting calibration achieving more accurate target localization and consistently stable reconstruction quality.
Keywords:
Analytical solution
cone-beam computed tomography (CBCT) calibration
direct linear transform (DLT)
medical measurement
surgical robot
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