Simultaneous calibration phantom commission and geometry calibration in cone beam CT

Area of Science:

• Medical Imaging
• Computed Tomography
• Geometric Calibration

Background:

• Cone beam computed tomography (CBCT) requires precise geometry calibration for accurate image reconstruction.
• Current methods separate phantom calibration and geometry calibration, making them susceptible to errors from ball-bearing positioning inaccuracies.
• These errors significantly degrade the quality of phantom calibration and subsequent CBCT reconstruction.

Purpose of the Study:

• To develop an integrated method for simultaneous geometry phantom commission and geometry calibration in CBCT systems.
• To overcome the limitations of independent calibration tasks and improve the accuracy of CBCT geometry determination.
• To enhance the overall quality and reliability of CBCT imaging.

Main Methods:

• An integrated workflow was proposed, treating ball-bearing (BB) centers as optimized parameters rather than assuming phantom accuracy.
• An evaluation phantom and contrast index were used to assess geometry artifacts and optimize BB coordinates.
• Particle swarm optimization was employed to simultaneously calibrate CBCT geometry and BB coordinates.

Main Results:

• The integrated method achieved accurate calibration of CBCT geometry and BB coordinates.
• Qualitative and quantitative evaluations on simulated and real CBCT data demonstrated the method's effectiveness.
• Reconstructed images using dental CBCT achieved a spatial resolution of up to 15 line pair cm⁻¹.
• The proposed method outperformed the Wiesent method in experimental comparisons.

Conclusions:

• The proposed integrated method enables simultaneous and accurate geometry phantom commission and geometry calibration.
• This approach offers a more robust and efficient solution for CBCT system calibration.
• The method is suitable for direct application in other CBCT systems, improving calibration accuracy and image quality.