Motion vector field phase-to-amplitude resampling for 4D motion-compensated cone-beam CT

Area of Science:

• Medical Imaging
• Image Reconstruction
• Computational Imaging

Background:

• Motion artifacts significantly degrade image quality in 4D cone-beam CT (CBCT) reconstructions.
• Conventional motion compensation (MoCo) methods, particularly phase-gating, struggle with irregular respiratory motion, leaving residual blurring.
• Accurate motion vector field (MVF) estimation is crucial for effective 4D CBCT but can be computationally intensive.

Purpose of the Study:

• To develop and validate a novel phase-to-amplitude resampling (PTAR) method for reducing motion blurring in 4D CBCT.
• To improve the image quality of MoCo 4D CBCT reconstructions, especially for irregular breathing patterns.
• To achieve these improvements without increasing the computational complexity of MVF estimation.

Main Methods:

• Proposed a phase-to-amplitude resampling (PTAR) technique integrating phase-gating with phase-adapted amplitude gating.
• Implemented MVF-resampling to ensure MVFs estimated on phase-gated data are valid for amplitude-gated reconstructions.
• Validated PTAR using a simulated deformed CT scan and patient data acquired on a TrueBeam imaging system.

Main Results:

• PTAR significantly reduced motion blurring around the diaphragm and in small lung structures in 4D CBCT images.
• Improved image sharpness was observed for both simulated and real patient data, confirmed by diaphragm sharpness quantification.
• PTAR demonstrated superior performance over conventional phase-gated MoCo, particularly for irregular respiratory motion.

Conclusions:

• PTAR effectively reduces motion blurring and enhances image quality in MoCo 4D CBCT reconstructions.
• The method improves robustness for CBCT imaging, especially with irregular breathing patterns.
• PTAR is computationally efficient and applicable to various imaging modalities beyond CBCT.