Performance studies of four-dimensional cone beam computed tomography

Area of Science:

• Medical Imaging
• Radiotherapy Physics
• Computational Imaging

Background:

• Four-dimensional cone beam computed tomography (4DCBCT) is crucial for characterizing tumor motion before radiotherapy.
• Image artifacts arise from data under-sampling during retrospective gating in 4DCBCT.
• Improving 4DCBCT image quality and motion accuracy is an ongoing research area.

Purpose of the Study:

• To evaluate the impact of data acquisition time and respiratory phase binning on 4DCBCT motion trajectory accuracy.
• To compare the performance of filtered backprojection (FBP), FBP with McKinnon-Bates correction (MB), and prior image constrained compressed sensing (PICCS) reconstruction algorithms in 4DCBCT.
• To determine optimal parameters for accurate tumor motion delineation in 4DCBCT.

Main Methods:

• Simulated 4DCBCT scans using a hybrid phantom with known 3D motion trajectories.
• Varying gantry rotation times (1-4 min) and phase bins (5, 10, 20) for data acquisition and sorting.
• Reconstruction using FBP, MB, and PICCS algorithms, followed by motion trajectory extraction via deformable registration.

Main Results:

• Increased acquisition time consistently improved motion trajectory accuracy across all tested methods.
• Utilizing 10 or more phase bins is essential for adequate temporal resolution in tumor motion tracking.
• PICCS and MB methods achieved comparable accuracy to FBP with significantly shorter acquisition times (1 min and 2 min, respectively).

Conclusions:

• Data acquisition time and the number of respiratory phase bins are critical factors for accurate 4DCBCT motion characterization.
• Advanced reconstruction algorithms like PICCS offer substantial improvements in efficiency and accuracy for 4DCBCT.
• These findings guide the optimization of 4DCBCT protocols for improved radiotherapy planning.