2393 - Development of a Time-Weighted Technique to Improve the Accuracy of Amplitude-Based 4D-CT in Lung Cancer Radiotherapy
Presenter(s)
J. Joo1, B. Cho2, H. Jeon3, D. W. Kim3, O. K. Noh4, W. Choi5, H. U. Je6, and S. Y. Song2; 1Department of Radiation Oncology, Pusan National University School of Medicine, Pusan National University Yangsan Hospital, Yangsan, Korea, Republic of (South), 2Department of Radiation Oncology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea, Republic of (South), 3Department of Radiation Oncology, Pusan National University Yangsan Hospital, Yangsan, Korea, Republic of (South), 4Department of Radiation Oncology, Ajou University School of Medicine, Suwon, Korea, Republic of (South), 5Department of Radiation Oncology, Gangneung Asan Hospital, University of Ulsan College of Medicine, Gangneung, Korea, Republic of (South), 6Department of Radiation Oncology, Ulsan University Hospital, Ulsan, Korea, Republic of (South)
Purpose/Objective(s): This study investigated the impact of respiratory motion on the accuracy of four-dimensional computed tomography (4D-CT) imaging in lung cancer radiotherapy and proposed a novel time-weighted amplitude-based method. We hypothesize that integrating time-weighted techniques into amplitude-based 4D-CT reconstruction improves tumor motion representation and enhances treatment planning accuracy.
Materials/Methods: Irregular breathing waveforms (amplitude, period, and mixed irregularities) were generated using a respiratory motion phantom. 4D-CT images were reconstructed using amplitude- and phase-based methods, and tumor volume and shape accuracy were analyzed. A time-weighted amplitude-based intensity projection (Tw_amp_IP) image was developed by integrating the respiratory occupancy data into the amplitude-based reconstruction. The performance of Tw_amp_IP was compared with that of amplitude-based average intensity projection (amp_AIP) images, and gamma pass rate testing was conducted using phase-based AIP (phase_AIP) as a reference.
Results: Phase-based reconstruction revealed substantial tumor volume and shape distortions under irregular breathing conditions with amplitude or period variations. Amplitude-based reconstruction provided consistent tumor volume and shape errors within 5% under period irregularities, but exhibited distortions with amplitude irregularities. Tw_amp_IP demonstrated superior performance compared to amp_AIP, achieving higher gamma pass rates under all respiratory conditions. For the 2%/2 mm gamma criterion, the pass rates were 0.733 vs. 0.822 (p=0.001) for the Sin condition, 0.644 vs. 0.814 (p<0.001) for the Sin4 condition, and 0.547 vs. 0.760 (p=0.001) for the Sin6 condition.
Conclusion: Amplitude-based 4D-CT reconstruction accurately captured tumor size and position under periodic irregularities, outperforming phase-based reconstruction. The integration of time-weighted techniques into amplitude-based CT effectively accounted for respiratory motion, demonstrating the potential of Tw_amp_IP to improve dose calculation precision in radiotherapy. Future research should explore the clinical implementation of Tw_amp_IP in adaptive radiotherapy workflows.