Work

Toward real-time dose-guided radiation therapy: deformable multileaf collimator tracking using motion-model-derived volumetric images in lung and liver cancer patients

Year: 2025

Type: article

Abstract: Objective . Accurate dose delivery in the presence of anatomical motion and deformation remains a major challenge in radiation therapy. Real-time dose-guided radiation therapy addresses this challenge by integrating volumetric imaging, dose accumulation, and adaptive treatment in a quasi-continuous manner. Unlike previous studies limited to rigid motion or phantom data, this study employs a motion model to generate real-time volumetric images, enabling deformable dose-guided multileaf collimator (MLC) tracking in lung and liver cancer patients. Approach . Deformable dose-guided MLC tracking was simulated for ten patients (4 lung, 6 liver). The workflow included: (1) training a patient-specific linear regression-based motion model relating external respiratory signals (RPMs) to deformation vector fields using planning 4DCT data, (2) generating volumetric images using treatment RPM signals, (3) simulating dose-guided MLC tracking comparing deformable, rigid and no tracking, and (4) evaluating the motion model accuracy using fiducial markers and kV imaging. Dosimetric accuracy was assessed using 3D Gamma analysis ( 2 % / 2 mm ) and normalized root mean squared error by comparing simulated delivered dose to a motion-compensated baseline. Motion model error was quantified as the distance between predicted and ground truth marker positions. Main results . Deformable tracking significantly outperformed rigid and no tracking ( p < 0.001 ), achieving a mean Gamma passing rate of 95.0 ± 6.0 % , compared to 86.3 ± 10.0 % and 74.8 ± 15.2 % , respectively. Lung patients showed a greater benefit in Gamma passing rate (deformable: 98 % vs rigid: 85 % , ±13%) than liver patients ( 93 % vs 89 % , + 4 % ). The dosimetric benefit correlated with respiratory amplitude, with larger motion yielding greater improvements. The motion model demonstrated high accuracy, with a mean error of 0.1 ± 2.9 mm . Significance . This study demonstrates the feasibility and dosimetric advantage of deformable dose-guided MLC tracking using motion-model-derived volumetric imaging in patient data. These findings represent a critical step toward the clinical implementation of real-time dose-guided radiation therapy.

Source: Physics in Medicine and Biology

DOI: 10.1088/1361-6560/ae24db