MR-guided beam gating: Residual motion, gating efficiency and dose reconstruction for stereotactic treatments of the liver and lung. (September 2022)

• Record Type: Journal Article
• Authors: Ehrbar, Stefanie; Braga Käser, Sarah; Chamberlain, Madalyne; Krayenbühl, Jérôme; Wilke, Lotte; Mayinger, Michael; Garcia Schüler, Helena; Guckenberger, Matthias; Andratschke, Nicolaus; Tanadini-Lang, Stephanie
• Is Part Of: Radiotherapy and oncology. Volume 174(2022)
• Page Start: 101
• Page End: 108
• Publication Date: 2022-09
• Subjects: MR-guided radiotherapy -- Gating -- Liver motion -- Lung motion -- Dose reconstruction; Oncology -- Periodicals; Radiotherapy -- Periodicals; Tumors -- Periodicals; Medical Oncology -- Periodicals; Neoplasms -- radiotherapy -- Periodicals; Radiotherapy -- Periodicals; Radiothérapie -- Périodiques; Cancérologie -- Périodiques; Tumeurs -- Périodiques; Electronic journals; 616.9940642
• DOI: 10.1016/j.radonc.2022.07.007
• Languages: English
• ISSNs: 0167-8140

Abstract

Highlights: Evaluation of MR-guided beam gating based on patient data. Estimation of residual motion during gating and its dosimetric effect. Dose reconstruction workflow for individual patient motion. Abstract: Purpose: This study aims to investigate the efficiency and the geometric as well as the dosimetric benefit of magnetic-resonance guided beam gating for stereotactic treatments in moving organs. Method: Patients treated with MR-guided (MRIdian system) SBRT for lung (n = 10) and liver (n = 10) targets were analyzed. Breath-hold gating was performed based on lesion tracking in sagittal cine MRI images. The target offset from the geometric center of the gating window with and without gating was evaluated. A dose reconstruction workflow based on convolution of these 2D position-probability maps and the daily 3D dose distribution was used to estimate the daily delivered dose including motion. The dose to the clinical target volume (CTV) and to a 2-cm ring structure around the planning target volume were evaluated. Results: The applied gating protocol resulted in a mean (±standard deviation) gating efficiency of 55%±16%. Over all patients, the mean target offset (2D-root-mean-square error) was 8.3 ± 4.3 mm, which reduced to 2.4 ± 0.6 mm during gating. The dose reconstruction showed a mean deviation in CTV coverage (D95) from the static plans of −1.7%±1.8% with gating and −12.0%±8.4% if no gating would have been used. The mean dose (Dmean) in the ring structure, with respect to the static plans, showed mean deviations of −0.1%±0.3% with gating and −1.6%±1.8% without gating. Conclusion: The MRIdian system enables gating based on the inner anatomy and the implemented dose reconstruction workflow demonstrated geometric robust delivery of the planned radiation doses.