Development of a Novel 4D-Quality Assurance Technique to Consider Patient Respiratory Motion for Adaptive Radiation Therapy
T Meyers1*, N Alsbou2, O Algan1, S Ahmad1, I Ali1, (1) University Of Oklahoma Health Sciences Center, Oklahoma City, OK, (2) Department of Engineering and Physics, University of Central Oklahoma, Edmond, OK
Presentations
PO-GePV-T-104 (Sunday, 7/10/2022) [Eastern Time (GMT-4)]
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Purpose: The goal of this project is to test a four-dimensional (4D) quality assurance phantom and quantify the dosimetric effects of respiratory motion on the dose distributions optimized and calculated in 3D on stationary CT-images.
Methods: Two-dimensional detectors (MapCheck2 and OCTAVIUS) were mounted on a mobile-platform (Standard Imaging) that moves with different motion patterns and controlled amplitude and frequency. The dose distributions from different treatment plans that included intensity-modulated radiation therapy (IMRT) or volumetric-modulated arc therapy (VMAT) with photons, or intensity-modulated proton therapy (IMPT) were delivered and measured with this mobile quality assurance phantom using different motion amplitudes (0-35mm) and frequencies (0.25-0.33Hz). The dose deviations induced by cyclic motion were quantified.
Results: For both the IMRT and VMAT-treatment plans, the dose profiles changed around the 40-60% isodose-line, with increasing dose spilling outside the field for increasing motion amplitudes. The gamma test of the various plans with criteria of 3%/3mm showed a significant decline in the passing rate for the plans with increased motion amplitude in all cases. While variations in motion amplitudes had substantial effects on the dose distributions, the changes in frequency in which the phantom was moving did not have any noticeable effects. For the IMPT-plan, the shift in the penumbra did not follow the same regular behavior as the IMRT and VMAT-plans, and the central axis dose and surrounding flat region was significantly altered because of the interplay effect between the scanning pencil proton beams and the phantom motion.
Conclusion: This phantom represent innovation for quality assurance and verification of 4D-dose optimization and calculation algorithms that will be developed and used for adaptive radiation therapy.4D-treatment planning and dose delivery provides a novel technique to account for respiratory motion in real time and represents an alternative for motion management of cancer patient to perform adaptive radiation therapy.
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