Development of Proton Digitally Reconstructed Radiographs for Image Guided Proton Radiotherapy
I Ali1*, N Alsbou2, S Ahmad1, (1) University of Oklahoma Health Sciences, Oklahoma City, OK, (2) Department of Engineering and Physics, University of Central Oklahoma, Edmond, OK.
Presentations
PO-GePV-M-184 (Sunday, 7/10/2022) [Eastern Time (GMT-4)]
ePoster Forums
Purpose: Development of a tracing algorithm to produce digitally-reconstructed-radiographs (DRR) using high energy proton beams with patient CT-images.
Methods: An algorithm was developed to generate proton DRR’s that uses the proton pencil-beams of 227MeV to simulate proton radiographs obtained from a MEVION-S250i proton therapy machine. The proton DRRs were generated by tracing pencil-beams that started from the proton source and transported through patient CT-images. The dose deposition by the pencil-beams was designed where the ranges were setup with the Bragg-peaks detected at the imager. One-energy-layer image was used where the Bragg-peak crossed different phantoms (CIRS, LEEDS and anatomical-phantoms) and deposited in the detector.
Results: The image quality of the proton DRR’s was evaluated for different phantoms and compared with the corresponding diagnostic 120kV photon DRR’s. The image quality of the proton DRR’s degraded with increasing depth of the testing objects in phantom. The contrast and spatial resolutions of the proton DRR’s decreased with increased range modulation, spot separation and size. The proton DRR’s has better contrast of the soft tissue features in the beam-view, while the photon DRR’s presented mainly high contrast object such as bones. This algorithm was able to handle the variations of head and pelvis phantom thicknesses, anatomical changes and surface irregularities. This algorithm is limited in modeling the proton beam interaction with the medium that is mainly due to Columbic interactions and it does not account well for scatting and bending of the proton beams.
Conclusion: The proton DRR’s developed by this algorithm provides a useful tool for image guided proton therapy with an onboard imaging system using high energy proton beam from proton therapeutic machines. The proton DRR’s has superior soft tissue contrast compared with the corresponding photon radiographs. Onboard imaging with proton provides an alternative from photon imaging systems for image guided proton therapy.
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