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Development of a Quality Assurance Phantom for Proton Radiographic Images Using the MEVION Spot Scanning Proton Therapy System

C Pelas1*, Z Richards1, N Alsbou2, 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


(Sunday, 7/12/2020)   [Eastern Time (GMT-4)]

Room: AAPM ePoster Library

Purpose: To develop a quality assurance phantom with soft tissue equivalent materials that can be used to evaluate image quality of proton radiographic images obtained from the 230-MeV MEVION-Spot-Scanning proton therapy system.
Methods: Different materials were tested to develop a quality assurance phantom for proton radiographic images. The phantom materials included different modules to test image contrast and spatial resolutions, linearity, uniformity and noise of the proton radiographs. High-z objects were employed to characterize spatial resolution of the proton images. The proton radiographs were obtained by irradiating different phantoms with a 230-MeV proton beam from the MEVION-proton therapy system. Proton beams of 3.5mm diameter in air and spot spacing ranging 1-10mm was used in this phantom testing and proton radiographic evaluation.
Results: The phantoms used for quality assurance of photon imaging kV-beams did not work well for evaluation of the image quality of proton radiographic images. The proton beam scattered with large angles from high-z materials such as lead that are used for evaluation of special resolution in photon beams. The soft tissue equivalent objects provided the tests needed to quantify contrast resolution. Phantom inserts from different materials from lung to bone were employed to evaluate linearity of the intensity in proton radiographic images. The solid water phantom regions was used to test uniformity of the proton radiographs. This phantom design provided an alternative to the Leeds phantom for image quality evaluation in proton radiography. The different phantom materials tested in this study were more imaging friendly for proton beams.
Conclusions: This phantom was built from different modules to characterize the imaging parameters for proton radiographic images including contrast and position resolutions, linearity, uniformity and noise of radiographic proton images obtained from therapeutic high energy proton beams. It provides an alternative image quality assurance tool for image –guided proton beams.

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