Intensity and Range Modulated Proton Radiography Using High Energy Therapeutic Proton Scanning Pencil Beams
C Pelas1*, N Alsbou2, S Ahmad1, I Ali1, (1) ,Oklahoma City, Ok, OK, (2) Department of Engineering and Physics, University of Central Oklahoma, Edmond, OK
Presentations
PO-GePV-M-87 (Sunday, 7/10/2022) [Eastern Time (GMT-4)]
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Purpose: To investigate the visibility of intensity- and range-modulated proton radiography proton with pencil beam using a high energy scanning proton therapy machine.
Methods: The MEVION-S250i-proton-therapy machine was used to acquire proton radiographs using a 227MeV scanning pencil beams with large open field of 20x20cm2. Different phantoms (LEEDS, CIRS) were used to investigate the image quality of the proton radiographs. A high sensitivity and high spatial and contrast resolutions plastic scintillation detector (LYNX) was used to acquire proton radiographs. The dependence of image quality parameters on dose, depth, modulation of the proton beam was evaluated quantitatively.
Results: The contrast and special resolutions of the proton radiographs were improved where the Bragg peak of each pencil beam in the imaging field crossed the phantom and deposited on the detector while keeping the patient imaging dose low (60%). The dose deposited in proton radiography from the flat dose region before the Bragg peak was lower nearly 20% than the dose deposited in photon radiograph. The contrast resolution was improved because of the high intensity gradient in the region of the Bragg-peak where small variations in water-equivalent-depths were represented by large variation in intensity at the high dose gradient in the Bragg peak region. The spatial resolution of imaging objects improved by passing the energetic proton beam through the phantom where its bending and scattering was smaller than the low energy proton (< 20 MeV) in the Bragg-peak at the end of the proton range.
Conclusion: Proton radiography using intensity and range-modulation of a scanning pencil beam from a proton therapy system provided an approach to account for variations in patient thickness, surface irregularities and different tissue densities along the beam path. On-board imaging with proton radiography provides an alternative imaging modality using on board imaging systems with kV diagnostic photons.
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