Development of an On-Board Medical Imaging System with Proton Radiography Using High Energy MeV Beams from Proton Therapy Machines

Most of currently available proton therapy machines use kV-photon imaging systems for image-guided proton therapy. The on-board imager provides planer radiographic or volumetric cone-beam CT-images that are used for image guided radiation therapy. The photon CT-images are associated with large uncertainties in the determination of actual tissue density and composition needed for dose calculations in proton therapy. Several studies investigated proton radiographic and CT-imaging which indicated their superiority to the corresponding photon images for treatment planning and patient setup of cancer patients treated with proton therapy. The intensity of the proton images directly represents the tissue composition and density instead of electron density measured with the CT-number values obtained from the corresponding kV-photon images. The proton radiographic images show higher contrast for soft tissue imaging in comparison with photon radiographic images where usually bone anatomy is enhanced. The purpose of this project is to investigate the feasibility of radiographic imaging with high energy therapeutic proton beams produced by the MEVION-S250i proton therapy system and integration of an on-board imaging system based on proton radiography for image guidance.