200 MeV proton radiography studies with a hand phantom using a prototype proton CT scanner

Proton radiography generates two-dimensional projection images of an object and has applications in patient alignment and verification procedures in preparation for proton beam radiation therapy. The quality of the image, both contrast and spatial resolution, is likely to be affected by the energy of the protons used in the creation of the radiograph, as well as by multiple Coulomb scattering and energy-loss straggling. Here we report an experiment which used 200 MeV protons to generate proton energy-loss and scattering radiographs of a hand phantom. It was found that while both radiographs displayed anatomical details of the hand phantom, the energy-loss radiograph has a noticeably higher spatial resolution. The scattering radiograph may yield sharper edges between soft and bone tissue more so than energy loss radograph, but this requires further study. These radiographs demonstrate the new promise of proton imaging (proton radiography and CT) now within reach of becoming a new, potentially low-dose medical imaging modality. The experiment used the current first-generation proton CT scanner prototype, which is installed on the research beam line of the clinical proton synchrotron at Lorna Linda University Medical Center. This study contributes to the optimization of radiography performance of a clinical proton CT scanner.