20 April 2005 The density measurements in pCT imaging
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In existing proton treatment centers, dose calculations are performed based on x-ray computerized tomography (CT). Alternatively, the therapeutic proton beam could be used to collect the data for treatment planning via proton CT (pCT). With the development of medical proton gantries, first at Loma Linda University Medical Center and now in several other proton treatment centers, it is of interest to continue the early pCT investigations of the 1970s and the early 1980s. From that time, the basic idea of the pCT method has advanced from average energy loss measurements to an individual proton tracking technique. This reduces the image degradation due to multiple Coulomb scattering. Thereby, the central pCT problem shifts to the fidelity of the physical information obtained about the scanned patient, which will be used for proton treatment planning. The accuracy of relative electron density distributions extracted from pCT images was investigated in this work using continuous slowing down approximation (CSDA) and water-equivalent-thickness (WET) concepts. Analytical results were checked against Monte Carlo simulations, which were obtained with SRIM2003 and GEANT4 Monte Carlo software packages. The range of applications and the sources of absolute errors are discussed.
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Ivan Evseev, Ivan Evseev, Joaquim Teixeira de Assis, Joaquim Teixeira de Assis, Olga Yevseyeva, Olga Yevseyeva, Hugo Reuters Schelin, Hugo Reuters Schelin, Margio Cezar Loss Klock, Margio Cezar Loss Klock, Joao Antonio Palma Setti, Joao Antonio Palma Setti, Ricardo Tadeu Lopes, Ricardo Tadeu Lopes, Ubirajara Maribondo Vinagre Filho, Ubirajara Maribondo Vinagre Filho, Reinhard W. Schulte, Reinhard W. Schulte, David C. Williams, David C. Williams, "The density measurements in pCT imaging", Proc. SPIE 5745, Medical Imaging 2005: Physics of Medical Imaging, (20 April 2005); doi: 10.1117/12.595720; https://doi.org/10.1117/12.595720

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