J. A. P. Setti

Comparison of SRIM, MCNPX and GEANT simulations with experimental data for thick Al absorbers

Proton computerized tomography deals with relatively thick targets like the human head or trunk. In this case precise analytical calculation of the proton final energy is a rather complicated task, thus the Monte Carlo simulation stands out as a solution. We used the GEANT4.8.2 code to calculate the proton final energy spectra after passing a thick Al absorber and compared it with the same conditions of the experimental data. The ICRU49, Ziegler85 and Ziegler2000 models from the low energy extension pack were used. The results were also compared with the SRIM2008 and MCNPX2.4 simulations, and with solutions of the Boltzmann transport equation in the Fokker-Planck approximation.

Computerized tomography with high-energy proton beams: tomographic image reconstruction from computer-simulated data

The use of protons instead of X-rays for computerized tomography (CT) studies has potential advantages, especially for medical applications in proton treatment planning. However, the spatial resolution of proton CT is limited by multiple Coulomb scattering (MCS). We used the Monte Carlo simulation tool GEANT4 to study the resolution achievable with different experimental arrangements of a proton CT scanner. The passage of a parallel 200MeV proton beam through a virtual cylindrical aluminum phantom with 50mm external diameter was simulated. In our study, the phantom contained a set of cylindrical holes with diameters ranging from 4mm to 0.5mm. The GEANT4 simulation consisted of a series of 180 projections at 2 degree intervals with 350 proton track histories for each one. The filtered back projection algorithm was used to reconstruct a 2D tomographic image of phantom.

GEANT4 simulations for low energy proton computerized tomography

This work presents the recent results of computer simulations for the low energy proton beam tomographic scanner installed at the cyclotron CV-28 of IEN/CNEN. New computer simulations were performed in order to adjust the parameters of previous simulation within the first experimental results and to understand some specific effects that affected the form of the final proton energy spectra. To do this, the energy and angular spread of the initial proton beam were added, and the virtual phantom geometry was specified more accurately in relation to the real one. As a result, a more realistic view on the measurements was achieved.

The density measurements in pCT imaging

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.

Proposal of custom made wrist orthoses based on 3D modelling and 3D printing

Accessibility to three-dimensional (3D) technologies, such as 3D scanning systems and additive manufacturing (like 3D printers), allows a variety of 3D applications. For medical applications in particular, these modalities are gaining a lot of attention enabling several opportunities for healthcare applications. The literature brings several cases applying both technologies, but none of them focus on the spreading of how this technology could benefit the health segment. This paper proposes a new methodology, which employs both 3D modelling and 3D printing for building orthoses, which could better fit the demands of different patients. Additionally, there is an opportunity for sharing expertise, as it represents a trendy in terms of the maker-movement. Therefore, as a result of the proposed approach, we present a case study based on a volunteer who needs an immobilization orthosis, which was built for exemplification of the whole process. This proposal also employs freely available 3D models and software, having a strong social impact. As a result, it enables the implementation and effective usability for a variety of built to fit solutions, hitching useful and smarter technologies for the healthcare sector.

Comparison of Geant4 version 9.3 simulations with experimental results from a prototype proton CT scanner

Charged particle interactions with matter have been continuously studied by simulations based on the Monte Carlo method. In particular, the Geant4 toolkit allows to develop and test new technologies by computer simulations. A proton computed tomography (pCT) prototype has been developed at the Lorna Linda University Medical Center (LLUMC), California, in collaboration with Northern Illinois University and the UC Santa Cruz. In order to evaluate the performance of the Geant4 version 9.3 configured to simulate this prototype, two polyethylene phantoms (PEA D) with 150 mm diameter and acrylic core were constructed. Each phantom was imaged with 10 projections by rotating the phantom in steps of 36, using a 200 MeV proton cone beam. The characteristics of the prototype and phantoms were modeled in Geant4. A comparison of the experimental data and simulated projections were performed and will be presented.

Comparison of the GEANT4 releases 8.2 and 9.2 in terms of a pCT reduced calibration curve

The GEANT4 simulations are essential for the development of medical tomography with proton beams — pCT. In the case of thin absorbers the latest releases of GEANT4 generate very similar final spectra which agree well with the results of other popular Monte Carlo codes like TRIM/SRIM, or MCNPX. For thick absorbers, however, the disagreements became evident. In a part, these disagreements are due to the known contradictions in the NIST PSTAR and SRIM reference data. Therefore, it is interesting to compare the GEANT4 results with each other, with experiment, and with diverse code results in a reduced form, which is free from this kind of doubts. In this work such comparison is done within the Reduced Calibration Curve concept elaborated for the proton beam tomography.

Energy Measurements in a Prototype Proton CT Scanner

In proton treatment planning, the use of protons instead of X‐rays for computerized tomography (CT) studies has potential advantages, especially for medical applications. Proton CT requires accurate measurement of the energy loss of protons passing through the object. The resolution of a proton CT scanner is determined by the resolution of the energy loss measurement, which is limited by the inherent energy straggling of protons. An experiment with a doped CsI(Tl) crystal was designed to determine the resolution of the energy loss measurement of protons in the energy range from 40 MeV to 250 MeV experimentally. It was found that, in principle, the resolution of a proton calorimeter is adequate to CT studies with objects of realistic size.

Particle Initial Energy Choice in Proton Computed Tomography for Medical Purposes

In the earliest works devoted to proton computed tomography (pCT) it was shown that the advantage of pCT image reconstruction appears when the energy is chosen as small as possible but sufficient to pass the object. At the same time there are two effects that work on the contrary, increasing the necessary irradiation dose with decreasing proton energy. In this work the radiation dose dependence from the proton initial energy was studded using analytical formulas and computer simulation. The carried out investigation shows that the irradiation dose practically does not depend on the proton energy except at the small energy region very close to the minimal energy.