Particle therapy facilities often require Monte Carlo (MC) simulations to overcome intrinsic limitations of analytical treatment planning systems (TPS) related to the description of the mixed ...radiation field and beam interaction with tissue inhomogeneities. Some of these uncertainties may affect the computation of effective dose distributions; therefore, particle therapy dedicated MC codes should provide both absorbed and biological doses. Two biophysical models are currently applied clinically in particle therapy: the local effect model (LEM) and the microdosimetric kinetic model (MKM). In this paper, we describe the coupling of the NIRS (National Institute for Radiological Sciences, Japan) clinical dose to the FLUKA MC code. We moved from the implementation of the model itself to its application in clinical cases, according to the NIRS approach, where a scaling factor is introduced to rescale the (carbon-equivalent) biological dose to a clinical dose level. A high level of agreement was found with published data by exploring a range of values for the MKM input parameters, while some differences were registered in forward recalculations of NIRS patient plans, mainly attributable to differences with the analytical TPS dose engine (taken as reference) in describing the mixed radiation field (lateral spread and fragmentation). We presented a tool which is being used at the Italian National Center for Oncological Hadrontherapy to support the comparison study between the NIRS clinical dose level and the LEM dose specification.
In this study a procedure for range verification in proton therapy by means of a planar in-beam PET system is presented. The procedure consists of two steps: the measurement of the β+-activity ...induced in the irradiated body by the proton beam and the comparison of these distributions with simulations. The experimental data taking was performed at the CNAO center in Pavia, Italy, irradiating plastic phantoms. For two different cases we demonstrate how a real-time feedback of the delivered treatment plan can be obtained with in-beam PET imaging.
This study was performed to evaluate the accuracy of a commercial treatment planning system (TPS), in optimising proton pencil beam dose distributions for small targets of different sizes (5-30 mm ...side) located at increasing depths in water. The TPS analytical algorithm was benchmarked against experimental data and the FLUKA Monte Carlo (MC) code, previously validated for the selected beam-line. We tested the Siemens syngo® TPS plan optimisation module for water cubes fixing the configurable parameters at clinical standards, with homogeneous target coverage to a 2 Gy (RBE) dose prescription as unique goal. Plans were delivered and the dose at each volume centre was measured in water with a calibrated PTW Advanced Markus® chamber. An EBT3® film was also positioned at the phantom entrance window for the acquisition of 2D dose maps. Discrepancies between TPS calculated and MC simulated values were mainly due to the different lateral spread modeling and resulted in being related to the field-to-spot size ratio. The accuracy of the TPS was proved to be clinically acceptable in all cases but very small and shallow volumes. In this contest, the use of MC to validate TPS results proved to be a reliable procedure for pre-treatment plan verification.
At the Centro Nazionale di Adroterapia Oncologica (CNAO Foundation), a two-dimensional high resolution scintillating dosimetry system has been developed and tested for daily Quality Assurance ...measurements (QA) in carbon ion radiotherapy with active scanning technique, for both single pencil beams and scanned fields produced by a synchrotron accelerator.
The detector consists of a thin plane organic scintillator (25×25cm2, 2mm thick) coupled with a high spatial resolution CCD camera (0.25mm) in a light-tight box.
A dedicated Labview software was developed for image acquisition triggered with the beam extraction, data post-processing and analysis. The scintillator system was preliminary characterized in terms of short-term reproducibility (found to be within±0.5%), linearity with the number of particles (linear fit χ2=0.996) and dependence on particle flux (measured to be <1.5%).
The detector was then tested for single beam spot measurements (Full Width at Half Maximum and position) and for 6×6cm2 reference scanned field (determination of homogeneity) for carbon ions with energy from 115MeV/u up to 400MeV/u. No major differences in the investigated beam parameters measured with scintillator system and the radiochromic EBT3 reference films were observed. The system allows therefore real-time monitoring of the carbon ion beam relevant parameters, with a significant daily time saving with respect to films currently used.
The results of this study show the suitability of the scintillation detector for daily QA in a carbon ion facility with an active beam delivery system.
•At the CNAO Foundation a scintillating dosimetry system has been developed for beam QA.•The detector response was tested for the first time for carbon ion pencil beams.•The system was preliminary characterized in terms of response linearity, reproducibility and homogeneity.•The detector performances were evaluated by performing a cross-check with reference radiochromic films.•The results showed that the scintillation detector is suitable for relative 2D dosimetry.
•Carbonaceous implants do not cause appreciable artifacts on CT images.•Carbonaceous devices cause slight perturbation on TPS dose calculation accuracy.•A precise modeling and material assignment of ...the device should always be performed.•Multiple beams and avoidance structures are recommended with metallic implants.
The aim of this study was to evaluate the dosimetric impact caused by recently introduced carbon fiber reinforced polyetheretherketone (CF/PEEK) stabilization devices, in comparison with conventional titanium (Ti) implants, for post-operative particle therapy (PT).
As a first step, protons and carbon ions Spread-Out Bragg Peaks (SOBPs) were delivered to CF/PEEK and Ti screws. Transversal dose profiles were acquired with EBT3 films to evaluate beam perturbation. Effects on image quality and reconstruction artifacts were then investigated. CT scans of CF/PEEK and Ti implants were acquired according to our clinical protocol and Hounsfield Unit (HU) mean values were evaluated in three regions of interest. Implants and artifacts were then contoured in the sample CT scans, together with a target volume to simulate a spine tumor. Dose calculation accuracy was assessed by comparing optimized dose distributions with Monte Carlo simulations. In the end, the treatment plans of nine real patients (seven with CF/PEEK and two with Ti stabilization devices) were retrospectively analyzed to evaluate the dosimetric impact potentially occurring if improper management of the spine implant was carried out.
As expected, CF/PEEK screw caused a very slight beam perturbation in comparison with Ti ones, leading to a lower degree of dose degradation in case of contouring and/or set-up uncertainties. Furthermore, CF/PEEK devices did not determine appreciable HU artifacts on CT images thus improving image quality and, as a final result, dose calculation accuracy.
CF/PEEK spinal fixation devices resulted dosimetrically more suitable than commonly-used Ti implants for post-operative PT.
Glioblastoma multiforme (GBM) is characterized by a poor prognosis and a median survival of ~12-18 months. GBM is usually managed by neurosurgery followed by both chemotherapy and radiotherapy. Since ...GBM develops resistance to conventional therapies, treatment with C-ions is promising to completely eradicate the tumoural mass. During cranial irradiation, exposure of healthy tissues is inevitable. Because of the presence of neural stem cells, a deep investigation on the effects of C-ion irradiation with respect to X-ray induced damage is mandatory to allow a better definition of treatments. In this work, the comparison of X-rays and C-ion irradiation-induced effects on human neural stem cell, focusing on multiple endpoints, such as cell viability, cytokine secretion and spheroid formation is presented. Results show different temporal and dose responses of human neural stem cells to the different radiation qualities, suggesting different underpinning mechanisms of radiation-induced damages.
We compute several ground-state properties and the dynamical structure factor of a zero-temperature system of Bosons interacting with the 2D screened Coulomb (2D-SC) potential. We resort to the exact ...shadow path integral ground state (SPIGS) quantum Monte Carlo method to compute the imaginary-time correlation function of the model, and to the genetic algorithm via falsification of theories (GIFT) to retrieve the dynamical structure factor. We provide a detailed comparison of ground-state properties and collective excitations of 2D-SC and
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He atoms. The roton energy of the 2D-SC system is an increasing function of density, and not a decreasing one as in
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He. This result is in contrast with the view that the roton is the soft mode of the fluid–solid transition. We uncover a remarkable quasi-universality of backflow and of other properties when expressed in terms of the amount of short-range order as quantified by the height of the first peak of the static structure factor.
In the context of the particle therapy a crucial role is played by Treatment Planning Systems (TPSs), tools aimed to compute and optimize the tratment plan. Nowadays one of the major issues related ...to the TPS in particle therapy is the large CPU time needed. We developed a software toolkit (FRED) for reducing dose recalculation time by exploiting Graphics Processing Units (GPU) hardware. Thanks to their high parallelization capability, GPUs significantly reduce the computation time, up to factor 100 respect to a standard CPU running software. The transport of proton beams in the patient is accurately described through Monte Carlo methods. Physical processes reproduced are: Multiple Coulomb Scattering, energy straggling and nuclear interactions of protons with the main nuclei composing the biological tissues. FRED toolkit does not rely on the water equivalent translation of tissues, but exploits the Computed Tomography anatomical information by reconstructing and simulating the atomic composition of each crossed tissue. FRED can be used as an efficient tool for dose recalculation, on the day of the treatment. In fact it can provide in about one minute on standard hardware the dose map obtained combining the treatment plan, earlier computed by the TPS, and the current patient anatomic arrangement.
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