RESUMO
OBJECTIVE: Pulmonary hypertension in the newborn (PPHN) is a significant clinical condition characterized by elevated pulmonary artery pressures, leading to serious health consequences. Magnesium sulfate, known for its vasodilatory properties, has been studied for its potential benefits in managing PPHN. This systematic review evaluates the efficacy and safety of magnesium sulfate in neonates with PPHN. MATERIALS AND METHODS: A systematic literature search was conducted on PubMed and Scopus up to March 10, 2024. Studies were included based on predefined Population, Intervention, Comparison, Outcome, Study (PICOS) criteria focusing on pediatric patients with PPHN treated with magnesium sulfate, compared against placebo or other pharmacological interventions. Outcomes of interest included resolution of PPHN, improved oxygenation, and decreased oxygenation index. RESULTS: From a total of 1,233 articles screened, four studies met the inclusion criteria, including three randomized controlled trials and one multicentric retrospective study. The comparisons included nebulized magnesium sulfate, oral sildenafil, and inhaled nitric oxide. The outcomes varied, with none reported consistently across more than two studies, making a meta-analysis unfeasible. Results indicated a potential benefit of magnesium sulfate in improving pulmonary pressures and oxygenation, but the evidence was insufficient to establish definitive conclusions due to the heterogeneity and a limited number of studies. CONCLUSIONS: The limited data suggest that, while magnesium sulfate may have a role in the management of PPHN, it should not replace established therapies. Further research is needed to better define its efficacy and safety profile.
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Hipertensão Pulmonar , Sulfato de Magnésio , Humanos , Sulfato de Magnésio/administração & dosagem , Sulfato de Magnésio/uso terapêutico , Recém-Nascido , Hipertensão Pulmonar/tratamento farmacológico , Vasodilatadores/administração & dosagem , Vasodilatadores/uso terapêutico , Vasodilatadores/efeitos adversos , Administração Intravenosa , Síndrome da Persistência do Padrão de Circulação Fetal/tratamento farmacológico , Óxido Nítrico/administração & dosagemRESUMO
PURPOSE: In order to translate the FLASH effect in clinical use and to treat deep tumors, Very High Electron Energy irradiations could represent a valid technique. Here, we address the main issues in the design of a VHEE FLASH machine. We present preliminary results for a compact C-band system aiming to reach a high accelerating gradient and high current necessary to deliver a Ultra High Dose Rate with a beam pulse duration of 3µs. METHODS: The proposed system is composed by low energy high current injector linac followed by a high acceleration gradient structure able to reach 60-160 MeV energy range. To obtain the maximum energy, an energy pulse compressor options is considered. CST code was used to define the specifications RF parameters of the linac. To optimize the accelerated current and therefore the delivered dose, beam dynamics simulations was performed using TSTEP and ASTRA codes. RESULTS: The VHEE parameters Linac suitable to satisfy FLASH criteria were simulated. Preliminary results allow to obtain a maximum energy of 160 MeV, with a peak current of 200 mA, which corresponds to a charge of 600 nC. CONCLUSIONS: A promising preliminary design of VHEE linac for FLASH RT has been performed. Supplementary studies are on going to complete the characterization of the machine and to manufacture and test the RF prototypes.
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Aceleradores de PartículasRESUMO
Objective.In the present hadrontherapy scenario, there is a growing interest in exploring the capabilities of different ion species other than protons and carbons. The possibility of using different ions paves the way for new radiotherapy approaches, such as the multi-ions treatment, where radiation could vary according to target volume, shape, depth and histologic characteristics of the tumor. For these reasons, in this paper, the study and understanding of biological-relevant quantities was extended for the case of4He ion.Approach.Geant4 Monte Carlo based algorithms for dose- and track-averaged LET (Linear Energy Transfer) calculations, were validated for4He ions and for the case of a mixed field characterised by the presence of secondary ions from both target and projectile fragmentation. The simulated dose and track averaged LETs were compared with the corresponding dose and frequency mean values of the lineal energy,yD¯andy¯F, derived from experimental microdosimetric spectra. Two microdosimetric experimental campaigns were carried out at the Italian eye proton therapy facility of the Laboratori Nazionali del Sud of Istituto Nazionale di Fisica Nucleare (INFN-LNS, Catania, I) using two different microdosimeters: the MicroPlus probe and the nano-TEPC (Tissue Equivalent Proportional Counter).Main results.A good agreement ofL¯dTotalandL¯tTotalwithy¯Dandy¯Texperimentally measured with both microdosimetric detectors MicroPlus and nano-TEPC in two configurations: full energy and modulated4He ion beam, was found.Significance.The results of this study certify the use of a very effective tool for the precise calculation of LET, given by a Monte Carlo approach which has the advantage of allowing detailed simulation and tracking of nuclear interactions, even in complex clinical scenarios.
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Transferência Linear de Energia , Radiometria , Algoritmos , Íons , Método de Monte Carlo , Prótons , Radiometria/métodosRESUMO
The aim of the NEPTUNE (Nuclear process-driven Enhancement of Proton Therapy UNravEled) project is to investigate in detail both the physical and radiobiological phenomena that could justify an increase of the proton-induced cytogenetic effects in cells irradiated in presence of an agent containing natural boron. In this work, a double-stage silicon telescope coupled to different boron converters was irradiated at the CATANA proton therapy facility (INFN-LNS) for studying the proton boron fusion and the neutron boron capture reactions by discriminating secondary particles from primary protons. Different boron targets were developed by depositing boric acid, enriched with a higher than 99% content of 10B or 11B, on a 50⯵m thick PolyMethilMetacrylate (PMMA) substrate. The 10B target allows to evaluate the contribution of lithium and alpha particles produced by the boron neutron capture reaction triggered by secondary thermal neutrons, while the 11B target is exploited for studying the effect of the p + 11Bâ¯ââ¯3α nuclear reaction directly triggered by primary protons. Experimental results clearly show the presence of alpha particles from both the reactions. The silicon telescope is capable of discriminating, by means of the so-called "scatter plots", the contribution of alpha particles originated by thermal neutrons on 10B with respect to the ones produced by protons impinging on 11B. Although a reliable quantitative study of the alpha production rate has not been achieved yet, this work demonstrates that low energy and, therefore, high-LET particles from both the reactions can be measured.
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Terapia por Captura de Nêutron de Boro , Terapia com Prótons , Boro , Nêutrons , PrótonsRESUMO
BACKGROUND: Geant4 is a Monte Carlo code extensively used in medical physics for a wide range of applications, such as dosimetry, micro- and nanodosimetry, imaging, radiation protection, and nuclear medicine. Geant4 is continuously evolving, so it is crucial to have a system that benchmarks this Monte Carlo code for medical physics against reference data and to perform regression testing. AIMS: To respond to these needs, we developed G4-Med, a benchmarking and regression testing system of Geant4 for medical physics. MATERIALS AND METHODS: G4-Med currently includes 18 tests. They range from the benchmarking of fundamental physics quantities to the testing of Monte Carlo simulation setups typical of medical physics applications. Both electromagnetic and hadronic physics processes and models within the prebuilt Geant4 physics lists are tested. The tests included in G4-Med are executed on the CERN computing infrastructure via the use of the geant-val web application, developed at CERN for Geant4 testing. The physical observables can be compared to reference data for benchmarking and to results of previous Geant4 versions for regression testing purposes. RESULTS: This paper describes the tests included in G4-Med and shows the results derived from the benchmarking of Geant4 10.5 against reference data. DISCUSSION: Our results indicate that the Geant4 electromagnetic physics constructor G4EmStandardPhysics_option4 gives a good agreement with the reference data for all the tests. The QGSP_BIC_HP physics list provided an overall adequate description of the physics involved in hadron therapy, including proton and carbon ion therapy. New tests should be included in the next stage of the project to extend the benchmarking to other physical quantities and application scenarios of interest for medical physics. CONCLUSION: The results presented and discussed in this paper will aid users in tailoring physics lists to their particular application.
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Benchmarking , Física , Radiometria , Simulação por Computador , Método de Monte CarloRESUMO
We exploited the power of the Geant4 Monte Carlo toolkit to study and validate new approaches for the averaged linear energy transfer (LET) calculation in 62 MeV clinical proton beams. The definitions of the averaged LET dose and LET track were extended, so as to fully account for the contribution of secondary particles generated by target fragmentation, thereby leading to a more general formulation of the LET total. Moreover, in the proposed new strategies for the LET calculation, we minimised the dependencies in respect to the transport parameters adopted during the Monte Carlo simulations (such as the production cut of secondary particles, voxel size and the maximum steplength). The new proposed approach was compared against microdosimetric experimental spectra of clinical proton beams, acquired at the Italian eye proton therapy facility of the Laboratori Nazionali del Sud, Istituto Nazionale di Fisica Nucleare (INFN-LNS, Catania, I) from two different detectors: a mini-tissue equivalent proportional chamber (TEPC), developed at the Legnaro National Laboratories of the National Institute for Nuclear Physics (LNL-INFN) and a silicon-on-insulator (SOI) microdosimeter with 3D sensitive volumes developed by the Centre for Medical Radiation Physics of Wollongong University (CMRP-UoW). A significant increase of the LET in the entrance region of the spread out Bragg peak (SOBP) was observed, when the contribution of the generated secondary particles was included in the calculation. This was consistent with the experimental results obtained.
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Algoritmos , Transferência Linear de Energia , Método de Monte Carlo , Terapia com Prótons , Doses de Radiação , Humanos , Dosagem RadioterapêuticaRESUMO
Proton beams are widely used worldwide to treat localized tumours, the lower entrance dose and no exit dose, thus sparing surrounding normal tissues, being the main advantage of this treatment modality compared to conventional photon techniques. Clinical proton beam therapy treatment planning is based on the use of a general relative biological effectiveness (RBE) of 1.1 along the whole beam penetration depth, without taking into account the documented increase in RBE at the end of the depth dose profile, in the Bragg peak and beyond. However, an inaccurate estimation of the RBE can cause both underdose or overdose, in particular it can cause the unfavourable situation of underdosing the tumour and overdosing the normal tissue just beyond the tumour, which limits the treatment success and increases the risk of complications. In view of a more precise dose delivery that takes into account the variation of RBE, experimental microdosimetry offers valuable tools for the quality assurance of LET or RBE-based treatment planning systems. The purpose of this work is to compare the response of two different microdosimetry systems: the mini-TEPC and the MicroPlus-Bridge detector. Microdosimetric spectra were measured across the 62 MeV spread out Bragg peak of CATANA with the mini-TEPC and with the Bridge microdosimeter. The frequency and dose distributions of lineal energy were compared and the different contributions to the spectra were analysed, discussing the effects of different site sizes and chord length distributions. The shape of the lineal energy distributions measured with the two detectors are markedly different, due to the different water-equivalent sizes of the sensitive volumes: 0.85 µm for the TEPC and 17.3 µm for the silicon detector. When the Loncol's biological weighting function is applied to calculate the microdosimetric assessment of the RBE, both detectors lead to results that are consistent with biological survival data for glioma U87 cells. Both the mini-TEPC and the MicroPlus-Bridge detector can be used to assess the RBE variation of a 62 MeV modulated proton beam along its penetration depth. The microdosimetric assessment of the RBE based on the Loncol's weighting function is in good agreement with radiobiological results when the 10% biological uncertainty is taken into account.
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Terapia com Prótons , Radiometria , Eficiência Biológica Relativa , Humanos , SilícioRESUMO
PURPOSE: The main purpose of this work is the inter-comparison between different devices devoted to the transversal dose profile recostruction for daily QA tests in proton therapy. METHODS: The results obtained with the EBT3 radiochromic films, used as a reference, and other common quality control devices, have been compared with those obtained with a beam profiling system developed at the "Laboratori Nazionali del Sud" of Italian Institute for Nuclear Physics (INFN-LNS, Catania, Italy). It consists of a plastic scintillator screen (thickness 1 mm), mounted perpendicularly to the beam axis and coupled with a highly sensitive CCD detector in a light-tight box. RESULTS AND CONCLUSION: The tests, carried out both at the INFN-LNS and Trento Proton Therapy Center facilities, show, in general, a good agreement between the different detectors. The beam profiling system, in particular, appears to be a promising quality control device for 2-D relative dosimetry, because of its linear response in a dose rate range useful for proton therapy treatments, its high spatial resolution and its short acquisition and processing time.
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Terapia com Prótons/instrumentação , Prótons , Radiometria/instrumentação , Contagem de Cintilação/instrumentação , Calibragem , Desenho de Equipamento , Humanos , Imagens de Fantasmas , Plásticos/química , Garantia da Qualidade dos Cuidados de Saúde , Dosagem Radioterapêutica , Planejamento da Radioterapia Assistida por Computador/métodos , Terapia Assistida por Computador/métodosRESUMO
The Time-of-Flight (TOF) technique coupled with semiconductorlike detectors, as silicon carbide and diamond, is one of the most promising diagnostic methods for high-energy, high repetition rate, laser-accelerated ions allowing a full on-line beam spectral characterization. A new analysis method for reconstructing the energy spectrum of high-energy laser-driven ion beams from TOF signals is hereby presented and discussed. The proposed method takes into account the detector's working principle, through the accurate calculation of the energy loss in the detector active layer, using Monte Carlo simulations. The analysis method was validated against well-established diagnostics, such as the Thomson parabola spectrometer, during an experimental campaign carried out at the Rutherford Appleton Laboratory (UK) with the high-energy laser-driven protons accelerated by the VULCAN Petawatt laser.
RESUMO
PURPOSE: The Geant4 Monte Carlo simulation toolkit was used to reproduce radiobiological parameters measured by irradiating three different cancerous cell lines with monochromatic and clinical proton beams. METHODS: The experimental set-up adopted for irradiations was fully simulated with a dedicated open-source Geant4 application. Cells survival fractions was calculated coupling the Geant4 simulations with two analytical radiobiological models: one based on the LEM (Local Effect Model) approach and the other on a semi-empirical parameterisation. Results was evaluated and compared with experimental data. RESULTS AND CONCLUSIONS: The results demonstrated the Geant4 ability to reproduce radiobiological quantities for different cell lines.
Assuntos
Método de Monte Carlo , Terapia com Prótons , Linhagem Celular Tumoral , Humanos , Radiobiologia , Dosagem Radioterapêutica , Reprodutibilidade dos TestesRESUMO
The main purpose of this paper is to quantitatively study the possibility of delivering dose distributions of clinical relevance with laser-driven proton beams. A Monte Carlo application has been developed with the Geant4 toolkit, simulating the ELIMED (MEDical and multidisciplinary application at ELI-Beamlines) transport and dosimetry beam line which is being currently installed at the ELI-Beamlines in Prague (CZ). The beam line will be used to perform irradiations for multidisciplinary studies, with the purpose of demonstrating the possible use of optically accelerated ion beams for therapeutic purposes. The ELIMED Geant4-based application, already validated against reference transport codes, accurately simulates each single element of the beam line, necessary to collect the accelerated beams and to select them in energy. Transversal dose distributions at the irradiation point have been studied and optimized to try to quantitatively answer the question if such kind of beam lines, and specifically the systems developed for ELIMED in Prague, will be actually able to transport ion beams not only for multidisciplinary applications, such as pitcher-catcher nuclear reactions (e.g. neutrons), PIXE analysis for cultural heritage and space radiation, but also for delivering dose patterns of clinical relevance in a future perspective of possible medical applications.
Assuntos
Lasers , Método de Monte Carlo , Aceleradores de Partículas , Terapia com Prótons/instrumentação , Doses de Radiação , Radiometria , Dosagem RadioterapêuticaRESUMO
Preclinical studies represent an important step towards a deep understanding of the biological response to ionizing radiations. The effectiveness of proton therapy is higher than photons and, for clinical purposes, a fixed value of 1.1 is used for the relative biological effectiveness (RBE) of protons considered 1.1. Recent in vitro studies have reported that the RBE along the spread-out Bragg peak (SOBP) is not constant and, in particular, the RBE value increases on the distal part of SOBP. The present work has been carried-out in the perspective of a preclinical hadrontherapy facility at LNS-INFN and was focused on the experimental preparation of an in vivo study concerning the RBE variation along the SOBP. The main purpose of this work was to determine, using GEANT4-based Monte Carlo simulations, the best configuration for small animal treatments. The developed GEANT4 application simulates the proton-therapy beam line of LNS-INFN (CATANA facility) and allows to import the DICOM-CT images as targets. The RBE will be evaluated using a deterministic radiation damage like myelopathy as end-point. In fact, the dose at which the 50% of animals will show the myelopathy is supposed to be LET-dependent. In this work, we studied different treatment configurations in order to choose the best two that maximize the LET difference reducing as much as possible the dose released to healthy tissue. The results will be useful to plan hadrontherapy treatments for preclinical in vivo studies and, in particular, for the future in vivo RBE studies.
Assuntos
Método de Monte Carlo , Terapia com Prótons/métodos , Eficiência Biológica Relativa , Animais , Órgãos em Risco/efeitos da radiação , Imagens de Fantasmas , Terapia com Prótons/efeitos adversos , Terapia com Prótons/instrumentaçãoRESUMO
Protontherapy is hadrontherapy's fastest-growing modality and a pillar in the battle against cancer. Hadrontherapy's superiority lies in its inverted depth-dose profile, hence tumour-confined irradiation. Protons, however, lack distinct radiobiological advantages over photons or electrons. Higher LET (Linear Energy Transfer) 12C-ions can overcome cancer radioresistance: DNA lesion complexity increases with LET, resulting in efficient cell killing, i.e. higher Relative Biological Effectiveness (RBE). However, economic and radiobiological issues hamper 12C-ion clinical amenability. Thus, enhancing proton RBE is desirable. To this end, we exploited the p + 11B â 3α reaction to generate high-LET alpha particles with a clinical proton beam. To maximize the reaction rate, we used sodium borocaptate (BSH) with natural boron content. Boron-Neutron Capture Therapy (BNCT) uses 10B-enriched BSH for neutron irradiation-triggered alpha particles. We recorded significantly increased cellular lethality and chromosome aberration complexity. A strategy combining protontherapy's ballistic precision with the higher RBE promised by BNCT and 12C-ion therapy is thus demonstrated.
Assuntos
Terapia por Captura de Nêutron de Boro/métodos , Boro/uso terapêutico , Terapia Combinada/métodos , Nêutrons , Neoplasias da Próstata/radioterapia , Terapia com Prótons , Terapia com Prótons/métodos , Partículas alfa/uso terapêutico , Animais , Boroidretos/química , Boro/química , Terapia por Captura de Nêutron de Boro/instrumentação , Isótopos de Carbono/química , Morte Celular/efeitos da radiação , Linhagem Celular Tumoral , Aberrações Cromossômicas/efeitos da radiação , Terapia Combinada/instrumentação , Ciclotrons , Dano ao DNA , DNA de Neoplasias/genética , DNA de Neoplasias/metabolismo , DNA de Neoplasias/efeitos da radiação , Relação Dose-Resposta à Radiação , Corantes Fluorescentes/química , Humanos , Cariotipagem , Transferência Linear de Energia , Masculino , Neoplasias da Próstata/patologia , Terapia com Prótons/instrumentação , Eficiência Biológica Relativa , Compostos de Sulfidrila/químicaRESUMO
Acoustic noise levels were measured in the Gulf of Catania (Ionian Sea) from July 2012 to May 2013 by a low frequency (<1000Hz) hydrophone, installed on board the NEMO-SN1 multidisciplinary observatory. NEMO-SN1 is a cabled node of EMSO-ERIC, which was deployed at a water depth of 2100m, 25km off Catania. The study area is characterized by the proximity of mid-size harbors and shipping lanes. Measured noise levels were correlated with the passage of ships tracked with a dedicated AIS antenna. Noise power was measured in the frequency range between 10Hz and 1000Hz. Experimental data were compared with the results of a fast numerical model based on AIS data to evaluate the contribution of shipping noise in six consecutive 1/3 octave frequency bands, including the 1/3 octave frequency bands centered at 63Hz and 125Hz, indicated by the Marine Strategy Framework Directive (2008/56/EC).
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Monitoramento Ambiental , Ruído , Navios , Acústica , ÁguaRESUMO
When a carbon beam interacts with human tissues, many secondary fragments are produced into the tumor region and the surrounding healthy tissues. Therefore, in hadrontherapy precise dose calculations require Monte Carlo tools equipped with complex nuclear reaction models. To get realistic predictions, however, simulation codes must be validated against experimental results; the wider the dataset is, the more the models are finely tuned.Since no fragmentation data for tissue-equivalent materials at Fermi energies are available in literature, we measured secondary fragments produced by the interaction of a 55.6 MeV u(-1) (12)C beam with thick muscle and cortical bone targets. Three reaction models used by the Geant4 Monte Carlo code, the Binary Light Ions Cascade, the Quantum Molecular Dynamic and the Liege Intranuclear Cascade, have been benchmarked against the collected data. In this work we present the experimental results and we discuss the predictive power of the above mentioned models.
Assuntos
Carbono/química , Simulação por Computador , Radioterapia com Íons Pesados/métodos , Modelos Teóricos , Método de Monte Carlo , Planejamento da Radioterapia Assistida por Computador/métodos , Algoritmos , Humanos , Dosagem RadioterapêuticaRESUMO
Fluence, depth absorbed dose and linear energy transfer (LET) distributions of proton and carbon ion beams have been investigated using the Monte Carlo code Geant4 (GEometry ANd Tracking). An open source application was developed with the aim to simulate two typical transport beam lines, one used for ocular therapy and cell irradiations with protons and the other for cell irradiations with carbon ions. This tool allows evaluation of the primary and total dose averaged LET and predict their spatial distribution in voxelized or sliced geometries. In order to reproduce the LET distributions in a realistic way, and also the secondary particles' contributions due to nuclear interactions were considered in the computations. Pristine and spread-out Bragg peaks were taken into account both for proton and carbon ion beams, with the maximum energy of 62 MeV/n. Depth dose distributions were compared with experimental data, showing good agreement. Primary and total LET distributions were analysed in order to study the influence of contributions of secondary particles in regions at different depths. A non-negligible influence of high-LET components was found in the entrance channel for proton beams, determining the total dose averaged LET by the factor 3 higher than the primary one. A completely different situation was obtained for carbon ions. In this case, secondary particles mainly contributed in the tail that is after the peak. The results showed how the weight of light and heavy secondary ions can considerably influence the computation of LET depth distributions. This has an important role in the interpretation of results coming from radiobiological experiments and, therefore, in hadron treatment planning procedures.
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Radioterapia com Íons Pesados/métodos , Transferência Linear de Energia , Método de Monte Carlo , Terapia com Prótons , Radiobiologia , Dosagem RadioterapêuticaRESUMO
GOAL: Proton treatment monitoring with Positron-Emission-Tomography (PET) is based on comparing measured and Monte Carlo (MC) predicted ß(+) activity distributions. Here we present PET ß(+) activity data and MC predictions both during and after proton irradiation of homogeneous PMMA targets, where protons were extracted from a cyclotron. METHODS AND MATERIALS: PMMA phantoms were irradiated with 62 MeV protons extracted from the CATANA cyclotron. PET activity data were acquired with a 10 × 10 cm(2) planar PET system and compared with predictions from the FLUKA MC generator. We investigated which isotopes are produced and decay during irradiation, and compared them to the situation after irradiation. For various irradiation conditions we compared one-dimensional activity distributions of MC and data, focussing on Δw50%, i.e., the distance between the 50% rise and 50% fall-off position. RESULTS: The PET system is able to acquire data during and after cyclotron irradiation. For PMMA phantoms the difference between the FLUKA MC prediction and our data in Δw50% is less than 1 mm. The ratio of PET activity events during and after irradiation is about 1 in both data and FLUKA, when equal time-frames are considered. Some differences are observed in profile shape. CONCLUSION: We found a good agreement in Δw50% and in the ratio between beam-on and beam-off activity between the PET data and the FLUKA MC predictions in all irradiation conditions.
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Ciclotrons , Método de Monte Carlo , Tomografia por Emissão de Pósitrons , Terapia com Prótons/instrumentação , Radioterapia Guiada por Imagem/instrumentação , Partículas beta/uso terapêutico , Imagens de Fantasmas , Polimetil MetacrilatoRESUMO
During particle therapy irradiation, positron emitters with half-lives ranging from 2 to 20 min are generated from nuclear processes. The half-lives are such that it is possible either to detect the positron signal in the treatment room using an in-beam positron emission tomography (PET) system, right after the irradiation, or to quickly transfer the patient to a close PET/CT scanner. Since the activity distribution is spatially correlated with the dose, it is possible to use PET imaging as an indirect method to assure the quality of the dose delivery. In this work, we present a new dedicated PET system able to operate in-beam. The PET apparatus consists in two 10 cm × 10 cm detector heads. Each detector is composed of four scintillating matrices of 23 × 23 LYSO crystals. The crystal size is 1.9 mm × 1.9 mm × 16 mm. Each scintillation matrix is read out independently with a modularized acquisition system. The distance between the two opposing detector heads was set to 20 cm. The system has very low dead time per detector area and a 3 ns coincidence window, which is capable to sustain high single count rates and to keep the random counts relatively low. This allows a new full-beam monitoring modality that includes data acquisition also while the beam is on. The PET system was tested during the irradiation at the CATANA (INFN, Catania, Italy) cyclotron-based proton therapy facility. Four acquisitions with different doses and dose rates were analysed. In all cases the random to total coincidences ratio was equal or less than 25%. For each measurement we estimated the accuracy and precision of the activity range on a set of voxel lines within an irradiated PMMA phantom. Results show that the inclusion of data acquired during the irradiation, referred to as beam-on data, improves both the precision and accuracy of the range measurement with respect to data acquired only after irradiation. Beam-on data alone are enough to give precisions better than 1 mm when at least 5 Gy are delivered.
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Tomografia por Emissão de Pósitrons/instrumentação , Terapia com Prótons/instrumentação , Radioterapia Guiada por Imagem/instrumentação , Algoritmos , Humanos , Processamento de Imagem Assistida por Computador , SoftwareRESUMO
Developments in hadron therapy require efforts to improve the accuracy of the dose delivered to a target volume. Here, the determination of the absorbed dose under reference conditions was analysed. Based on the International Atomic Energy Agency TRS-398 code of practice, for hadron beams, the combined standard uncertainty on absorbed dose to water under reference conditions, derived from ionisation chambers, is too large. This uncertainty is dominated by the beam quality correction factors, [Formula: see text], mainly due to the mean energy to produce one ion pair in air, wair. A method to reduce this uncertainty is to carry out primary dosimetry, using calorimetry. A [Formula: see text]-value can be derived from a direct comparison between calorimetry and ionometry. Here, this comparison is performed using a graphite calorimeter in an 80-MeV A(-1) carbon ion beam. Assuming recommended TRS-398 values of water-to-graphite stopping power ratio and the perturbation factor for an ionisation chamber, preliminary results indicate a wair-value of 35.5 ± 0.9 J C(-1).
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Calorimetria/métodos , Grafite/química , Radiometria/métodos , Ar , Calibragem , Carbono , Temperatura Alta , Humanos , Íons , Método de Monte Carlo , Radiometria/instrumentação , Dosagem Radioterapêutica , Valores de Referência , Reprodutibilidade dos Testes , Água/químicaRESUMO
Based on experiments and numerical simulations, a study is carried out pertaining to the conversion of dose-to-graphite to dose-to-water in a carbon ion beam. This conversion is needed to establish graphite calorimeters as primary standards of absorbed dose in these beams. It is governed by the water-to-graphite mass collision stopping power ratio and fluence correction factors, which depend on the particle fluence distributions in each of the two media. The paper focuses on the experimental and numerical determination of this fluence correction factor for an 80 MeV/A carbon ion beam. Measurements have been performed in the nuclear physics laboratory INFN-LNS in Catania (Sicily, Italy). The numerical simulations have been made with a Geant4 Monte Carlo code through the GATE simulation platform. The experimental data are in good agreement with the simulated results for the fluence correction factors and are found to be close to unity. The experimental values increase with depth reaching 1.010 before the Bragg peak region. They have been determined with an uncertainty of 0.25%. Different numerical results are obtained depending on the level of approximation made in calculating the fluence correction factors. When considering carbon ions only, the difference between measured and calculated values is maximal just before the Bragg peak, but its value is less than 1.005. The numerical value is close to unity at the surface and increases to 1.005 near the Bragg peak. When the fluence of all charged particles is considered, the fluence correction factors are lower than unity at the surface and increase with depth up to 1.025 before the Bragg peak. Besides carbon ions, secondary particles created due to nuclear interactions have to be included in the analysis: boron ions ((10)B and (11)B), beryllium ions ((7)Be), alpha particles and protons. At the conclusion of this work, we have the conversion of dose-to-graphite to dose-to-water to apply to the response of a graphite calorimeter in an 80 MeV/A carbon ion beam. This conversion consists of the product of two contributions: the water-to-graphite electronic mass collision stopping power ratio, which is equal to 1.115, and the fluence correction factor which varies linearly with depth, as k(fl, all) = 0.9995 + 0.0048(zw-eq). The latter has been determined on the basis of experiments and numerical simulations.