Objective.One major advantage of proton therapy (PT) over conventional photon radiotherapy is reduced dose delivered to normal tissue. However, the complexity of the secondary radiation field composed of a mixture of particles with a wide energy range makes its characterization a challenging task.Approach.Measurements with a miniaturized Timepix detector were carried out in three positions out-of-field (7.4 cm, 14.1 cm, and 18.5 cm from the isocenter), inside a phantom resembling a 5 year old undergoing proton pencil beam scanning treatment for a brain tumor. Total and particle-specific deposited energy, absorbed dose, and dose equivalent in water were calculated. Results were compared with thermoluminescent detectors (TLDs) measurements and Monte Carlo (MC) simulations modelling the experimental setup.Main results.The proton absorbed dose in water normalized to the target dose, ranged from 4.8 mGy Gy-1to 65.5µGy Gy-1, while the gamma dose, which remained consistently lower, ranged between 88.4µGy Gy-1and 6.1µGy Gy-1. The measured dose equivalent varied between 6.3 mSv Gy-1and 82.3µSv Gy-1. Good agreement was observed for the two farthest-locations when comparing the absorbed dose in water estimated by the MiniPIX Timepix detector with TLD measurements and MC simulations. However, the closest position showed an overestimation for both the absorbed dose and the dose equivalent, while the farthest position exhibited an underestimation for the dose equivalent.Significance.Out-of-field dosimetry in PT is challenging due to the complexity of the secondary mixed radiation field. Multiple detectors are typically required, but many are too large for use in anthropomorphic phantoms. This study demonstrates that the MiniPIX Timepix detector can accurately determine absorbed dose, dose equivalent and particle-specific contributions (electrons/gammas, protons, and ions). Unlike passive detectors such as TLDs, it enables active measurements with high time resolution, allowing dose rates analysis. The results, validated through experimental data and MC simulations, support the detector's potential for reliable out-of-field dose assessment and improved patient safety.
- Klíčová slova
- MiniPIX Timepix detector, Monte Carlo (MC) simulations, TOPAS, anthropomorphic phantom, out-of-field dose, proton therapy (PT), thermoluminescent detectors (TLDs),
- MeSH
- časové faktory MeSH
- celková dávka radioterapie MeSH
- fantomy radiodiagnostické MeSH
- lidé MeSH
- metoda Monte Carlo MeSH
- protonová terapie * přístrojové vybavení metody MeSH
- radiometrie * přístrojové vybavení MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
BACKGROUND: FLASH radiotherapy necessitates the development of advanced Quality Assurance methods and detectors for accurate monitoring of the radiation field. This study introduces enhanced time-resolution detection systems and methods used to measure the delivered number of pulses, investigate temporal structure of individual pulses and dose-per-pulse (DPP) based on secondary radiation particles produced in the experimental room. METHODS: A 20 MeV electron beam generated from a linear accelerator (LINAC) was delivered to a water phantom. Ultra-high dose-per-pulse electron beams were used with a dose-per-pulse ranging from ̴ 1 Gy to over 7 Gy. The pulse lengths ranged from 1.18 µs to 2.88 µs at a pulse rate frequency of 5 Hz. A semiconductor pixel detector Timepix3 was used to track single secondary particles. Measurements were performed in the air, while the detector was positioned out-of-field at a lateral distance of 200 cm parallel with the LINAC exit window. The dose deposited was measured along with the pulse length and the nanostructure of the pulse. RESULTS: The time of arrival (ToA) of single particles was measured with a resolution of 1.56 ns, while the deposited energy was measured with a resolution of several keV based on the Time over Threshold (ToT) value. The pulse count measured by the Timepix3 detector corresponded with the delivered values, which were measured using an in-flange integrating current transformer (ICT). A linear response (R2 = 0.999) was established between the delivered beam current and the measured dose at the detector position (orders of nGy). The difference between the average measured and delivered pulse length was ∼0.003(30) μs. CONCLUSION: This simple non-invasive method exhibits no limitations on the delivered DPP within the range used during this investigation.
- Klíčová slova
- FLASH electron, FLASH electron radiotherapy, Fast neutrons, Out-of-field dose, Particle flux, Single pulse, Time measurement, Timepix3 pixel detector,
- MeSH
- časové faktory MeSH
- částice - urychlovače * MeSH
- celková dávka radioterapie * MeSH
- fantomy radiodiagnostické MeSH
- radiometrie * přístrojové vybavení metody MeSH
- radioterapie přístrojové vybavení MeSH
- Publikační typ
- časopisecké články MeSH
Objective.There is an increasing interest in calculating and measuring linear energy transfer (LET) spectra in particle therapy in order to assess their impact in biological terms. As such, the accuracy of the particle fluence energy spectra becomes paramount. This study focuses on quantifying energy depositions of distinct proton, helium, carbon, and oxygen ion beams using a silicon pixel detector developed at CERN to determine LET spectra in silicon.Approach.While detection systems have been investigated in this pursuit, the scarcity of detectors capable of providing per-ion data with high spatial and temporal resolution remains an issue. This gap is where silicon pixel detector technology steps in, enabling online tracking of single-ion energy deposition. The used detector consisted of a 300µm thick silicon sensor operated in partial depletion.Main results.During post-processing, artifacts in the acquired signals were identified and methods for their corrections were developed. Subsequently, a correlation between measured and Monte Carlo-based simulated energy deposition distributions was performed, relying on a two-step recalibration approach based on linear and saturating exponential models. Despite the observed saturation effects, deviations were confined below 7% across the entire investigated range of track-averaged LET values in silicon from 0.77 keVµm-1to 93.16 keVµm-1.Significance.Simulated and measured mean energy depositions were found to be aligned within 7%, after applying artifact corrections. This extends the range of accessible LET spectra in silicon to clinically relevant values and validates the accuracy and reliability of the measurements. These findings pave the way towards LET-based dosimetry through an approach to translate these measurements to LET spectra in water. This will be addressed in a future study, extending functionality of treatment planning systems into clinical routine, with the potential of providing ion-beam therapy of utmost precision to cancer patients.
- Klíčová slova
- Monte Carlo simulations, energy deposition measurements, ion beam radiotherapy, linear energy transfer, particle tracking, radiation quality, silicon pixel Timepix3 detectors,
- MeSH
- křemík MeSH
- lineární přenos energie * MeSH
- metoda Monte Carlo MeSH
- radiometrie přístrojové vybavení MeSH
- Publikační typ
- časopisecké články MeSH
- Názvy látek
- křemík MeSH
The development of ultra-intense electron pulse for applications needs to be accompanied by the implementation of a practical dosimetry system. In this study four different systems were investigated as dosimeters for low doses with a very high-dose-rate source. First, the effects of ultra-short pulses were investigated for the yields of the Fricke dosimeter based on acidic solutions of ferrous sulfate; it was established that the yields were not significantly affected by the high dose rates, so the Fricke dosimeter system was used as a reference. Then, aqueous solutions of three compounds as fluorescence chemical dosimeters were utilized, each operated at a different solution pH: terephthalic acid - basic, trimesic acid - acidic, and coumarin-3-carboxylic acid (C3CA) - neutral. Fluorescence chemical dosimeters offer an attractive alternative to chemical dosimeters based on optical absorption for measuring biologically relevant low doses because of their higher sensitivity. The effects of very intense dose rate (TGy/ s) from pulses of fast electrons generated by a picosecond linear accelerator on the chemical yields of fluorescence chemical dosimeters were investigated at low peak doses (<20 Gy) and compared with yields determined under low-dose-rate irradiation from a 60 Co gamma-ray source (mGy/s). For the terephthalate and the trimesic acid dosimeters changes in the yields were not detected within the estimated (∼10%) precision of the experiments, but, due to the complexity of the mechanism of the hydroxyl radical initiated reactions in solutions of the relevant aromatic compounds, significant reductions of the chemical yield (-60%) were observed when the C3CA dosimeter was irradiated with the ultra-short pulses.
- MeSH
- časové faktory MeSH
- dávka záření MeSH
- dozimetry MeSH
- elektrony * MeSH
- fluorescence MeSH
- koncentrace vodíkových iontů MeSH
- kumariny chemie analýza MeSH
- kyseliny ftalové chemie analýza MeSH
- radiometrie metody přístrojové vybavení MeSH
- vztah dávky záření a odpovědi MeSH
- železnaté sloučeniny chemie MeSH
- Publikační typ
- časopisecké články MeSH
- Názvy látek
- coumarin-3-carboxylic acid MeSH Prohlížeč
- ferrous sulfate MeSH Prohlížeč
- kumariny MeSH
- kyseliny ftalové MeSH
- terephthalic acid MeSH Prohlížeč
- železnaté sloučeniny MeSH
Neutron detection using nuclear emulsions can offer an alternative in personal dosimetry. The production of emulsions and their quality have to be well controlled with respect to their application in dosimetry. Nuclear emulsions consist mainly of gelatin and silver halide. Gelatin contains a significant amount of hydrogen, which can be used for fast neutron detection. The addition of B-10 in the emulsion is convenient for thermal neutron detection. In this paper, standard nuclear emulsions BR-2 and nuclear emulsions BR-2 enriched with boron produced at the Slavich Company, Russia, were applied for evaluation of fast and thermal neutron fluences. The results were obtained by calculation from the presumed emulsion composition without prior calibration. Evidence that nuclear emulsions used in the experiment are suitable for neutron dosimetry is provided.
- MeSH
- bor chemie MeSH
- bromidy chemie MeSH
- emulze * MeSH
- fantomy radiodiagnostické MeSH
- helium analýza MeSH
- kalibrace MeSH
- lithium analýza MeSH
- neutrony * MeSH
- počítačové zpracování obrazu MeSH
- radiometrie přístrojové vybavení metody MeSH
- rychlé neutrony * MeSH
- sloučeniny stříbra chemie MeSH
- vodík chemie MeSH
- želatina chemie MeSH
- Publikační typ
- časopisecké články MeSH
- Názvy látek
- bor MeSH
- bromidy MeSH
- emulze * MeSH
- helium MeSH
- lithium MeSH
- silver bromide MeSH Prohlížeč
- sloučeniny stříbra MeSH
- vodík MeSH
- želatina MeSH
Linearity of response belongs to fundamental characteristics of neutron detection systems. Research reactors are valuable tools for neutron detector non-linearity studies as they offer a wide range of neutron fluxes. For neutron detection systems working in pulse mode they enable to characterise detector response non-linearity from some hundreds of cps up to the maximum reachable count rates. The paper presents comparison of two methods for neutron pulse-mode detector non-linearity characterisation using VR-1 zero power reactor: (1) comparative method utilising the comparison of studied pulse-mode detection system with a response of gamma compensated ionisation chamber working in current mode, and (2) kinetics method utilising the asymptotic exponential power rise after positive reactivity insertion as a source of information on true signal. Further several approaches for dead time determination based on theoretical formulae describing paralysable and non-paralysable dead time behaviour of detectors were studied and their usability to characterise the count-rate dependent detector response was analysed.
- MeSH
- algoritmy * MeSH
- lidé MeSH
- metoda Monte Carlo MeSH
- neutrony * MeSH
- radiometrie přístrojové vybavení MeSH
- záření gama MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
- srovnávací studie MeSH
Unique 3D tomography apparatus was built and successfully tested in Research Centre Rez. The apparatus allows three-dimensional view into the interior of low-dimension radioactive samples with a diameter up to several tens of millimeters with a betterresolution then 1 mm3 and is designed to detect domains with different levels of radioactivity. Structural inhomogeneities such as cavities, cracks or regions with different chemical composition can be detected using this equipment. The SPECT scanner has been successfully tested on several samples composed of a 3-mm radionuclide source located eccentrically within homogeneous steel bushings. To detect fine cracks inside a small sample, an ultrafine scan of the sample was carried out in the course of 24 hours with a 0.5-mm longitudinal and transverse step and 18° angular step. The exact location and orientation of a fine crack artificially formed inside a sample has been detected.
- MeSH
- algoritmy MeSH
- difuze MeSH
- geologie MeSH
- jednofotonová emisní výpočetní tomografie * MeSH
- oxid křemičitý MeSH
- počítačové zpracování obrazu metody MeSH
- poréznost MeSH
- radioizotopy kobaltu MeSH
- radiometrie přístrojové vybavení metody MeSH
- radon MeSH
- scintilace - počítání MeSH
- software MeSH
- teoretické modely MeSH
- wolfram MeSH
- záření gama MeSH
- zobrazování trojrozměrné * MeSH
- Publikační typ
- časopisecké články MeSH
- Názvy látek
- granite MeSH Prohlížeč
- oxid křemičitý MeSH
- radioizotopy kobaltu MeSH
- radon MeSH
- wolfram MeSH
Mobile phones and common chip cards are very widespread items that almost everyone owns. They contain some radiation-sensitive materials that can be used for dosimetry based on stimulated luminescence. We investigated and compared reproducibility, dose response and fading of luminescence signal for the particular materials. Subsequently, we performed an experiment of a dose reconstruction using mobile phones and chip cards, which were fixed to a slab phantom and irradiated by a 137Cs radiation source in our laboratory. Doses obtained were compared with reference values. The materials investigated can be used for dosimetry in cases of serious radiation accidents or malevolent acts with radioactive materials, when it is extremely important to identify as quickly as possible individuals who received high-radiation doses.
- MeSH
- dávka záření MeSH
- design vybavení MeSH
- fantomy radiodiagnostické MeSH
- kalibrace MeSH
- luminiscence * MeSH
- mobilní telefon * MeSH
- radioizotopy cesia analýza MeSH
- radiometrie přístrojové vybavení metody MeSH
- reprodukovatelnost výsledků MeSH
- teplota MeSH
- termoluminiscenční dozimetrie MeSH
- únik radioaktivních látek * MeSH
- vztah dávky záření a odpovědi MeSH
- Publikační typ
- časopisecké články MeSH
- Názvy látek
- Cesium-137 MeSH Prohlížeč
- radioizotopy cesia MeSH
PURPOSE: The aim of this paper is to investigate the limits of LET monitoring of therapeutic carbon ion beams with miniaturized microdosimetric detectors. METHODS: Four different miniaturized microdosimeters have been used at the 62 MeV/u 12C beam of INFN Southern National Laboratory (LNS) of Catania for this purpose, i.e. a mini-TEPC and a GEM-microdosimeter, both filled with propane gas, and a silicon and a diamond microdosimeter. The y-D (dose-mean lineal energy) values, measured at different depths in a PMMA phantom, have been compared withLET¯D (dose-mean LET) values in water, calculated at the same water-equivalent depth with a Monte Carlo simulation setup based on the GEANT4 toolkit. RESULTS: In these first measurements, no detector was found to be significantly better than the others as a LET monitor. The y-D relative standard deviation has been assessed to be 13% for all the detectors. On average, the ratio between y-D and LET¯D values is 0.9 ± 0.3, spanning from 0.73 ± 0.08 (in the proximal edge and Bragg peak region) to 1.1 ± 0.3 at the distal edge. CONCLUSIONS: All the four microdosimeters are able to monitor the dose-mean LET with the 11% precision up to the distal edge. In the distal edge region, the ratio of y-D to LET¯D changes. Such variability is possibly due to a dependence of the detector response on depth, since the particle mean-path length inside the detectors can vary, especially in the distal edge region.
- MeSH
- celková dávka radioterapie MeSH
- design vybavení MeSH
- fantomy radiodiagnostické MeSH
- izotopy uhlíku terapeutické užití MeSH
- kalibrace MeSH
- metoda Monte Carlo MeSH
- miniaturizace MeSH
- počítačová simulace MeSH
- polymethylmethakrylát MeSH
- radiometrie přístrojové vybavení MeSH
- radioterapie těžkými ionty přístrojové vybavení MeSH
- voda MeSH
- Publikační typ
- časopisecké články MeSH
- srovnávací studie MeSH
- Názvy látek
- izotopy uhlíku MeSH
- polymethylmethakrylát MeSH
- voda MeSH
197Au, 209Bi, 59Co, natFe and 169Tm samples were irradiated several times with quasi-monoenergetic neutrons from the p+7Li reaction in the energy range of 18-34 MeV. The activities of the samples were measured with the HPGe detector and the reaction rates were calculated. The cross sections were extracted using the SAND-II code with the reference cross sections from the IRDFF database.
