ANSTO :: Browsing by Author "Guatelli, S"

Browsing by Author "Guatelli, S"

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3D sensitive volume microdosimeter with improved tissue equivalency: charge collection study and its application in 12C ion therapy
(IOP Publishing, 2018-02-06) James, B; Tran, LT; Bolst, D; Prokopovich, DA; Reinhard, MI; Lerch, MLF; Petasecca, M; Guatelli, S; Povoli, M; Kok, A; Matsufuji, N; Jackson, M; Rosenfeld, AB
This research focuses on the characterisation of a new 3D sensitive volume (SV) microdosimeter covered with polyimide – a material which closely mimics human tissue. The electrical and charge collection properties of the device were investigated and its application in 12C ion therapy were studied. Charge collection studies revealed uniform charge collection and no cross talk between adjacent SVs. To study the microdosimetric response in 12C ion therapy, the new polyimide mushroom microdosimeter were placed at various positions along the central axis of a 290 MeV/u 12C ion spread out Bragg peak (SOBP) at the Heavy Ion Medical Accelerator in Chiba (HIMAC), Japan. From these microdosimetric spectra, dose mean lineal energy $(\overline{{y}_{D})}$ and RBE10 results were obtained, with RBE10 increasing from 1.3 at the entrance to 2.7 at the end of the SOBP. The results obtained in this work show that the new generation of mushroom microdosimeters, covered with tissue equivalent polyimide material, are a useful tool for quality assurance in heavy ion therapy applications. © Open Access - CC BY - IOP Publishing Ltd.
Application of an SOI microdosimeter for monitoring of neutrons in various mixed radiation field environments
(Institute of Electrical and Electronics Engineers (IEEE), 2022-03-01) Pan, VA; Vohradsky, J; James, B; Pagani, F; Chartier, L; Debrot, E; Pastuovic, Z; Cutajar, D; Poder, J; Nancarrow, M; Pereloma, E; Bolst, D; Lee, SH; Inaniwa, T; Safavi-Naeini, M; Prokopovich, DA; Guatelli, S; Petasecca, M; Lerch, MLF; Povoli, M; Kok, A; Tran, LT; Rosenfeld, AB
Radiation monitoring in space radiation is complex due to galactic cosmic rays (GCRs), solar particle events (SPEs), and albedo particles. Thermal neutrons are an important component in the Moon radiation albedo field which can cause single event upset (SEU) in electronics when they interact with the 10 B present in electronic components. In this work, we studied an application of silicon on insulator (SOI) microdosimeters for neutron monitoring in various mixed radiation field environments. A 10- μm SOI microdosimeter was utilized in conjunction with a 10 B 4 C thin-film converter to successfully measure the thermal neutron contribution out of field of a therapeutic proton beam as well as an 18-MV X-ray linear accelerator (LINAC). The microdosimeter was placed downstream of the Bragg peak (BP) as well as laterally out of field of the proton beam and at two positions along the treatment couch of the 18-MV LINAC. It was demonstrated that the 10- μm SOI microdosimeter with 10 B 4 C converter is suitable for detection of thermal neutrons with excellent discrimination of gamma, fast and thermal neutron components in the presence of a gamma-neutron pulsed field of an 18-MV LINAC. To reduce the gamma contribution and further improve detection of neutrons in mixed radiation fields, a new 2 μm Mushroom-planar microdosimeter was fabricated and characterized in detail using an ion beam induced charge collection (IBIC) technique with 1.78 MeV He2+ ions. It was demonstrated that this 2 μm SOI microdosimeter can be operated in a passive mode. The SOI microdosimeter with the 10 B 4 C converter can be recommended for the detection of thermal neutrons for SEU prediction in the mixed gamma-neutron fields during space missions, especially for the Moon mission.© Copyright 2025 IEEE
Characterisation of a well-type NaI(T1) detector by means of a Monte Carlo simulation for radionuclide metrology application
(Elsevier B. V., 2021-10) Heranudin, H; Smith, ML; van Wyngaardt, WM; Guatelli, S; Li, E; Rosenfeld, AB
A well-type NaI(Tl) detector was modelled and characterised by means of a Monte Carlo simulation, as part of a project to develop a 4πβ (Plastic Scintillator)-4πγ instrument to be used for the primary standardisation of radionuclides at ANSTO. The simulation based on GEANT4 was used to characterise the 4πγ detector in terms of potential dead layer/inactive materials, full energy peak efficiency, coincidence-summing correction, and energy resolution. An excellent agreement was obtained between the simulation results and the experimental measurements. © 2021 Elsevier Ltd.
Characterization of prompt gamma rays for in-vivo range verification in hadron therapy: a geant4 simulation study
(Institute of Physics Publishing, 2018-02-06) Zarifi, M; Guatelli, S; Qi, Y; Bolst, D; Prokopovich, DA; Rosenfeld, AB
Prompt gamma (PG) rays have been proposed for in-vivo beam range verification during treatment delivery. As a secondary by-product emitted almost instantaneously upon ion-nuclear interaction, PG rays offer real-time tracking of the Bragg peak (BP). However their detection is challenging since they have a broad energy spectrum with interference from neutrons and stray gamma rays. Numerous approaches have been proposed to utilise PG for in-vivo beam range verification. In this work, Geant4 Monte Carlo (MC) simulations have been used to study the spectral, spatial, temporal and angular distribution characteristics of PG emission and detection from hadron radiation fields of varying energy. Proton, 12C and 4He beams irradiated homogeneous water phantoms. These studies will provide valuable information for the development of clinically suitable and reliable PG detector systems. © The Authors. Open Access.
Charge collection in SOI microdosimeters and their radiation hardness
(IEEE, 2023-02-03) Pan, VA; Tran, LT; Pastuovic, Z; Hill, D; Williams, JB; Kok, A; Povoli, M; Pogossov, A; Peracchi, S; Boardman, DA; Davis, J; Guatelli, S; Petasecca, M; Lerch, MLF; Rosenfeld, AB
A new batch of microdosimeters has been extensively studied for their charge collection efficiency (CCE) properties, as well as their radiation hardness for medical, space and accident applications. Silicon-on-insulator (SOI) microdosimeters with an active layer thickness of 10, 20 and 50 μm have been investigated and were characterized with a 24 MeV carbon ion beam as well as a Co-60 gamma source. A negative pulse was observed in addition to the positive pulses generated within the sensitive volumes (SVs) by incident ions which led to undesirable low energy events in the SOI microdosimeters response. To study this phenomenon, the microdosimeters were irradiated with gamma radiation from a Co-60 source with a total dose of 3 and 10 Mrad(Si). It was determined that the negative pulse was originating from the support wafer due to the displacement current phenomenon. Irradiation with the Co-60 source led to a disappearing of the negative pulse due to an increase in recombination within the support wafer while almost no changes in CCE were observed. A radiation hardness study was also performed on the 50 μm SOI microdosimeter with 16 SVs being irradiated with a fluence of ~ 10 8 12 C ions/cm 2 . A CCE deficit of approximately 2% was observed at an operation bias of 10V within the SVs. The findings of this work demonstrate that the SOI microdosimeters can be utilized in space and medical applications as they can handle typical levels of dose encountered in these applications. Additionally, evidence for SOI microdosimeter fabrication standards in terms of support wafer resistivity and buried oxide (BOX) thickness is shown. © 2023 IEEE
Comparative study of alternative Geant4 hadronic ion inelastic physics models for prediction of positron-emitting radionuclide production in carbon and oxygen ion therapy
(IOP Publishing, 2019-08-01) Chacon, A; Guatelli, S; Rutherford, H; Bolst, D; Mohammadi, A; Ahmed, A; Nitta, M; Nishikido, F; Iwao, Y; Tashima, H; Yoshida, E; Akamatsu, G; Takyu, S; Kitagawa, A; Hofmann, T; Pinto, M; Franklin, DR; Parodi, K; Yamaya, T; Rosenfeld, AB; Safavi-Naeini, M
The distribution of fragmentation products predicted by Monte Carlo simulations of heavy ion therapy depend on the hadronic physics model chosen in the simulation. This work aims to evaluate three alternative hadronic inelastic fragmentation physics options available in the Geant4 Monte Carlo radiation physics simulation framework to determine which model most accurately predicts the production of positron-emitting fragmentation products observable using in-beam PET imaging. Fragment distributions obtained with the BIC, QMD, and INCL + + physics models in Geant4 version 10.2.p03 are compared to experimental data obtained at the HIMAC heavy-ion treatment facility at NIRS in Chiba, Japan. For both simulations and experiments, monoenergetic beams are applied to three different block phantoms composed of gelatin, poly(methyl methacrylate) and polyethylene. The yields of the positron-emitting nuclei 11C, 10C and 15O obtained from simulations conducted with each model are compared to the experimental yields estimated by fitting a multi-exponential radioactive decay model to dynamic PET images using the normalised mean square error metric in the entrance, build up/Bragg peak and tail regions. Significant differences in positron-emitting fragment yield are observed among the three physics models with the best overall fit to experimental 12C and 16O beam measurements obtained with the BIC physics model. © 2019 Commonwealth of Australia, Australian Nuclear Science and Technology Organisation, ANSTO.
Detection and discrimination of neutron capture events for NCEPT dose quantification
(Springer Nature Limited, 2022-04-07) Chacon, A; Kielly, M; Rutherford, H; Franklin, DR; Caracciolo, A; Buonanno, L; D'Adda, I; Rosenfeld, AB; Guatelli, S; Carminati, M; Fiorini, C; Safavi-Naeini, M
Neutron Capture Enhanced Particle Therapy (NCEPT) boosts the effectiveness of particle therapy by capturing thermal neutrons produced by beam-target nuclear interactions in and around the treatment site, using tumour-specific 10B or 157Gd-based neutron capture agents. Neutron captures release high-LET secondary particles together with gamma photons with energies of 478 keV or one of several energies up to 7.94 MeV, for 10B and 157Gd, respectively. A key requirement for NCEPT’s translation is the development of in vivo dosimetry techniques which can measure both the direct ion dose and the dose due to neutron capture. In this work, we report signatures which can be used to discriminate between photons resulting from neutron capture and those originating from other processes. A Geant4 Monte Carlo simulation study into timing and energy thresholds for discrimination of prompt gamma photons resulting from thermal neutron capture during NCEPT was conducted. Three simulated 300×300×300 mm3 cubic PMMA targets were irradiated by 4He or 12C ion beams with a spread out Bragg peak (SOBP) depth range of 60 mm; one target is homogeneous while the others include 10×10×10 mm3 neutron capture inserts (NCIs) of pure 10B or 157Gd located at the distal edge of the SOBP. The arrival times of photons and neutrons entering a simulated 50×50×50 mm3 ideal detector were recorded. A temporal mask of 50–60 ns was found to be optimal for maximising the discrimination of the photons resulting from the neutron capture by boron and gadolinium. A range of candidate detector and thermal neutron shielding materials were simulated, and detections meeting the proposed acceptance criteria (i.e. falling within the target energy window and arriving 60 ns post beam-off) were classified as true or false positives, depending on their origin. The ratio of true/false positives (RTF) was calculated; for targets with 10B and 157Gd NCIs, the detector materials which resulted in the highest RTF were cadmium-shielded CdTe and boron-shielded LSO, respectively. The optimal irradiation period for both carbon and helium ions was 1 µs for the 10B NCI and 1 ms for the 157Gd NCI. © The Authors, Creative Commons Attribution 4.0 International Licence.
Dose quantification in carbon ion therapy using in-beam positron emission tomography
(IOP Publishing, 2020-12-07) Rutherford, H; Chacon, A; Mohammadi, A; Takyu, S; Tashima, H; Yoshida, E; Nishikido, F; Hofmann, T; Pinto, M; Franklin, DR; Yamaya, T; Parodi, K; Rosenfeld, AB; Guatelli, S; Safavi-Naeini, M
This work presents an iterative method for the estimation of the absolute dose distribution in patients undergoing carbon ion therapy, via analysis of the distribution of positron annihilations resulting from the decay of positron-emitting fragments created in the target volume. The proposed method relies on the decomposition of the total positron-annihilation distributions into profiles of the three principal positron-emitting fragment species - 11C, 10C and 15O. A library of basis functions is constructed by simulating a range of monoenergetic 12C ion irradiations of a homogeneous polymethyl methacrylate phantom and measuring the resulting one-dimensional positron-emitting fragment profiles and dose distributions. To estimate the dose delivered during an arbitrary polyenergetic irradiation, a linear combination of factors from the fragment profile library is iteratively fitted to the decomposed positron annihilation profile acquired during the irradiation, and the resulting weights combined with the corresponding monoenergetic dose profiles to estimate the total dose distribution. A total variation regularisation term is incorporated into the fitting process to suppress high-frequency noise. The method was evaluated with 14 different polyenergetic 12C dose profiles in a polymethyl methacrylate target: one which produces a flat biological dose, 10 with randomised energy weighting factors, and three with distinct dose maxima or minima within the spread-out Bragg peak region. The proposed method is able to calculate the dose profile with mean relative errors of 0.8%, 1.0% and 1.6% from the 11C, 10C, 15O fragment profiles, respectively, and estimate the position of the distal edge of the SOBP to within an average of 0.7 mm, 1.9 mm and 1.2 mm of its true location. © 2020 Commonwealth of Australia, ANSTO
Experimental investigation of the characteristics of radioactive beams for heavy ion therapy
(Wiley, 2020-07) Chacon, A; James, B; Tran, LT; Guatelli, S; Chartier, L; Prokopovich, DA; Franklin, DR; Mohammadi, A; Nishikido, F; Iwao, Y; Akamatsu, G; Takyu, S; Tashima, H; Yamaya, T; Parodi, K; Rosenfeld, AB; Safavi-Naeini, M
Purpose This work has two related objectives. The first is to estimate the relative biological effectiveness of two radioactive heavy ion beams based on experimental measurements, and compare these to the relative biological effectiveness of corresponding stable isotopes to determine whether they are therapeutically equivalent. The second aim is to quantitatively compare the quality of images acquired postirradiation using an in‐beam whole‐body positron emission tomography scanner for range verification quality assurance. Methods The energy deposited by monoenergetic beams of C at 350 MeV/u, O at 250 MeV/u, C at 350 MeV/u, and O at 430 MeV/u was measured using a cruciform transmission ionization chamber in a water phantom at the Heavy Ion Medical Accelerator in Chiba (HIMAC), Japan. Dose‐mean lineal energy was measured at various depths along the path of each beam in a water phantom using a silicon‐on‐insulator mushroom microdosimeter. Using the modified microdosimetric kinetic model, the relative biological effectiveness at 10% survival fraction of the radioactive ion beams was evaluated and compared to that of the corresponding stable ions along the path of the beam. Finally, the postirradiation distributions of positron annihilations resulting from the decay of positron‐emitting nuclei were measured for each beam in a gelatin phantom using the in‐beam whole‐body positron emission tomography scanner at HIMAC. The depth of maximum positron‐annihilation density was compared with the depth of maximum dose deposition and the signal‐to‐background ratios were calculated and compared for images acquired over 5 and 20 min postirradiation of the phantom. Results In the entrance region, the was 1.2 ± 0.1 for both C and C beams, while for O and O it was 1.4 ± 0.1 and 1.3 ± 0.1, respectively. At the Bragg peak, the was 2.7 ± 0.4 for C and 2.9 ± 0.4 for C, while for O and O it was 2.7 ± 0.4 and 2.8 ± 0.4, respectively. In the tail region, could only be evaluated for carbon; the was 1.6 ± 0.2 and 1.5 ± 0.1 for C and C, respectively. Positron emission tomography images obtained from gelatin targets irradiated by radioactive ion beams exhibit markedly improved signal‐to‐background ratios compared to those obtained from targets irradiated by nonradioactive ion beams, with 5‐fold and 11‐fold increases in the ratios calculated for the O and C images compared with the values obtained for O and C, respectively. The difference between the depth of maximum dose and the depth of maximum positron annihilation density is 2.4 ± 0.8 mm for C, compared to −5.6 ± 0.8 mm for C and 0.9 ± 0.8 mm for O vs −6.6 ± 0.8 mm for O. Conclusions The values for C and O were found to be within the 95% confidence interval of the RBEs estimated for their corresponding stable isotopes across each of the regions in which it was evaluated. Furthermore, for a given dose, C and O beams produce much better quality images for range verification compared with C and O, in particular with regard to estimating the location of the Bragg peak. © 2024 American Association of Physicists in Medicine.
From imaging to dosimetry: GEANT4-based study on the application of medipix to neutron dosimetry
(Elsevier, 2009-10-12) Othman, MAR; Marinaro, DG; Petasecca, M; Guatelli, S; Cutajar, DL; Lerch, MLF; Prokopovich, DA; Reinhard, MI; Uher, J; Jakubek, J; Pospisil, S; Rosenfeld, AB
An application of Medipix2 using a newly developed segmented multiple thickness polyethylene (PE) converter for fast neutron detection is presented. The system has the ability to provide an energy independent response for the dose equivalent for fast neutrons. The application of weighting factors to each defined thickness of PE allows for a flattening of the response of the detector system for dosimetry applications. Six PE converter segments were applied, and their thicknesses and weighting factors were optimised to obtain the required energy independent detector response. The study performed by means of GEANT4. Its suitability for neutron dosimetry was studied with respect to a previously published work. © 2013 Elsevier B.V.
Geant4 x-ray fluorescence with updated libraries
(Elsevier B. V., 2021-11-15) Bakr, S; Cohen, DD; Siegele, R; Archer, JW; Incerti, S; Ivanchenko, V; Mantero, A; Rosenfeld, AB; Guatelli, S
We present the results concerning the development in Geant4 of a new data driven library, called here the ANSTO HF library. This X-ray fluorescence library is based on an approach of particular interest for PIXE simulation applications; however, it can be used in any Geant4 applications where X-ray fluorescence needs to be described. The X-ray fluorescence transition probabilities were calculated within the Hartree-Fock (HF) approach, which is recognised to better reproduce PIXE experimental values compared with the Hartree-Slater approach, adopted in the current default Geant4 EADL data library. These HF X-ray fluorescence transition probabilities were integrated into a new Geant4 library and will be released within Geant4 in the near future. In this paper, we compare the fluorescence X-ray spectra generated by the ANSTO HF library and by the currently available library (EADL-1991 [1]) within Geant4, for targets irradiated with protons and α particles with energies up to 10 MeV, a range of interest for PIXE applications. The comparisons were performed for a large set of sample materials spanning a broad range of target atomic numbers. These two approaches were compared to existing experimental measurements performed at the ANSTO heavy ion microprobe beamline using 2 MeV and 3 MeV proton and 10 MeV He2+ ion beams. This work represents a useful upgrade to the Geant4 atomic de-excitation package. © 2021 Elsevier B.V.
An inception network for positron emission tomography based dose estimation in carbon ion therapy
(IOP Publishing, 2022-09-23) Rutherford, H; Turai, RS; Chacon, A; Franklin, DR; Mohammadi, A; Tashima, H; Yamaya, T; Parodi, K; Rosenfeld, AB; Guatelli, S; Safavi-Naeini, M
Objective. We aim to evaluate a method for estimating 1D physical dose deposition profiles in carbon ion therapy via analysis of dynamic PET images using a deep residual learning convolutional neural network (CNN). The method is validated using Monte Carlo simulations of 12C ion spread-out Bragg peak (SOBP) profiles, and demonstrated with an experimental PET image. Approach. A set of dose deposition and positron annihilation profiles for monoenergetic 12C ion pencil beams in PMMA are first generated using Monte Carlo simulations. From these, a set of random polyenergetic dose and positron annihilation profiles are synthesised and used to train the CNN. Performance is evaluated by generating a second set of simulated 12C ion SOBP profiles (one 116 mm SOBP profile and ten 60 mm SOBP profiles), and using the trained neural network to estimate the dose profile deposited by each beam and the position of the distal edge of the SOBP. Next, the same methods are used to evaluate the network using an experimental PET image, obtained after irradiating a PMMA phantom with a 12C ion beam at QST’s Heavy Ion Medical Accelerator in Chiba facility in Chiba, Japan. The performance of the CNN is compared to that of a recently published iterative technique using the same simulated and experimental 12C SOBP profiles. Main results. The CNN estimated the simulated dose profiles with a mean relative error (MRE) of 0.7% ± 1.0% and the distal edge position with an accuracy of 0.1 mm ± 0.2 mm, and estimate the dose delivered by the experimental 12C ion beam with a MRE of 3.7%, and the distal edge with an accuracy of 1.7 mm. Significance. The CNN was able to produce estimates of the dose distribution with comparable or improved accuracy and computational efficiency compared to the iterative method and other similar PET-based direct dose quantification techniques. © 2022 Institute of Physics and Engineering in Medicine.
Incorporating clinical imaging into the delivery of microbeam radiation therapy
(MDPI, 2021-09-30) Paino, JR; Barnes, M; Engels, E; Davis, JA; Guatelli, S; de Veer, M; Hall, CJ; Häusermann, D; Tehei, M; Corde, S; Rosenfeld, AB; Lerch, MLF
Synchrotron microbeam radiation therapy is a promising pre-clinical radiation treatment modality; however, it comes with many technical challenges. This study describes the image guidance protocol used for Australia’s first long-term pre-clinical MRT treatment of rats bearing 9L gliosarcoma tumours. The protocol utilises existing infrastructure available at the Australian Synchrotron and the adjoining Monash Biomedical Imaging facility. The protocol is designed and optimised to treat small animals utilising high-resolution clinical CT for patient specific tumour identification, coupled with conventional radiography, using the recently developed SyncMRT program for image guidance. Dosimetry performed in small animal phantoms shows patient dose is comparable to standard clinical doses, with a CT associated dose of less than 1.39cGy and a planar radiograh dose of less than 0.03cGy. Experimental validation of alignment accuracy with radiographic film demonstrates end to end accuracy of less than ±0.34mm in anatomical phantoms. Histological analysis of tumour-bearing rats treated with microbeam radiation therapy verifies that tumours are targeted well within applied treatment margins. To date, this technique has been used to treat 35 tumour-bearing rats. © 2021 by the Authors. Licensee MDPI, Basel, Switzerland.
Latest Geant4 developments for PIXE applications
(Elsevier B. V., 2018-12-01) Bakr, S; Cohen, DD; Siegele, R; Incerti, S; Ivanchenko, V; Mantero, A; Rosenfeld, AB; Guatelli, S
We describe the recent inclusion in Geant4 of state-of-the-art proton and alpha particle shell ionisation cross sections based on the ECPSSR approach as calculated by Cohen et al., called here ANSTO ECPSSR. The new ionisation cross sections have been integrated into Geant4. We present a comparison of the fluorescence X-ray spectra generated by the ANSTO ECPSSR set of cross sections and, alternatively, the currently available sets of Geant4 PIXE cross sections. The comparisons are performed for a large set of sample materials spanning a broad range of atomic numbers. The two alternative PIXE cross sections approaches (Geant4 and ANSTO) have been compared to existing experimental measurements performed at ANSTO with gold, tantalum and cerium targets of interest for nanomedicine applications. The results show that, while the alternative approaches produce equivalent results for vacancies generated in the K and L shell, differences are evident in the case of M shell vacancies. This work represents the next step in the effort to improve the Geant4 modelling of the atomic relaxation and provide recommended approaches to the Geant4 user community. This new Geant4 development is of interest for applications spanning from life and space to environmental science. Crown Copyright © 2018 Published by Elsevier B.V
A Monte Carlo model of the Dingo thermal neutron imaging beamline
(Springer Nature, 2023-12-01) Jakubowski, K; Charcon, A; Tran, LT; Stopic, A; Garbe, U; Bevitt, JJ; Olsen, SR; Franklin, DR; Rosenfeld, AB; Guatelli, S; Safavi-Naeini, M
In this study, we present a validated Geant4 Monte Carlo simulation model of the Dingo thermal neutron imaging beamline at the Australian Centre for Neutron Scattering. The model, constructed using CAD drawings of the entire beam transport path and shielding structures, is designed to precisely predict the in-beam neutron field at the position at the sample irradiation stage. The model’s performance was assessed by comparing simulation results to various experimental measurements, including planar thermal neutron distribution obtained in-beam using gold foil activation and BC-coated microdosimeters and the out-of-beam neutron spectra measured with Bonner spheres. The simulation results demonstrated that the predicted neutron fluence at the field’s centre is within 8.1% and 2.1% of the gold foil and BC-coated microdosimeter measurements, respectively. The logarithms of the ratios of average simulated to experimental fluences in the thermal (E 0.414 eV), epithermal (0.414 eV < E 11.7 keV) and fast (E 11.7 keV) spectral regions were approximately − 0.03 to + 0.1, − 0.2 to + 0.15, and − 0.4 to + 0.2, respectively. Furthermore, the predicted thermal, epithermal and fast neutron components in-beam at the sample stage position constituted approximately 18%, 64% and 18% of the total neutron fluence. © The Authors - Open Access Open Access This article is licensed under a Creative Commons Attribution 4.0 International.
Neutron dosimeter development based on Medipix2
(Institute of Electrical and Electronics Engineers (IEEE), 2010-12) Othman, MAR; Petasecca, M; Guatelli, S; Uher, J; Marinaro, DG; Prokopovich, DA; Reinhard, MI; Lerch, MLF; Jakubek, J; Pospisil, S; Rosenfeld, AB
A novel neutron dosimetry system for avionics and space applications is described. The new dosimetric system is based on Medipix2, a high density silicon based pixilated detector with integrated readout and digital interface circuitry. Real time dose equivalent response to fast neutron fields with flattened energy response is achieved through the coupling of a structured variable thickness polyethylene (PE) over layer with the high density pixilated detector. Experimental results obtained to 14 MeV D-T and Am-Be neutron fields are described along with a comparison to results obtained with GEANT4 simulations. © 2010, Institute of Electrical and Electronics Engineers (IEEE)
A novel silicon microdosimeter using 3D sensitive volumes: modeling the response in neutron fields typical of aviation
(IEEE Xplore Digital Library, 2014-08-04) Tran, LT; Guatelli, S; Prokopovich, DA; Petasecca, M; Lerch, MLF; Reinhard, MI; Zeigler, JF; Zaider, M; Rosenfeld, AB
A 4th generation silicon microdosimeter has been designed by the Centre for Medical Radiation Physics (CMRP) at the University of Wollongong using three dimensional (3D) Sensitive Volumes (SVs). This new microdosimeter design has the advantage of well-defined 3D SVs as well as the elimination of lateral charge diffusion by removal of silicon laterally adjacent to the 3D SVs. The gaps between the sensitive volumes are to be backfilled with PolyMethyl MethAcrylate (PMMA) to produce a surrounding tissue equivalent medium. The advantage of this design avoids the generation of secondary particles from inactive silicon lateral to SVs. The response of the microdosimeter to the neutron field from , Pu-Be sources and an avionic radiation environment were simulated using the Geant4 Monte Carlo toolkit for design optimisation. The simulated energy deposition in the SVs from the neutron fields and microdosimetric spectra is presented. The simulation study shows a significant reduction in silicon nuclear recoil contribution to the energy deposition for the novel microdosimeter design. The reduction of silicon recoil events from outside of the SV’s will consequently reduce the uncertainty in the calculateddose equivalent. The simulations have demonstrated that a 3D silicon microdosimeter surrounded by PMMA can produce microdosimetric spectra similar to those of a tissue equivalent microdosimeter. © 2014, IEEE.
Opportunistic dose amplification for proton and carbon ion therapy via capture of internally generated thermal neutrons
(Springer Nature, 2018-11-02) Safavi-Naeini, M; Chacon, A; Guatelli, S; Franklin, DR; Bambery, KR; Grégoire, MC; Rosenfeld, AB
This paper presents Neutron Capture Enhanced Particle Therapy (NCEPT), a method for enhancing the radiation dose delivered to a tumour relative to surrounding healthy tissues during proton and carbon ion therapy by capturing thermal neutrons produced inside the treatment volume during irradiation. NCEPT utilises extant and in-development boron-10 and gadolinium-157-based drugs from the related field of neutron capture therapy. Using Monte Carlo simulations, we demonstrate that a typical proton or carbon ion therapy treatment plan generates an approximately uniform thermal neutron field within the target volume, centred around the beam path. The tissue concentrations of neutron capture agents required to obtain an arbitrary 10% increase in biological effective dose are estimated for realistic treatment plans, and compared to concentrations previously reported in the literature. We conclude that the proposed method is theoretically feasible, and can provide a worthwhile improvement in the dose delivered to the tumour relative to healthy tissue with readily achievable concentrations of neutron capture enhancement drugs. © 2024 The Authors published by Springer Nature Limited. Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/.
P219 / #908 - advancements in NCEPT: animal study outcomes and technological developments toward clinical application
(Elsevier, 2024-06) Hirayama, R; Tashima, H; Hamato, A; Howell, NR; Sierro, F; Kielly, M; Caracciolo, A; Franklin, DR; Guatelli, S; Yamaya, T; Rosenfeld, AB; Fiorini, C; Carminati, M; Safavi-Naeini, M
Background and aims: Neutron Capture Enhanced Particle Therapy (NCEPT) represents a promising advancement in cancer treatment, utilising neutron capture agents (NCAs) to enhance therapeutic efficacy of proton/heavy ion radiation. This work focuses on animal experiments and concurrent technological developments aimed at translating NCEPT into clinical practice. Methods: Animal studies were conducted to assess the therapeutic impact of NCEPT. Baseline dose response of U87MG xenograft Balb/c nu/nu mice to 12C and 4He ion radiation was evaluated at HIMAC (February 2021, January 2022). NCEPT dose-response experiments with 10B-BPA as the NCA and using the same animal model were conducted in two campaigns in 2023. 200 mice were irradiated with helium or carbon ions across four dose levels (0 Gy, 5 Gy, 10 Gy, and 15 Gy, n = 6 mice/ion/dose); tumour growth was measured at different time points. In parallel, a scintillator-based detector for measurement of photon spectrum changes due to neutron capture was developed and evaluated in simulations and experiments with boron-loaded PMMA targets irradiated by helium/carbon ion beams. Results: Baseline experiments showed expected dose-response relationships, with tumour response and measured neutron fluence informing the NCEPT study protocol. NCEPT experiments demonstrated significant tumour volume reductions (33%/46% for helium/carbon ion irradiation, respectively) and delays in tumour growth relative to baseline. The prototype detector measured increases in the area of the 478 keV peak by 26%/45% for helium/carbon beams, respectively, compared to simulation-based values of 57%/45%. >65% of these photons originated from 10B captures in the detector's PCB, highlighting the need for neutron shielding and boron-free materials in detector construction. The linear increase in neutron capture photons at 10B concentrations up to 20000 ppm, with potential for detection down to 100 ppm using temporal windowing, paves the way for a SPECT-like neutron capture imaging system, crucial for NCEPT quality assurance. Conclusion: The combined animal study outcomes and technological advancements underscore the potential of NCEPT as a highly effective cancer therapy. The progress in dosimetry and imaging techniques mark significant steps toward the clinical translation of NCEPT, promising improved patient outcomes in cancer treatment. © 2024 Elsevier B.V. Open Access under a CC-BY-NC-ND 4.0 licence
A quantitative assessment of Geant4 for predicting the yield and distribution of positron-emitting fragments in ion beam therapy
(IOP Publishing, 2024-06-21) Chacon, A; Rutherford, H; Hamato, A; Nitta, M; Nishikido, F; Iwao, Y; Tashima, H; Yoshida, E; Akamatsu, G; Takyu, S; Kang, HG; Franklin, DR; Parodi, K; Yamaya, T; Rosenfeld, AB; Guatelli, S; Safavi-Naeini, M
Objective. To compare the accuracy with which different hadronic inelastic physics models across ten Geant4 Monte Carlo simulation toolkit versions can predict positron-emitting fragments produced along the beam path during carbon and oxygen ion therapy. Approach. Phantoms of polyethylene, gelatin, or poly(methyl methacrylate) were irradiated with monoenergetic carbon and oxygen ion beams. Post-irradiation, 4D PET images were acquired and parent 11C, 10C and 15O radionuclides contributions in each voxel were determined from the extracted time activity curves. Next, the experimental configurations were simulated in Geant4 Monte Carlo versions 10.0 to 11.1, with three different fragmentation models—binary ion cascade (BIC), quantum molecular dynamics (QMD) and the Liege intranuclear cascade (INCL++) - 30 model-version combinations. Total positron annihilation and parent isotope production yields predicted by each simulation were compared between simulations and experiments using normalised mean squared error and Pearson cross-correlation coefficient. Finally, we compared the depth of the maximum positron annihilation yield and the distal point at which the positron yield decreases to 50% of peak between each model and the experimental results. Main results. Performance varied considerably across versions and models, with no one version/model combination providing the best prediction of all positron-emitting fragments in all evaluated target materials and irradiation conditions. BIC in Geant4 10.2 provided the best overall agreement with experimental results in the largest number of test cases. QMD consistently provided the best estimates of both the depth of peak positron yield (10.4 and 10.6) and the distal 50%-of-peak point (10.2), while BIC also performed well and INCL generally performed the worst across most Geant4 versions. Significance. The best predictions of the spatial distribution of positron annihilations and positron-emitting fragment production along the beam path during carbon and oxygen ion therapy was obtained using Geant4 10.2.p03 with BIC or QMD. These version/model combinations are recommended for future heavy ion therapy research. © 2024 The Author(s). Published on behalf of Institute of Physics and Engineering in Medicine by IOP Publishing Ltd - Open Access - Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 license. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.

Browsing by Author "Guatelli, S"

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