ANSTO :: Browsing by Author "Lerch, MLF"

Browsing by Author "Lerch, MLF"

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3D radiation detectors: charge collection characterisation and applicability of technology for microdosimetry
(IEEE Xplore, 2014-08-04) Tran, LT; Prokopovich, DA; Petasecca, M; Lerch, MLF; Kok, A; Summanwar, A; Hansen, T; Via, CD; Reihnard, MI; Rosenfeld, AB
A study of charge collection in SINTEF 3D active edge silicon detectors was carried out at ANSTO using Ion Beam Induced Charge (IBIC) technique. An IBIC study has shown that several different geometries of 3D detectors have full depletion under low applied bias. The effect of fast neutron and gamma radiation on their charge collection efficiency was also investigated. A 3D active edge silicon detector technology has demonstrated extremely promising performance for application of the 3D Sensitive Volumes (SVs) fabrication methods to SOI microdosimetry.© 2014, IEEE.
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.
Angular independent silicon detector for dosimetry in external beam radiotherapy
(American Association of Physicists in Medicine, 2015-07-17) Petasecca, M; Alhujaili, S; Aldosari, AH; Fuduli, I; Newal, M; Porumb, CS; Carolan, MG; Nitschke, K; Lerch, MLF; Kalliopuska, J; Perevertaylo, VL; Rosenfeld, AB
Purpose: In this work, the “edgeless” silicon detector technology is investigated, in combination with an innovative packaging solution, to manufacture silicon detectors with negligible angular response. The new diode is also characterized as a dosimeter for radiotherapy with the aim to verify its suitability as a single detector for in vivo dosimetry as well as large area 2D array that does not require angular correction to their response. Methods: For the characterisation of the “edgeless-drop-in” detector technology, a set of samples have been manufactured with different sensitive areas (1 × 1 and 0.5 × 0.5 mm2) and different thicknesses (0.1 and 0.5 mm) in four different combinations of top and peripheral p–n junction fabricated on p-type and n-type silicon substrates. The diode probes were tested in terms of percentage depth dose (PDD), dose rate, and linearity and compared to ion chambers. Measurements of the output factor have been compared to film. The angular response of the diodes probes has been tested in a cylindrical PMMA phantom, rotated with bidirectional accuracy of 0.25° under 10 × 10 cm2 6 MV Linac photon beam. The radiation hardness has been investigated as well as the effect of radiation damage on the angular and dose rate response of the diode probes when irradiated with photons from a Co-60 gamma source up to dose of 40 kGy. Results: The PDDs measured by the edgeless detectors show an agreement with the data obtained using ion chambers within ±2%. The output factor measured with the smallest area edgeless diodes (0.5 × 0.5 mm2—0.1 and 0.5 mm thick) matches EBT3 film to within 2% for square field size from 10 to 0.5 cm side equivalent distance. The dose rate dependence in a dose per pulse range of 0.9 × 10−5–2.7 × 10−4 Gy/pulse was less than −7% and +300% for diodes fabricated on p-type and n-type substrates, respectively. The edgeless diodes fabricated on the p-type substrate demonstrated degradation of the response as a function of the irradiation dose within 5%–15%, while diodes on the n-type substrate show a variation of approximately 30% after 40 kGy. The angular response of all probes is minimal (within 2%) but the N on N and P on P configurations show the best performances with an angular dependence of ±1.0% between 0° and 180° in the transversal direction. In this configuration, the space charge region of the passive diode extends from the behind and sidewall toward the anode on the top providing beneficial electric field distribution in the peripheral area of the diode. Such performance has also been tested after irradiation by Co-60 up to 40 kGy with no measurable change in angular response. Conclusions: A new edgeless-drop-in silicon diode fabrication and packaging technology has been used to develop detectors that show no significant angular dependence in their response for dosimetry in radiation therapy. From the characterisation of the diodes, proposed in a wide range of different geometries and configurations, the authors recommend the P-on-P detectors in conjunction with “drop in” packaging technology as the candidate for further development as single diode probe or 2D diode array for dosimetry in radiotherapy. © 2015 American Association of Physicists in Medicine
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 and evaluation of a PNP strip detector for synchrotron microbeam radiation therapy
(IOP Publishing, 2018-06-21) Davis, JA; Paino, JR; Dipuglia, A; Cameron, M; Siegele, R; Pastuovic, Z; Petasecca, M; Perevertaylo, VL; Rosenfeld, AB; Lerch, MLF
The Quality Assurance requirements of detectors for Synchrotron Micro-beam Radiation Therapy are such that there are limited commercial systems available. The high intensity and spatial fractionation of synchrotron microbeams requires detectors be radiation hard and capable of measuring high dose gradients with high spatial resolution sensitivity. Silicon single strip detectors are a promising candidate for such applications. The PNP strip detector is an alternative design of an already proven technology and is assessed on its contextual viability. In this study, the electrical and charge collection efficiency properties of the device are characterised. In addition, a dedicated TCAD model is used to support ion beam induced charge measurements to determine the spatial resolution of the detector. Lastly, the detector was used to measure the full width half maximum and peak to valley dose ratio for microbeams with only a slight over response. With the exception of radiation hardness the PNP detector is a promising candidate for quality assurance in microbeam radiation therapy. Copyright 2024 IOP Publishing
Characterisation of a ΔE–E particle telescope using the ANSTO heavy ion microprobe
(Elsevier, 2007-07) Siegele, R; Reinhard, MI; Prokopovich, DA; Ionescu, M; Cohen, DD; Rosenfeld, AB; Cornelius, IM; Wroe, A; Lerch, MLF; Fazzi, A; Pola, A; Agosteo, S
Semiconductor planar processing technology has spurned the development of novel radiation detectors with applications in space, high energy physics, medical diagnostics, radiation protection and cancer therapy. The ANSTO heavy ion microprobe, which allows a wide range of ions to be focused into spot sizes of a few micrometers in diameter, has proven to be an essential tool for characterising these detectors using the Ion Beam Induced Charge (IBIC) imaging technique. The use of different ions and the wide range of available energies on the heavy ion microprobe, allows the testing of these devices with ionising particles associated with different values of linear energy transfer (LET). Quadruple coincidence measurements have been used to map the charge collection characteristics of a monolithic ΔE-E telescope, This was done through simultaneous measurement of the spatial coordinates of the microbeam relative to the sample and the response of both detector elements. The resulting charge collection maps were used to better understand the functionality of the device as well as to ascertain ways in which future device designs could be modified to improve performance. © 2007, Elsevier Ltd.
Characterization of MOSFET sensors for dosimetry in alpha particle therapy
(Australian Nuclear Science and Technology Organisation, 2021-11-24) Su, FY; Biasi, G; Tran, LT; Pan, VA; Hill, D; Lielkajis, M; Cutajar, D; Petasecca, M; Lerch, MLF; Pastuovic, Z; Poder, J; Joseph, B; Jackson, M; Anatoly, RB
Alpha particle therapy, such as diffusing alpha-emitters radiation therapy (DaRT) and targeted alpha-particle therapy (TAT), exploits the short-range and high linear energy transfer (LET) of alpha particles to destroy cancer cells locally with minimal damage to surrounding healthy cells. Dosimetry for DaRT and TAT is challenging, as their radiation sources produce mixed radiation fields of α particles, β particles, and γ rays. There is currently no dosimeter for real-time in vivo dosimetry of DaRT or TAT. Metal-oxide-semiconductor field-effect transistors (MOSFETs) have features that are ideal for this scenario. Owing to their compactness, MOSFETs can fit into fine-gauge needle applicators, such as those used to carry the radioactive seeds into the tumour. This study characterized the response of MOSFETs designed at the Centre for Medical and Ra diation Physics, University of Wollongong. MOSFETs with three different gate oxide thicknesses (0.55 µm, 0.68 µm, and 1.0 µm) were irradiated with a 5.5 MeV mono-energetic helium ion beam (He2+) using SIRIUS 6MV accelerator tandem at the Australian Nuclear Science and Technology Organization (ANSTO) and an Americium-241 (241Am) source. The sensitivity and dose-response linearity were assessed by analysing the spatially resolved median energy maps of each device and their corresponding voltage shift values. The re sults showed that the response of the MOSFET detectors was linear with alpha dose up to 25.68 Gy. Also, it was found that a gate bias of between 15 V and 60 V would optimize the sensitivity of the detectors to alpha particles with energy of 5.5 MeV. © The Authors.
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
Chemical disorder in a frustrated J1/J2 quantum spin chain material
(Australian Institute of Physics, 2018-01-30) Rule, KC; Mole, RA; Zanardo, J; Krause-Heuer, AM; Darwish, TA; Lerch, MLF
Recently a new one-dimensional (1D) quantum spin chain system has been synthesised: catena-dichloro(2-Cl-3Mpy)copper(II), [where 2-Cl-3Mpy=2-chloro-3-methylpyridine]. We shall refer to this compound as cd-Cu. Preliminary calculations and bulk magnetic property measurements indicate that this system does not undergo magnetic ordering down to 1.8K and is a prime candidate for investigating frustration in a J1/J2 system (where the nearest neighbour interactions, J1, are ferromagnetic and the next nearest neighbour interactions, J2, are antiferromagnetic) [1]. Calculations predicted 3 possible magnetic interaction strengths for J1 below 6meV depending on the orientation of the ligand [2]. For one of the predicted J1values, the existence of a quantum critical point is implied. A deuterated sample of cd-Cu was produced at the National Deuteration Facility and the excitations measured using the PELICAN TOF spectrometer. Scattering was weak from this sample, but indicated the most likely scenario involves an average of the 3 possible magnetic excitations in this material, rather than the random array of exchange interactions as predicted by Herringer et al., [2]. This may indicate the possibility of tuning the chemical structure to favour a system which may exhibit a quantum critical point.
Crystal growth and characterisation of a new J1-J2 spin-chain material
(Australian Institute of Nuclear Science and Engineering, 2016-11-29) Zanardo, J; Rule, KC; Krause-Heuer, AM; Mole, RA; Lerch, MLF
Recently a new one-dimensional (1D) quantum spin chain system has been synthesised: catena-dichloro(2-Cl-3Mpy)copper(II), [where 2-Cl-3Mpy=2-chloro-3-methylpyridine] [1]. Preliminary calculations and bulk magnetic property measurements indicate that this system does not undergo magnetic ordering down to 1.8K and is a prime candidate for investigating frustration in a J1/J2 system (where the next nearest neighbour interactions, J2, are antiferromagnetic and the nearest neighbour interactions, J1, are ferromagnetic) [2]. Calculations predict 3 possible magnetic excitations below 6meV which may reveal the nature of the random static structural disorder predicted in this material. One method for directly observing the magnetic excitations is neutron scattering and measurements have been performed on the neutron Time of Flight spectrometer PELICAN at ANSTO [3]. To a first approximation, linear spin-wave theory has been used to model the expected neutron excitations for this J2/J1 system using the Matlab package SpinW. The results of this project may provide valuable insight into the nature of magnetic frustration in materials. To optimise the observed magnetic signal via the reduction of incoherent neutron scattering, this compound was deuterated at the National Deuteration Facility at ANSTO. In this presentation we will outline our deuterated growth procedure as well as the characterisation methods performed to understand the material further. This work forms the Honours thesis project of Jack Zanardo from University of Wollongong.
Development of a large-area silicon α-particle detector
(Elsevier, 2014-09) Tran, LT; Prokopovich, DA; Lerch, MLF; Petasecca, M; Siegele, R; Reinhard, MI; Perevertaylo, VL; Rosenfeld, AB
Circular ion-implanted silicon detector of α-particles with a large, 5-cm2, sensitive area has been developed. An advantage of the detector is that the detector surface is easily cleanable with chemicals. The hardened surface of the detector shows no signs of deterioration of the spectroscopic and electrical characteristics upon repeated cleaning. The energy resolution along the diameters of the detector was (1.0±0.1)% for the 5.486-MeV α-particles. Detailed tests of the charge collection efficiency and uniformity of the detector entrance window were also performed with a 5.5-MeV He2+ microbeam. © 2014, Elsevier Ltd.
Evaluation of silicon detectors with integrated JFET for biomedical applications
(Institute of Electrical and Electronics Engineers (IEEE), 2009-06) Safavi-Naeini, M; Franklin, DR; Lerch, MLF; Petasecca, M; Pignatel, G; Reinhard, MI; Dalla Betta, GF; Zorzi, N; Rosenfeld, AB
This paper presents initial results from electrical, spectroscopic and ion beam induced charge (IBIC) characterisation of a novel silicon PIN detector, featuring an on-chip n -channel JFET and matched feedback capacitor integrated on its p-side (frontside). This structure reduces electronic noise by minimising stray capacitance and enables highly efficient optical coupling between the detector back-side and scintillator, providing a fill factor of close to 100%. The detector is specifically designed for use in high resolution gamma cameras, where a pixellated scintillator crystal is directly coupled to an array of silicon photodetectors. The on-chip JFET is matched with the photodiode capacitance and forms the input stage of an external charge sensitive preamplifier (CSA). The integrated monolithic feedback capacitor eliminates the need for an external feedback capacitor in the external electronic readout circuit, improving the system performance by eliminating uncontrolled parasitic capacitances. An optimised noise figure of 152 electrons RMS was obtained with a shaping time of 2 mus and a total detector capacitance of 2 pF. The energy resolution obtained at room temperature (2°C) at 27 keV (direct interaction of I-125 gamma rays) was 5.09%, measured at full width at half maximum (FWHM). The effectiveness of the guard ring in minimising the detector leakage current and its influence on the total charge collection volume is clearly demonstrated by the IBIC images. © 2009, Institute of Electrical and Electronics Engineers (IEEE)
First extensive study of lanthanum manganite nanoparticles to target deadly brain cancer
(Australian Institute of Nuclear Science and Engineering (AINSE), 2020-11-11) Khochaiche, A; Westlake, M; O'Keefe, A; Engels, E; Li, N; Vogel, S; Valceski, M; Konstantinov, K; Corde, S; Lerch, MLF; Tehei, M; Rule, KC; Horvat, J
The ability to successfully target deep-seated tumours in sensitive areas of the body is limited to adequate targeting strategies. More specifically, brain and central nervous system (CNS) cancers can be the most aggressive, have higher mortality rates and lower accessibility to chemotherapeutic drugs. A proposed solution to target these concerns is through introducing high atomic number (Z) nanoparticles (NPs) such as silver-doped lanthanum manganite (LAGMO) to aid in common treatments such as radiation therapy. These NPs can bypass the blood brain barrier and are capable of increasing the damage from the radiation due to their high-Z. Most importantly they have potential to cause cancer cells to undergo hyperthermia (a cell death precursor) as the NPs heat up in their environment due to their Curie temperature being in the hyperthermia range of interest.
First extensive study of silver-doped lanthanum manganite nanoparticles for inducing selective chemotherapy and radio-toxicity enhancement
(Elsevier B. V., 2021-04) Khochaiche, A; Westlake, M; O'Keefe, A; Engels, E; Vogel, S; Valceski, M; Li, N; Rule, KC; Horvat, J; Konstantinov, K; Rosenfeld, AB; Lerch, MLF; Corde, S; Tehei, M
Nanoparticles have a great potential to increase the therapeutic efficiency of several cancer therapies. This research examines the potential for silver-doped lanthanum manganite nanoparticles to enhance radiation therapy to target radioresistant brain cancer cells, and their potential in combinational therapy with magnetic hyperthermia. Magnetic and structural characterisation found all dopings of nanoparticles (NPs) to be pure and single phase with an average crystallite size of approximately 15 nm for undoped NPs and 20 nm for silver doped NPs. Additionally, neutron diffraction reveals that La0.9Ag0.1MnO3 (10%-LAGMO) NPs exhibit residual ferromagnetism at 300 K that is not present in lower doped NPs studied in this work, indicating that the Curie temperature may be manipulated according to silver doping. This radiobiological study reveals a completely cancer-cell selective treatment for LaMnO3, La0.975Ag0.025MnO3 and La0.95Ag0.05MnO3 (0, 2.5 and 5%-LAGMO) and also uncovers a potent combination of undoped lanthanum manganite with orthovoltage radiation. Cell viability assays and real time imaging results indicated that a concentration of 50 μg/mL of the aforementioned nanoparticles do not affect the growth of Madin-Darby Canine Kidney (MDCK) non-cancerous cells over time, but stimulate its metabolism for overgrowth, while being highly toxic to 9L gliosarcoma (9LGS). This is not the case for 10%-LAGMO nanoparticles, which were toxic to both non-cancerous and cancer cell lines. The nanoparticles also exhibited a level of toxicity that was regulated by the overproduction of free radicals, such as reactive oxygen species, amplified when silver ions are involved. With the aid of fluorescent imaging, the drastic effects of these reactive oxygen species were visualised, where nucleus cleavage (an apoptotic indicator) was identified as a major consequence. The genotoxic response of this effect for 9LGS and MDCK due to 10%-LAGMO NPs indicates that it is also causing DNA double strand breaks within the cell nucleus. Using 125 kVp orthovoltage radiation, in combination with an appropriate amount of NP-induced cell death, identified undoped lanthanum manganite as the most ideal treatment. Real-time imaging following the combination treatment of undoped lanthanum manganite nanoparticles and radiation, highlighted a hinderance of growth for 9LGS, while MDCK growth was boosted. The clonogenic assay following incubation with undoped lanthanum manganite nanoparticles combined with a relatively low dose of radiation (2 Gy) decreased the surviving fraction to an exceptionally low (0.6 ± 6.7)%. To our knowledge, these results present the first biological in-depth analysis on silver-doped lanthanum manganite as a brain cancer selective chemotherapeutic and radiation dose enhancer and as a result will propel its first in vivo investigation. © 2021 Elsevier B.V.
Flexible polymer X‑ray detectors with non-fullerene acceptors for enhanced stability: Toward printable tissue equivalent devices for medical applications
(American Chemical Society (ACS), 2021-12-08) Large, MJ; Posar, JA; Mozer, AJ; Nattestad, A; Alnaghy, S; Carolan, M; Sellin, PJ; Davies, J; Pastuovic, Z; Lerch, MLF; Guatelli, S; Rosenfeld, AB; Griffith, MJ; Petasecca, M
There is growing interest in the development of novel materials and devices capable of ionizing radiation detection for medical applications. Organic semiconductors are promising candidates to meet the demands of modern detectors, such as low manufacturing costs, mechanical flexibility, and a response to radiation equivalent to human tissue. However, organic semiconductors have typically been employed in applications that convert low energy photons into high current densities, for example, solar cells and LEDs, and thus existing design rules must be re-explored for ionizing radiation detection where high energy photons are converted into typically much lower current densities. In this work, we report the optoelectronic and X-ray dosimetric response of a tissue equivalent organic photodetector fabricated with solution-based inks prepared from polymer donor poly(3-hexylthiophene) (P3HT) blended with either a non-fullerene acceptor (5Z,5′Z)-5,5′-((7,7′-(4,4,9,9-tetraoctyl-4,9-dihydro-s-indaceno[1,2-b:5,6-b′]dithiophene-2,7-diyl)bis(benzo[c][1,2,5]thiadiazole-7,4-diyl))bis(methanylylidene))bis(3-ethyl-2-thioxothiazolidin-4-one) (o-IDTBR) or a fullerene acceptor, [6,6]-phenyl-C61-butyric acid methyl ester (PCBM). Indirect detection of X-rays was achieved via coupling of organic photodiodes with a plastic scintillator. Both detectors displayed an excellent response linearity with dose, with sensitivities to 6 MV photons of 263.4 ± 0.6 and 114.2 ± 0.7 pC/cGy recorded for P3HT:PCBM and P3HT:o-IDTBR detectors, respectively. Both detectors also exhibited a fast temporal response, able to resolve individual 3.6 μs pulses from the linear accelerator. Energy dependence measurements highlighted that the photodetectors were highly tissue equivalent, though an under-response in devices compared to water by up to a factor of 2.3 was found for photon energies of 30-200 keV due to the response of the plastic scintillator. The P3HT:o-IDTBR device exhibited a higher stability to radiation, showing just an 18.4% reduction in performance when exposed to radiation doses of up to 10 kGy. The reported devices provide a successful demonstration of stable, printable, flexible, and tissue-equivalent radiation detectors with energy dependence similar to other scintillator-based detectors used in radiotherapy. © 2021 American Chemical Society.
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.
Gd-TPP-DOTA reduces cell viability in cancer cells via synchrotron radiotherapy
(Australian National University, 2021-08-24) Middleton, RJ; Howell, NR; Livio, E; Wyatt, NA; Chacon, A; Fraser, BH; Barnes, M; Cameron, M; Rendina, LM; Häusermann, D; Lerch, MLF; Safavi-Naeini, M
High-Z elements have been proposed as radiosensitisers in X-ray photon radiotherapy due to their emission of multiple high-LET photo- and Auger electrons following X-ray irradiation. Gadolinium is a particularly attractive candidate radiosensitiser, since it can also be used as an MRI contrast agent. In this study, we report on the efficacy of Gd-triphenylphosphonium salt-DOTA (Gd(III)-TPP-DOTA) for synchrotron microbeam radiation therapy dose enhancement. The compound utilises the mitochondrial targeting moiety triphenylphosphonium (TPP) to accumulate Gd in the inner mitochondrial membrane. Experiments were conducted using the dynamic mode option at hutch 2B of the Imaging and Medical Beamline at the Australian Synchrotron. Human glioblastoma multiforme cells (T98G cell line) were cultured to 80-90% confluence in T12.5 flasks. Approximately 24 hours prior to irradiation, the cultures were either treated with a 500 μM solution of Gd(III)DOTA-TPP or a vehicle control. Spatial dose distribution of synchrotron broad beam (BB) and single/multiple microbeams were measured using a micron-scale X-Tream dosimetry system and Gafchromic films in air and at 2 cm depth in solid water (same depth as the monolayer of cells in T12.5 flasks). A total of 96 flasks were irradiated, with doses of 0, 1, 2, 3, 4, 5, 10 and 16 Gy delivered in valley (MRT) or uniformly (BB). Post irradiation, each flask was re-seeded into 7 x 96 well-plates to perform the resazurin cell proliferation assay up to 7 days after irradiation. Our preliminary analysis indicates that for cells irradiated by 3 Gy of BB or MRT radiation, the addition of Gd(III)DOTA-TPP results in a reduction in viable cell mass by 24.25% and 25.79%, respectively, compared with untreated flasks. © The Authors
IBIC microscopy – the powerful tool for testing micron – sized sensitive volumes in segmented radiation detectors used in synchrotron microbeam radiation and hadron therapies
(Elsevier B. V., 2019-11-01) Pastuovic, Z; Davis, J; Tran, LT; Paino, JR; Dipuglia, A; James, B; Povoli, M; Kok, A; Perevertaylo, VL; Siegele, R; Prokopovich, DA; Lerch, MLF; Petasecca, M; Rosenfeld, AB; Cohen, DD
Ion Beam Induced Charge (IBIC) microscopy performed using highly tuned microbeams of accelerated ions with energies in the MeV range is the powerful tool for analysis of charge carrier transport properties in semiconductor devices based on semiconductor hetero-junction, metal-on-semiconductor and semiconductor-on-insulator configurations. Here we present two cases of recent applications of the IBIC microscopy in the field of medical radiation physics. The reduced-rate ion microbeams with energies in the MeV range and sub-micrometer spot-sizes have been used for the investigations of the charge collection efficiency (CCE) in sensitive volumes of segmented radiation detectors in order to measure the spatial distribution and uniformity of CCE in different polarization conditions. This information allows the determination of the charge carrier transport properties in selected substructures of a particular device and to quantify its ability to accurately determine the energy deposited by incident ionizing radiation - two fundamental requirements of any microdosimeter or detector of ionizing radiation. © 2019 Elsevier B.V.
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.
Investigations into the controllable change of Curie temperature in silver doped lanthanum manganite nanoparticles
(Australian Institute of Nuclear Science and Engineering, 2016-11-29) Westlake, M; Lerch, MLF; Konstantinov, K; Rule, KC; Yu, DH; Pan, AV; Cardillo, D; Horvat, J; Tehei, M
Our team is focused on research into the design, production, characterisation and implementation of optimized nanostructured particles for principally the diagnosis (as CT and MRI contrast agents) and treatment of cancer (using radiation, oncothermia and hyperthermia modalities). One magnetic nanoparticle of current interest is Lanthanum Manganite (LaMnO3) and its silver doped counterpart (La1-xAgxMnO3). The high effective atomic number and magnetic moment of LaMnO3 [1] makes this material appropriate for the basis of an MRI and CT contrast agent and enhancing radiation therapies. In addition La1-xAgxMnO3 is also considered as a good candidate for hyperthermia cancer therapy [2].For the characterization of our samples we used XRD, PPMS, SEM, EDS and SEM. We observed that the Curie temperature increased with the increase of the silver doping concentration in the nanoparticles. This has led to an investigation into the mechanism behind this change. The spin-phonon interaction was considered to represent one potential mechanism and Time of Flight measurements where conducted on PELICAN at ANSTO. A lack of phonon evolution was seen within the temperature range of 1.5K - 300K. In order to access phonon density of states over a broader range of energies, we are then planning to use the Beryllium filter on TAIPAN and scan through a wide energy range while measuring scattered neutron over a vastly increased solid angle. The following poster will focus on the characterizations of our samples, our first experiments on PELICAN and our future planed experiments in the aim to better understand the mechanism that provokes the change of Curie temperature upon silver doping.

Browsing by Author "Lerch, MLF"

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