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The spatial distribution of radiation-induced ionisations in sub-cellular structures plays an important role in the initial formation of radiation damage to biological tissues. Using the nanodosimetry approach, physical characteristics of the track structure can be measured and correlated to DNA damage. In this work, a novel nanodosimeter is presen...
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... operational principle of the detector was previously presented in Bashkirov et al. (4) . The detector is a combination of a hole-type micro-pattern detector, such as gas electron multipliers (GEM), and a resistive plate chamber (RPC) operating at reverse polarity in low-pressure gas. The detector design is shown in Figure 1. The main component is a 3-mm thick dielectric board, in which a two-dimensional array of sub-millimeter diameter cylindrical holes (cells) is created by means of printed circuit board (PCB) technology. A resistive cathode, in contact with the bottom side of the PCB is connected to a power supply which provides high voltage (HV) of the order of hundreds of volts. Positive ions, produced by charged particles traversing the working gas, drift towards the detector plane under an electric field E d of the order of tens of V cm 2 1 . The drifting ions are focused into the cells and accelerated by the electric field ( E a ) . Operating in a gas pressure of the order of hundreds of Pascals, the reduced electric field inside each cell is of the order of 10 V cm 2 1 .Pa. Under these conditions, the cross section for the ion- induced impact ionisation increases substantially and ionisation probability close to 100 % can be obtained for a cell height of the order of a few millimetres (5) . The secondary electrons produced in this interaction process initiate an avalanche propagating towards the top of the cell with a gain of the order of 10 8 . The avalanche is confined in time due to the high-volume resistivity of the cathode and it is spatially confined by the dielectric walls. As a consequence, each cell element operates as an independent Geiger counter. The top side of the PCB provides three readout strip layers: two orthogonal strip series, along each row and column of the cell array, respectively, and a third strip series with diagonal orientation (Figure 2). With this readout configuration, the position of the fired cell can be reconstructed. By registering positive ions rather than electrons, the diffusion is minimised and a series of two-dimensional time projections of the initial ionisation positions can be obtained. Additionally, the complete three-dimensional track image can be reconstructed by measuring the ion drift time. Two versions of the detector prototype were assembled combining a PCB with a common top readout elec- trode with two different cathode types, a high resistivity glass and a semiconductor glass. The prototype was installed into a low-gas-pressure chamber providing a controlled gas environment. The chamber was filled with propane with a pressure value ranging from 133 to 667 Pa. This allows a simulated tissue-equivalent SV of the order of a few tens of m m 3 . The operation with working gases as argon, nitrogen, and air was also tested. As primary radiation field, a 241 Am alpha source combined with a 2-mm diameter collimator was used. A silicon photodiode connected to a charge sensitive preamplifier was placed opposite to the source to measure the alpha rate and providing the trigger for data acquisition. Both the array detector signal and the trigger signal were sent to the data acquisition system. A field-programmable gate array (FPGA) was used to measure the distribution of the number of pulses per trigger and the distribution of the pulse arrival time with respect to the trigger. The measurements were performed applying a HV in the range of 650–850 V and a drift field in the range of 5–10 V cm 2 1 depending upon the working gas ...
Citations
... When colliding with a gas molecule, an ion reaching a hole can extract one electron and yield an avalanche towards the THGEM-top electrode. The concept was further optimized in [469,470,471,472,473,474]. The efficiency of the detector is estimated to be of the order of several %; it increases with the electrode thickness (up to 10 mm) due to higher probability of primary ion to extract an electron. ...
The Thick Gas Electron Multiplier (THGEM) is a robust high-gain gas-avalanche electron multiplier - a building block of a variety of radiation detectors. It can be manufactured economically by standard printed-circuit drilling and etching technology. We present a detailed review of the THGEM and its derivatives. We focus on the physics phenomena that govern their operation and performances under different operation conditions. Technological aspects associated with the production of these detectors and their current and potential applications are discussed.
... Only recently, approaches to image particle track structure have been developed in terms of instruments detecting ionisation clusters formed in several nanometric targets along a particle track (Casiraghi et al., 2015;Venkatraman and Sureka, 2019;Vasi et al., 2021) or visualising the colocation of ion tracks and DSBs formed in irradiated cells (Rübe et al., 2011;Kodaira et al., 2015;Lorat et al., 2015;McFadden et al., 2020). In addition, attempts have been mode to study the spatial correlation of ionisation clusters based on established nanodosimetric instruments Hilgers and Rabus, 2020). ...
The production of two double strand breaks in spatially separated locations on the DNA molecule can cause the loss of a whole DNA loop. This loss, which can be of substantial length depending on the geometrical position of the two damaged sites, depends on the degree of correlation between ionisation clusters formed in sites of several nanometres in size. The first part of this paper reported on nanodosimetric measurements of alpha particle tracks in 1.2 mbar H2O, 1.2 mbar C3H8 and 1.2 mbar C4H8O with the PTB ion counter nanodosimeter. In this second part, the focus is on the geometrical characterisation of the two sites simulated with the nanodosimeter in the three target gases and on the comparison of the measurement results with Monte Carlo simulations. The measurements in 1.2 mbar C3H8 were simulated with PTra, a track structure code dedicated to modelling the PTB ion counter nanodosimeter. Further simulations were performed with Geant4-DNA for ²⁴¹Am alpha particle tracks in liquid water. Simulations of the experiment were found to be in good agreement with the measurements for the investigated irradiation geometries.
... • Develop density scaling relationships for microand nano-dosimetry (19,20) using theoretical and simulation studies as well as the characterisation of existing (21) and emerging nanodosimetric detectors (22)(23)(24) . • Identify biologically relevant target sizes from a comprehensive characterisation of track structure; develop track structure imaging techniques (25,26) , complemented by experimental investigations of radiation interactions in condensed phase nanometric objects (22,27,28) . • Establish uncertainty estimations for measured track structure quantities and develop computational methods for track simulations, including the fundamental challenge of incorporating quantum mechanical descriptions of particle interactions (29,30) . ...
Since 2012, the European Radiation Dosimetry Group (EURADOS) has developed its Strategic Research Agenda (SRA), which contributes to the identification of future research needs in radiation dosimetry in Europe. Continued scientific developments in this field necessitate regular updates and, consequently, this paper summarises the latest revision of the SRA, with input regarding the state of the art and vision for the future contributed by EURADOS Working Groups and through a stakeholder workshop. Five visions define key issues in dosimetry research that are considered important over at least the next decade. They include scientific objectives and developments in (i) updated fundamental dose concepts and quantities, (ii) improved radiation risk estimates deduced from epidemiological cohorts, (iii) efficient dose assessment for radiological emergencies, (iv) integrated personalised dosimetry in medical applications and (v) improved radiation protection of workers and the public. This SRA will be used as a guideline for future activities of EURADOS Working Groups but can also be used as guidance for research in radiation dosimetry by the wider community. It will also be used as input for a general European research roadmap for radiation protection, following similar previous contributions to the European Joint Programme for the Integration of Radiation Protection Research, under the Horizon 2020 programme (CONCERT). The full version of the SRA is available as a EURADOS report (www.eurados.org).
... The new device, developed starting from previous attempts of constructing a nanodosimeter small and simple enough to deploy [17][18][19], has the intriguing characteristic of being simple enough to be replicated in almost every physics laboratory, without the need for reproducing the relatively large facilities which have been employed since the beginning of this century for measuring the size distributions of ionization clusters produced by the interaction of ionizing radiation with atoms and molecules [20][21][22][23]. ...
Radiation metrology is crucial in space, for instance in monitoring the conditions on-board space vehicles. The energy released in matter by ionizing radiation is due to the atomic and molecular ionization processes, which have been investigated for several decades from both a theoretical and an experimental point of view. Electronic excitation and ionization cross-section are of particular interest in radiation physics, because of their role in the radiation–matter interaction process. Recently, experimental findings have shown that the interplay with a laser field can strongly modify the electronic interaction probabilities and emission spectra. These phenomena are still not completely understood from a theoretical point of view, and the available empirical data concern a few, simple atomic species. We represent a possible dosimetric effect of the interaction with laser light, inferring from experiments the characteristics of laser-assisted cross-sections. Using a Monte-Carlo calculation for simulating the micro-dosimetric aspects of the irradiation of a simple geometry, we show the need of new experimental data and more detailed theoretical approaches to these phenomena in complex molecular systems.
... Several attempts have been made for downsizing nanodosimeters. 18,20 Although with the new compact detector design single ionizations could be measured, it was not yet possible to measure complete cluster size distributions. 20 Here we report on first measurements of cluster size distributions of 5 MeV alpha particles with a ceramic nanodosimeter detector. ...
Purpose
A nanodosimeter is a type of detector which measures single ionizations in a small gaseous volume in order to obtain ionization cluster size probability distributions for characterization of radiation types. Working nanodosimeter detectors are usually bulky machines which require a lot of space. In this work, the authors present a compact ceramic nanodosimeter detector and report on first measurements of cluster size distributions of 5 MeV alpha particles.
Methods
Single ionization measurements are achieved by applying a weak electric field to collect positive ions in a hole in a ceramic plate. Inside the ceramic plate, due to a strong electric field, the ions are accelerated and produce impact‐ionizations. The resulting electron avalanche is detected in a read‐out electrode. A Bayesian unfolding algorithm is then applied to the experimentally obtained cluster size distributions to reconstruct the true cluster size distributions.
Results
Experimentally obtained cluster size distributions by the compact nanodosimeter detector are presented. The reconstructed cluster size distributions agreed well with Monte Carlo simulated cluster size distributions for small volumes (diameter = 2.5 nm). For larger volumes, discrepancies between the reconstructed cluster size distributions and cluster size distributions from Monte Carlo simulations were observed.
Conclusions
For the first time, ionization cluster size probability distributions could be obtained by a small and compact nanodosimeter detector. This signifies the achievement of a critical step toward the wide application of nanodosimetric characterization of radiation types including in clinical environments.
... Such a detector needs to be able to measure single ionizations over a large area with high resolution. One possible nanodosimetric detector which could be able to measure such cluster sizes along the primary particle track is the track imaging detector currently developed at University of Zurich and firstly suggested by Bashkirov et al. 2,[27][28][29][30] The difference of the "fast" method and the "slow and detailed" method when the same Monte Carlo code is used presumably comes from excessive number of electrons in the "slow and detailed" method which ionize outside of the basic interaction volume where they were created. The "fast" method only takes the electrons into consideration which are generated and ionize inside the basic interaction volumes. ...
Purpose
In view of the potential of treatment plan optimization based on nanodosimetric quantities, fast Monte Carlo methods for obtaining nanodosimetric quantities in macroscopic volumes are important. In this work, a “fast” method for obtaining nanodosimetric parameters from a clinical proton pencil beam in a macroscopic volume is compared with a slow and detailed method. Furthermore, the variations of these parameters, when obtained with the Monte Carlo codes TOPAS and NOREC, are investigated.
Methods
Monte Carlo track structure simulations of 1 keV–100 MeV protons and 12 eV–1 MeV electrons in a volume of 8 nm liquid water provided us with an atlas of cluster size distributions. Two kinds of ionization cluster size distributions were recorded, counting all ionizations or only ionizations directly produced by the primary particle. The simulations of the proton pencil beam were performed in two different ways. A “fast” method where only the protons were simulated and a “slow and detailed” method where protons and electrons were simulated in order to obtain spectra at different depths. The obtained spectra were then convoluted with cluster size distributions.
Results
It was shown that the nanodosimetric quantity F2 from the “fast” method is, depending on the location, between 43.6% and 63.6% smaller than the F2 obtained by the “slow and detailed” method. However, it was also shown that variations of nanodosimetric quantities are even larger when the cluster size distributions of the electrons are simulated with the Monte Carlo code NOREC, that is, the cumulative F2 probabilities obtained with NOREC were between 50.8% and 75.5% smaller than the F2 probabilities obtained with TOPAS.
Conclusions
As long as the uncertainties of different Monte Carlo codes are not improved, it is feasible to only simulate protons in a macroscopic volume. It must be noted, however, that the uncertainty is in the order of 100%.
... And the third layer (Y layer) of readout strips are oriented at 45°to the first two layers to resolve hit ambiguity. The detector is constructed to have 3.483 mm thickness which includes 3.261 mm dielectric materials and 0.222 mm gold [14][15][16][17][18]. ...
Nanodosimetry is a technique that measures the energy deposited by ionizing radiation under the principle of ion induced impact ionization in low pressure gas volume which correlates the number of ionization produced in nanometric scale of the DNA. In the modern field of nanodosimetry, the multilayer Printed Circuit Board (PCB) technology based 3D positive ion detector plays a more prominent role in the field of radiation biology, radiation dosimetry, oncology, and also as gamma spectrometer and gas sensor. The present study is targeted to analyze the performance of the 3D positive ion detector as gas sensor under propane, methane, argon, nitrogen, and air medium at various pressures ranging from 0 to 10 Torr using Co-60 source. From this study, it is observed that the detector shows varying magnitude in its efficiency and amplitude under different media with a maximum efficiency of 12.286% and amplitude of 168 V under propone medium at 0.9 Torr. The detector also shows variation in its cluster size distribution and ion drift time under different media. Hence, it is concluded that the 3D positive ion detector can be considered as a gas sensor.
... In consequence, respective new developments have been started in the field of experimental nanodosimetry that aim at measuring the correlations of cluster-size distributions induced within a particle track in two separate nanometric targets in proximity [27], [28] or at obtaining a 3D image of the nanometric particle track structure for track segments of few 100 nm in length [29], [30], [31]. The latter would to some extent bridge towards microdosimetric measurements at the few-hundred nanometer regime [12]. ...
Biological effectiveness of a certain absorbed dose of ionizing radiation depends on the radiation quality, i. e. the spectrum of ionizing particles and their energy distribution. As has been shown in several studies, the biological effectiveness is related to the pattern of energy deposits on the microscopic scale, the so-called track structure. Clusters of lesions in the DNA molecule within site sizes of few nanometers play a particular role in this context. This work presents a brief overview of nanodosimetric approaches to relate biological effects with track structure derived quantities and experimental techniques to derive such quantities.
... In the present work, we have put forth an attempt to confirm the suitability of an indigenously fabricated multilayer PCB (Printed Circuit Board) technology based hole type 3D positive ion detector to detect breast and lung malignancy by analysing its signal variation that occurs due to variation in the emission of VOC from malignant cells. Basically, this detector combines the working principle of thick gas electron multiplier (THGEM) 33 and resistive plate counter as presented by Bashkirov et al. [34][35][36][37][38] . In continuation to their research, we improved the efficiency of the detector by updating the detector structure and the same was confirmed as a gas sensor in addition to other applications 39 . ...
Since the early detection of cancer increases the chance of successful treatment, the present study focused to confirm the suitability of an indigenously fabricated multilayer PCB technology based 3D positive ion detector to detect breast and lung malignancy at an early stage. The 3D positive ion detector is a type of gas filled radiation detector works under the principle of ion induced ionization using an exempted micro curie activity source. Earlier studies report that malignant cells can be detected by analyzing the Volatile Organic Compounds (VOCs) exhaled by those cells that serve as eminent biomarkers for malignant detection. Based on this, the present study analyzed the signals produced in the detector by VOCs exhaled from 140 biopsy tissue samples that include tissue of normal and all stages of breast and lung malignancy. To strengthen the present data, the normal and advanced breast and lung malignant tissues were also analyzed using the Gas Chromatography- Mass Spectrometry (GC-MS). From this study, it is confirmed that the present 3D positive ion detector can be used to detect both breast and lung malignancy and also to distinguish them based on the variation in four basic physical parameters of the output pulse such as frequency, amplitude, rise time and fall time and four derived parameters of the pulse such as FWHM, area of the pulse, ionization cluster size, and ion drift time.
... A second layer (X layer) of orthogonal strips located just below the top strip layer provides 2D readout of individual holes. The third layer (Y layer) of readout strips oriented at 45°to the first two layers is added to resolve hit ambiguity [20][21][22]. The detector was constructed to have 3.220 mm thickness which includes 3.00 mm dielectric materials and 0.220 mm gold. ...
... The top side of the PCB detector was kept at zero potential and the active area of its bottom side were connected with the ceramic coated with gold conducting electrode, whereas the remaining region was covered with a teflon material which forms the cathode assembly. The negative high voltage (−470 V to −500 V) was applied at the top side (coated side) of the cathode in order to protect the detector as well as to trigger ion induced ionization [18][19][20][21][22][23]. The present experimental setup used a four channel Digital Storage Oscilloscope (DSO). ...
Nanodosimetry is a technique that measures the energy deposited by ionizing radiation in low pressure gas volume which correlates the number of ionization produced in nanometric scale of the DNA. In the modern field of nanodosimetry, the structure of the PCB technology based positive ion detector play a more prominent role to improve its efficiency. Hence, the present study analyzes the variation in efficiency of the PCB technology based detector in terms of its thickness. In our study, the copper strips, cathode material and insulating material of the PCB technology based detector proposed by Bashkirov et al., were modified and it is used for further analysis. The detector 1 was constructed to have 3.220 mm thickness which includes 3.0 mm dielectric materials and 0.220 mm gold. The detector 2 was constructed to have 3.483 mm thickness which includes 3.261 mm dielectric materials and 0.222 mm gold. These two detectors were characterized by Nanodosimeter under Propane and argon medium at 0 to 10 Torr pressure using Am-241 and Co-60 sources. It is concluded that as the thickness of the PCB technology based positive ion detector increases, the ion collection efficiency is also increased. This is due to the increase in dielectric materials thickness which enhances the ion impact ionization.
