Research Centre for Sustainable Solar Cell Technology (SuSolTech)

• Dalla Betta, Gian-Franco & Povoli, Marco (2022). Progress in 3D Silicon Radiation Detectors. Frontiers in Physics. ISSN 2296-424X. 10. doi: 10.3389/fphy.2022.927690. Fulltekst i vitenarkiv
• James, B.; Tran, Linh T.; Vohradsky, J.; Bolst, David; Pan, Vladimir M. & Carr, M [Vis alle 19 forfattere av denne artikkelen] (2019). SOI Thin Microdosimeter Detectors for Low Energy Ions and Radiation Damage Studies. IEEE Transactions on Nuclear Science. ISSN 0018-9499. 66(1), s. 320–326. doi: 10.1109/TNS.2018.2885996. Fulltekst i vitenarkiv Vis sammendrag

  The responses of two silicon on insulator (SOI) 3-D microdosimeters developed by the Centre for Medical Radiation Physics were investigated with a range of different low energy ions, with high linear energy transfer (LET). The two microdosimeters n-SOI and p-SOI were able to measure the LET of different ions including 7 Li, 12 C, 16 O, and 48 Ti with ranges below 350 μm in silicon. No plasma effects were seen in the SOI microdosimeters when irradiated with the high LET ions. A Monte Carlo simulation using Geant4 was compared to the experimental measurements, whereby some discrepancies were observed for heavier ions at lower energies. This discrepancy can be partly attributed to uncertainties in the thickness of the energy degraders and overlayers of the devices. The microdosimetric measurements of low energy 16 O ions were obtained and compared to a therapeutic 16 O ion beam. The radiation hardness of the two devices was studied using the ion beam induced charge collection technique. Both types of the microdosimeters when biased had no essential changes in charge collection efficiency in the sensitive volume after irradiation with low energy ions.

• Bolst, David; Gautelli, Susanna; Tran, Linh T.; Davis, Jeremy; Chartier, Lachlan & Prokopovich, Dale A. [Vis alle 16 forfattere av denne artikkelen] (2019). Validation of Geant4 for silicon microdosimetry in heavy ion therapy. Physics in Medicine and Biology. ISSN 0031-9155. 65(4). doi: 10.1088/1361-6560/ab586a. Fulltekst i vitenarkiv Vis sammendrag

  Microdosimetry is a particularly powerful method to estimate the relative biological effectiveness (RBE) of any mixed radiation field. This is particularly convenient for therapeutic heavy ion therapy (HIT) beams, referring to ions larger than protons, where the RBE of the beam can vary significantly along the Bragg curve. Additionally, due to the sharp dose gradients at the end of the Bragg peak (BP), or spread out BP, to make accurate measurements and estimations of the biological properties of a beam a high spatial resolution is required, less than a millimetre. This requirement makes silicon microdosimetry particularly attractive due to the thicknesses of the sensitive volumes commonly being ∼10 µm or less. Monte Carlo (MC) codes are widely used to study the complex mixed HIT radiation field as well as to model the response of novel microdosimeter detectors when irradiated with HIT beams. Therefore it is essential to validate MC codes against experimental measurements. This work compares measurements performed with a silicon microdosimeter in monoenergetic 12C , 14N and 16O ion beams of therapeutic energies, against simulation results calculated with the Geant4 toolkit. Experimental and simulation results were compared in terms of microdosimetric spectra (dose lineal energy, d(y)), the dose mean lineal energy, yD and the RBE10, as estimated by the microdosimetric kinetic model (MKM). Overall Geant4 showed reasonable agreement with experimental measurements. Before the distal edge of the BP, simulation and experiment agreed within ∼10% for yD and ∼2% for RBE10. Downstream of the BP less agreement was observed between simulation and experiment, particularly for the 12C and 16O beams. Simulation results downstream of the BP had lower values of yD and RBE10 compared to the experiment due to a higher contribution from lighter fragments compared to heavier fragments.

• Tran, Linh T.; Bolst, David; Guatelli, Susanna; Pogossov, Alex; Petasecca, Marco & Lerch, Michael L.F. [Vis alle 16 forfattere av denne artikkelen] (2018). The relative biological effectiveness for carbon, nitrogen, and oxygen ion beams using passive and scanning techniques evaluated with fully 3D silicon microdosimeters. Medical Physics (Lancaster). ISSN 0094-2405. 45(5), s. 2299–2308. doi: 10.1002/mp.12874. Fulltekst i vitenarkiv Vis sammendrag

  Background: The aim of this study was to measure the microdosimetric distributions of a carbon pencil-beam scanning (PBS) and passive scattering system as well as to evaluate the relative biological effectiveness (RBE) of different ions, namely 12C, 14N and 16O, using a silicon-on-insulator (SOI) microdosimeter with well-defined 3D sensitive volumes (SV). Geant4 simulations were performed with the same experimental setup and results were compared to the experimental results for benchmarking. Method: Two different silicon microdosimeters with rectangular parallelepiped and cylindrical shaped SVs, both 10 µm in thickness were used in this study. The microdosimeters were connected to low noise electronics which allowed for the detection of lineal energies as low as 0.15 keV/μm in tissue. The silicon microdosimeters provide extremely high spatial resolution and can be used for in-field and out-of-field measurements in both passive scattering and PBS deliveries. The response of the microdosimeters was studied in 290 MeV/u 12C, 180 MeV/u 14N, 400 MeV/u 16O passive ion beams, and 290 MeV/u 12C scanning carbon therapy beam at Heavy Ion Medical Accelerator in Chiba and Gunma University Heavy Ion Medical Center, Japan, respectively. The microdosimeters were placed at various depths in a water phantom along the central axis of the ion beam, and at the distal part of the Spread Out Bragg Peak (SOBP) in 0.5 mm increments. The RBE values of the pristine Bragg peak (BP) and SOBP were derived using the microdosimetric lineal energy spectra and the modified microdosimetric kinetic model (MKM), using MKM input parameters corresponding to human salivary gland (HSG) tumour cells. Geant4 simulations were performed in order to verify the calculated depth-dose distribution from the treatment planning system and to compare the simulated dose-mean lineal energy to the experimental results. Results: For a 180 MeV/u 14N pristine BP, the dose-mean lineal energy (yD) ̅obtained with two types of silicon microdosimeters started from approximately 29 keV/µm at the entrance to 92 keV/µm at the BP, with a maximum value in the range of 412 to 438 keV/µm at the distal edge. For 400 MeV/u 16O ions, the dose-mean lineal energy (yD) ̅started from about 24 keV/µm at the entrance to 106 keV/µm at the BP, with a maximum value of approximately 381 keV/µm at the distal edge. The maximum derived RBE10 values for 14N and 16O ions were found to be 3.10 ± 0.47 and 2.93 ± 0.45, respectively. Silicon microdosimetry measurements using pencil beam scanning 12C ions were also compared to the passive scattering beam. Conclusions: These SOI microdosimeters with well-defined 3D SVs have applicability in characterising heavy ion radiation fields and measuring lineal energy deposition with sub-millimetre spatial resolution. It has been shown that the dose-mean lineal energy increased significantly at the distal part of the BP and SOBP due to very high LET particles. Good agreement was observed for the experimental and simulation results obtained with silicon microdosimeters in 14N and 16O ion beams, confirming the potential application of SOI microdosimeter with 3DSV for quality assurance in charged particle therapy.

• Tran, Linh T.; Chartier, Lachlan; Bolst, David; Davis, Jeremy; Prokopovich, Dale A. & Pogossov, Alex [Vis alle 16 forfattere av denne artikkelen] (2018). In-field and out-of-file application in 12C ion therapy using fully 3D silicon microdosimeters. Radiation Measurements. ISSN 1350-4487. 115, s. 55–59. doi: 10.1016/j.radmeas.2018.06.015. Fulltekst i vitenarkiv Vis sammendrag

  This paper presents recent development of Silicon on Insulator (SOI) detectors for microdosimetry at the Centre for Medical Radiation Physics (CMRP) at the University of Wollongong. A new CMRP SOI microdosimeter design, the 3D mushroom microdosimeter is presented. Modification of SOI design and changes to the fabrication processes have led to improved definition of the microscopic sensitive volumes (SV), and thus to better modelling of the deposition of ionizing energy in a biological cell. The electrical and charge collection properties of the devices have been presented in previous works. In this study, the response of the microdosimeters in monoenergetic and spread out Bragg peak therapeutic 12C ion beam at Heavy Ion Medical Accelerator in Chiba (HIMAC, Japan) are presented. Derived relative biological effectiveness (RBE) in 12C ion radiation therapy matches the tissue equivalent proportional counter (TEPC) well, along with outstanding spatial resolution. The use of SOI technology in experimental microdosimetry offers simplicity (no gas system or HV supply), high spatial resolution, low cost, high count rates capabilities for beam characterisation and quality assurance (QA) in charged particle therapy.

• Tran, Linh T.; Chartier, Lachlan; Prokopovich, Dale A.; Bolst, David; Povoli, Marco & Summanwar, Anand [Vis alle 16 forfattere av denne artikkelen] (2017). Thin silicon microdosimeter utilizing 3D MEMS fabrication technology: Charge collection study and its application in mixed radiation fields. IEEE Transactions on Nuclear Science. ISSN 0018-9499. 65(1), s. 467–472. doi: 10.1109/TNS.2017.2768062. Fulltekst i vitenarkiv Vis sammendrag

  New 10-μm-thick silicon microdosimeters utilizing 3-D technology have been developed and investigated in this paper. The TCAD simulations were carried out to understand the electrical properties of the microdosimeters’ design. A charge collection study of the devices was performed using 5.5-MeV He2+ ions which were raster scanned over the surface of the detectors and the charge collection median energy maps were obtained and the detection yield was also evaluated. The Devices were tested in a 290 MeV/u carbon ion beam at the Heavy Ion Medical Accelerator in Chiba (HIMAC) in Japan. Based on the microdosimetric measurements, the quality factor and dose equivalent out of field were obtained in a mixed radiation field mimicking the radiation environment for spacecraft in deep space.

• Bräuer-Krisch, Elke; Adam, Jean-Francois; Alagoz, Enver; Bartzsch, Stefan; Crosbie, Jeff & DeWagter, Carlos [Vis alle 22 forfattere av denne artikkelen] (2015). Medical physics aspects of the synchrotron radiation therapies: Microbeam radiation therapy (MRT) and synchrotron stereotactic radiotherapy (SSRT). Physica Medica. ISSN 1120-1797. 31(6), s. 568–583. doi: 10.1016/j.ejmp.2015.04.016. Fulltekst i vitenarkiv Vis sammendrag

  Stereotactic Synchrotron Radiotherapy (SSRT) and Microbeam Radiation Therapy (MRT) are both novel approaches to treat brain tumor and potentially other tumors using synchrotron radiation. Although the techniques differ by their principles, SSRT and MRT share certain common aspects with the possibility of combining their advantages in the future. For MRT, the technique uses highly collimated, quasi-parallel arrays of X-ray microbeams between 50 and 600 keV. Important features of highly brilliant Synchrotron sources are a very small beam divergence and an extremely high dose rate. The minimal beam divergence allows the insertion of so called Multi Slit Collimators (MSC) to produce spatially fractionated beams of typically ∼25–75 micron-wide microplanar beams separated by wider (100–400 microns center-to-center(ctc)) spaces with a very sharp penumbra. Peak entrance doses of several hundreds of Gy are extremely well tolerated by normal tissues and at the same time provide a higher therapeutic index for various tumor models in rodents. The hypothesis of a selective radio-vulnerability of the tumor vasculature versus normal blood vessels by MRT was recently more solidified. SSRT (Synchrotron Stereotactic Radiotherapy) is based on a local drug uptake of high-Z elements in tumors followed by stereotactic irradiation with 80 keV photons to enhance the dose deposition only within the tumor. With SSRT already in its clinical trial stage at the ESRF, most medical physics problems are already solved and the implemented solutions are briefly described, while the medical physics aspects in MRT will be discussed in more detail in this paper.

• Tran, Linh T.; Prokopovich, Dale A.; Petasecca, Marco; Lerch, Michael L.F.; Kok, Angela & Summanwar, Anand [Vis alle 10 forfattere av denne artikkelen] (2014). 3D Radiation Detectors: Charge Collection Characterisation and Applicability of Technology for Microdosimetry. IEEE Transactions on Nuclear Science. ISSN 0018-9499. 61(4), s. 1537–1543. doi: 10.1109/TNS.2014.2301729. Fulltekst i vitenarkiv Vis sammendrag

  A study of charge collection in SINTEF 3D active edge silicon detectors was carried out at ANSTO using Ion Beam InducedCharge (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.

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• Kok, Angela; Povoli, Marco; Summanwar, Anand; Tran, Linh T.; Petasecca, Marco & Lerch, Michael L.F. [Vis alle 7 forfattere av denne artikkelen] (2019). Fabrication challenges of silicon-based microdosimeter using 3D technology. Vis sammendrag

  Microdosimetry provides measurements of stochastic lineal energy deposition on a micrometric sensitive volume (SV), comparable to human cell dimensions. Conventional microdosimeter uses a tissue equivalent proportional counter (TEPC) that requires high voltage operation, are bulky and have poor spatial resolution. Silicon-on-insulator (SOI) microdosimeter fabricated using the so-called '3D technology', provides true cell-like SV that is encapsulated by a through substrate electrode. Furthermore, such detectors provide many attractive advantages such as micrometric spatial resolution, compact design, and easy coupling to readout electronics that provide real-time on-line monitoring. SINTEF in collaboration with Centre for Medical Radiation Physics (CMRP), have developed a full 3D SOI microdosimeter, a 5th generation SOI microdosimeter. Characterisation results of the first prototype run at several heavy ion therapy (HIT) centres demonstrated excellent results with derived radiobiological effectiveness (RBE), comparable with TEPC. Foreseen future manufacture of such dosimeters remains a challenge. One of the major difficulties is the integrity of metal connection joining individual sensitive volumes where the metal must trespass the the 3D circular electrodes encapsulating the entire SVs. The problem is further exasperated by the further enhancement in microdosimetry where all silicon surrounding the SVs is removed. This paper presents the first fabrication review of results and challenges over the several prototype runs carried out at SINTEF Minalab. The review and investigation aim to generate a fabrication technology that have a potential to provide a commercially viable manufacture process with a high yield throughput. Challenging processes such as removal of bulk silicon outside of the microscopic SVs and deposition of tissue equivalent material will also be discussed.

• James, Benjamin; Tran, Linh T.; Bolst, David; Pan, Vladimir M.; Prokopovich, Dale A. & Petasecca, Marco [Vis alle 13 forfattere av denne artikkelen] (2018). Fully 3D Sensitive Volume Microdosimeter Charge Collection and Radiation Damage Studies. Vis sammendrag

  In the course of this research, a radiation damage study of 3D microdosimeter structures were carried out using 5.5 MeV He2+ and 24 MeV C-12 ions microbeam. Radiation damage study post irradiation of the microdosimeters with low energy Li, C, O, ti ion was also investigated. Additionally, electrical and charge collection properties were studied for a new 3D SV microdosimeter covered with a tissue equivalent material.

• Kok, Angela & Povoli, Marco (2016). New technology allows radiology treatments to become more focused. Vis sammendrag

  A new technology, originally developed in 2012 to provide sensors that can tolerate extremely high radiation doses, has proven effective in particle therapy and has many advantages over x-ray photon therapy. Marco Povoli, Angela Kok and a team of world-renowned medical physicists, sensor technologists and medical personnel formed the microscopic sensor developed at SINTEF in Trondheim, Norway. They partnered with the Centre for Medical Radiation Physicists at the University of Wollongong, Australia.

• Kok, Angela; Povoli, Marco & Schjølberg-Henriksen, Kari (2016). Microscopic sensor for more precise radiology treatments. [Internett]. Geminiresearchnews.com.
• Kok, Angela (2015). Recent results on silicon multi-strip sensors for MRT.
• Stugu, Bjarne (2014). Detector Resolution Effects in Measuring Microstructured Beam Profiles. Vis sammendrag

  The purpose of the “3DMiMiC” project [1] is twofold. The first aim is to develop high resolution silicon detectors for the fast monitoring of microstructured synchrotron beams. The second aim is to develop silicon microdosimeters. Here, we address the resolution requirements of monitoring devices. Microstructured X-ray beams are resulting from synchrotoron radiation passing through masks with slits of very narrow widths [2]. The purpose of the monitoring system is to provide reliable intensity profiles, and estimates of the Peak to Valley Dose Ratios (PVDR). By (semi)analytical means we study the effects on the measurements due to finite resolution functions of different shapes. We also make case studies of a few PVDR measurements from the literature [2],[3], to understand if resolution effects would alter the conclusions made. References [1] http://www.sintef.no/home/Information-and-Communication-Technology-ICT/Microsystems-and-Nanotechnology/Competence-and-services-/Silicon-radiation-sensors/3DMiMic/ Downloaded Feb 14th 2014 [2] E.Bräuer-Kirch et al.: ‘Potential High Resolution Dosimeters for MRT’, AIP Conf.Proc. 1266, 89 (2010). [3] M. Petasecca et al.: ‘X-Tream: A Novel Dosimetry System for Synchrotron Microbeam Radiation Therapy’, JINST 7 P07022 (2012)

• Kok, Angela (2014). Thin silicon micro-strip detectors as beam monitoring for micro-beam radiation therapy on behalf of 3DMiMic collaboration.
• Povoli, Marco; Alagoz, Enver; Bravin, Alberto; Cornelius, Iwan; Bräuer-Krisch, Elke & Fournier, P. [Vis alle 17 forfattere av denne artikkelen] (2014). Simulation and Testing of Thin Microstrip Silicon Dosimeters for the Microbeam Radiation Therapy.
• Stugu, Bjarne (2014). High resolution fast beam monitors for microbeam radiation therapy.
• Kok, Angela (2014). Micro-machining and micro-fabrication for micro-dosimetry.
• Tran, Linh T.; Prokopovich, Dale A.; Petasecca, M; Lerch, Michael L.F.; Kok, Angela & Summanwar, Anand [Vis alle 9 forfattere av denne artikkelen] (2013). 3D Radiation Detectors: Charge Collection Characterisation and Applicability of Technology for Microdosimetry.
• Alagoz, Enver (2013). Novel silicon detectors for the microbeam radiation therapy on behalf of the 3DMiMic collaboration.
• Kok, Angela (2013). Micromachining and 3D technology for microdosimetry in charged particle therapy and space radiation protection on behalf of 3DMiMic collaboration.
• Kok, Angela (2012). Proposed fabrication of 3D silicon sensors as a mini and micro-dosimeter for quality assurance in conventional and hadron therapy (on behalf of 3DMiMic collaboration). Vis sammendrag

  3D silicon sensors with active edges where the electrodes penetrate through the entire silicon substrate have been investigated in high energy physics applications in recent years. The key to 3D fabrication is the use of plasma micro-machining to etch narrow deep vertical openings that allow dopants to be diffused in and form electrodes of p-i-n junctions. The use of such micro-machining is an emerging technology in the fabrication of such radiation sensors. Several leading institutions in semiconductor fabrication, both in Europe and in the US, have collaborated in an attempt to bring the maturity of 3D sensors to a level suitable to satisfy the needs of high energy physics research. These efforts include increasing detector size, optimization of compatibility with readout electronics and improvement in overall fabrication yield. The results so far are promising and physicists are now encouraged to explore the use of 3D sensors in a wider field of nuclear related science and technologies outside high energy physics. Sensors with 3D electrodes provide a strong electric field in the p-i-n junction and reduce the charge trapping probability of generated charge carriers by incident radiation making them more radiation hard. Moreover, this structure can provide higher spatial resolution, low operating voltage, better irradiation stability, improved regular response and radiation hardness for both mini-dosimetry in conventional radiotherapy and micro-dosimetry for hadron therapy. The resulting 3-dimensional structures, derived from micro-machining, can further improve the current status of micro-dosimetry by providing well-defined sensitive volumes to better mimic biological cells. This presentation will give a summary of the development of 3D sensors in the past year and their suitability in dosimetry for both conventional and hadron therapy. An international collaboration of leading institutions is currently underway a research project strongly funded by the Norwegian Research Council, which will investigate the performance of 3D microdosimeters.

• Kok, Angela ; Hansen, Thor-Erik; Schjølberg-Henriksen, Kari; Rosenfeld, Anatoly B.; Lerch, Michael L.F. & Petasecca, M [Vis alle 15 forfattere av denne artikkelen] (2012). Proposed fabrication of 3D silicon sensors as a mini and micro-dosimeter for quality assurance in conventional and hadron therapy.

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