bluuebunny/crossref_metadata_2025 huggingface dataset:
Permanent magnet vernier generator under dynamic eccentricity fault: diagnosis and detection
Authors: Ghods Mehrage , Faiz Jawad
Published: October 2020

Permanent magnet vernier generators (PMVGs) are suitable for meeting power concussion requirements of traffic enforcement cameras and traffic‐driven applications. In this study, the performance of PMVGs at no‐load and full‐load are analysed in healthy machines and machines under different types of mechanical faults including static eccentricity, dynamic eccentricity, inclined rotor, and run‐out faults. Furthermore, an analytical model is developed to estimate the air‐gap permeance and the induced voltages in the healthy generator and generator under the above‐mentioned mechanical faults. Then, the performance of the generator is predicted using a two‐dimensional and three‐dimensional time stepping finite‐element method. Finally, from the stator current spectrum of the PMVG under dynamic eccentricity fault, the amplitude of the side‐band components with a specific frequency pattern is extracted and compared with experimental results.
Computationally efficient hybrid PM loss prediction method for surface‐mounted permanent magnet machine over entire working conditions
Authors: Sheng Zhiyu , Wang Dong
Published: October 2020

This study proposes a computationally efficient hybrid approach to calculating permanent magnet (PM) loss in surface‐mounted PM machine (SPMM) over the whole working points. By analysing the impact of current amplitude, current angle, rotor speed, and PM temperature on the corresponding subdomain PM loss results, a simplified model that considers harmonic current and explicitly expresses the relationship between PM loss and working point variables is derived. Unlike the corresponding subdomain method, the proposed model does not involve a Fourier expansion or summation over a large number of terms, which simplifies the calculation and makes the PM loss under any operating condition can be acquired instantly. Thus, the needs for PM loss table and massive experiments or calculations are eliminated. The accuracy of this hybrid approach is validated against the finite element method results of a six‐phase SPMM over a wide range of working conditions. However, the cross‐verification studies demonstrate that the proposed method has good efficiency and high precision, making it a promising tool for online PM loss prediction.
Market power assessment through modelling of effective anti‐competitive behaviour of participants
Authors: Halakou Ehsan , Akbari Foroud Asghar
Published: October 2020

Market power is an anti‐competitive issue in the electricity markets, the identification and monitoring of which require using comprehensive and accurate indices. In this study, two new behavioural indices are introduced for the effective and accurate monitoring of market power. The suggested indices determine the actual level of market power in the transmission‐constrained electricity markets by analysing the bidding behaviour of participants. The proposed indices necessarily consider the success of the participant's anti‐competitive behaviour in a price increase on the basis for computation. First, the effective physical withholding index is presented, which can determine the amount of physical withholding that has led to the acceptance of a more expensive block. The effective financial distortion rate index is then proposed, which can specify the degree of financial deviation of the participants resulting from the successful exercise of each participant's withholding (financial–physical) strategy. Investigation of the results obtained from a three‐bus test system and the IEEE 57‐bus test system verifies the effective and accurate performance of the proposed indices in assessing the market power.
Non‐local harmonic current and reactive power compensation for a multi‐microgrid system using a series–shunt network device
Authors: John Thomas , Patsios Charalampos , Greenwood David
Published: October 2020

In this study, a new non‐local active compensation method is developed for a multi‐microgrid (MMG) system. The current industry practice is to utilise local harmonic current and reactive power compensation methods, however, local compensation methods are not practical for large MMG system with widely dispersed non‐linear loads, because each non‐linear load would require its own compensator. To overcome this problem, a novel compensating technology called a series–shunt network device (SSND) is installed between a pair of microgrids in the proposed MMG system. The SSND reduces the number of local compensators required while also performing additional functions in comparison with conventional devices. For effective control of the SSND, an improved model predictive control (MPC) algorithm, which gives better tracking accuracy and faster set‐point change than that of a conventional proportional–integral controller, is also presented. Analysis and simulations verify the capability of SSND in performing both local and non‐local active compensation of harmonic current and reactive power in the proposed MMG system under various test scenarios. Simulation results show that the MPC‐controlled SSND can achieve effective compensation, thereby resulting in a very low current total harmonic distortion value of 2.4% and a unity power factor at the distribution grid side.
Lumped‐parameter‐based electromagnetic transients simulation of non‐uniform single‐phase lines using state variable method
Authors: Mamiş Mehmet Salih
Published: October 2020

The characteristic impedance of a transmission line, a wire or a conductor changes in a non‐uniform manner if the distance to the ground at all points longitudinally is not the same. Vertical conductors, transmission towers and sagging overhead lines are examples for the non‐uniform lines. In this study, lumped‐parameter‐based state variable representation of the single‐phase non‐uniform line is described. From the lumped‐parameter non‐uniform line model a linear set of first‐order differential equations is obtained in the form of state equations and this analytical expression is solved in closed form using MATLAB to obtain the transient response directly in the time domain. The closed‐form solution has the advantage of obtaining the response of the system at an instant without the need for data in the previous states except for the initial conditions. The method also allows attaining the voltage and current profile of the system for any instant. In the illustrative cases presented, the systems with different surge impedance variations are considered and the surge response of a vertical conductor, an exponential line, and a horizontal cone and a vertical cone with constant and also varying propagation velocity are computed. The results are verified by those obtained using s‐domain simulations of distributed‐parameter transmission line and inverse Laplace transform.
Hybrid deep learning for power generation forecasting in active solar trackers
Authors: Frizzo Stefenon Stéfano , Kasburg Christopher , Nied Ademir , Rodrigues Klaar Anne Carolina , Silva Ferreira Fernanda Cristina , Waldrigues Branco Nathielle
Published: October 2020

To meet the growing electricity demand for consumers, it is necessary to use more efficient systems. The solar trackers stand out among the applications that can improve the efficiency of photovoltaic panel generation by increasing their solar uptake. For solar trackers to be more efficient, they can base their position update on a generation forecast and thus perform the control action only when there is greater efficiency in this update. For generation forecast, the long–short‐term memory (LSTM) can handle a large volume of non‐linear data. Furthermore, to improve the analysis, it is possible to apply signal filtering techniques. The wavelet energy coefficient is a technique used to reduce signal noise and extract features; this technique performs the filter and preserves the signal characteristic. In this study, the authors present a combination of wavelet energy coefficient and LSTM, defined as wavelet LSTM, to perform photovoltaic power forecasting in the dual‐axis solar trackers.
Automated UHF RFID‐based book positioning and monitoring method in smart libraries
Authors: Yaman Orhan , Ertam Fatih , Tuncer Turker , Firat Kilincer Ilhan
Published: October 2020

In this study, a method is proposed for ultra high frequency radio frequency identification (UHF RFID)‐based book positioning and counting developed for smart libraries. In the experimental setup created, RFID tags placed in books were automatically detected using three RFID antennas. Using received signal strength indicator information from each antenna for each book, the locations of the books are determined. In addition, classification was made by using machine learning approaches for the study. For this purpose, the best result for sequence determination in the classification study using ensemble trees, K nearest neighbours (KNN), and support vector machine algorithms was obtained with the ensemble subspace KNN algorithm with 94.1%. The best result for cabinet detection was obtained in the study using the ensemble subspace KNN algorithm and a 78.5% accuracy rate was achieved. The best result for rack detection was obtained with the ensemble subspace KNN algorithm with 95.4%. The study is thought to be useful in the automatic determination of the row, cabinet, and rack of books in smart libraries.
Multi‐bit Boolean model for chemotactic drift of Escherichia coli
Authors: Deshpande Anuj , Samanta Sibendu , Govindarajan Sutharsan , Layek Ritwik Kumar
Published: October 2020

Dynamic biological systems can be modelled to an equivalent modular structure using Boolean networks (BNs) due to their simple construction and relative ease of integration. The chemotaxis network of the bacterium Escherichia coli (E. coli ) is one of the most investigated biological systems. In this study, the authors developed a multi‐bit Boolean approach to model the drifting behaviour of the E. coli chemotaxis system. Their approach, which is slightly different than the conventional BNs, is designed to provide finer resolution to mimic high‐level functional behaviour. Using this approach, they simulated the transient and steady‐state responses of the chemoreceptor sensory module. Furthermore, they estimated the drift velocity under conditions of the exponential nutrient gradient. Their predictions on chemotactic drifting are in good agreement with the experimental measurements under similar input conditions. Taken together, by simulating chemotactic drifting, they propose that multi‐bit Boolean methodology can be used for modelling complex biological networks. Application of the method towards designing bio‐inspired systems such as nano‐bots is discussed.
Applications of non‐invasive sensor devices to personalised health care
Authors: Lin Yan , Ye JianHong , Jin MengSi , Zheng YuHang
Published: October 2020

The application of non‐invasive devices in personal health care is becoming more and more widespread, especially sleep quality, which is a critical part of personal health because it is often associated with many diseases. Using some sensor devices such as pressure sensors, photoplethysmography and heart rate devices, the authors can collect a lot of physiological signals. In this work, they provide a method of fuzzy inference to evaluate the sleep phase, which uses the values of heart rate, heart rate variation, and body movement as input parameters that collected by the sensor devices. This method has been applied to the actual product. The results show that the measurement results of this method are consistent with polysomnography, which is recognised as the best method for measuring sleep quality currently. At the same time, the device can make some additional contributions to monitoring personal health. Combining personal activity information collected by GPS with heart rate information collected by heart rate sensors and using process mining to analyse those data, they can provide good recommendations for personal health care.
In vitro evolution of antibody affinity via insertional scanning mutagenesis of an entire antibody variable region
Authors: Skamaki Kalliopi , Emond Stephane , Chodorge Matthieu , Andrews John , Rees D. Gareth , Cannon Daniel , Popovic Bojana , Buchanan Andrew , Minter Ralph R. , Hollfelder Florian
Published: October 2020

Significance

Insertion/deletion (InDel) mutations play key roles in genome and protein evolution. Despite their prominence in evolutionary history, the potential of InDels for changing function in protein engineering by directed evolution remains unexplored. Instead point mutagenesis is widely used. Here we create antibody libraries containing InDels and demonstrate that affinity maturation can be achieved in this way, establishing an alternative to the point mutation strategies employed in all previous in vitro selections. These InDels mirror the observation of considerable length variation in loops of natural antibodies originating from the same germline genes and be combined with point mutations, making both natural sources of functional innovation available for artificial evolution in the test tube.
Prediction and prevention of disproportionally dominant agents in complex networks
Authors: Lera Sandro Claudio , Pentland Alex , Sornette Didier
Published: October 2020

Significance

Proportional growth is the driver behind the dynamics of a large class of complex networks. However, if left uncontrolled a few agents may become so dominant that their actions compromise the entire system. We present a framework that monitors the system’s distance from such imbalanced states. When the system approaches an imbalanced state, we show how to structure an optimal, cost-efficient intervention policy. Focusing only on either helping the least-fit agents or punishing the most dominant ones in isolation turns out to be inefficient. Instead, our results call for a more wholistic approach, with important implications for the structure of regulatory matters such as antitrust policies, taxation law, subsidies, or development aid.
Desmosome architecture derived from molecular dynamics simulations and cryo-electron tomography
Authors: Sikora Mateusz , Ermel Utz H. , Seybold Anna , Kunz Michael , Calloni Giulia , Reitz Julian , Vabulas R. Martin , Hummer Gerhard , Frangakis Achilleas S.
Published: October 2020

Significance

The desmosome is a major cell–cell junction connecting cells in tissues under high mechanical load. Currently, while structures of the constituent cadherins are known, the desmosome architecture has remained elusive. The primary reason is the high plasticity of the cadherins. As many other cellular structures, their high flexibility cannot be easily addressed by conventional structural techniques that rely on averaging many identical structures. For this, we combine high-end cryo-electron tomography with large-scale molecular dynamics simulations to produce a molecular model of the desmosome that integrates new with decades-old observations, accounts for the remarkable biophysical properties, and maps the intermolecular interactions.
Voluntary leadership and the emergence of institutions for self-governance
Authors: Andersson Krister P. , Chang Kimberlee , Molina-Garzón Adriana
Published: October 2020

Significance

We offer evidence on the role of local, voluntary leaders during the initial stages of the self-governance process. Our findings, which show that unselfish leadership actions can foster self-governance under conditions that are unfavorable for collective action, provide hope for efforts to address creeping environmental degradation problems, such as climate change and biodiversity loss. The significance of these findings goes beyond environmental policy and speaks to the potential role of voluntary leaders in the formulation of policy responses to new, emerging threats to human well-being for which there are no established governance institutions.
Mapping glycan-mediated galectin-3 interactions by live cell proximity labeling
Authors: Joeh Eugene , O’Leary Timothy , Li Weichao , Hawkins Richard , Hung Jonathan R. , Parker Christopher G. , Huang Mia L.
Published: October 2020

Significance

Because of the weak interactions between individual glycan-binding proteins (GBPs), such as galectin-3, and glycans, strategies that enable the direct interrogation of these interactions in living cells remain limited. Thus, the glycan and glycoprotein ligands that are physiologically relevant for galectin-3 binding are insufficiently described. Here we used a proximity labeling approach that catalytically tags interactors for galectin-3 and identified its pertinent glycan and glycoprotein counter-receptors in live cells. This study demonstrates that proximity labeling is a powerful tool for mapping GBP complexes in living cells, and when coupled with chemical inhibitors, it can discriminate between protein–protein and protein–glycan interactions.
Diatom modulation of select bacteria through use of two unique secondary metabolites
Authors: Shibl Ahmed A. , Isaac Ashley , Ochsenkühn Michael A. , Cárdenas Anny , Fei Cong , Behringer Gregory , Arnoux Marc , Drou Nizar , Santos Miraflor P. , Gunsalus Kristin C. , Voolstra Christian R. , Amin Shady A.
Published: October 2020

Significance

Phytoplankton are major primary producers in the marine environment that excrete a wide range of metabolites. These exudates support the growth of surrounding bacteria that in turn provide phytoplankton cells with resources and growth cofactors to proliferate. Unlike multicellular eukaryotes with dedicated structures housing microbiomes, mechanisms enabling unicellular eukaryotic phytoplankton hosts to modulate potential symbionts and opportunists within a natural microbial community are unknown. Exposure of a host phytoplankton cell to its natural microbial community triggers major transcriptional and metabolic reprogramming to release unique secondary metabolites that selectively enable growth and attachment of symbiotic taxa while simultaneously suppressing the colonization of nonsymbiont bacteria. These results suggest strong and highly selective microbiome-modulating strategies shared across the unicellular and multicellular eukaryotic lineages.
Conjunctive Markers of Contrast in English and French
Authors: Dupont Maïté
Published: October 2020

Situated at the interface between corpus linguistics and Systemic Functional Linguistics, this volume focuses on conjunctive markers expressing contrast in English and French. The frequency and placement patterns of the markers are analysed using large corpora of texts from two written registers: newspaper editorials and research articles. The corpus study revisits the long-standing but largely unsubstantiated claim that French requires more explicit markers of cohesive conjunction than English and shows that the opposite is in fact the case. Novel insights into the placement preferences of English and French conjunctive markers are provided by a new approach to theme and rheme that attaches more importance to the rheme than previous studies. The study demonstrates the significant benefits of a combined corpus and Systemic Functional Linguistics approach to the cross-linguistic analysis of cohesion.
Tunable metal–insulator transition in LaTiO3/CaVO3 superlattices: A theoretical study*
Authors: Weng Ya-Kui , Shen Meng-Lan , Li Jie , Li Xing-Ao
Published: October 2020

As one of intriguing physical results of electronic reconstruction, the metal–insulator transition plays an important role in exploring new electronic devices. In this study, the density functional theory is employed to investigate the metal–insulator transition in (LaTiO3)
m
/(CaVO3)
n
superlattices. Herein, three kinds of physical avenues, i.e., stacking orientation, epitaxial strain, and thickness periods, are used to tune the metal–insulator transition. Our calculations find that the [001]- and [110]-oriented (LaTiO3)1/(CaVO3)1 superlattices on SrTiO3 substrate are insulating, while [111]-oriented case is metallic. Such metallic behavior in [111] orientation can also be modulated by epitaxial strain. Besides the structural orientation and strain effect, the highly probable metal–insulator transition is presented in (LaTiO3)
m
/(CaVO3)
n
superlattices with increasing thickness. In addition, several interesting physical phenomena have also been revealed, such as selective charge transfer, charge ordering, and orbital ordering.
Effect of spatially nonlocal versus local optical response of a gold nanorod on modification of the spontaneous emission*
Authors: Wen Sha-Sha , Tian Meng , Yang Hong , Xie Su-Jun , Wang Xiao-Yun , Li Yun , Liu Jie , Peng Jin-Zhang , Deng Ke , Zhao He-Ping , Huang Yong-Gang
Published: October 2020

The spontaneous emission rate of a two-level quantum emitter (QE) near a gold nanorod is numerically investigated. Three different optical response models for the free-electron gas are adopted, including the classical Drude local response approximation, the nonlocal hydrodynamic model, and the generalized nonlocal optical response model. Nonlocal optical response leads to a blueshift and a reduction in the enhancement of the spontaneous emission rate. Within all the three models, the resonance frequency is largely determined by the aspect ratio (the ratio of the nanorod length to the radius) and increases sharply with decreasing aspect ratio. For nanorod with a fixed length, it is found that the larger the radius is, the higher the resonance frequency is, and the smaller the enhancement is. However, if the length of the nanorod increases, the peak frequency falls sharply, while the spontaneous emission enhancement grows rapidly. For nanorod with a fixed aspect ratio, the peak frequency decreases slowly with increasing nanorod size. Larger nanorod shows smaller nonlocal effect. At a certain frequency, there is an optimal size to maximize the enhancement of the spontaneous emission rate. Higher order modes are more affected by the nonlocal smearing of the induced charges, leading to larger blueshift and greater reduction in the enhancement. These results should be significant for investigating the spontaneous emission rate of a QE around a gold nanorod.
Application of portal dosimetry and Dolphin in clinical machine and patient-specific quality assurance
Authors: Cai M , Archibald-Heeren B , Wang Y
Published: October 2020

This paper introduces Varian portal dosimetry and IBA dolphin detector. Clinical machine QA examples were presented including DLG measurement and monthly beam constancy check. For patient-specific QA, both detectors generated similar passing rates to film and were able to identify an erroneous delivery with 3mm MLC offset.
Test of innovative silicon detectors for the monitoring of a therapeutic proton beam
Authors: Sacchi R , Ahmadi Ganjeh Z , Arcidiacono R , Attili A , Cartiglia N , Donetti M , Fausti F , Ferrero M , Giordanengo S , Hammad Ali O , Mandurrino M , Manganaro L , Mazza G , Monaco V , Sola V , Staiano A , Vignati A , Cirio R
Published: October 2020

Beam monitoring in particle therapy is a critical task that, because of the high flux and the time structure of the beam, can be challenging for the instrumentation. Recent developments in thin silicon detectors with moderate internal gain, optimized for timing applications (Ultra Fast Silicon Detectors, UFSD), offer a favourable technological option to conventional ionization chambers. Thanks to their fast collection time and good signal-to-noise ratio, properly segmented sensors allow discriminating and counting single protons up to the high fluxes of a therapeutic beam, while the excellent time resolution can be exploited for measuring the proton beam energy using time-of-flight techniques. We report here the results of the first tests performed with UFSD detector pads on a therapeutic beam. It is found that the signal of protons can be easily discriminated from the noise, and that the very good time resolution is confirmed. However, a careful design is necessary to limit large pile-up inefficiencies and early performance degradation due to radiation damage.
Evaluation of RBE-weighted doses for various radiotherapy beams based on a microdosimetric function implemented in PHITS
Authors: Takada Kenta , Sato Tatsuhiko , Kumada Hiroaki , Sakurai Hideyuki , Sakae Takeji
Published: October 2020

University of Tsukuba is developing a new TPS for boron neutron capture therapy (BNCT) equipped with Monte Carlo dose-calculation engine based on Particle and Heavy Ion Transport code System PHITS. It is currently in the process of extending its adaptation to other radiotherapy beams. For this extension, not only physical doses but also their relative biological effectiveness (RBE) must be evaluated for various radiotherapy in the same framework. Frequent and dose probability densities of lineal energy, y, are the key quantities in the RBE estimation, and they must be precisely evaluated for various locations in a patient. In this study, the probability densities of y for a site diameter of 0.564 µm were calculated for X-ray, proton, carbon-ion, and BNCT beams with appropriate geometry settings using the microdosimetric function implemented in PHITS, and they were converted to the corresponding RBE-weighted doses using the microdosimetric kinetic model. The accuracy of the calculated data were well verified by several experimental data, indicating the adequacy of the use of PHITS and microdosimetric kinetic model in the dose-calculation engine for TPS applicable to various radiotherapy.
Carbon Ion Radiotherapy for Prostate Cancer: Current Status in Japan
Authors: Tsuji H
Published: October 2020

Clinical trials on carbon ion radiotherapy (C-ion RT) for the prostate cancer were conducted at the NIRS for over 20 years. The results so far have been quite satisfactory in both toxicity and tumour control. In addition, advancement of hypofractionation has been successfully progressed and 12-fraction C-ion RT could be established. To obtain the outcomes of multi-institutional clinical trials, a study group, J-CROS, was organized and conducts several multicenter clinical trials including the prospective study for the high-risk prostate cancer. It is expected that the outcomes of these clinical studies would result in widening the coverage of National Health Insurance for the C-ion RT. Technical progression has been also achieved at the NIRS. The scanning irradiation became available in 2011 and all the prostate cancers are treated with scanning at present. A new clinical trial of 4-fraction C-ion RT for the locally recurrent prostate cancer has been started using dose painting of scanning beam. The rotating gantry of heavy ion beam was also installed. These technical progressions enable to perform the intensity modulated ion therapy with carbon beam alone or with various ion species.
Microdosimetry at the 62 MeV Proton Beam of CATANA: preliminary comparison of three detectors
Authors: Bianchi A , Colautti P , Conte V , Selva A , Agosteo S , Bortot D , Mazzucconi D , Pola A , Reniers B , Parisi A , Struelens L , Vanhavere F , Tran Linh , Rosenfeld A B , Cirrone G A P , Petringa G
Published: October 2020

A microdosimetric characterization of the 62 MeV proton beam line of CATANA has been performed all along the Spread Out Bragg Peak with three different detectors. Two silicon detectors and a Tissue Equivalent Proportional Counter measured at approximately the same depths of the SOBP. The TEPC is a new miniaturized gas counter developed at the Legnaro National Laboratories of INFN, modified to work without gas flow. The first silicon detector has been developed at the Politecnico of Milano and it is a monolithic telescope composed by a matrix of 2 µm thick cylindrical diodes with a diameter 9 µm. that compose the ΔE layer. The E and ΔE layers are fabricated on a single substrate of silicon. The third detector is the MicroPlus probe developed at the CMRP - University of Wollongong, it is an array of 3D sensitive volumes each with dimension 30x30 µm and 10 µm thick fabricated on SOI. Measurements performed with the three detectors are presented and discussed.
The use of a new 2D array of diodes for small-field dosimetry of a CyberKnife equipped with a novel multi-leaf collimator
Authors: Biasi G , Munoz L , Hug B , Ebert M A , Petasecca M , Bucci J , Jackson M , Rosenfeld A B
Published: October 2020

In the present work, we reported on the use of a new 2D array of diodes, the Duo, for dosimetry of small beams produced with a CyberKnife system, and shaped with a novel multi-leaf collimator, the InCise 2.
Experimental measurements confirm decreased supralinearity in the thermoluminescence of beta/gamma irradiated LiF:Mg,Ti (TLD-100) following 3.6 eV and 5 eV optical excitation
Authors: Ginzburg D , Oster L , Eliyahu I , Reshes G , Biderman S , Horowitz Y S
Published: October 2020

Photon excitation at selected energies following beta/gamma irradiation is found to significantly reduce the supralinearity of the thermoluminescence dose response of composite peak 5 in LiF:Mg,Ti (TLD-100). Following a dose of 100 Gy, photon excitation at an energy of 5 eV and fluence of 1.3 × 1018 ph cm−2 reduces the normalized TL efficiency from 2.8 to 1.9 and at 400 Gy from 3.5 to 2.7. Excitation by photons of energy 3.65 eV (1019 ph cm−2) reduces the normalized efficiency of glow peak 5a (a low temperature satellite of peak 5) at 100 Gy from 2.9 to a value of 0.95 thereby resulting in a linear dose response. The high values of dose of 100 Gy and 400 Gy well beyond the normal dose range of clinical radiation therapy were chosen for demonstrative purposes in order to evaluate the likelihood of success of the proposed technique. Additional experiments are underway to determine the photon levels of fluence, which will result in a linear dose response for both glow peaks 5, and 5a in the range of doses 1-30 Gy of interest to radiotherapy and intraoperative electron therapy.
The black box problem of AI in oncology
Authors: Hagenbuchner Markus
Published: October 2020

The rapidly increasing amount and complexity of data in healthcare, the pace of published research, drug development, biomarker discovery, and clinical trial enrolment in oncology renders AI an approach of choice in the development of machine assisted methods for data analysis and machine assisted decision making.

Machine learning algorithms, and artificial neural networks in particular, drive recent successes of AI in oncology. Performances of AI driven methods continue to improve with respect to both speed and precision thus leading to a great potential for AI to improve clinical practice. But the acceptance and a lasting breakthrough of AI in clinical practice is hampered by the black box problem. The black box problem refers to limits in the interpretability of results and to limits in explanatory functionality. Addressing the black box problem has become a major focus of research [1]. This talk describes recent attempts to addressing the black box problem in AI, offers a discussion on the suitability of those attempts for applications to oncology, and provides some future directions.
Monte Carlo based corrections for the dosimetry of x-ray microbeams with diamond detectors
Authors: Hugtenburg Richard P. , Reynard Dimitri D. H.
Published: October 2020

X-ray microbeams are a potential, novel mode of radiation therapy and dosimetry methods are under development that require micrometric spatial precision. The microDiamond detector has the requisite resolution and is composed of diamond which is closely tissue-equivalent. The high density of diamond however perturbs of secondary electrons and Monte Carlo methods are needed to determine corrections to accurately measure clinical parameters. The PENELOPE Monte Carlo code has been used to calculate corrections for the output factor (OF) and peak-to-valley dose ratio (PVDR). A high-performance computing (HPC) system was found to be necessary and the calculation took 72 hours when performed on a cluster of 100 CPUs. The correction for the output factor was found to be 1.009±0.016 (2 s.d.). The correction factor for the peak-to-valley ratio was found to be 1.144±0.013 (2 s.d.) and was larger due to Compton scattering of the microbeam in the extracameral components of the detector, in particular the 300 micron bulk diamond crystal. It was found that considerable improvements in efficiency could be achieved without loss of precision by switching off electron transport for electrons that are generated far from the sensitive element of the detector.
Development of wide-bandgap semiconductor-based dosimeter for LET distribution measurement in carbon therapy filed
Authors: Kada W , Ohsaki K , Ohki Y , Yamazaki Y , Makino T , Ohshima T , Mattsumura A , Sakai M
Published: October 2020

This paper presents a proof of concept of silicon carbide (SiC), a type of wideband semiconductor, based dosimeter for linear energy transfer (LET) distribution measurement at clinical carbon beam therapy field. SiC Schottky barrier diode (SBD), which has been designed for ionization detector, was utilized for spectroscopy of pristine 290 MeV/u 12C heavy ion therapy beams at Gunma University Heavy Ion Medical Centre (GHMC) facility, Japan. Measurement of LET distribution was successfully demonstrated at different depth with developed SiC SBD dosimeter. Also SiC SBD was exposed with clinical carbon beam with high intensity condition. Through CCE and deep level defect evaluation, sufficient radiation tolerance was examined for SiC SBD for futuristic usage in clinical carbons. Those results suggested that preliminary evaluation of SiC SBD was successful as energy-dispersive dosimeter for heavy ion therapy field.
Training and validation of a commercial deep learning contouring platform
Authors: Koo J , Caudell J , Feygelman V , Moros E , Latifi K
Published: October 2020

We present our experience with training and validation of a commercially available deep learning algorithm for organs at risk(OAR) auto-contouring. Computed tomography(CTs) with OARs from a cohort of 213 head and neck(H&N) patients were used for training the deep learning model. A separate cohort of 85 CTs and structure sets was used for validation. All OARs (13) were contoured by a single physician. Metrics such as the DICE similarity coefficient (DSC), Jaccard similarity coefficient (JSC), and volumetric difference (VD) were used to analyze contouring variation. Mean DSC and JSC values ranged 0.48-0.89 and 0.32-0.8, respectively, depending on OAR. A DSC value ≥0.7 indicated low inter-observer variability. In our study, all but one of the contours were above this threshold. DSC for the middle pharyngeal constrictor had the lowest value of all the contours. This may be due to the small volume of this structure. Qualitative assessment of auto-segmented structure samples confirmed the reliability of DSC by demonstrating the compatibility between the expert’s evaluation and DSC values. Overall, we found that deep learning auto contouring is a useful tool to speed up the process of contouring in radiotherapy treatment planning.
FASTRACK II magnetic resonance imaging sub-study Diffusion and perfusion biomarkers for renal SABR response
Authors: Korte J C , Reynolds H , Lasocki A , Vanneste B G L , Miclea R , Backes W H , Sridharan S , Sidhom M , Rai R , Kron T , Hardcastle N , Siva S
Published: October 2020

Stereotactic ablative body radiotherapy (SABR) is demonstrating good local control for patients with inoperable primary renal cell carcinoma. In a previous pilot study we identified magnetic resonance imaging (MRI) early response biomarkers that correlate with later morphological changes in computed tomography (CT) images. These early functional changes in diffusion and perfusion following radiotherapy were observed on MRI and have the potential to identify non-responders who may benefit from adjuvant or salvage therapies. Here we detail the imaging protocol for an MRI sub-study of the Focal Ablative STereotactic Radiosurgery for Cancers of the Kidney (FASTRACK II) trial. A preliminary patient case demonstrates the high quality of the imaging data, with discussion of the improvements made from the pilot protocol for improved motion management and correction. We aim to validate the previously identified early response MRI biomarkers with this rich prospective multi-centre dataset.
Multimodal Monte Carlo treatment system capable of microdosimetry with PHITS
Authors: Kumada H , Takada K , Sato T , Sakurai H , Sakae T
Published: October 2020

Boron neutron capture therapy (BNCT) is a radiation therapy that combines neutrons and boron drugs. An industry-academia-government collaboration team is currently developing the linac-based treatment device and several peripheral devices to establish this therapy. In the project, a demonstration device, “iBNCT001”, for a linac-based neutron source applicable to BNCT treatment is being developed. We are developing Tsukuba Plan, a multimodal Monte Carlo-based treatment planning system, in addition to the linac-based neutron source device. Tsukuba-Plan has adopted a Particle and Heavy Ion Transport code System (PHITS) as the Monte Carlo-based dose calculation engine. PHITS has a microdosimetric function that can compute a lineal energy distribution and determine relative biological effectiveness through combination with the stochastic microdosimetric kinetic model parameters. By utilising these functions, Tsukuba-Plan is expected to estimate the weighted doses administered to the tumour region and normal tissues in the irradiation field more accurately.
Modelling ICRP110 Adult Reference Voxel Phantoms for dosimetric applications: Development of a new Geant4 Advanced Example
Authors: Large M J , Malaroda A , Petasecca M , Rosenfeld A B , Guatelli S
Published: October 2020

The reference adult male and female voxel phantoms described in the International Commission on Radiological Protection (ICRP) publication 110 have been successfully implemented in a Geant4 application named ICRP110Phantoms. The application allows users to simulate either the whole or a partial phantom, including as little as a single cross-sectional slice. The Geant4 application allows users to estimate the absorbed dose in individual voxels and in entire organs. As example of application, the ICRP110Phantoms was used to estimate the dose deposited by a mono-energetic 125 MeV proton pencil beam, incident on the left breast and passing through the lungs and heart, modelled in partial chest phantoms of both male and female ICRP110 phantoms. The ICRP110Phantoms will be released in Geant4 as an Advanced Example to allow its use in the wider scientific community. This Geant4 Advanced Example application can be utilised for dosimetric studies in radiotherapy, nuclear medicine and radiation protection.
Assessing small-field output factors using a 2D monolithic diode array on a beam-matched Elekta linear accelerator
Authors: Muñoz L , Petasecca M , Metcalfe P , Bucci J , Jackson M , Rosenfeld A B , Biasi G
Published: October 2020

The goal of this work was to assess small-field output factors (OPF) on a newly commissioned linear accelerator (linac) using a ‘correction-less’ 2D monolithic array of diodes, the Duo, which has a spatial resolution of 0.2 mm. The results would validate a set of OPF extracted from the golden beam data (GBD) used to represent the dosimetric characteristics of that linac, an Elekta Versa HD (Elekta, Crawley), fit with an Agility multileaf collimator (MLC). The Duo acquired relative OPF in real time for square fields of nominal side 1, 2, 3 and 4 cm, for 6 MV with flattening filter (WFF) and 6 MV flattening filter free (FFF) photon energies. Results revealed at most a 1.0% difference in OPF when compared to baseline, and bolstered confidence in the acceptance and commissioning of the linac using local GBD as a baseline match.
Nanoscale calculation of the relative efficiency of 7LiF:Mg,Ti (MTS-7) and 7LiF:Mg,Cu,P (MCP-7) thermoluminescent detectors for measuring electrons and positrons
Authors: Parisi Alessio , Struelens Lara , Vanhavere Filip
Published: October 2020

Using the Microdosimetric d(z) Model in combination with PHITS-simulated specific energy probability density distributions, the relative efficiency of 7LiF:Mg,Ti (MTS) and 7LiF:Mg,Cu,P (MCP-7) thermoluminescent detectors was assessed as function of the incident energy for electrons and positrons spanning from 2 keV to 1 GeV. Additionally, the effect of the dopant concentration on the determined efficiency values was carefully investigated. Finally, the results are presented in combination with calculated specific energy frequency mean values and possible correlations were discussed.
Electron Paramagnetic Resonance Spectroscopy for Gamma Knife Dosimetry
Authors: Ramachandran P , Noble C , Jones C , Seshadri V , Foote M
Published: October 2020

Alanine chips exposed to high doses of radiation produces long lived free radicals that could be easily measured with electron paramagnetic resonance (EPR) spectrometers. In this study, the feasibility of using alanine dosimeters for performing rapid quality assurance of Leksell Gamma Knife (LGK) treatment plans was demonstrated. A 3D printed grid was placed inside the LGK spherical solid water phantom (SWP) for measurement of doses at isocentre and off-axis points. The EPR spectroscopy was performed on a Magnettech MS-5000 EPR/ESR spectrometer. A set of dose calibration curves were established prior to the use of alanine chips for LGK dosimetry. Absolute dose, transit dose and dose/timer linearity were performed with the alanine chips positioned at the centre of the LGK solid water phantom (SWP). Five patients of different sites were selected, and patient specific quality assurance (PSQA) was performed in the LGK SWP. The absolute dose measured with the EPR alanine dosimeter agreed well within 2% of the ion chamber results and PSQA results were within 2.1%. Alanine-based EPR dosimetry offers rapid dose measurement with high accuracy and can also be used as a dosimeter for Gamma Knife PSQA.
Evaluation of spot size using volumetric repainting technique on a ProteusPLUS PBS Proton Therapy System
Authors: Rana S , Bennouna J , Gutierrez A , Rosenfeld A
Published: October 2020

Volumetric repainting is considered as one of the techniques for motion mitigation in proton therapy. Faster layer switching time to deliver a volumetric repainting proton plan is very critical to reduce the overall treatment time. Recently, IBA (proton therapy vendor at the Miami Cancer Institute) has implemented a “field regulation” – a new feature to reduce the switching time between layers by applying a magnetic field setpoint to specific groups of magnets. In order to investigate the impact of field regulation and volumetric repainting technique on the spot size, several spot maps were generated. The spot sizes were measured at the isocenter and four off-axis points using the Lynx 2D scintillation detector. The average difference in spot size between two delivery sequences (“down” vs. “up” directions) for given energy at all five locations was 0.6±0.5%. The measurement results from the current study demonstrated that the impact of field regulation on the spot size was very minimal, and this was true for both the volumetric and non-volumetric techniques on a ProteusPLUS proton system with a PBS dedicated nozzle.
Challenges in dosimetry of particle beams with ultra-high pulse dose rates
Authors: Romano F. , Subiel A. , McManus M. , Lee N. D. , Palmans H. , Thomas R. , McCallum S. , Milluzzo G. , Borghesi M. , McIlvenny A. , Ahmed H. , Farabolini W. , Gilardi A. , Schüller A.
Published: October 2020

Recent results from pre-clinical studies investigating the so-called FLASH effect suggest that the ultrahigh pulse dose rates (UHPDR) of this modality reduces normal tissue damage whilst preserving tumour response, when compared with conventional radiotherapy (RT). FLASH-RT is characterized by average dose rates of dozens of Gy/s instead of only a few Gy/min. For some studies, dose rates exceeding hundreds of Gy/s have been used for investigating the tissue response. Moreover, depending on the source of radiation, pulsed beams can be used with low repetition rate and large doses per pulse. Accurate dosimetry of high dose-rate particle beams is challenging and requires the development of novel dosimetric approaches, complementary to the ones used for conventional radiotherapy. The European Joint Research Project “UHDpulse” will develop a measurement framework, encompassing reference standards traceable to SI units and validated reference methods for dose measurements with UHPDR beams. In this paper, the UHDpulse project will be presented, discussing the dosimetric challenges and showing some first results obtained in experimental campaigns with pulsed electron beams and laser-driven proton beams.
Evaluating the use of Silica and PMMA Optical Fibres as Proton Beam Monitors
Authors: Santos A M C , Depauw N
Published: October 2020

Recent reports have shown both poly (methyl methacrylate) (PMMA) and silica optical fibres to be ionization quenching free, making them possibly very useful dosimeters for proton beams. In this study, the response from PMMA and silica optical fibres to therapeutic proton beams are evaluated. The light output was recorded from both optical fibres, exposed to varying dose-rates of 0.5 Gy/min to 20 Gy/min from a 235 MeV isochronous cyclotron. The PMMA optical fibre was observed to have a linear dose-rate response, and a constant light emission for a constant dose-rate exposure. However, in the case of the silica optical fibres, the light output was observed to increase during a constant dose-rate exposure. If uncorrected, this accumulated dose sensitivity observed in the silica optical fibres can result in erroneous measurements.
Real-time in-vivo dosimetry for DaRT
Authors: Su Fang-Yi , Tran Linh T , Biasi Giordano , Petasecca Marco , Lerch Michael L F , Cutajar Dean L , Bucci Joseph , Jackson Michael , Rosenfeld Anatoly B
Published: October 2020

Diffusing alpha-emitters radiation therapy (DaRT) is a revolutionary brachytherapy technique used to treat solid tumours. Implant seeds are coated with 224Ra which, along its shortlived daughter atoms, emits alpha particles of high linear energy transfer (LET) and of high relative biological efficiency (RBE), creating a tumour-killing dose distribution a few mm wide. Those alpha particles are of energy between 5.67 and 8.78 MeV. DaRT is under investigation in clinical trials, but there currently is no obvious solution for dosimetry aimed at quality assurance of treatment. This study introduces alpha-RAD, a dosimeter based on a metal-oxide-semiconductor (MOS) sensor technology. Alpha-RAD was characterized with 241Am, which emits alpha particles of energy 5.49 MeV. The results showed that alpha-RAD had good linearity with dose, with the signal increasing linearly in the range from 0 to 6.84 Gy. Also, an external bias in the range between 15 and 60 V, applied on the gate of alpha-RAD during irradiation, would optimize sensitivity to alpha particles of energies typical of DaRT. Alpha-RAD, owing to its compactness, can fit into a brachytherapy needle, to be placed next to 224Ra seed implants in the tumour, for real-time in vivo dosimetry.