1,244 research outputs found
Evaluation of the proton range accuracy using Single and Dual Energy Computed Tomography
No full textProton therapy is a highly advanced form of external beam radiotherapy, which uses proton beams to treat cancers. Protons are particularly suited for radiotherapy because heavy particles, interacting with matter, deposit most of their energy at the end of their track. It allows for well-conformed dose distributions to the target area while minimizing exposure to surrounding healthy tissues and organs at risk. In addition, ongoing research reveals that protons have distinct biological, immunological, and clinical effects compared to photons, beyond just dose distribution differences.
X-ray CT images are currently the standard for proton beam planning, but they have limitations due to the need to convert electron density maps into stopping power ratios (SPR) maps. CT numbers (HU values) noise and the lack of a consistent conversion to SPR lead to imperfect dose calculations and introduce density uncertainties. Additionally, CT scans only capture a single snapshot of patient anatomy, while daily variations during treatment cause setup uncertainties. Treatment planning systems (TPSs) are designed for account density and setup uncertainties through robust optimization. Density and setup uncertainty values are not uniquely defined. They are institution-specific, depending on the utilized treatment modalities, the clinical experience and the target anatomic localization. Density uncertainty typically ranges within 3% and 3.5%, whereas, setup uncertainty varies from 1 mm up to 5mm.
Within the scientific community, there is a strong interest in reducing the density uncertainties. The advent of Dual-Energy CT (DECT) scanners has introduced new options to increase the SPR conversion accuracy compared to Single-Energy CT (SECT). The Siemens Syngo.via software is an available commercial solution to perform the DE raw image processing, generating Dual Energy Monoenergetic Plus images. In addition, the software includes a tool, DirectSPR, able to directly calculate voxel by voxel the proton SPR, without resorting to HU conversion.
This work aims to evaluate the impact of HU to SPR conversion methods on TPS proton
range estimation. HU to SPR conversion relationships were derived from CT calibrations. The following methods were implemented and evaluated: the SECT tissue-substitute method and, on the other hand, the SECT and Dual Energy Monoenergetic Plus Stoichiometric calibration methods. In different scenarios, the proton range was directly measured with a multi-layer ion chamber and compared with the one derived from TPS dose calculation on DirectSPR maps and SECT and DECT images.
Firstly, tissue-surrogate solid plugs were individually irradiated with a single pencil beam
of 226 MeV proton. DirectSPR-derived proton range showed a better agreement with measurements than CT calibration-based methods differing at most by 1% (SECT and 75KeV Monoenergetic Plus with the stoichiometric calibration respectively by 6.5% and 4.5%), for all the plugs except for high-density ones. All the TPS calculated proton ranges significantly differed (up to 32%) from the measurement for the He Cortical Bone plug. This result will require additional investigation. Plug results can not be fully translated to human tissues, since they have different chemical compositions. For this purpose, animal organ samples were used. They were irradiated with single pencil beams of different energies (100 MeV, 150 MeV and 226 MeV) and with a simple intensity modulated proton therapy (IMPT) plan (a dose cube). Three irradiation points were identified on each sample surface and the proton range was probed at each of them. Proton range differences between measures and TPS-derived ones had no dependency
on beam energy. However, the results of this investigation do not confirm the high accuracy in SPR assignment of DirectSPR than SECT and DECT calibration-based methods, indeed, proton range differences with measures were very close within the various approaches.
The density uncertainty was evaluated on the data derived from IMPT irradiation on animal organ samples, given the closeness to clinical treatment conditions. A value of 2% could be taken as density uncertainty associated with the use of SECT and Monoenergetic Plus75keV image with the relative stoichiometric calibration curve in proton dose calculation, while the value obtained for the DirectSPR was higher, 2.8%. The high standard deviations of the multiple irradiation point measurements suggest the presence of residual setup errors affecting the results and the necessity to improve setup repeatability for further investigations.
The results of this study confirm the feasibility of the use of DirectSPR and Monoenergetic
Plus images generated by the Syngo.via software as input to the Raystation TPS for
proton dose calculation. Although preliminary, the results of this study support the reduction of the 3.5% clinical density uncertainty enabled by the implementation of dual-energy CT as suggested by many authors
A new MIP Heuristic based on Randomized Neighborhood Search
No full textA new simple MIP heuristic, called Randomized Neighborhood Search (RANS) is proposed, whose purpose is to produce within short time bounds high quality solutions especially for large size MIP problems as the ones characterizing real industrial applications. Starting from starts from a feasible incumbent solution RANS iterates solutions' neighborhood exploration randomly defined by calling a MIP solver as a black box tool. RANS rationale is similar to the one of other MIP heuristics recently appeared in literature but, differently, it exploits only a randomization mechanism to guide the MIP solver. RANS has some self-tuning rules so that it needs as single input parameter the maximum computation time. RANS also includes a procedure for generating the first incumbent solution based on the same randomization concepts, that can be used as an initialization alternative for particularly hard instances. RANS effectiveness is shown by an experimental comparison with other MIP heuristics
Correction to: When terminology hinders research: the colloquialisms of transitions of control in automated driving (Cognition, Technology & Work, (2022), 10.1007/s10111-022-00705-3)
No full textIn the original article, author affiliation published with error. The correct affiliations are: Davide Maggi—Institute for Transport Studies, Leeds, UK. Richard Romano—Institute for Transport Studies, Leeds, UK. Oliver Carsten—Institute for Transport Studies, Leeds, UK. Joost C. F. De Winter—Faculty of Mechanical, Maritime and Materials Engineering, Delft University of Technology, Delft, The Netherlands. The original article has been corrected.Human-Robot Interactio
Admiel Kosman, Siamo giunti a Dio
No full textInternational audienceSix poems from Israeli poet Admiel Kosman translated from the Hebrew into Italian. Selection of poems, presentation of the author, translation and notes by Davide Mano
Admiel Kosman, Siamo giunti a Dio
No full textInternational audienceSix poems from Israeli poet Admiel Kosman translated from the Hebrew into Italian. Selection of poems, presentation of the author, translation and notes by Davide Mano
Starchitecture: Scenes, Actors and Spectacles in Contemporary Cities
No full textHow and why do spectacular buildings get commissioned and procured? What are their visible urban effects? What can urban planners, architects, and policymakers learn in order to engage in more successful citymaking?
In recent years, media and critical attention has been lavished on famous architects, and the contributions of their designs to the branding of cities. The post-“Bilbao effect” global landscape is one where cities compete for the highest-profile skyscrapers, cultural projects, and high-profile developments designed by star architects whom even casual readers know by first name: Frank Gehry, Bjarke Ingels, Jean Nouvel, Zaha Hadid, Norman Foster, Rem Koolhaas. Far less is known about the decision-making processes behind these projects and their subsequent urban effects.
A unique combination of urban studies and photography, Starchitecture investigates projects designed by star architects in cities including Paris, New York, Abu Dhabi, Bilbao, and the architectural microcosm of the Vitra campus in Weil am Rhein, Germany. Author Davide Ponzini and photographer Michele Nastasi seek to explain and critique a growing global condition by revealing how starchitecture has been and continues to be deployed in cities around the world. The arguments they raise are vital to understanding the urban landscapes of today, and tomorrow
Multa videntur hic impossibilia implicari. Duns Scoto e la «fisica dell’Eucaristia» in Ordinatio IV
No full textIl necessitarismo greco-arabo implicava un netto ridimensionamento della potenza divina, mediante un’evidente sopravvalutazione di un determinismo naturalistico fondato su un’interpretazione (eterodossa) di alcuni princìpi aristotelici. Di qui, il massiccio ricorso – non solo in sede teologica – alla pur già esistente distinzione istituita tra potentia Dei absoluta e potentia Dei ordinata. Una denuncia emblematica di tale determinismo è rappresentata dall’articolo 147 della Condanna del 1277 come quello che in modo più chiaro testimonia lo spirito dell’intervento di Tempier: «Quod impossibile simpliciter non potest fieri a Deo, vel ab agente alio. – Error, si de impossibili secundum naturam intelligatur». La rilevanza di tale intervento ha evidentemente una portata determinante anche nell’ambito relativo alla filosofia naturale. Ci proponiamo qui di rintracciare l’eco di tale condanna che risuona nell’applicazione di princìpi di filosofia naturale nelle questioni relative all’Eucaristia, osservatorio privilegiato da cui assistere e verificare il concorso in questo ambito delle due discipline: teologica e filosofica. In particolare, saranno tre i nuclei tematici, tra loro reciprocamente innestati, che si innervano nella teologia eucaristica di Duns Scoto a partire dalla fede nella presenza reale: luogo, quantità, moviment
Design and characterization of a fractal-inspired multi-frequency piezoelectric energy converter
No full textA promising harvesting technique, in terms of simplicity and efficiency, is the conversion of ambient kinetic energy through piezoelectric materials. This work aims to design and investigate a piezoelectric converter conform to a fractal-inspired, multi-frequency structure previously presented by the author. A physical prototype of the converter is built and experimentally examined, up to 120 Hz, in terms of modal response and power output. Three eigenfrequencies are registered and the power output is particularly good at the fundamental eigenfrequency. Also the effect of the resistive load applied to the converter is investigated
Checking Flavour Models at Neutrino Facilities
No full textAbstractIn the recent years, the industry of model building has been the subject of the intense activity, especially after the measurement of a relatively large values of the reactor angle. Special attention has been devoted to the use of non-abelian discrete symmetries, thanks to their ability of reproducing some of the relevant features of the neutrino mixing matrix. In this Letter, we consider two special relations between the leptonic mixing angles, arising from models based on S4 and A4, and study whether, and to which extent, they can be distinguished at superbeam facilities, namely T2K, NOνA and T2HK
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