1,720,970 research outputs found
A Low-Cost Flexible Pipe Sheath for Multi-Parameter Monitoring of Water Distribution
No full textA pervasive diffusion of wireless sensors distributed in the environment can be sustained by a significant reduction of the cost of the transducers. Water represents a fundamental resource whose management can be optimized by real-time monitoring, especially in agriculture (irrigation). To this aim we present a low-cost flexible pipe sheath to detect water leakage, as well as conductivity and temperature, by means of contactless impedance measurements. Finite-element simulations show the potential to detect water leaks as small as 1 liter across a pipe length of 2 m, corresponding to a 1% change of a 5 k Omega impedance at 1 kHz, easily detectable by off-the-shelf impedance chips
BENEdiCTE (Boron Enhanced NEutron CapTurE) Gamma-Ray Detection Module
No full textWe present a gamma-ray detection module for Neutron Capture Enhanced Particle Therapy (NCEPT). The system has been optimised for boron-10 neutron capture agents that can be used for dose enhancement in proton and heavy ion therapy. The goal of the module is to distinguish the photopeak at 478 keV from the prompt-gamma emission resulting from the ion-target nuclear interactions. The module consists of a compact 64-channel module, with a large array of SiPM coupled to a 2" diameter and 2" thickness cylindrical LaBr3:Ce scintillator crystal (63 ph/keV conversion efficiency, 16 ns decay time). The electronic front-end ASIC features low-noise processing of photodetector signals, while the pixellated SiPMs detector and individual readout allows for position sensitivity in the crystal. We have characterised the energy resolution of the system experimentally, demonstrating an excellent energy resolution (3.27% at 662 keV), together with the capability of the FPGA-based DAQ integrated in the module to deploy an external synchronization signal to the ion beam bunches, in order to generate anti-coincidence windows. This feature provides a mechanism to distinguish and reject scintillation events from prompt gammas, enhancing the signal-to-background ratio of the spectrometer
PSD Neutron Discrimination for Dose Monitoring Applications in Particle Therapy
No full textThis work presents an analytical and experimental study aiming to validate two implementations of neutron rejection in medical imaging applications, with particular focus on dose monitoring in hadrontherapy. This topic is of particular interest for carbon ion beam therapy, where the neutron background fluctuations challenge the prompt gammas profile identification associated to the Bragg peak. The first solution facilitates pulse shape discrimination: leveraging an ASIC, a dense waveform sampling is avoided, allowing the embedding of PSD analysis in a simple microcontroller. Preliminary experimental results demonstrate the possibility to perform PSD with our integrated circuit solution. An analytical model was also developed, that describes the sources of noise connected to the PSD calculation; the analytical model is in good agreement with our experimental measurements. The second solution, based on a integrated circuit, leverages the typical temporal structures of beams delivered by cyclotrones. Rejection of interaction generating the scintillation light outside a short gate correlated with prompt gamma photons time of arrival might allow to reduce the neutron background
BeNEdiCTE (Boron NEutron CapTurE): a Versatile Gamma-Ray Detection Module for Boron Neutron Capture Therapy
No full textWe present a gamma-ray detection module for quantifying the boron neutron capture events that occur in Boron Neutron Capture Therapy (BNCT) and Neutron Capture Enhanced Particle Therapy (NCEPT). The goal of the module is to differentiate between the background prompt gamma peaks and the 478 keV neutron capture photopeak, in order to estimate the dose delivered to the patient. It is a compact module, coupling a large array of 64 SiPMs with a 2"×2" cylindrical LaBr3(Ce+Sr) scintillator crystal (73 ph/keV light yield, 25 ns decay time). The electronic front-end ASIC features low-noise processing of photodetector signals, while SiPMs pixellation and individual readout allow for position sensitivity in the crystal, although position estimation is not the object of this work. The module experimental characterization shows excellent energy resolution (2.7% FWHM at 662 keV), that allows to discriminate the neutron capture photons at 478 keV from the annihilation photons at 511 keV. The module features also an anti-coincidence circuit that provides a mechanism to distinguish and reject scintillation events created within specific temporal windows, thus enhancing the signal-to-background ratio of the spectrometer
Characterization and tuning of a clinical MRI-compatible SPECT INSERT
No full textLAUREA MAGISTRALELa realizzazione di scanner per imaging multimodale rappresenta uno
dei principali argomenti di ricerca e sviluppo nel campo della diagnostica
medica. L’integrazione di informazioni funzionali e anatomo-morfologiche
permette di aumentare l’accuratezza delle diagnosi, in particolare di quelle
precoci, di migliorare il monitoraggio e la valutazione dell’efficacia delle
terapie mediche. L’integrazione fisica dei sistemi di imaging, permettendo
una scansione simultanea, riduce i tempi di esame e fornisce alle acquisizioni
consistenza nel tempo e nello spazio, migliorando la registrazione e di
conseguenza la qualità finale delle immagini. In questo ambito, lo sviluppo
di sistemi integrati SPECT/MRI è stato frenato da vincoli tecnici relativi alla
compatibilità reciproca dei due tipi di scanner.
Il progetto INSERT, finanziato dalla Comunità Europea nel contesto del
programma FP7- HEALTH, ha portato alla realizzazione del primo scanner
SPECT clinico basato su SiPM compatibile con la risonanza magnetica. Lo
scanner SPECT è costituito da un insieme di 20 gamma camere disposte ad
anello, per un totale di 1440 pixel. Lo strumento clinico è stato progettato
per l’imaging cerebrale, con lo scopo principale di migliorare la stratificazione
dei pazienti affetti da glioma, facilitando radio e chemioterapia personalizzate.
Il progetto è stato avviato sei anni fa, ha previsto lo sviluppo di una
versione preclinica e clinica dello strumento, ed ora è vicino alle fasi finali.
Nell’ambito di questa tesi di laurea, il sistema clinico è stato messo in funzione,
testando imoduli che compongono lo scanner e risolvendone i problemi
operativi e introducendo un doppio circuito di raffreddamento. Il software
per la ricostruzione dell’immagine è stato ottimizzato per la presenza di canali
difettosi e un’attenzione particolare è stata data alla ricostruzione della
profondità di interazione (DOI) degli eventi gamma, che è stata analizzata
mediante simulazioni Monte Carlo e misure sperimentali preliminari. Infine,
lo strumento è stato calibrato e testato presso l’Ospedale San Raffaele,
principalmente in termini di count-rate, risoluzione energetica e spaziale.
La discussione è stata organizzata in cinque capitoli: il primo introduce
le tecniche di imaging multimodale più comuni, descrivendone vantaggi e
svantaggi. Inoltre, fornisce una panoramica del progetto INSERT e ne elenca
i requisiti clinici.
Il secondo capitolo contiene la descrizione delle componenti generali di una
gamma camera, e in particolare di quelle implementate nei moduli del sistema
INSERT. Inoltre, viene presentato il sistema di acquisizione e l’architettura
completa dello strumento. Nella parte finale viene caratterizzata la
strategia di raffreddamento.
Il terzo capitolo riguarda i metodi di ricostruzione utilizzati per la ricostruzione
planare delle proiezioni, e li confronta tra loro.
Il quarto capitolo introduce la ricostruzione della terza coordinata di scintillazione
e ne mostra i primi risultati sperimentali.
Infine, il quinto capitolo riporta la caratterizzazione delle prestazioni dello
scanner SPECT, testato come sistema stand-alone.Multimodal imaging scanners represent one of the main research and
development topics in the field of medical diagnostics. The combination
of techniques providing correlated functional and anatomical information,
increases the accuracy of disease diagnosis, therapymonitoring and assessment.
As a matter of fact, they give the possibility to map areas of abnormal
molecular activity to the patient-specific anatomy. Physical integration
of the imaging systems represents the best solution to achieve consistency
in space and time: a simultaneous acquisition reduces clinical examination
times and enhances the co-registration, optimizing the quality of the fused
images. In this context, the development of integrated SPECT/MRI systems
was restrained by the technical constraints related to the mutual compatibility
of the scanners.
INSERT project, founded by 7th Framework Programme of European Commission,
has brought to the development of the first SiPM-based clinical
SPECT scanner suitable for insertion inside a commercial MRI. The SPECT
INSERT is composed by a static set of 20 gamma cameras organized in a
ring shape for a total of 1440 pixels. The clinical instrument was designed
for brain imaging, primarily for enhanced stratification of glioma patients
prior to patient-specific radio-chemo therapy and for the early assessment
of treatment efficacy. INSERT project started six years ago, the scanner has
been realized in two versions (preclinical and clinical), and now it is close
to its final stages. In the framework of this master thesis, the system was
put into operation: the functionality of single gamma cameras composing
the SPECT scanner were assessed, solving operating issues, and it was introduced
a dual-cooling circuit. The image reconstruction software was optimized
for the presence of faulty channels. A particular attention was given to
the depth of interaction (DOI) reconstruction, which was analyzed bymeans
ofMonte Carlo simulations and through preliminary experimental measurements.
Finally, the instrument was calibrated and tested at San RaffaeleHospital,
to be evaluated mainly in terms of count-rate, energy and spatial resolution.
The discussion is organized into five chapters: the first one concerns the
most common multimodality imaging techniques and describes the corresponding
advantages and disadvantages. Then, it gives an overview of
INSERT project, listing the clinical requirements.
The second chapter contains the description of the general components of a
gammacamera, focusing on the ones implemented inside INSERT detection
modules. The acquisition system and the full architecture of the instrument
are also presented. The final part characterizes the cooling strategy.
The third chapter describes the reconstruction methods that are used for the
planar reconstruction of the projections, showing their pros and cons.
The reconstruction of the third coordinate of scintillation is addressed inside
the fourth chapter, which provides also preliminary experimental results.
The fifth and final chapter concerns the evaluation of the performances of
the SPECT scanner, tested as a stand-alone system
Experimental Assessment of PCA and DT Classification for Streamlined Position Reconstruction in Anger Cameras
Full text linkIn this paper we present a study of machine learning (ML) algorithms to simplify the computation of the planar scintillation coordinates in Anger Cameras for emission tomography applications. Two ML-based techniques for data inference and one technique for speed-up the training procedure are explored within the framework of a multimodal SPECT scanner. Firstly, the use of Principal Component Analysis (PCA), a dimensionality reduction algorithm, is explored to reduce the computational complexity of maximum-likelihood statistical estimation method. The analysis indicates a 3-fold reduction of computational complexity for typical Anger Camera architectures (with 72 channels). Secondly, the estimation of the scintillation coordinates is formulated as a classification problem, addressed by means of a Decision Tree (DT) classifier. No degradation of the achievable intrinsic spatial resolution (1.2 mm FWHM) of the detection module was observed when applying PCA (reducing from 72 to 25 components). The DT classifier was trained on experimental data obtained using a parallel-hole collimator: again no degradation of spatial resolution is observed and the computation cost is reduced by more than two orders of magnitude. Finally, in order to overcome the limits of a cumbersome training procedure involving the translation of the collimator, data augmentation was successfully leveraged for the generation of artificial data
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