37 research outputs found
Valutazione dell’esposizione ai campi elettromagnetici generati dalle nuove tecnologie Wireless Power Transfer
No full textIl trasferimento di potenza senza contatto, o wireless power transfer (WPT), consiste nella trasmissione di energia elettrica da un dispositivo primario trasmittente (TX), collegato alla fonte di alimentazione, a un dispositivo secondario ricevente (RX), collegato al carico elettrico, senza l'uso di connettori fisici bensì mediante accoppiamento elettromagnetico. Nikola Tesla, all’inizio del XX secolo, dedicò molti sforzi alla progettazione e realizzazione di sistemi elettrici in grado di trasportare l’energia in modalità wireless. Tuttavia, a causa della limitata efficienza di trasferimento nonché dei campi elettrici elevatati, tale tecnologia è rimasta di fatto poco più di una curiosità ingegneristica fino a circa 30 anni fa, allorché è iniziata la diffusione massiva di dispositivi elettronici personali (ad es. laptop, tablets, telefoni cellulari, ecc.) per i quali la tecnologia WPT rappresenta un’opzione interessante soprattutto in relazione alla flessibilità di utilizzo. Più recentemente, lo sviluppo della tecnologia WPT basata sull’accoppiamento magnetico risonante ha consentito un significativo incremento dell’efficienza di trasferimento della potenza in tempi abbastanza rapidi, aprendo così la strada alla penetrazione della tecnologia WPT nel mercato dei veicoli elettrici per il quale si prevede una forte espansione nei prossimi anni. Ciò pone una serie di sfide, sia dal punto di vista tecnologico, vista l’esigenza di realizzare sistemi WPT in grado di trasferire potenze anche elevate in maniera efficiente e in tempi contenuti, sia dal punto di vista protezionistico, poiché si pone la necessità di limitare l’esposizione umana ai campi elettromagnetici (CEM) che vengono generati durante il trasferimento di potenza wireless affinché siano rispettati i limiti di legge. Con riferimento a quest’ultimo aspetto, si pone quindi la necessità di definire procedure standardizzate per la valutazione dell’esposizione umana ai CEM generati dai sistemi WPT ai fini della verifica di conformità ai pertinenti limiti normativi: a questo stanno attualmente lavorando i comitati elettrotecnici normatori preposti, sia in ambito nazionale (Comitato Elettrotecnico Italiano, CEI-CT106) che internazionale (International Electrotechnical Commission, IEC-TC106). Il presente articolo vuole fornire una descrizione della tecnologia WPT e delle sue principali applicazioni, nonché delle metodologie standardizzate per la valutazione dell’esposizione ai campi elettromagnetici generati dai sistemi WPT secondo i requisiti della normativa tecnica
Valutazione e gestione dei rischi per la salute e la sicurezza derivanti dall’esposizione ai campi elettromagnetici (CEM) − una bussola per mantenere la giusta rotta sul campo
No full textNonostante l’ampia letteratura scientifica e normativa in merito al tema dell’esposizione umana ai campi elettromagnetici nell’intervallo di frequenza tra 0 Hz e 300 GHz, vi sono alcuni aspetti che ancora oggi sono oggetto di interpretazioni talvolta controverse. Lo sviluppo, la diffusione e la continua evoluzione tecnologica, in cui i campi elettromagnetici sono un veicolo di trasmissione sia dell’energia (reti di trasporto elettrico e, più recentemente, sistemi wireless per il trasferimento di potenza) sia dell’informazione (reti di telecomunicazioni fisse e mobili, telefonia cellulare, sistemi radiotelevisivi, ecc.), nonché uno strumento funzionale sempre più pervasivo nelle applicazioni industriali, mediche e civili, ha fatto sì che nell’opinione pubblica si innescasse una percezione talvolta distorta dei rischi che possono derivare dall'esposizione ai campi elettromagnetici, anche a causa di informazioni non sempre fondate su basi scientifiche. Ciò ha de-terminato reazioni contrastanti, sia riguardo all’accettazione e alla convivenza con le diverse fonti di esposizione ai campi elettromagnetici, ormai ubiquitarie negli ambienti di vita e di lavoro, sia riguardo all’approccio alla valutazione e gestione dei rischi derivanti dall’esposizione. Lo scopo di questo Dossier sul tema dell’esposizione umana ai campi elettromagnetici è duplice. Da una parte si vuole descrivere cosa e come sta cambiando negli ambienti di vita e di lavoro a seguito dell’introduzione e della diffusione delle principali nuove tecnologie basate sui campi elettromagnetici, senza tralasciare l’evoluzione delle tecnologie consolidate. Dall’altra si vogliono illustrare le metodologie e le procedure di valutazione dell’esposizione umana ai fi ni della verifica di conformità ai pertinenti limiti di protezione, sulla base delle indicazioni della Guida CEI 106-45:2021, nonché sulla base dello stato dell’arte e degli sviluppi, tuttora in corso, della normativa tecnica nazionale d internazionale. A tale scopo il Dossier propone una rassegna di lavori, a partire dalla valutazione e gestione dei rischi per la salute e la sicurezza derivanti dall’esposizione ai campi elettromagnetici, le modifiche al D.Lgs. 81/08 apportate dal D.Lgs. 159/2016, le indicazioni sulla sorveglianza sanitaria dei lavori esposti ai campi elettromagnetici e le condizioni di particolare sensibilità al rischio. Si illustrano, quindi, le metodologie di valutazione dell’esposizione ai campi in bassa frequenza generati dai sistemi di trasporto e trasformazione dell’energia elettrica. Successivamente si illustrano le nuove tecnologie per il trasferimento wireless di potenza (Wireless Power Transfer, WPT), le principali applicazioni e le metodologie per la valutazione dell’esposizione in base ai nuovi sviluppi della normativa tecnica nazionale e internazionale, nonché un approfondimento sui sistemi WPT per la ricarica induttiva dei veicoli elettrici. Infine, vengono descritti il sistema 5G, gli aggiornamenti della normativa tecnica nazionale e inter-nazionale, la tecnologia Dynamic Spectrum Sharing tra 4G e 5G, la procedura di estrapolazione per i segnali di telefonia mobile applicata alla tecnologia 5G, le nuove metodiche di misura ambientale su segnali 5G e una procedura a basso costo per la verifica del rispetto dei limiti
Microwave thermal ablation. Effects of tissue properties variations on predictive models for treatment planning
No full textMicrowave thermal ablation (MTA) therapy for cancer treatments relies on the absorption of electromag- netic energy at microwave frequencies to induce a very high and localized temperature increase, which causes an irreversible thermal damage in the target zone. Treatment planning in MTA is based on exper- imental observations of ablation zones in ex vivo tissue, while predicting the treatment outcomes could be greatly improved by reliable numerical models. In this work, a fully dynamical simulation model is exploited to look at effects of temperature-dependent variations in the dielectric and thermal properties of the targeted tissue on the prediction of the temperature increase and the extension of the thermally coagulated zone. In particular, the influence of measurement uncertainty of tissue parameters on the numerical results is investigated. Numerical data were compared with data from MTA experiments per- formed on ex vivo bovine liver tissue at 2.45 GHz, with a power of 60 W applied for 10 min. By including in the simulation model an uncertainty budget (CI = 95%) of ±25% in the properties of the tissue due to inaccuracy of measurements, numerical results were achieved in the range of experimental data. Obtained results also showed that the specific heat especially influences the extension of the thermally coagulated zone, with an increase of 27% in length and 7% in diameter when a variation of −25% is considered with respect to the value of the reference simulation model
Experimental characterisation of the thermal lesion induced by microwave ablation
No full textPurpose: This work focuses on the characterisation of the ablated area induced by a microwave thermal ablation (MTA) procedure. An experimental methodology for establishing a straight-forward correlation between the temperature gradient and the changes in the dielectric properties of the tissue is presented and discussed. Materials and methods: Temperature measurements were performed during an ablation procedure in ex vivo bovine liver, at different distances from the antenna, whereas measurements of complex permittivity were conducted in sagittal sections of the ablated samples. The measured temperatures and dielectric properties were then correlated to obtain the dependence of the dielectric properties' spatial variation on the temperature gradient. The obtained correlation has been validated through comparison with previously obtained experimental data. A weighted cubic polynomial function and a weighted sigmoid function have been tested for best-fit interpolation of the measured data. Results: Temperatures in the range 23-105 degrees C were measured during the MTA procedure, while, after the end of the MTA trials, relative permittivities in the range 7-43 and electric conductivities in the range 0.3-1.8 S/m were measured according to the distance from the antenna's axis. The polynomial function showed better regression coefficients than the sigmoid one for both the relative permittivity (R-2 0.9947 versus R-2 0.9912, respectively) and the conductivity (R-2 0.9919 versus R-2 0.9866, respectively). However, the weighted cubic function showed an unrealistic behaviour for the relative permittivity at temperatures lower than 40 degrees C. Conclusions: According to the results obtained, information on the changes in the dielectric properties of the tissue under MTA treatment could be inferred from measured temperature data. Once validated by in vivo studies, the proposed methodology could be exploited to develop predictive tools for treatment planning.Purpose: This work focuses on the characterisation of the ablated area induced by a microwave
thermal ablation (MTA) procedure. An experimental methodology for establishing a straightforward
correlation between the temperature gradient and the changes in the dielectric
properties of the tissue is presented and discussed. Materials and methods: Temperature
measurements were performed during an ablation procedure in ex vivo bovine liver, at different
distances from the antenna, whereas measurements of complex permittivity were conducted in
sagittal sections of the ablated samples. The measured temperatures and dielectric properties
were then correlated to obtain the dependence of the dielectric properties’ spatial variation on
the temperature gradient. The obtained correlation has been validated through comparison
with previously obtained experimental data. A weighted cubic polynomial function and a
weighted sigmoid function have been tested for best-fit interpolation of the measured data.
Results: Temperatures in the range 23–105 C were measured during the MTA procedure, while,
after the end of the MTA trials, relative permittivities in the range 7–43 and electric
conductivities in the range 0.3–1.8 S/m were measured according to the distance from the
antenna’s axis. The polynomial function showed better regression coefficients than the sigmoid
one for both the relative permittivity (R21⁄40.9947 versus R21⁄40.9912, respectively) and the
conductivity (R21⁄40.9919 versus R21⁄40.9866, respectively). However, the weighted cubic
function showed an unrealistic behaviour for the relative permittivity at temperatures lower
than 40 C. Conclusions: According to the results obtained, information on the changes in the
dielectric properties of the tissue under MTA treatment could be inferred from measured
temperature data. Once validated by in vivo studies, the proposed methodology could be
exploited to develop predictive tools for treatment planning
Changes in the dielectric properties of ex vivo bovine liver during microwave thermal ablation at 2.45 GHz
No full textIn microwave thermal ablation (MTA) therapy, the dielectric properties of the target tissue play an important role in determining the radiation properties of the microwave ablation antenna. In this work, the ex vivo dielectric properties of bovine liver were experimentally characterized as a function of the temperature during MTA at the frequency of 2.45 GHz. The obtained data were compared with measurements performed at the end of the MTA treatment, and considering the heating achieved with a temperature-controlled water bath. Finally, measured data were used to perform a numerical study evaluating the effects of changes in tissue's dielectric properties during the MTA treatment on the radiation properties of a microwave interstitial ablation antenna, as well as on the obtained thermal lesion. Results evidenced a significant decrease of both relative permittivity (about 38%) and electric conductivity (about 33%) in the tissue during treatment as the temperature increased to over 60 °C, with a dramatic drop when the temperature approached 100 °C. Moreover, the numerical study evidenced that changes in tissue's dielectric properties during the MTA treatment affect the distribution of the power absorbed by the tissue (specific absorption rateSAR, W kg 1) surrounding the microwave interstitial ablation antenna, leading to a peak SAR up to 20% lower, as well as to a thermal lesion up to 8% longer. This work may represent a preliminary step towards the future development of a procedure for MTA treatment planning. © 2012 Institute of Physics and Engineering in Medicine
Microwave technology for image-guided thermal ablation
No full textThermal ablation treatments are gaining an increasing interest in the clinics thanks to their reduced invasiveness and their capability of treating non-surgical patients. They exploit local heating to induce coagulative necrosis of tumour cells. In particular, in microwave thermal ablation, which has recently progressed in the clinical practice, the heating source is represented by an electromagnetic field at microwaves frequencies. However, effectiveness of thermal ablation treatments and their impact in the hospital’s routine would significantly increase if paired with a monitoring technique able to control the evolution of the treated area in real-time.
This is particularly relevant in microwave thermal ablation, given its capability of treating large tumours in a short time.
Since currently adopted monitoring techniques suffer from several limitations, microwave tomography has been recently proposed as an alternative modality, based on the significant, temperature-dependent, changes that occurs to the dielectric properties of tissues during thermal ablation. In addition, microwave tomography is appealing as it exploits low-cost devices and components, thus being economically sustainable. This chapter explores the potential of microwave tomography to address this open clinical issue. First, the main features of microwave ablation procedure and the basic aspects of microwave tomography are recalled. Then, the results of an experimental proof-of-concept validation on ex vivo bovine liver sample, which confirms the capability of microwave tomography to image the transition between ablated and untreated tissue, are reporte
Assessment and Management of Risks from Occupational Exposure to Electromagnetic Fields (0 Hz to 300 GHz): A Compass to Keep the Right Course Through European and Italian Regulations
No full textThis paper outlines the specific provisions of Italian legislation regarding workers’ exposure to electromagnetic fields (EMFs) from 0 Hz to 300 GHz compared to the minimum health and safety requirements set in European Directive 2013/35/EU. In particular, the path to be followed to assess and manage occupational exposure to EMFs is outlined in relation to the distinction between ‘professional’ and ‘non-professional’ exposure of workers, as well as to the precautionary limits regarding exposures from power lines (50 Hz) and broadcast and telecommunication fixed systems (100 kHz–300 GHz) established by Italian regulations. The reasons underlying such an approach—mainly relying on the intent to reconcile scientific evidence with risk perception in public opinion—are analysed and discussed with the aim of increasing the knowledge of national regulatory provisions on occupational risk assessment, which may be more stringent than the requirements envisaged by international guidelines and community regulations
A full-wave numerical assessment of microwave tomography for monitoring cancer ablation
No full textIn this communication, we present a full-wave numerical study aimed at showing the potential of microwave tomography as a tool to monitor microwave ablation of solid tumors. The goal is to track the changes in dielectric properties of the tissue undergoing the treatment, in order to appraise the evolving dimension and shape of the thermally ablated area surrounding the applicator. Such an in-line monitoring capability would entail a significant improvement in the therapeutic effectiveness of cancer treatments exploiting microwave ablation, both in terms of optimization/ personalization of the therapeutic protocol and of reduction of unwanted side effects due to the unwanted increase of temperature in healthy tissues. The numerical study involves a scenario inspired by an existing experimental set-up, already used for the ex-vivo assessment of microwave ablation treatments. Hence, the promising results we have obtained, fully motivate us to progress towards the experimental demonstration of the concept in ex-vivo conditions
Ex vivo dielectric properties of fat. Influence of the experimental conditions on the measured data
No full textThe recent developments of medical applications of electromagnetic fields in both diagnostic and therapeutic scenarios has posed the attention on the accurate knowledge of the dielectric properties of human tissues. Accordingly, several studies were recently devoted to the measurements of such properties under various physiological conditions. Since biological tissues show a high variability, to compare the different data it is necessary to thoroughly control the experimental conditions. In this work, an ex vivo study is performed on rat fat tissue to look for possible confounders linked to the time between excision and measurement
