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Continuous respiratory monitoring is important to assess adequate ventilation. We present a fiber optic-based smart textile for respiratory monitoring able to work during Magnetic Resonance (MR) examinations. The system is based on the conversion of chest wall movements into strain of two fiber Bragg grating (FBG) sensors, placed on the upper thorax (UT). FBGs are glued on the textile by an adhesive silicon rubber. To increase the system sensitivity, the FBGs positioning was led by preliminary experiments performed using an optoelectronic system: FBGs placed on the chest surface experienced the largest strain during breathing. System performances, in terms of respiratory period (TR), duration of inspiratory (TI) and expiratory (TE) phases, as well as left and right UT volumes, were assessed on four healthy volunteers. The comparison of results obtained by the proposed system and an optoelectronic plethysmography highlights the high accuracy in the estimation of TR, TI, and TE: Bland-Altman analysis shows mean of difference values lower than 0.045 s, 0.33 s, and 0.35 s for TR, TI, and TE, respectively. The mean difference of UT volumes between the two systems is about 8.3%. The promising results foster further development of the system to allow routine use during MR examinations.Continuous respiratory monitoring is important to assess adequate ventilation. We present a fiber optic-based smart textile for respiratory monitoring able to work during Magnetic Resonance (MR) examinations. The system is based on the conversion of chest wall movements into strain of two fiber Bragg grating (FBG) sensors, placed on the upper thorax (UT). FBGs are glued on the textile by an adhesive silicon rubber. To increase the system sensitivity, the FBGs positioning was led by preliminary experiments performed using an optoelectronic system: FBGs placed on the chest surface experienced the largest strain during breathing. System performances, in terms of respiratory period (TR), duration of inspiratory (TI) and expiratory (TE) phases, as well as left and right UT volumes, were assessed on four healthy volunteers. The comparison of results obtained by the proposed system and an optoelectronic plethysmography highlights the high accuracy in the estimation of TR, TI, and TE: Bland-Altman analysis shows mean of difference values lower than 0.045 s, 0.33 s, and 0.35 s for TR, TI, and TE, respectively. The mean difference of UT volumes between the two systems is about 8.3%. The promising results foster further development of the system to allow routine use during MR examinations.

Minimally invasive thermal techniques are gaining acceptance in cancer removal. These approaches aim at destroying the tumour while minimizing the damage of surrounding healthy structures. Several solutions have already proved their effectiveness in improving treatment outcomes and in minimizing adverse events. However, it is still challenging to selectively remove the cancer. To help tackle this challenge, several groups of research are focusing on the use of thermometry for monitoring the effects on biological tissue of hyperthermal treatments, since the irreversible damage of tissue depends on temperature and time of application. Given the rising complexity of treatment settings, a temperature feedback may be useful to improve the clinical outcome by minimizing the thermal damage of surrounding healthy tissue. Fiber Bragg grating (FBG) sensors are used in this scenario thanks to several advantages, such as the small size, Magnetic Resonance (MR) compatibility and the possibility to perform spatially distributed measurements; moreover, with the use of specific coating their thermal sensitivity may be increased. However, they are fragile and their insertion within the organ can be challenging and time consuming. In this paper we describe the fabrication of three thermal probes embedding FBG sensors. Each probe consists of a MR-compatible needle which embeds a FBG sensor glued with epoxy adhesive. The three probes showed a sensitivity of about 24 pm/°C, which his higher than the one showed by non-encapsulated FBG (about 10 pm/°C). Moreover, the output of the three probes showed a negligible output drift and a negligible sensitivity drift after 4 thermal cycles in a wide range of temperature (i.e., from environmental temperature up to about 80 °C). The investigated solution shows some advantages considering the specific field of application: it allows an easy insertion within the organ being embedded within a needle; the probes' sensitivity is better than non-encapsulated FBGs; it can be used also during MR-guided procedures since both the needle and the FBG are MR-compatible. Future testing will assess the feasibility for temperature monitoring during thermal ablation treatment of the probes in ex vivo and in vivo animal model. © 2017 IEEE.

Comfortable and easy to wear smart textiles have gained popularity for continuous respiratory monitoring. Among different emerging technologies, smart textiles based on fiber optic sensors (FOSs) have several advantages, like Magnetic Resonance (MR)-compatibility and good metrological properties. In this paper we report on the development and assessment of an MR-compatible smart textiles based on FOSs for respiratory monitoring. The system consists of six fiber Bragg grating (FBG) sensors glued on the textile to monitor six compartments of the chest wall (i.e., right and left upper thorax, right and left abdominal rib cage, and right and left abdomen). This solution allows monitoring both global respiratory parameters and each compartment volume change. The system converts thoracic movements into strain measured by the FBGs. The positioning of the FBGs was optimized by experiments performed using an optoelectronic system. The feasibility of the smart textile was assessed on 6 healthy volunteers. Experimental data were compared to the ones estimated by an optoelectronic plethysmography used as reference. Promising results were obtained on both breathing period (maximum percentage error is 1.14%), inspiratory and expiratory period, as well as on total volume change (mean percentage difference between the two systems was ∼14%). The Bland-Altman analysis shows a satisfactory accuracy for the parameters under investigation. The proposed system is safe and non-invasive, MR-compatible, and allows monitoring compartmental volumes. © 2016 IEEE.

In this work a spatially-resolved fiber optic temperature sensor has been characterized in a wide range of gradient applied on its active area (from -35 °C to +35 °C). Preliminary experiments to assess its feasibility for application in laser ablation have been performed. The sensor under test is a linearly chirped fiber Bragg grating (FBG), with 1.5 cm-length of active area. It can be considered as a chain of several FBGs, each able to sense local temperature. The sensor response to the gradient has been analyzed in terms of its spectrum width (full width at half maximum). There is a linear relationship between the full width at half maximum and the gradient, with a sensitivity of 0.0087 nm°C-1. The feasibility test using the linearly chirped FBG during laser ablation showed promising results: it is able to detect both the thermal gradients along is active area and the average temperature increment during the procedure. © 2016 IEEE.

Gaseous detectors are commonly used in HEP (High Energy Physics) experiments to reconstruct the track of elementary particles. They are often made by a very large number of chambers with relatively small individual volume, arranged in thick layers placed approximately all around the vertex of the experiment in order to detect elementary particles produced in any direction. The large volume of gas inside the detector must be monitored for many parameters as they can affect both the efficiency and the working life of the detector. The temperature of the gas inside the individual chambers is a critical parameter to be monitored, as it can both affect the efficiency of the detector and point out on-board electronic circuitry overheating. In this paper we propose a novel gas temperature sensing system based on optical fibre technology. The adopted technology is well suited to make distributed sensing systems with large number of sensors, it is immune to electromagnetic disturbances and it has adequate radiation hardness. A prototype of the basic sensor of the proposed system was tested at the experimental facility for Resistive Plate Chamber characterization available at the INFN laboratories in Frascati. Results are presented and discussed.

During thermal procedures, the monitoring of tissue temperature is useful to improve therapy success. The aim of this study is the feasibility assessment of a Fiber Bragg Grating (FBG)-based probe, which contains six FBGs, to obtain distributed temperature measurement in tissue undergoing laser ablation (LA). Among different thermometric techniques, FBG sensors show valuable characteristics, even though their sensitivity to strain entails measurement error for patient respiratory movement. We performed: i) the static calibration of the FBG-based probe to estimate the thermal sensitivity of the six FBGs; ii) the estimation of the response time of the FBGs. All FBGs have a thermal sensitivity of 10 pm·°C-1 and a time constant in the order of < 250 ms. Additionally, we performed a preliminary estimation of the error due to the strain and caused by respiratory movements. Experiments were carried out by simulating a typical respiratory movement on ex vivo swine liver. The measurement error was

The present study investigates the influence of uniform FBG length on temperature measurement under substantial temperature gradient. This analysis is particularly relevant in the scenario of laser ablation (LA), where the temperature gradient close to the optical applicator is significant (e.g., up to 50 °C/mm). Aiming to assess how the sensor length affects the measurement process in LA, both bench and ex vivo experiments were carried out by applying temperature gradient in the range 5 °C/cm-30 °C/cm on 1 mm-length FBG and 10 mm-length FBG. Results showed that the use of small-sized FBGs is recommended in LA for two main reasons: i) the spectrum reflected by shorter sensors has not shown significant alterations with the gradient. Alterations of the spectrum shape could compromise peak detection algorithms, and, therefore, the estimation of the actual temperature; ii) Arrays of shorter sensors can provide multipoint temperature measurements, with quiet good spatial resolution (e.g., 3 mm), by inserting a single fiber in the tissue. © 2016 IEEE.

Temperature distribution monitoring in tissue undergoing laser ablation (LA) could be beneficial for improving treatment outcomes. Among several thermometric techniques employed in LA, fiber Bragg grating (FBG) sensors show valuable characteristics, although their sensitivity to strain entails measurement error for patient respiratory movements. Our work describes a solution to overcome this issue by housing an FBG in a surgical needle. The metrological properties of the probes were assessed in terms of thermal sensitivity (0.027 nm °C−1 versus 0.010 nm °C−1 for epoxy liquid encapsulated probe and thermal paste one, respectively) and response time (about 100 ms) and compared with properties of nonencapsulated FBG (sensitivity of 0.010 nm °C−1, response time of 43 ms). The error due to the strain caused by liver movements, simulating a typical respiratory pattern, was assessed: the strain induces a probes output error less than 0.5 °C, which is negligible when compared to the response of nonencapsulated FBG (2.5 °C). The metallic needle entails a measurement error, called artifact, due to direct absorption of the laser radiation. The analysis of the artifact was performed by employing the probes for temperature monitoring on liver undergoing LA. Experiments were performed at two laser powers (i.e., 2 W and 4 W) and at nine distances between the probes and the laser applicator. The artifact decreases with the distance and increases with the power: it exceeds 10 °C at 4 W, when the encapsulated probes are placed at 3.6 mm and 0 deg from the applicator, and it is lower than 1 °C for distance higher than 5 mm and angle higher than 30 deg.

The employment of sensors in harsh environments [1] is a challenging engineering task, occurring more frequently than it might be expected. So, the availability of reliable and accurate sensors is a task in great demand. However, this imply an effort demanding and an expensive design. In this frame we can place the present contribution which aims to develop a simple, robust magnetic filed sensor to be exploited in harsh conditions, such as the the Tokamak vessel for nuclear fusion experiments [2] where the presence of standard sensors based on electronic circuits based and hall effect is almost impossible. © 2015 IEEE.

Fiber Bragg Grating (FBG) technology is very attractive to develop sensors for the measurement of thermal and mechanical parameters in biological applications, particularly in presence of electromagnetic interferences. This work presents the design, working principle and experimental characterization of a force sensor based on two FBGs, with the feature of being compatible with Magnetic Resonance. Two prototypes based on different designs are considered and characterized: 1) the fiber with the FBGs is encapsulated in a polydimethylsiloxane (PDMS) sheet; 2) the fiber with the FBGs is free without the employment of any polymeric layer. Results show that the prototype which adopts the polymeric sheet has a wider range of measurement (4200 mN vs 250 mN) and good linearity; although it has lower sensitivity (≈0.1 nm-N1 vs 7 nm-N1). The sensor without polymeric layer is also characterized by employing a differential configuration which allows neglecting the influence of temperature. This solution improves the linearity of the sensor, on the other hand the sensitivity decreases. The resulting good metrological properties of the prototypes here tested make them attractive for the intended application and in general for force measurement during biomedical applications in presence of electromagnetic interferences. © 2014 IEEE.

Monitoring of local temperature in tissue undergoing Laser Ablation (LA) could be particularly beneficial to optimize treatment outcomes. A number of both invasive and non-invasive thermometric techniques may be employed to perform this task. Among others, Fiber Bragg Grating (FBG) sensors show the following valuable characteristics for temperature monitoring during LA: good sensitivity and accuracy, and immunity from electromagnetic interferences. The main drawbacks are their intrinsic invasiveness and the sensitivity to strain, which can entail measurement error for respiratory and patient movements. © 2015 IEEE.

Temperature monitoring in tissue undergone Laser Ablation (LA) may be particularly beneficial to optimize treatment outcome. Among many techniques, fiber Bragg grating (FBG) sensors show valuable characteristics for temperature monitoring in this medical scenario: good sensitivity and accuracy, and immunity from electromagnetic interferences. Their main drawback is the sensitivity to strain, which can entail measurement error for respiratory and patient movements. The aims of this work are the design, the manufacturing and the characterization of a needle-like probe which houses 4 FBGs. Three FBGs have sensitive length of 1 mm and are used as temperature sensors; one FBG with length of 10 mm is used as reference and to sense eventual strain. The optical fiber housing the FBGs was encapsulated within a needle routinely used in clinical practice to perform MRI-guided biopsy. Two materials were used for the encapsulation: i) thermal paste for the 3 FBGs used for temperature monitoring, to maximize the thermal exchange with the needle; ii) epoxy resin for the reference FBG, to improve its sensitivity to strain. The static calibration of the needle-like probe was performed to estimate the thermal sensitivity of each FBG; the step response was investigated to estimate the response time. FBGs 1 mm long have thermal sensitivity of 0.01 nm·°C(-1), whereas the reference FBG presents 0.02 nm·°C(-1). For all FBGs, the response time was in the order of 100 ms. Lastly, experiments were performed on ex vivo swine liver undergoing LA to i) evaluate the possible presence of measurement artifact, due to the direct absorption of laser light by the needle and ii) assess the feasibility of the probe in a quasi clinical scenario.

Temperature monitoring in tissue undergoing Laser Ablation (LA) is particularly beneficial to optimize therapy outcomes. During last decades several approaches have been proposed to perform thermometry during thermal ablation. Among others, Fiber Bragg Grating (FBG) sensors show valuable characteristics for such measurement, but their sensitivity to strain entails measurement error for patient respiratory movements. In this work two needle-like probes were developed using two different procedures to encapsulate an FBG into a surgical needle, aiming to allow safe insertion into the patient tissue and to neglect mechanical disturbance due to tissue movements occurring during breathing. The static calibration of the two probes has been carried out in a wide range of temperature (i.e., from 18 °C up to 100 °C), and their response time has been estimated. The calibration curves of the two probes show good linearity and a different sensitivity, and their response time is fast enough to meet the criteria set for temperature monitoring during LA. Since the metallic needle entails a measurement error, called artifact, due to the direct absorption of the laser radiation, the two abovementioned probes have been employed during LA on ex vivo liver. Then, their measurements have been compared to the measurement provided by an FBG without needle, which does not experience artifacts. The good results in terms of both static and dynamic properties of the two probes encourage to perform further analysis regarding the amplitude of the artifacts due to the direct absorption of the metallic needle and regarding the capability of the probes to neglect mechanical disturbance. © 2014 IEEE.

We propose to adopt Fiber Bragg Grating technology to develop an innovative sensor for monitoring relative humidity of the gas fluxed in Resistive Plate Counters. Use of Fiber Bragg Grating as sensing device makes the proposed sensor well suited to develop distributed real-time monitoring systems to be installed on large volume detectors operated in high electromagnetic fields. In fact Fiber Bragg Gratings are fully immune from electromagnetic disturbances and allow simplified wiring by in-series interconnection of tens of them along a single optical fiber. In this paper we present results intended to investigate the feasibility of our proposal. © 2013 IOP Publishing Ltd and Sissa Medialab srl.