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Fiber Bragg grating sensors (FBGs) are considered a valid sensing solution for a variety of medical applications. The last decade witnessed the exploitation of these sensors in applications ranging from minimally invasive surgery to biomechanics and monitoring physiological parameters. Recently, preliminary studies investigated the potential impact of FBGs in the management of epidural procedures by detecting when the needle reaches the epidural space with the loss of resistance (LOR) technique. In this article, we propose a soft and flexible FBG-based system capable of detecting the LOR, we optimized the solution by considering different designs and materials, and we assessed the feasibility of the optimized soft sensor (SS) in clinical settings. The proposed SS addresses some of the open challenges in the use of a sensing solution during epidural punctures: it has high sensitivity, it is non-invasive, the sensing element does not need to be inserted within the needle, and the clinician can follow the standard clinical practice. Our analysis highlights how the material and the design impact the system response, and thus its performance in this scenario. We also demonstrated the system’s feasibility of detecting the LOR during epidural procedures.

Temperature monitoring inside tissue undergoing minimally invasive thermal ablation is a primary goal to improve the clinical outcomes. Existing techniques for temperature measurements, classified as invasive or contactless, have limited clinical practice applications due to several practical issues. Fiber Bragg grating sensors (FBG) can be a valid solution since they can perform accurate and multi-point temperature measurements by inserting a single and small fiber optic within the tissue. Notwithstanding, their cross-sensitivity to strain may cause measurement errors during thermal procedures. Indeed, several organs (e.g., lungs, liver, pancreas) can strain gratings due to movements caused by breathing. To date, only a few studies have specifically addressed this concern, despite the wide use of FBGs in this field. To overcome this lack, we estimated the artefact of the FBGs output in response to lungs’ movements induced by breathing. This investigation was carried out by inserting FBGs within a manually ventilated lung model ( ex vivo swine lungs). We measured both the lungs’ movements during breathing by a Motion Capture system and the related fluctuations of the FBGs’ output. Moreover, we performed the same experiments during thermal ablation of lungs to assess the mentioned artefact’s influence. In this study, we demonstrated the relevance of the respiratory artefact on FBGs, and also the possibility to correct this error during thermal ablation.

The demand for wearable devices to simultaneously monitor heart rate (HR) and respiratory rate (RR) values has grown due to the incidence increase in cardiovascular and respiratory diseases. The use of inertial measurement unit (IMU) sensors, embedding both accelerometers and gyroscopes, may ensure a non-intrusive and low-cost monitoring. While both accelerometers and gyroscopes have been assessed independently for both HR and RR monitoring, there lacks a comprehensive comparison between them when used simultaneously. In this study, we used both accelerometers and gyroscopes embedded in a single IMU sensor for the simultaneous monitoring of HR and RR. The following main findings emerged: (i) the accelerometer outperformed the gyroscope in terms of accuracy in both HR and RR estimation; (ii) the window length used to estimate HR and RR values influences the accuracy; and (iii) increasing the length over 25 s does not provide a relevant improvement, but accuracy improves when the subject is seated or lying down, and deteriorates in the standing posture. Our study provides a comprehensive comparison between two promising systems, highlighting their potentiality for real-time cardiorespiratory monitoring. Furthermore, we give new insights into the influence of window length and posture on the systems’ performance, which can be useful to spread this approach in clinical settings.

Given the importance of respiratory frequency (fR) as a valid marker of physical effort, there is a growing interest in developing wearable devices measuring fR in applied exercise settings. Biosensors measuring chest wall movements are attracting attention as they can be integrated into textiles, but their susceptibility to motion artefacts may limit their use in some sporting activities. Hence, there is a need to exploit sensors with signals minimally affected by motion artefacts. We present the design and testing of a smart facemask embedding a temperature biosensor for fR monitoring during cycling exercise. After laboratory bench tests, the proposed solution was tested on cyclists during a ramp incremental frequency test (RIFT) and high-intensity interval training (HIIT), both indoors and outdoors. A reference flowmeter was used to validate the fR extracted from the temperature respiratory signal. The smart facemask showed good performance, both at a breath-by-breath level (MAPE = 2.56% and 1.64% during RIFT and HIIT, respectively) and on 30 s average fR values (MAPE = 0.37% and 0.23% during RIFT and HIIT, respectively). Both accuracy and precision (MOD ± LOAs) were generally superior to those of other devices validated during exercise. These findings have important implications for exercise testing and management in different populations.

The devastating effects of global climate change on crop production and exponential population growth pose a major challenge to agricultural yields. To cope with this problem, crop performance monitoring is becoming increasingly necessary. In this scenario, the use of sensors and biosensors capable of detecting changes in plant fitness and predicting the evolution of their morphology and physiology has proven to be a useful strategy to increase crop yields. Flexible sensors and nanomaterials have inspired the emerging fields of wearable and on-plant portable devices that provide continuous and accurate long-term sensing of morphological, physiological, biochemical, and environmental parameters. This review provides an overview of novel plant sensing technologies by discussing wearable and integrated devices proposed for engineering plant and monitoring its morphological traits and physiological processes, as well as plant-environment interactions. For each application scenario, the state-of-the-art sensing solutions are grouped according to the plant organ on which they have been installed highlighting their main technological advantages and features. Finally, future opportunities, challenges and perspectives are discussed. We anticipate that the application of this technology in agriculture will provide more accurate measurements for farmers and plant scientists with the ability to track crop performance in real time. All of this information will be essential to enable rapid optimization of plants development through tailored treatments that improve overall plant health even under stressful conditions, with the ultimate goal of increasing crop productivity in a more sustainable manner.

Epidural analgesia represents a clinical common practice aiming at pain mitigation. This loco-regional technique is widely used in several applications such as labor, surgery and lower back pain. It involves the injections of anesthetics or analgesics into the epidural space (ES). The ES detection is still demanding and is usually performed by the techniques named loss of resistance (LOR). In this study, we propose a novel soft system (SS) based on one fiber Bragg grating sensor (FBG) embedded in a soft polymeric matrix for LOR detection during the epidural puncture. The SS was designed to allow instrumenting the syringe’s plunger without relevant modifications of the anesthetist’s sensations during the procedure. After the metrological characterization of the SS, we assessed the capability of this solution in detecting LOR by carrying it out in silico and in clinical settings. For both trials, results revealed the capability of the proposed solutions in detecting the LOR and then in recording the force exerted on the plunger.

A continuous monitoring of cardiorespiratory activity can play an essential role in the health prevention since the cardiovascular and ventilatory systems regulate several vital functions of the human body and adapt themselves in response to various stressors. Typically, early detection of cardiorespiratory irregularities is performed by monitoring respiratory and heart rate (RR and HR) at rest. Among several technological solutions, the most promising are based on mechanical and optical systems such as gyroscopes (GYRs) and accelerometers in inertial measurement units, and fiber Bragg gratings (FBGs) embedded into wearable and non-wearable items.In this work, we investigated the capability of a mechanical system (i.e., a GYR) and an optical system (i.e., a flexible sensor based on FBG) to perform the simultaneous RR and HR monitoring. The system placement varied according to the sensor type to ensure the best unobtrusive cardiorespiratory monitoring: the GYR was worn on the chest, and the FBG-based flexible sensor was placed on a chair in contact with the chest back. Results showed similar performances between the mechanical and optical systems when compared to a reference instrument (mean absolute percentage error -MAPE < 7.7% and 6.1% for HR and MAPE ≤ 0.23% and 1.7% for RR for the FBG and the GYR, respectively).

Strain sensors based on conductive and flexible textiles are gaining great relevance in research applications, rehabilitation, and sports medicine for monitoring human joints movements, thanks to their flexibility, negligible weight, and easy integration into substrates and wearable systems. The purpose of this work was twofold: i) to carry out the static characterization and to analyze the hysteresis of two textile-based strain sensors integrated into a polymeric matrix, and ii) to evaluate the feasibility of these sensors in monitoring scapular movements during bilateral arms abduction-adduction and flexion-extension. Results showed a comparable range of resistance variation at 0-20% strain during static characterization, with a mean absolute gauge factor of 2.65 (sensor A) and 2.12 (sensor B). The maximum hysteresis error was always lower than 31% for sensor A and lower than 27% for sensor B. Both sensors showed promising results in monitoring scapular motion during the two selected single-plane upper limb movements.

Early diagnosis can be crucial to limit both the mortality and economic burden of cardiovascular diseases. Recent developments have focused on the continuous monitoring of cardiac activity for a prompt diagnosis. Nowadays, wearable devices are gaining broad interest for a continuous monitoring of the heart rate (HR). One of the most promising methods to estimate HR is the seismocardiography (SCG) which allows to record the thoracic vibrations with high non-invasiveness in out-of-laboratory settings. Despite significant progress on SCG, the current state-of-the-art lacks both information on standardized sensor positioning and optimization of wearables design. Here, we introduce a soft wearable system (SWS), whose novel design, based on a soft polymer matrix embedding an array of fiber Bragg gratings, provides a good adhesion to the body and enables the simultaneous recording of SCG signals from multiple measuring sites. The feasibility assessment on healthy volunteers revealed that the SWS is a suitable wearable solution for HR monitoring and its performance in HR estimation is strongly influenced by sensor positioning and improved by a multi-sensor configuration. These promising characteristics open the possibility of using the SWS in monitoring patients with cardiac pathologies in clinical (e.g., during cardiac magnetic resonance procedures) and everyday life settings.

AIMS: Real-time monitoring of tissue temperature during percutaneous tumor ablation improves treatment efficacy, leading clinicians in adjustment of treatment settings. This study aims at assessing feasibility of ultrasound thermometry during laser ablation of biological tissue using a specific ultrasound imaging techniques based on elastography acoustic radiation force impulse (ARFI). METHODS: ARFI uses high-intensity focused ultrasound pulses to generate ‘radiation force’ in tissue; this provokes tissue displacements trackable using correlation-based ultrasound methods: the sensitivity of shear waves velocity is able to detect temperature changes. Experiments were carried out using a Nd:YAG laser (power: 5 W) in three non-perfused ex vivo pig livers. In each organ, a thermocouple was placed close to the applicator tip (distance range 1.5–2.5 cm) used to record a reference temperature. Positioning of laser applicator and thermocouple was eco-guided. The organ was scanned by an echography system equipped with ARFI; propagation velocity was measured in a region of interest of 1 × 0.5 cm located close to thermocouple, to investigate influence of tissue temperature on shear waves velocity. RESULTS: Shear wave velocity has a very low sensitivity to temperature up to 55–60 °C, and in all cases, velocity is 55–60 °C, velocity shows a steep increment. The system measures a value “over limit”, meaning a velocity > 5 m s(−1). CONCLUSIONS: Ultrasound thermometry during laser ablation of biological tissue based on elastography shows an abrupt output change at temperatures > 55–60 °C. This issue can have a relevant clinical impact, considering tumor necrosis when temperature crosses 55 °C to define the boundary of damaged volume. GRAPHIC ABSTRACT: [Image: see text]

The current challenge in the field of thermo-ablative treatments of tumors is to achieve a balance between complete destruction of malignant cells and safeguarding of the surrounding healthy tissue. Blood perfusion plays a key role for thermal ablation success, especially in the case of highly vascularized organs like liver. This work aims at monitoring the temperature within perfused swine liver undergoing laser ablation (LA). Temperature was measured through seven arrays of Fiber Bragg Grating sensors (FBGs) around the laser applicator. To mimic reality, blood perfusion within the ex-vivo liver was simulated using artificial vessels. The influence of blood perfusion on LA was carried out by comparing the temperature profiles in two different spatial configurations of vessels and fibers. The proposed setup permitted to accurately measure the heat propagation in real-time with a temperature resolution of 0.1 °C and to observe a relevant tissue cooling near to the vessel up to 65%.

Among the existing thermal ablation techniques, microwave ablation (MWA) is gaining momentum due to its great potentialities in the treatment of several organs. MWA effectiveness is influenced by several factors, such as ablation system design and patients' anatomical characteristics. The presence of large blood vessel in the proximity of tumor masses dissipates heat by convection (phenomenon known in the literature as heat sink effect). The potential consequence is the risk of incomplete tumor ablation. In this study, we experimentally investigated such phenomenon in ex vivo swine liver during MWA. The blood vessel was mimicked through a silicone tube inserted within the organ. To evaluate the influence of the heat sink effect on MWA, we measured the tissue temperature by fiber Bragg grating sensors (FBGs) in two different configurations (i.e., with and without blood vessel nearby the MW applicator). The notable differences in terms of temperature recorded in the two different scenarios demonstrated the cooling effect caused by blood vessel.

Radiofrequency ablation (RFA) is the most widely used technique for the treatment of cardiac arrhythmias. A variety of factors, such as the electrode tip shape, the force exerted on the tissue by the catheter and the delivered power, combine to determine the temperature distribution, and as consequence, the lesion shape and size. In this context, being able to know the temperature reached in the myocardium during the RFA can be helpful for predicting the lesion dimensions to prevent the occurrence of undesired tissue damage. The catheters used so far in such procedures provide single-point temperature measurements within the probe (by means of embedded thermocouples or thermistors), so no information regarding the temperature changes occurring in myocardial tissues can be retrieved. The aim of this study was to assess the feasibility of fiber Bragg grating sensors (FBGs) to perform multi-point and millimetric-scale temperature measurements within myocardium subjected to RFA. The assessment has been performed on ex vivo porcine myocardium specimens undergoing RFA. Data show the feasibility of the proposed solution in providing spatial temperature distribution within the myocardial tissue during the entire RFA. These high-resolved measurements may allow reconstructing the temperature distribution in the tissue. This study lays the foundations for the implementation of 3D thermal maps to investigate how the supplied power, treatment time, force of contact and irrigation flow of the catheter influence the thermal effects within the tissue.

The desynchronisation between the rib cage and the abdomen known as thoraco-abdominal asynchrony (TAA) is an important parameter in the respiratory field. It can provide useful information about respiratory failures and work of breathing in different scenarios (e.g., clinical setting, sports science) and populations (e.g., neonates, athletes). The purpose of this work was to evaluate the capability of a multi-sensor smart garment to quantifity the TAA. The proposed garment is composed by three elastic bands embedding two conductive sensing element each. Experimental trials were carried out on five healthy volunteers who worn the elastic bands at the level of the upper rib cage, lower rib cage and abdomen. TAA was investigated by analysing the time shift between the rib cage and abdomen respiratory waveform. Data analysis demonstrated the ability of the garment to identify the thoracoabdominal time shift. This result is testified by the good agreement between the data of the proposed system and a commercial motion capture system used as gold standard: the Bland-Altman analysis showed a mean of difference of 170 ms.

Many minimally invasive thermal techniques, such as radiofrequency ablation, laser ablation, and microwave ablation (MWA) have gained substantial attention and broad clinical acceptance for the treatment of several tumors. All these treatments cause a high temperature increment, cytotoxic for the cells within the target organ. The knowledge of the ablation process effects in terms of temperature increment can be crucial to optimize the treatment settings and to avoid the occurrence of damages the healthy structures located around the tumor. During the last years, several feasibility studies on the use of MWA for bone tumor have been carried out, but an experimental analysis of the temperature reached within the bone during the treatment has not been performed. The aim of this work is to present a multi-point temperature measurement reached within the bone during MWA. Experiments were performed on an ex vivo bovine femur using a MWA system at a power of 75 W and a treatment time of 8 min. Femur temperature was measured in 30 points inside the bone and around the MW antenna, covering a large area. The measurements were performed by using three fiber optics embedding 10 fiber Bragg grating sensors each. Results of this pilot study showed the capability of the proposed approach for a multi-point temperature monitoring in bone undergoing MWA. Together, these experiments represent the first step towards the design of a system capable of understanding the effects of MWA on bone tumors, to rationally define the best MWA settings for the treatment of a specific tumor, and so to improve the treatment outcomes in this promising clinical application.

Thermal ablation procedures are gaining ever-growing acceptance in the treatment of hepatic tumors. In this context, the use of microwave ablation (MWA) has been firmly consolidated during the last decades. Being able to monitor the temperature increment within tissues undergoing MWA can be beneficial for improving the treatment outcome, especially for liver tissue which is notoriously not homogeneous and reports the presence of large vessels.In this work a multi-point temperature monitoring was performed on ex vivo liver tissue undergoing MWA. The aim was to investigate the transient phase of the tissue temperature in terms of the constant time (τ). The influence on τ of the following two aspects has been assessed: i) the blood perfusion due to the presence of a blood vessel and ii) the distance between the heat source (i.e., antenna) and the site where the temperature was measured. A power of 50 W was delivered for a treatment time of 480 s by means of a MW system. An aluminum duct providing a flowrate of 0.8 L•min-1 of water at 37 °C was inserted to mimic the presence of a blood vessel. A multi-point temperature measurement was carried out by using three fiber optics, each embedding an array of 10 fiber Bragg Grating (FBGs) sensors. The fibers were placed into the tissue sample at different distances from both the antenna and the blood vessel. The temperature variations (ΔT) recorded by the FBGs were then plotted, and τ values were calculated. The high dependence of the temperature transient dynamics on both the abovementioned distance and the presence of the vessel was found.

Over the last few decades, minimally invasive treatments have garnered much interest as alternatives to surgical resection. Among others, laser ablation has gained a broad clinical acceptance in the treatment of a certain number of solid tumors (e.g., liver, lung, and prostate). In this context, the knowledge of temperature during the treatment may be useful to better control the amount of damaged tissue and to subsequently improve clinical outcomes. The objective of this paper is to assess the feasibility of two multipoint probes for temperature monitoring during laser ablation. The probes consist of a needle made up of a carbon fiber tube. Each probe embeds an array of seven fiber Bragg grating sensors. Experiments performed in in vivo animal models (pig livers) show that the probe can reach deep-seated organs and offer the possibility to monitor tissue temperature in seven different positions. This information may be crucial to guide clinicians in the optimization of treatment settings and to improve the accuracy of theoretical models, which will pilot future studies to design new heating devices and to develop patient-specific treatments.

Respiratory assessment and the biomechanical analysis of chest and abdomen motion during\ud breathing can be carried out using motion capture systems. An advantage of this methodology is\ud that it allows analysis of compartmental breathing volumes, thoraco-abdominal patterns,\ud percentage contribution of each compartment and the coordination between compartments. In the\ud literature, mainly, two marker models are reported, a full marker model of 89 markers placed on\ud the trunk and a reduced marker model with 32 markers. However, in practice, positioning and\ud post-process a large number of markers on the trunk can be time-consuming. In this study, the\ud full marker model was compared against the one that uses a reduced number of markers, in order\ud to evaluate i) their capability to obtain respiratory parameters (breath-by-breath tidal volumes)\ud and thoracoabdominal motion pattern (compartmental percentage contributions, and coordination\ud between compartments) during quiet breathing, and ii) their response in different groups such as\ud trained and untrained, male and female. Although tests revealed strong correlations of the tidal volume values in all the groups (R2\ud >0.93), the reduced model underestimated the trunk volume compared with the 89 marker model. The\ud highest underestimation was found in trained males (bias of 0.43 L). The three-way ANOVA test\ud showed that the model did not influence the evaluation of compartmental contributions and the\ud 32 marker model was adequate to distinguish thoracoabdominal breathing pattern in the studied\ud groups. Our findings showed that the reduced marker model could be used to analyse the\ud thoracoabdominal motion in both trained and untrained populations but performs poorly in\ud estimating tidal volume.

Breathing parameters can be measured by motion capture systems by placing photo-reflective markers on the chest wall. A computational model is mandatory to compute the breathing volume and to calculate temporal and kinematical features by the gathered markers trajectories. Despite different methods based on different geometrical approaches can be adopted to compute volumes, no information about their differences in the respiratory evaluation are available. This study investigated the performances of four methods (conventional, prism-based, convex hull with boundary condition, based on Delaunay triangulation) using an optoelectronic motion capture system, on twelve healthy participants during 30 s of breathing. Temporal trends of volume traces, tidal volume values, and breathing durations were compared between methods and spirometry (used as reference instrument). Additionally, thoraco-abdominal motion patterns were compared between methods by analysing the compartmental contributions and their variability. Results shows comparable similarities between the volume traces obtained using spirometry, prism-based and conventional methods. Prism-based and convex hull with boundary condition methods show lower bias in tidal volumes estimation up to 0.06 L, compared to the conventional and Delaunay triangulation methods. Prism-based method shows maximum differences of 30 mL in the comparison of compartmental contributions to the total volume, by resulting in a maximum deviation of 1.6% in the percentage contribution analysis. In conclusion, our finding demonstrated the accuracy of the non-invasive MoCap-based breathing analysis with the prism-based method tested. Data provided in this study will lead researchers and clinicians in the computational method choice for temporal and volumetric breathing analysis.

The detection of epidural space is usually performed by the technique of loss of resistance (LOR) without technological support, although there are few commercial options. We sought to design and develop a new noninvasive system able to detect the LOR without any changes to the conventional procedure. It allows detecting the LOR by a custom made algorithm. The system provides a visual and acoustic feedback when the LOR is detected. We optimized the detection algorithm and investigated the performance of the system during experiments on a custom simulator. During the experiments performed by 10 anesthetists and 10 trainees, the pressure exerted on the syringe plunger was monitored using the custom-made system. Each participant performed four experiments using the system on the simulator. The performance of the system in LOR detection was evaluated comparing the feedback activation and the breaches of the last layer of the simulator. Moreover, each participant filled out a questionnaire to assess how the procedure with the simulator mimics the clinical scenario. A higher questionnaire score corresponds to a more realistic condition (0 = not real, 5 = extremely real). Results showed that the LOR was detected in 74 of the 80 trials (92.5% of the cases); the anesthetists obtained better results than trainees: 97.5 versus 87.5%. The questionnaires showed that all the participants found the trial realistic (score ≥3); anesthetists found it more realistic than trainees (4.2 ± 0.78 vs. 3.8 ± 0.78, mean ± SD). In summary, the proposed system successfully detected the LOR in the large part of the trials. The participants found the trials realistic. A higher success rate was observed in the anesthetists group.

Among the different thermal therapies known in the clinical practice, the technique based on laser light appears to be fast and relatively tissue insensitive. Improvement of the procedure for inducing thermal damage only within the tumor volume and safety margins, while spearing the surrounding healthy tissue and structures, is still a priority for research groups and companies working in this field.

This study focuses on the development of a noninvasive system for monitoring the force exerted by the anesthesiologist on the syringe during peripheral nerve blocks (PNBs). During this procedure, local anesthetic solutions are injected around a specific peripheral nerve. The injection pressure, and in turn the force exerted by the anesthesiologist may be related to the efficacy and safety of PNBs. The proposed system is based on i) a mechanical part fixed to the syringe used for the injection; ii) three piezoresistive force sensors which measure the force exerted by the anesthesiologist to inject the anesthetic solution. Indeed, the clinician performs the PNB by pushing with three fingers on three different parts of the syringe; iii) a custom printed circuit board, which pre-processes, collects and transmits the relevant signals.During the calibration of the three sensors, the clinical scenario has been mimicked by interposing the finger of a volunteer between the indenter of the testing machine and the active area of each sensor. These experiments provide the calibration curve of the system (for each sensor), which allows estimating the force exerted by the anesthesiologist during the injection of the anesthetic solution during PNB. Finally, the system has been tested on a patient undergoing PNB on adductor canal. During the whole experiment, the system was able to correctly follow the force exerted by the three fingertips of the clinician. These results are promising, but they can be considered just a first step toward the development of a system for supporting the clinician during PNB.

The goal of thermal ablation is to destroy cancerous cells by increasing the temperature of the target tissue. Among the ablative techniques, radiofrequency (RF) ablation is the most widespread since it can be used in both percutaneous and surgical settings, in safety and with relative ease of use. However, efforts to optimize the RF treatment are needed, considering that the size of necrotized lesions remains a central issue in the application of the ablative procedure. In this work we aimed to evaluate the temperature distribution around the RF probe during radiofrequency ablation (RFA) of ex-vivo animal livers. Temperature maps in the ablated area are obtained by equipping a commercial RF probe with 27 Fiber Bragg Grating sensors (FBGs). The experiments demonstrate the ability of the proposed setup to conduct multi-point measurements in tissues undergoing RFA and the dependence of temperature and thermal damage on insertion depth of the RF probe.

The treatment of choice for the unresectable cholangiocarcinoma is based on biliary decompression procedures. Despite stent placement is the standard of care, it is related to well-known complications. Hence, alternative techniques were proposed. Ideally, they should guarantee an adequate intraductal disobstruction, without injuring the surrounding tissues.This pre-clinical study aims to investigate the thermal effects of the laser ablation (LA) in the biliary tree, in terms of intraductal and surrounding tissue temperature achieved with different laser settings. The common bile ducts (in their upper and lower portions) of two pigs were ablated for 6 minutes with a diode laser at 3 W and 5 W. A custom-made laser applicator was used to obtain a circumferential ablation within the ducts. The intraductal temperature (T id ) was monitored by means of a fiber Bragg grating (FBG) sensor, while an infrared thermal camera monitored the T distribution in the surrounding tissues (T sup ). A maximum T difference of 65 °C and 57 °C was evidenced between the two power settings for the T id measured in the upper and lower ducts, respectively. The mean difference between T id and the averaged T sup values was evaluated. At 5 W, a difference of 37±3 °C and 44±10 °C were obtained for the upper and lower ducts, respectively. At 3 W, a T difference of 2±1 °C was obtained for the upper biliary duct, while a difference of 8±1 °C was documented for the lower duct. Based on the results obtained in this preliminary study, the possibility to equip the laser probe with temperature sensor can improve the control and the safety of the procedure; this solution will guarantee the monitoring of the treatment while preserving the lumen and the surrounding structures.

There is a growing demand for strain sensors that can be embedded into wearables for several potential applications. Among others, respiratory and cardiac rates’ monitoring from chest wall displacements have driven the development of strain sensors based on fiber Bragg gratings (FBGs) coupled with polymers. In this paper, we addressed the fabrication of a flexible sensor based on an FBG encapsulated into Dragon skin 20 silicone rubber. The sensor is intended to be used for developing a wearable system for respiratory and cardiac rates’ monitoring. The sensor’s response to strain, temperature changes, and relative humidity variations has been experimentally assessed. By considering the repetitive strains induced on the chest wall by the phenomena of interest, the hysteresis response has also been analyzed. Then, an elastic band was equipped with the flexible sensor. The feasibility of this wearable system has been preliminarily assessed on healthy volunteers to evaluate its suitability for monitoring respiratory frequency ( $f_{\mathbf {R}}$ ) and heart rate (HR). The interesting results suggest that the proposed system is easy to be worn, non-invasive, stretchy, and seems to be suitable to well-match the chest wall displacements for monitoring $f_{\mathbf {R}}$ and HR. Such findings call for further investigation targeted to evaluate the accuracy of the FBG-based wearable system in monitoring respiratory and cardiac activities and the system usability in both clinical and sports sciences.

Hyperthermal techniques are spreading as an alternative to conventional surgery for cancer removal. A real-time temperature feedback can be used to adjust the treatment settings, in order to improve the clinical outcomes. In this paper, we experimentally assessed the feasibility for distributed temperature monitoring of a custom probe, which consists of a needle embedding six fiber Bragg gratings (FBGs). Since FBGs are also sensitive to strain, we focused on the analysis of the measurement error (artifact) caused by respiratory movements. We assessed the artifact both on ex vivo pig liver and lung (by mimicking the movement of these organs caused by respiration) and on in vivo trial on pig liver. Lastly, we proposed an algorithm to detect and minimize the artifact during ex vivo liver laser ablation. During both ex vivo and in vivo trials, the probe insertion within the organ was easy and safe. The artifact was significant (up to 3 °C), but the correction algorithm allows minimizing the error. The main advantages of the proposed probe are: 1) spatially resolved temperature monitoring (in six points of the tissue by inserting a single needle) and 2) the needle is magnetic resonance (MR)-compatible, hence can be used during MR-guided procedure. Even if the model is close to humans, further trials are required to investigate the feasibility of the probe for clinical applications.

Laser ablation (LA) is a minimally invasive technique for the treatment of tumors as an alternative to surgical resection. The light absorbed by tissue is converted into heat, and causes irreversible cell damage when temperatures higher than 60 °C are reached. The knowledge in real time of temperature may be particularly beneficial for adjusting laser settings applied during treatment and to be notified in real time about its end-point. As a consequence, several techniques for temperature monitoring within the tissue have been investigated along the last decades. In the field of LA, particularly attractive are non-invasive methods. Among these techniques, thermometry based on the analysis of Magnetic Resonance Imaging (MR-thermometry) has gaining large acceptance in this field. MR-thermometry allows estimating the temperature variation thanks to the thermal dependence of several MRI parameters, among others the most promising are T 1 relaxation time, and proton resonance frequency shift. The aim of this study is to assess the sensitivity of MRI thermometry using three T 1 -weighted sequences (i.e., Inversion Recovery Turbo-FLASH, IRTF, Saturation Recovery Turbo-FLASH, SRTF, and FLASH) using an 1.5-T MR scanner on healthy swine pancreases undergoing LA. The reference temperature was measured by MRI-compatible fiber optic sensors (fiber Bragg grating sensors). The sensitivity of the proposed techniques was estimated and compared. The thermal sensitivity of the three sequences was −1.47 ± 0.08 °C −1 , −0.95 ± 0.05 °C −1 , and −0.56 ± 0.04 °C −1 for IRTF, SRTF and FLASH, respectively. Results show that the proposed technique may be adequate for temperature monitoring during LA.

The quantitative monitoring of breathing, sucking, and swallowing is required to predict newborns’ neurodevelopmental outcomes. In particular, the coordination of breathing timing with respect to sucking cycle is crucial. In this work, we present the characterization of a low-cost flowmeter designed for noninvasive recording of breathing pattern during bottle feeding. The transducer is designed to be integrated on a commercial feeding bottle also instrumented with a system for sucking monitoring. The flowmeter consists of two transistors (hot bodies) supplied at constant current, which are placed in a duct used to convey the inspiratory and expiratory flow coming from the newborn’s nostrils. The transducer design, its static calibration, and its response time are discussed. Moreover, a custom-made active lung simulator was used to perform a feasibility assessment of the proposed flowmeter for respiratory monitoring of neonatal respiratory patterns. The flowmeter has a discrimination threshold −1and a response time of347±12 ms. The breathing period estimated by the proposed transducer was compared with the one measured by a high performance flowmeter, used as reference: the mean absolute error was

Bones are a frequent site of metastases that cause intolerable cancer-related pain in 90% of patients, making their quality of life poor. In this scenario, being able to treat bone oncology patients by means of minimally invasive techniques can be crucial to avoid surgery-related risks and decrease hospitalization times. The use of microwave ablation (MWA) is gaining broad clinical acceptance to treat bone tumors. It is worth investigating temperature variations in bone tissue undergoing MWA because the clinical outcomes can be inferred from this parameter. Several feasibility studies have been performed, but an experimental analysis of the temperature trends reached into the bone during the MWA has not yet been assessed. In this work, a multi-point temperature study along the bone structure during such treatment is presented. The study has been carried out on ex vivo bovine femur and tibia, subjected to MWA. An overall of 40 measurement points covering a large sensing area was obtained for each configuration. Temperature monitoring was performed by using 40 fiber Bragg grating (FBGs) sensors (four arrays each housing 10 FBGs), inserted into the bones at specific distances to the microwave antenna. As result, the ability of this experimental multi-point monitoring approach in tracking temperature variations within bone tissue during MWA treatments was shown. This study lays the foundations for the design of a novel approach to study the effects of MWA on bone tumors. As consequence, the MWA treatment settings could be optimized in order to maximize the treatment effects of such a promising clinical application, but also customized for the specific tumor and patient.

In recent years, no-invasive and small size systems are meeting the demand of the new healthcare system, in which the vital signs monitoring is gaining in importance. In this context, Fiber Bragg grating (FBG) sensors are becoming very popular and FBG-based systems could be used for monitoring vital signs. At the same time, FBG could be able to sense chemical parameters by the polymer functionalization. The aim of our study was investigating the ability of a polymer-coated FBG-based probe for monitoring breathing patterns and respiratory rates. We tested the proposed FBG-based probe on 9 healthy volunteers during spirometry, the most common pulmonary function test. Results showed the high accuracy of the proposed probe to detect respiratory rate. The comparison between the respiratory rates estimated by the probe with the ones by the spirometer showed the absolute value of the percentage errors lower than 2.07% (in the 78% of cases

Epidural injection is a local-regional anesthesia technique used both for analgesic and anesthetic purposes. During the procedure, a needle is inserted between two spinous processes, and it is advanced through interspinous ligament, supraspinous ligament skin, ligamentum flavum, and finally it reaches the epidural space. It is crucial the optimal positioning of the needle's tip within this space to avoid incorrect medication administration or dural puncture. Nowadays, the anaesthetist detects the epidural space by a sense of a resistance loss due to the different density of the mentioned anatomical tissues. In a previous work, we described a bespoke system called Epidural Sensing Management Tool (ESMT) designed to support the anaesthetist in the detection of the epidural space. The system is based on a piezoresistive sensor which measures the pressure exerted by the clinician on the syringe plunger during the procedure. The resistance of the sensor is converted in voltage by a Wheatstone bridge, then is recorded and visualized on a laptop. The aim of this study is twofold: i) to assess the influence of the sensor's active area on the ESMT response; ii) to assess the influence of the resistance value of the Wheatstone bridge on the ESMT response. At this scope, two sensors with different circular area and Wheatstone bridge with three different resistance values were used. The influence of the two mentioned parameters on the ESMT response was investigated by applying known force in a wide range of values. These experiments were performed considering two different configurations: i) the first set of tests was carried out with a 3 mm-thick cylinder of silicon material (taken from an upper limb of cosmetic prosthetic gloves) interposed between the indenter and the sensor; ii) The second set of tests was carried out by placing the thumb of a volunteer between the indenter and the sensor. Also, the sensor is placed on a syringe plunger used during epidural puncture. This configuration is very close to the clinical settings (force applied to the whole area of the plunger by the thumb). As expected, both the sensor model and the Wheatstone bridge resistance significantly influence the metrological characteristics of the proposed system.

In this work, we report on the integration of fiber Bragg gratings sensors in a commercial radio frequency probe for real-time temperature monitoring during thermal ablation of biological tissues. The experiments were conducted on ex-vivo pig liver and bovine kidney tissues and the results confirm that the proposed setup is able to conduct a multi-point real-time temperature monitoring during the RF discharges with a temperature resolution of 0.1 °C and a minimum spatial resolution of 1 mm. During these experiments the blood perfusion was implemented by injecting water at a temperature of 37 °C inside the organ under examination. This solution aimed at simulating the Radio Frequency Thermal Ablation (RFTA) treatments made in clinical practice. © 2018 IEEE.

Temperature mapping is a key asset in supporting the clinician during thermal ablation (TA) treatment of tumors without adding additional risk to the TA procedure. Herein we report our experiments on multidimensional thermal mapping during radio frequency (RF) thermal ablation treatments of an ex-vivo animal organ. The temperature was monitored using several arrays of fiber Bragg gratings properly positioned around the RF applicator. The results show the effectiveness of our proposed method at assessing the TA probe depth and demonstrating how the insertion depth directly influences the maximum temperature and the treated area of the radio frequency ablation. © 2018 Optical Society of America.

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.

The growing interest in the development of smart textiles for medical applications is driven by the aim to increase the mobility of patients who need a continuous monitoring of such physiological parameters. At the same time, the use of fiber optic sensors (FOSs) is gaining large acceptance as an alternative to traditional electrical and mechanical sensors for the monitoring of thermal and mechanical parameters. The potential impact of FOSs is related to their good metrological properties, their small size and their flexibility, as well as to their immunity from electromagnetic field. Their main advantage is the possibility to use textile based on fiber optic in a magnetic resonance imaging environment, where standard electronic sensors cannot be employed. This last feature makes FOSs suitable for monitoring biological parameters (e.g., respiratory and heartbeat monitoring) during magnetic resonance procedures. Research interest in combining FOSs and textiles into a single structure to develop wearable sensors is rapidly growing. In this review we provide an overview of the state-of-the-art of textiles, which use FOSs for monitoring of mechanical parameters of physiological interest. In particular we briefly describe the working principle of FOSs employed in this field and their relevant advantages and disadvantages. Also reviewed are their applications for the monitoring of mechanical parameters of physiological interest.

Accurate monitoring of flow rate and volume exchanges is essential to minimize ventilator-induced lung injury. Mechanical ventilators employ flowmeters to estimate the amount of gases delivered to patients and use the flow signal as a feedback to adjust the desired amount of gas to be delivered. Since flowmeters play a crucial role in this field, they are required to fulfill strict criteria in terms of dynamic and static characteristics. Therefore, mechanical ventilators are equipped with only the following kinds of flowmeters: linear pneumotachographs, fixed and variable orifice meters, hot wire anemometers, and ultrasonic flowmeters. This paper provides an overview of these sensors. Their working principles are described together with their relevant advantages and disadvantages. Furthermore, the most promising emerging approaches for flowmeters design (i.e., fiber optic technology and three dimensional micro-fabrication) are briefly reviewed showing their potential for this application.

Laser Ablation (LA) is a minimally invasive technique for tumor removal. The laser light is guided into the target tissue by a fiber optic applicator; thus the physical features of the applicator tip strongly influence size and shape of the tissue lesion. This study aims to verify the geometry of the lesion achieved by a tapered-tip applicator, and to investigate the percentage of thermally damaged cells induced by the tapered-tip fiber optic applicator. A theoretical model was implemented to simulate: i) the distribution of laser light fluence rate in the tissue through Monte Carlo method, ii) the induced temperature distribution, by means of the Bio Heat Equation, iii) the tissue injury, by Arrhenius integral. The results obtained by the implementation of the theoretical model were experimentally assessed. Ex vivo porcine liver underwent LA with tapered-tip applicator, at different laser settings (laser power of 1 W and 1.7 W, deposited energy equal to 330 J and 500 J, respectively). Almost spherical volume lesions were produced. The thermal damage was assessed by measuring the diameter of the circular-shaped lesion. The comparison between experimental results and theoretical prediction shows that the thermal damage discriminated by visual inspection always corresponds to a percentage of damaged cells of 96%. A tapered-tip applicator allows obtaining localized and reproducible damage close to spherical shape, whose diameter is related to the laser settings, and the simple theoretical model described is suitable to predict the effects, in terms of thermal damage, on ex vivo liver. Further trials should be addressed to adapt the model also on in vivo tissue, aiming to develop a tool useful to support the physician in clinical application of LA.

The use of wearable systems for monitoring vital parameters has gained wide popularity in several medical fields. The focus of the present study is the experimental assessment of a smart textile based on 12 fiber Bragg grating sensors for breathing monitoring and thoraco‐abdominal motion pattern analysis. The feasibility of the smart textile for monitoring several temporal respiratory parameters (ie, breath‐by‐breath respiratory period, breathing frequency, duration of inspiratory and expiratory phases), volume variations of the whole chest wall and of its compartments is performed on 8 healthy male volunteers. Values gathered by the textile are compared to the data obtained by a motion analysis system, used as the reference instrument. Good agreement between the 2 systems on both respiratory period (bias of 0.01 seconds), breathing frequency (bias of −0.02 breaths/min) and tidal volume (bias of 0.09 L) values is demonstrated. Smart textile shows good performance in the monitoring of thoraco‐abdominal pattern and its variation, as well.

The response of a fiber optic sensor [linearly chirped fiber Bragg grating (LCFBG)] to a linear thermal gradient applied on its sensing length (i.e., 1.5 cm) has been investigated. After these bench tests, we assessed their feasibility for temperature monitoring during thermal tumor treatment. In particular, we performed experiments during ex vivo laser ablation (LA) in pig liver and in vivo thermal ablation in animal models (pigs). We investigated the following: (i) the relationship between the full width at half maximum of the LCFBG spectrum and the temperature difference among the extremities of the LCFBG and (ii) the relationship between the mean spectrum wavelength and the mean temperature acting on the LCFBG sensing area. These relationships showed a linear trend during both bench tests and LA in animal models. Thermal sensitivity was significant although different values were found with regards to bench tests and animal experiments. The linear trend and significant sensitivity allow hypothesizing a future use of this kind of sensor to monitor both temperature gradient and mean temperature within a tissue undergoing thermal treatment.

Thermal therapies are minimally invasive procedures used to locally remove tumor in several organs by means of cytotoxic temperature. Among several techniques, laser ablation (LA) is appreciated for the possibility to be performed by flexible optical fibers, hence to be coupled with MR imaging for procedure guidance. In this work, we present the first in vivo trial on pig pancreas undergoing LA and simultaneous multipoint temperature monitoring by means of fiber optic sensors (Fiber Bragg gratings -FBGs-). The clinical procedure has been performed through percutaneous access to the pancreas. The optical output of the FBGs, measuring both the temperature evolution and the breathing movement, is post-processed to neglect possible artifacts on the signal. Temperature data were also employed to estimate the thermal dose induced within the pancreas. The findings of this study may be useful for the definition of the safe LA to the patients, and allow understanding the effects of the laser light on the pancreatic tissue, paving the way for a controlled therapy in clinical settings.

In this work, we propose the use of fiber Bragg grating (FBG) sensor arrays for real-time temperature monitoring during RadioFrequency Thermal Ablation (RFTA) tumor treatment. Real-time temperature monitoring of RF-treatment to the tumors lesion of an organ could prove to be highly beneficial for intra-operative surgical planning and subsequently ensure a successful outcome of a thermo-ablation procedure. An adequate configuration was designed in order to create a thermal multipoint map. In particular, the RF probe of a commercial medical device was properly packaged with FBG sensors. In order to discern the treatment areas as accurately as possible, a second 3.5 cm long array, consisting of several FBGs was also employed. The experiments were conducted on ex vivo animal liver tissues and results confirm that we were successfully able to conduct a multipoint measurement and to distinguish between different and consecutive RF discharges with a temperature resolution of 0.1 °C and a minimum spatial resolution of 5mm.

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.

Laser ablation (LA) is gaining acceptance for the treatment of tumors as an alternative to surgical resection. This paper reviews the use of lasers for ablative and surgical applications. Also reviewed are solutions aimed at improving LA outcomes: hyperthermal treatment planning tools and thermometric techniques during LA, used to guide the surgeon in the choice and adjustment of the optimal laser settings, and the potential use of nanoparticles to allow biologic selectivity of ablative treatments. Promising technical solutions and a better knowledge of laser-tissue interaction should allow LA to be used in a safe and effective manner as a cancer treatment.

Epidural blockade procedures have gained large acceptance during last decades. However, the insertion of the needle during epidural blockade procedures is challenging, and there is an increasing alarming risk in accidental dural puncture. One of the most popular approaches to minimize the mentioned risk is to detect the epidural space on the base of the loss of resistance (LOR) during the epidural needle insertion. The aim of this paper is to illustrate an innovative and non-invasive system able to monitor the pressure exerted during the epidural blockade procedure in order to detect the LOR. The system is based on a Force Sensing Resistor (FSR) sensor arranged on the top of the syringe's plunger. Such a sensor is able to register the resistance opposed to the needle by the different tissues transducing the pressure exerted on the plunger into a change of an electrical resistance. Hence, on the base of a peculiar algorithm, the system automatically detects LOR providing visual and acoustic feedbacks to the operator improving the safety of the procedure. Experiments have been performed to characterize the measurement device and to validate the whole system. Notice that the proposed solution is able to perform an effective detection of the LOR.

Radiofrequency ablation (RFA) is a minimally invasive procedure used to treat tumors by means of hyperthermia, mostly through percutaneous approach. The tissue temperature plays a pivotal role in the achievement of the target volume heating, while sparing the surrounding healthy tissue from thermal damage. Several techniques for thermometry during RFA are investigated, most of them based on the use of single-point measurement system (e.g., thermocouples). The measurement of temperature map is crucial for the real-time control and fine adjustment of the treatment settings, to optimize the shape and size of the ablated volume. The recent interest about fiber optic sensors and, among them, fiber Bragg gratings (FBGs) for the monitoring of thermal effects motivated further investigation. In particular, the feature of FBGs to form an array of several elements, thus to be inscribed within the same fiber, allows the use of a single probe for the multi-points monitoring of the tissue temperature during RFA. Hence, the aim of this study is the development and characterization of a needle-like probe embedding an array of three FBGs, which was tested on pig liver during in vivo trials. The needle allows a safe and easy insertion of the fiber optic within the liver. It was inserted by ultrasound guidance into the liver, and monitored the change of tissue temperature during RFA controlled by the roll-off technique. Also the measurement error induced by breathing movements of the liver was assessed (less than 3 °C). Results encourage the use of the probe in clinical settings, as well as the improvement of some features, e.g., a higher number of FBGs for performing quasi-distributed measurement. © 2016 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.

Microfabricated tactile sensors gain importance for their application in bio-robotics. They are useful for the measurement of contact properties, in particular force and pressure, in three main fields, i.e., prosthetics and artificial skin, minimal access surgery and collaborative robotics. Among the different technological solutions, piezoresistive materials proved to be suitable for such an application. These materials show a change of electrical resistivity as a function of the applied strain. This work describes the design of a 2×2 array of piezoresistive elements and the experimental setup arranged for the array characterization, intended to be embedded within an artificial fingertip. The size of the bare array is 1.5×1.5×0.65 mm3. The finger has been designed to bio-mimic the behaviour of a human finger tip, thanks to the external layer of dragon skin. The static calibration of the sensors has been carried out by applying quasistatic normal loads on the mesa of each sensor of the array in two configurations (i.e., bare array and the array embedded in a fingertip). The sensors showed a linear response; the sensitivity ranges from 34 mV/N to 65 mV/N for the bare array, and from 16 mV/N to 39 mV/N for the array in the fingertip. No significant cross-talk (∼2%) has been observed during the test on the bare array. Further tests will be designed to characterize the response to tangential loads and assess the dynamic response of the sensors, as well as additional features which can be crucial for bio-robotic applications.

Wearable sensorized smart textile are gaining interests in medicine for monitoring physiological parameters. Moreover, sensing solutions based on fiber optic technologies have shown promising results for applications in Magnetic Resonance (MR) environment. The aim of the present study was to evaluate the functionality of an MR-compatible smart textile based on six fiber Bragg grating (FBG) sensors inside the MR environment for the monitoring of both respiratory and cardiac activities during apnea and quiet breathing stages. The proposed textile was tested on two healthy volunteers undergoing 1.5 Tesla MR examination. By analyzing the raw data collected by the six FBGs, respiratory parameters (i.e., respiratory rate, inspiratory and expiratory periods, inspiratory/respiratory ratio and inspiratory/expiratory ratio) have been computed. Thus, considering the raw data collected by the FBG sensor closest to the heart the resting heart rate was calculated by using the Fast Fourier transform (FFT). Results show that both the big displacements at low frequency (related to the breathing) and the small displacements at higher frequency (related to the heart activity) can be collected with the proposed system allowing the evaluation of both the respiratory and cardiac activities during quiet breathing and apnea without artifacts on images, providing useful information about patient condition. © 2017 IEEE.

Tissue temperature distribution plays a crucial role in the outcome of laser-induced thermotherapy (LITT), a technique employed for neoplasias removal. Since recent studies proposed LITT for pancreatic tumors treatment, assessment of temperature and of its effects around the laser applicator could be useful to define optimal laser settings. The aims of this work are temperature monitoring and measurement of ablated tissue volume in an ex vivo porcine pancreas undergoing double-applicator LITT. A three-dimensional numerical model is implemented to predict temperature rise and volumes of ablated tissue in treated pancreas. Experiments are performed to validate the model, with two modalities: (1) 12-fiber Bragg grating sensors are adopted to monitor the heating and cooling during LITT at several distances from the applicators tip, and (2) 1.5-T MR imaging is used to estimate the ablated volume. Experimental data agree with theoretical ones: at 2 mm from both applicators tips, the maximum temperature increase is approximately 60°C downward from the tips, while it increases of about 40°C and 30°C, respectively, at the level and upward from the tips. This behavior occurs also at other distances, proving that the tissue downward from the tip is mostly heated. Furthermore, the estimated volume with MRI agrees with theoretical one (i.d., 0.91±0.09 vs. 0.95 cm 3). The encouraging results indicate that the model could be a suitable tool to choose the optimal laser settings, in order to control the volume of ablated tissue. © 2013 Springer-Verlag.