Error of a temperature probe for cancer ablation monitoring caused by respiratory movements: Ex vivo and in vivo analysis

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)

Special Issue “Fibre Optic Sensors for Structural and Geotechnical Monitoring”

In this editorial on the special issue “Fibre Optic Sensors for Structural and Geotechnical Monitoring” a review of the contribution papers selected for publication is given. Each paper is briefly summarized, presenting its objective and methods, then a comment is given about the relevance of the work with respect to the advance and the spreading of the fibre optic technology for monitoring applications

Humidity Sensing by Chitosan-Coated Fibre Bragg Gratings (FBG)

In this work, we report novel relative humidity sensors realized by functionalising fibre Bragg gratings with chitosan, a moisture-sensitive biopolymer never used before for this kind of fibre optic sensor. The swelling capacity of chitosan is fundamental to the sensing mechanism. Different samples were fabricated, testing the influence of coating design and deposition procedure on sensor performance. The sensitivity of the sensors was measured in an airtight humidity-controlled chamber using saturated chemical salt solutions. The best result in terms of sensitivity was obtained for a sensor produced on filter paper substrate. Tests for each design were performed in the environment, lasted several days, and all designs were independently re-tested at different seasons of the year. The produced sensors closely followed the ambient humidity variation common to the 24-h circadian cycle

Improving FBG sensor sensitivity at cryogenic temperature by metal coating

Commercially available fiber Bragg grating (FBG) sensors cannot be used for measuring cryogenic temperatures because they are made of silica the thermal expansion coefficient of which tends to zero when approaching 4 K. Because of the many advantages of fiber optic sensors with respect to conventional ones, in this paper it is shown how to circumvent such a limitation by applying a proper metal coating. This approach drastically increases temperature measuring capability of FBGs at cryogenic environments typically encountered in application involving liquid gases or in space. Various metals have been deposited by electrowinning on the external fiber surface previously treated with an aluminum precoating. Also, a special casting process has been developed. The explored temperature region was 4.2-40 K. The paper reports the characterization of FBG sensors coated with different metals and shows the validity of this new temperature sensor with respect to conventional ones

Fiber Bragg Grating Probe for Relative Humidity and Respiratory Frequency Estimation: Assessment during Mechanical Ventilation

Fiber Bragg grating (FBG) sensors have gained popularity in medicine for some valuable features, such as small size, immunity to electromagnetic interferences, and good metrological properties. Among several applications, this technology has been used in the analysis of gases in mechanical ventilation. In this field, in particular during invasive ventilation, the gas delivered by the ventilator must be warmed and humidified in order to reach the patients with optimal conditions (100% of relative humidity and 37 °C). The most popular device used to accomplish this task is the heated wire humidifiers (HWHs). Unfortunately, their performances are influenced by ventilatory settings (e.g., respiratory frequency) and environmental conditions. The aim of this paper is to fabricate a probe based on an FBG sensor able to monitor both the gas relative humidity and the respiratory frequency. This information can be used as a feedback to improve the performance of the HWHs. The probe consists of a needle, which houses an FBG sensor coated by hygroscopic material (i.e., agar). This solution allows an easy insertion of the probe within the ducts connecting the ventilator to the patient. The proposed system has been assessed during mechanical ventilation at different respiratory frequencies. Future testing will be focused on the development of a system able to monitor other parameters that influence the HWHs performances (e.g., gas temperature and minute volume)

New magnetic connector for embedding of optical sensors in composite materials

Since the early '80s we begun to talk about the possibility of inserting the optical fiber within the next generation (composite) materials. At the time the optical fiber was used primarily to signals transportation, for communications, and therefore were used primarily multi-modal fibers, not suitable for use with fiber optical sensors, particularly Fiber Bragg Grating (FBG) sensors. It has been started to develop connectors that would allow the embedding of the fibers themselves, allowing an easier outgoing of the termination pigtails from the material itself, [1-3]. Several patents were developed for this purpose, focusing attention, given the almost complete immunity to magnetic fields of optical fiber, to connectors magnetized to facilitate the operation of plug-in. Over the years we have lost trace of these connectors. Today, given the enormous development perspective that the FBG sensors play in the field of real time structural health monitoring, we are turning our attention to the need for a connector easy, quick and effective to plug, that size does not interfere with the structure to be monitored, easy to make and assemble, in a word, practical, from all points of view. For this reason we have designed a miniaturized magnetic connector that is optimized for connecting the single-mode optical fiber, typically used for FBG sensors, which allows efficient transport of the signal, minimizing losses and allow seamless integration with the material, and the structure to be monitored, in other words, this connecting system has been designed in order to develop a product which solves the problem shown by commercial available connectors during their embedding inside materials.. © 2011 IEEE

Smart Textile Based on 12 Fiber Bragg Gratings Array for Vital Signs Monitoring

Over the last decades, wearable systems have gained interest for vital signs monitoring. Among several technologies, fiber Bragg grating (FBG) sensors are becoming popular for some advantages, such as high sensitivity, magnetic resonance compatibility, and the capability of performing distributed measurements. The aim of this paper is twofold: the description of the design and the fabrication of a smart textile based on an array of 12 FBGs; its feasibility assessment for monitoring respiratory parameters (i.e., respiratory rate, respiratory period, and inspiratory and expiratory periods) and heart rate on healthy volunteers in two positions (standing and supine). The increased number of FBGs embedded in this system with respect to previous developed prototypes aims at improving its accuracy in the estimation of the mentioned parameters. Future testing will be performed to investigate if the proposed solution allows improving the measurements of respiratory volumes exchanges and in new scenarios (e.g., sports medicine, including walking, running, and cycling activities)