In this paper a novel patent pending high resolution optical fibre temperature sensor, based on an optical fibre pressure and temperature sensor (OFTPS), which is surrounded by an oil filled chamber, is presented. The OFPTS is based on a Fabry Perot interferometer (FPI) which has an embedded fibre Bragg grating (FBG). The high ratio between the volume of the oil filled outer cavity and the FPIs air filled cavity, results in a highly sensitive temperature sensor. The FBG element of the device can be used for wide range temperature measurements, and combining this capability with the high resolution capability of the FPI/oil cavity results in a wide range and high resolution temperature sensing device. The outer diameter of the sensor is less than 1mm in diameter and can be designed to be even smaller. The sensors temperature response was measured in a range of ΔT = 7K and resulted in a shift in the optical spectrum of ΔλF = 61.42nm. Therefore the Q-point of the reflected optical FPI spectrum is shifting with a sensitivity of sot = 8.77 nm/K . The sensitivity can easily be further increased by changing the oil/air volumetric ratio and therefore adapt the sensor to a wide variety of applications.
This paper presents an optical fibre pressure and temperature sensor (OFPTS) system, which is adapted for use as a urodynamic pressure measurement system (UPS) for differential pressure measurement with temperature compensation. The OFTPS is based on a Fabry Perot interferometer (FPI), which acts as a pressure sensor and includes an embedded fibre Bragg grating (FBG) for temperature measurement. The sensor system is evaluated in a lower urinary tract (LUT) simulator, which simulates the bladder, rectum and detrusor muscle. The system was benchmarked against a commercially available urodynamic system, at the University Hospital Limerick (UHL) Urology Clinic. Both systems demonstrate a high correlation with a relative pressure variation of less than ±2.8cmH2O for abdominal and ±4cmH2O for vesical pressure. The repetitive measurement of the OFPTS system in the LUT simulator against the commercial system demonstrated the high repeatability. Furthermore, the low fabrication cost makes the OFPTS a potentially interesting instrument for urodynamic and other medical applications.
Optical fibre sensors have been applied to perform biophysical measurement in ex-vivo laser ablation (LA), on pancreas animal phantom. Experiments have been performed using Fibre Bragg Grating (FBG) arrays for spatially resolved temperature detection, and an all-glass Extrinsic Fabry-Perot Interferometer (EFPI) for pressure measurement. Results using a Nd:YAG laser source as ablation device, are presented and discussed.
In this paper, two optical fibre sensors are presented: 1) based on extrinsic Fabry-Perot Interferometer (EFPI) with Fibre Bragg Grating array and 2) and EFPI sensor with a chirped Fibre Bragg grating (CFBG). The CFBG with EFPI sensor fabrication technique is described and temperature response of both sensors is presented. Such sensors have many potential applications including applications in the aerospace industry and medical industry (e.g. radio frequency thermal ablation of tumors).
Thermal ablation (TA) is an interventional procedure for selective treatment of tumors, that results in low-invasive outpatient care. The lack of real-time control of TA is one of its main weaknesses. Miniature and biocompatible optical fiber sensors are applied to achieve a dense, multi-parameter monitoring, that can substantially improve the control of TA. Ex vivo measurements are reported performed on porcine liver tissue, to reproduce radiofrequency ablation of hepatocellular carcinoma. Our measurement campaign has a two-fold focus: (1) dual pressure-temperature measurement with a single probe; (2) distributed thermal measurement to estimate point-by-point cells mortality.
We present in this paper an optical fiber pressure and temperature sensor (OFPTS) with multi Fibre Bragg Grating (FBG) array. The sensor based on an extrinsic Fabry Perot interferometer and is fabricated from silica glass. A femtosecond laser (FSL) was used to inscribe multiple FBGs proximately close to the diaphragm, parallel to each other. This concepts allows a chain of FBGs with miniature active length which can be a significant important tool for medical application, like radio frequency ablation (RFA) cancer treatment.
Thermal ablation, using radiofrequency, microwave, and laser sources, is a common treatment for hepatic tumors. Sensors allow monitoring, at the point of treatment, the evolution of thermal ablation procedures. We present optical fiber sensors that allow advanced capabilities for recording the biophysical phenomena occurring in the tissue in real time. Distributed or quasi-distributed thermal sensors allow recording temperature with spatial resolution ranging from 0.1 mm to 5 mm. In addition, a thermally insensitive pressure sensor allows recording pressure rise, supporting advanced treatment of encapsulated tumors. Our investigation is focused on two case studies: (1) radiofrequency ablation of hepatic tissue, performed on a phantom with a stem-shaped applicator; (2) laser ablation of a liver phantom, performed with a fiber laser. The main measurement results are discussed, comparing the technologies used for the investigation, and drawing the potential for using optical fiber sensors for "smart"-ablation.
Urodynamic analysis is the predominant method for evaluating dysfunctions in the lower urinary tract. The exam measures the pressure during the filling and voiding process of the bladder and is mainly interested in the contraction of the bladder muscles. The data arising out of these pressure measurements enables the urologist to arrive at a precise diagnosis and prescribe an adequate treatment. A technique based on two optical fiber pressure and temperature sensors with a resolution of better than 0.1 cm H2O (∼10 Pa), a stability better than 1 cm H2O/hour, and a diameter of 0.2 mm in a miniature catheter with a diameter of only 5 Fr (1.67 mm), was used. This technique was tested in vivo on four patients with a real-time urodynamic measurement system. The optical system presented showed a very good correlation to two commercially available medical reference sensors. Furthermore, the optical urodynamic system demonstrated a higher dynamic and better sensitivity to detect small obstructions than both pre-existing medical systems currently in use in the urodynamic field.
In this paper new algorithms and procedures are reported which enable miniaturization and optimization of the thickness of a diaphragm for an all-glass extrinsic Fabry-Perot interferometer (EFPI)-based pressure sensor. Diaphragm etching improves the EFPI sensors ability to detect relatively small changes in pressure (0.1mmHg) and the resulting sensor exhibits excellent stability over time (drift < 1 mmHg / hour) for measurement in air and liquid. The diaphragm etching procedure involves fiber polishing followed by etching in hydrofluoric (HF) acid. An additional Ion-beam etching technique was investigated separately to compare with the HF-etching technique. A sensitivity better than 10 10 nm/kPa, which provides a pressure resolution of 0.05mmHg, is achieved by reducing the EFPI diaphragm thickness down to less than 2μm for the miniature pressure sensor used in this investigation (overall diameter of 200μm). The techniques reported is also applicable for the fabrication of high sensitivity sensors using a smaller fiber diameter e.g. 80μm.
We present a miniature and biocompatible fiber-optic sensing system, for specific application in monitoring of the
radiofrequency thermal ablation (RFA) process. The sensing system is based on combination of Extrinsic Fabry-Perot
Interferometry (EFPI) sensor for pressure detection, and Fiber Bragg Grating (FBG) for temperature measurement. The
dual pressure/temperature measurement shows an extremely low cross-sensitivity. Measurements have been performed
ex-vivo on porcine liver, recording several RFA procedures in different location. Maximum values of 164°C and 162 kPa
have been recorded on the ablation point.
We report a fiber-optic sensing system based on Extrinsic Fabry-Perot Interferometry (EFPI), for pressure detection in medical applications. The system allows dual channel detection, with probes having typical sensitivity of 1.3 nm/kPa and accuracy of 0.6 cmH2O, diameter of 0.2 mm, and perfect biocompatibility. Pressure probes have been applied to urodynamic analysis, measuring both bladder and abdominal pressure. Measurements have been carried out in-vivo on seven patients having different bladder conditions. The fiber-optic probes have been compared with a PICO2000 urodynamic instrument, showing improved accuracy, a good reproduction of bladder-related events, and increased responsivity to local pressure variations.
A fibre optic extrinsic Fabry Perot Interferometer (EFPI) sensor is developed for monitoring pressure in the underwater and sub-seabed under simulated conditions. The sensor is robust in design and is fabricated entirely from Silica glass. The EFPI is formed at the tip of the fibre, where the single mode is spliced to a 200μm capillary, sealed by a 200μm Multimode, which forms the diaphragm. The diaphragm thickness is reduced by polishing and etching with hydrofluoric (HF) acid to about 2-3μm for a high sensitivity. The thickness of the diaphragm is monitored online during polishing and HF etching. The spectrum of the fibre optic sensor (FOS) is interrogated using a broad band optical light source and an optical spectrometer. The sensitivity of the sensor achieved is 0.6cmH2O, excellent for small depth-changes. Experimental measurements with saturated salt water and chlorophyll pigmentation of different standards were tested, to simulate the sub-sea conditions where a stability of 0.7cmH2O was reached with a drift of less than 10% under the simulated conditions.
KEYWORDS: Sensors, Fiber Bragg gratings, Temperature metrology, In vivo imaging, Temperature sensors, Optical fibers, Biomedical optics, Bladder, Interferometers, Heart
The all-glass optical fibre pressure and temperature sensor (OFPTS), present here is a combination of an extrinsic Fabry Perot Interferometer (EFPI) and an fiber Bragg gratings (FBG), which allows a simultaneously measurement of both pressure and temperature. Thermal effects experienced by the EFPI can be compensated by using the FBG. The sensor achieved a pressure measurement resolution of 0.1mmHg with a frame-rate of 100Hz and a low drift rate of < 1 mmHg/hour drift. The sensor has been evaluated using a cardiovascular simulator and additionally has been evaluated in-vivo in a urodynamics application under medical supervision.
A fiber-optic pressure sensor based in extrinsic Fabry-Perot interferometer (EFPI) is presented and discussed. The
sensing probe is based on an inexpensive all-silica biocompatible design, with 0.2 mm outer diameter, suitable for
disposable operation in medical catheters. A white-light interrogation system has been implemented, achieving a target
accuracy of 1 mmHg and pressure stability of 1 mmHg/hour for long-term operation. A fiber Bragg grating (FBG) is
added in proximity of the sensing tip, compensating temperature variations with 0.5°C accuracy. Design, simulation, and
preliminary experimental validation are discussed.
A combined optical fiber pressure/temperature sensing system based on low-finesse extrinsic Fabry-Perot interferometer (EFPI) in conjunction with a fiber Bragg grating (FBG) for biomedical measurement applications is presented. The sensing probe has 200 μm outer diameter, and is biocompatible, meeting the requirements for the most demanding biomedical applications. High accuracy (<1mmHg) is achieved by means of fiber polishing and diaphragm etching in hydrofluoric acid, and optimizing the sensitivity to <1nm/kPa. A white light interrogation system based on spectrometric analysis has been developed which implements several pressure detection algorithms. A measurement campaign has been carried out to validate the proposed system, showing 1mmHg accuracy, air-gap compression linearity, and temperature compensation.
A miniature optical fiber pressure sensor based on extrinsic Fabry-Perot interferometer (EFPI) is presented. The sensing
probe has 0.2 mm outer diameter, and is based on an all-silica biocompatible structure, with a pressure sensitivity <1
nm/kPa. The probe is complemented by a fiber Bragg grating (FBG), in proximity of the EFPI tip, for temperature
compensation. Interrogation is based on a low-cost white-light setup, whereas several pressure detection algorithms have
been developed. Preliminary experimental validation and medical applications are discussed.
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