Fiber-optic Thermometer Research Articles

EPI proton resonant frequency temperature mapping at 0.5T in the brain: Comparison to single-echo gradient recalled echo.

Evaluate the use of both single-echo gradient recalled echo (SE-GRE) and EPI approaches to creating temperature maps on a mid-field head-only scanner, both in vivo and on a tissue mimicking gel. Three 2D protocols were investigated (an SE-GRE, single-shot EPI, and an averaged single-shot EPI). The protocols used either a gradient recalled acquisition or an echo planar acquisition, with EPI parameters optimized for the longer at lower field-strengths. Phantom experiments were conducted to evaluate temperature tracking while cooling, comparing protocol to measurements from an optical fiber thermometer. Studies were performed on a 0.5T head only MR scanner. Temperature stability maps were produced in vivo for the various protocols to evaluate precision. The use of an EPI protocol for thermometry improved temperature precision in a temperature control phantom and provided an 18% improvement in temperature measurement precision in vivo. Temperature tracking using a fast (<2 s) update rate EPI thermometry sequence provided a similar precision to the slower SE-GRE protocol. While SE-GRE PRF thermometry shows good performance, EPI methods offer improved tracking precision or update rate, making them a better option for thermometry in the brain at mid-field.

Mn4+/Eu3+ co-doped fluoride toward a blue light-excited optical fiber thermometer.

The ongoing development of ratiometric optical thermometry is mainly trapped in thermally coupled levels of rare-earth ions and inefficient ultraviolet excitation. Herein, a new-type multiple sharp line emitting, blue light-excited K2NaInF6:Mn4+, Eu3+ fluoride phosphor has been reported as a ratiometric thermometer. The f-f transition of Eu3+ paves a steady reference to a highly temperature sensitive Mn4+d-d transition and enables high relative sensitivity of 1.65% K-1 at 573 K. An optical fiber thermometry on a household oven with a relative standard deviation of 0.11% surpasses the standard of precision measurement, showing great potential in practical application. This discovery offers a highly sensitive neotype blue light-excitable ratiometric temperature sensor, that is Mn4+-doped fluoride, promoting practical applications of optical thermometry.

Combinatorial ratiometric strategy for continuously highly sensitive thermometry in transparent germanate glass-ceramic containing upconversion nanocrystals

Ratiometric luminescence thermometry is a promising method for non-contact and non-invasive thermometry. Maintaining consistently high temperature sensitivity over a wide temperature range is still a challenge for many ratiometric luminescence thermometers. Here, we have developed a novel transparent germanate glass-ceramic containing NaY3F10:Yb3+/Tm3+/Er3+ nanocrystals. The crystalline content of which remained highly stable during a tunable heat treatment process. Compared with glass, the upconversion luminescence of the glass-ceramic, which originated from the thermally and non-thermally coupled energy levels of Tm3+ and Er3+, was significantly enhanced. Using the temperature-dependent fluorescence intensity ratios of selected upconversion emissions, a ratiometric thermometry scheme with high temperature sensitivity was constructed. The relative sensitivity maintained at a high level (1.30–2.61 %K−1) over the experimental temperature range (323–573 K). The best resolution and repeatability were ±0.13 K and 99.6%, respectively. This transparent glass-ceramic is an excellent candidate for ratiometric thermometry, which is expected to be applied to fibre-optic thermometers.

Developing a special microwave oven: Assessment of its performance for dough fermentation and nutrient soup elaboration

Bread and soup are two of the most important foods in daily life, thus dough fermentation and nutrient soup elaboration are more and more popular, but there is a lack of relevant low-cost and high-reliable household appliances on the market. Therefore, this paper proposes automatic control methods for dough fermentation and nutrient soup elaboration based on a special microwave oven. Fermentation theory, run-up microwave fermentation principle, microwave extraction principle, NTC temperature probe design and scalable fuzzy control algorithm are described in detail. Besides, the experimental platform is set up with a temperature chamber, an optical fiber thermometer and a power meter. Experimental results demonstrate that the relationship between the heating time and flour's mass is linear. For different ambient temperature tests, the volume ratios of the fermented dough to unfermented dough of different cases range from 2.2 to 2.62, and the inside of the dough after fermentation is fluffy, with small and dense cavities. Meanwhile, there is no acid taste and skin dryness, and the power consumption of microwave fermentation is less than half of that induced by grill, convection or steam fermentation. The detection error of the NTC temperature probe with microwave shielded is 0.48 °C, and the control error of the closed loop system is less than 0.5 °C. The temperature-rise slope of water is lower than that of ingredient, and the water's temperature is about 1 °C less than that of the ingredient. The soup after microwave elaboration is amber and clear, the ingredients are intact, the water loss is less than 50 g, and the total power consumption is 684 Wh. In short, microwave-based control methods for dough fermentation and nutrient soup elaboration are effective.

A low power microwave room-temperature air plasma jet at atmospheric pressure

An atmospheric pressure low power microwave-induced air plasma source at 2.45 GHz is presented in this Letter. The device was capable of self-igniting air and generating plasma with only 50 W microwave input power and without any extra trigger. Its sustaining power was as low as 10 W, and the gas temperature of plasma tail flame measured by a fiber optic thermometer was about 32 °C. Spectroscopic measurements showed strong OH(A2Σ+→X2Π) bands at 306–310 nm and oxygen atomic lines OI (3p5P → 3s5S) at 777.1 nm and OI (3p3P → 3s3S) at 844.6 nm. NO−γ(A2Σ+→X2Πr) from 200 to 300 nm was also detected in this air plasma jet. This portable plasma apparatus offers potential for air plasma applications in the biomedical fields.

Enhancing process efficiency through improved temperature measurement: the EMPRESS projects

EMPRESS 2 is a European project to enhance the efficiency of high value manufacturing processes by improving temperature measurement and control capability. This project seeks to address four contemporary thermometry challenges in this sector, and new developments from this and its predecessor project, EMPRESS, will be described:• Below 1000°C many industrial processes require reliable surface thermometry e.g. welding, coating, forging and forming. Conventional non-contact surface thermometry techniques e.g. thermal imaging are prone to large errors (tens of degrees) due to reflected thermal radiation and unknown emissivity. Contact thermometry approaches are prone to similarly large errors. Traceable imaging phosphor thermometry is being developed to overcome these difficulties, and is being combined with quantitative thermography to determine emissivity for thermometry over wide fields of view.• Above 1300°C sensor drift is a significant unaddressed issue for casting, forging and heat treatment, causing large errors. There is a need for more stable sensors and standardisation of at least one new thermocouple type to fill the gap from 1300°C to 1800°C. This is being addressed through improved Pt-Rh thermocouples and optimisation of double-walled mineral insulated, metal sheathed thermocouples by mitigating insulation breakdown and drift effects.• Combustion temperature measurement is very challenging and traceability is almost non-existent; for example, thermocouple measurements of flame temperatures can be in error by hundreds of degrees. A ‘standard flame’ that can be transported to users’ sites has been developed, and is being deployed in several high value manufacturing and industrial applications to a) demonstrate the possibility of reducing flame temperature uncertainties by at least an order of magnitude and b) for the first time to demonstrate in-situ traceability to the International Temperature Scale of 1990 (ITS-90).• Many processes are not amenable to any conventional thermometry techniques due to inaccessibility, ionising radiation, electromagnetic interference, and contamination; here methods based on optical fibres are ideal but there are no traceable calibration techniques for such sensors currently available. A suite of different fibre-optic thermometers and calibration techniques is being developed to address this. In some cases (ionising radiation) darkening of the fibre is a problem, and this is being overcome by the development of novel thermometry approaches based on practical ‘hollow core’ fibres.

Heating of Large Endovascular Stents and Stent Grafts in Magnetic Particle Imaging—Influence of Measurement Parameters and Isocenter Distance

PurposeMagnetic particle imaging (MPI) is a tomographic imaging modality with the potential for cardiovascular applications. In this context, the extent to which stents are heated should be estimated from safety perspective. Furthermore, the influence of the measurement parameters and stent distance to the isocenter of the MPI scanner on stent heating were evaluated.Materials and MethodsNine different endovascular stents and stent grafts were tested in polyvinyl-chloride tubes. The stents had diameters from 10 to 31 mm, lengths between 25 and 100 mm and were made from stainless steel, nitinol or cobalt-chromium. The temperature differences were recorded with fiber-optic thermometers. All measurements were performed in a preclinical commercial MPI scanner. The measurement parameters were varied (drive field strengths: 3, 6, 9, 12 mT and selection field gradients: 0, 1.25 and 2.5 T/m). Furthermore, measurements with different distances to the scanner’s isocenter were performed (100 to 0 mm).ResultsAll stents showed heating (maximum 53.1 K, minimum 4.6 K). The stent diameter directly correlated with the temperature increase. The drive field strength influenced the heating of the stents, whereas the selection field gradient had no detectable impact. The heating of the stents decreased with increasing distance from the scanner’s isocenter and thus correlated with the loss of the scanner’s magnetic field.ConclusionStents can cause potentially harmful heating in MPI. In addition to the stent diameter and design, the drive field strength and the distance to the MPI scanner’s isocenter must be kept in mind as influencing parameters.

Assessment of Heating on Titanium Alloy Cerebral Aneurysm Clips during 7T MRI.

Patients with cerebral aneurysms often undergo MR imaging after microsurgical clipping. Ultra-high-field MR imaging at 7T may provide high diagnostic capability in such clinical situations. However, titanium alloy clips have safety issues such as adverse interactions with static magnetic fields and radiofrequency-induced heating during 7T MR imaging. The purpose of this study was to quantitatively assess temperature increases on various types of titanium alloy aneurysm clips during 7T MR imaging. Five types of titanium alloy aneurysm clips were tested, including combinations of short, long, straight, angled, and fenestrated types. Each clip was set in a phantom filled with gelled saline mixed with polyacrylic acid and underwent 7T MR imaging with 3D T1WI with a spoiled gradient recalled acquisition in the steady-state technique. Temperature was chronologically measured at the tips of the clip blade and head, angled part of the clip, and 5 mm from the tip of the clip head using MR imaging-compatible fiber-optic thermometers. Temperature increases at all locations for right-angled and short straight clips were <1°C. Temperature increases at the angled part for the 45° angled clip and the tip of the clip head for the straight fenestrated clip were >1°C. Temperature increases at all locations for the long straight clip were >2°C. Temperature increases on the right-angled and short straight clips remained below the regulatory limit during 7T MR imaging, but temperature increases on the 45° angled, straight fenestrated, and long straight clips exceeded this limit.

A Comparative Review of Thermocouple and Infrared Radiation Temperature Measurement Methods during the Machining of Metals.

During the machining process, substantial thermal loads are generated due to tribological factors and plastic deformation. The increase in temperature during the cutting process can lead to accelerated tool wear, reducing the tool’s lifespan; the degradation of machining accuracy in the form of dimensional inaccuracies; and thermally induced defects affecting the metallurgical properties of the machined component. These effects can lead to a significant increase in operational costs and waste which deviate from the sustainability goals of Industry 4.0. Temperature is an important machining response; however, it is one of the most difficult factors to monitor, especially in high-speed machining applications such as drilling and milling, because of the high rotational speeds of the cutting tool and the aggressive machining environments. In this article, thermocouple and infrared radiation temperature measurement methods used by researchers to monitor temperature during turning, drilling and milling operations are reviewed. The major merits and limitations of each temperature measurement methodology are discussed and evaluated. Thermocouples offer a relatively inexpensive solution; however, they are prone to calibration drifts and their response times are insufficient to capture rapid temperature changes in high-speed operations. Fibre optic infrared thermometers have very fast response times; however, they can be relatively expensive and require a more robust implementation. It was found that no one temperature measurement methodology is ideal for all machining operations. The most suitable temperature measurement method can be selected by individual researchers based upon their experimental requirements using critical criteria, which include the expected temperature range, the sensor sensitivity to noise, responsiveness and cost.

Application and comparison of thermistors and fiber optic temperature sensor reference for ILP measurement of magnetic fluids in double cell magnetic hyperthermia

One of the simplest way to characterize the heating efficiency of magnetic fluids used in hyperthermia treatment is the calorimetric measurement of the specific loss power with direct temperature detection. However, the performance of metallic sensors in an alternating magnetic field is degraded by the self-heating of the probes, and electromagnetic interference can be also significant. In our double cell differential thermometric system these disturbing effects can be compensated. Specific loss power measurements of EMG700 magnetic fluid with negative temperature coefficient thermistors in differential configuration are presented, and control measurements were performed with an optical fiber thermometer in f=470kHz–1020kHz frequency and H=0.13kAm−1–1.19kAm−1 magnetic field strength range. We found that the specific loss power is proportional to the frequency and shows a quadratic dependence on the field strength in the low field strength region, therefore we calculated the intrinsic loss power of the fluid from the measured specific loss power. At this field conditions intrinsic loss power up to 0.53nHm2kg−1 was determined.

In Vivo Magnetic Resonance Thermometry for Brain and Body Temperature Variations in Canines under General Anesthesia

The core body temperature tends to decrease under general anesthesia. Consequently, monitoring the core body temperature during procedures involving general anesthesia is essential to ensure patient safety. In veterinary medicine, rectal temperature is used as an indicator of the core body temperature, owing to the accuracy and convenience of this approach. Some previous studies involving craniotomy reported differences between the brain and core temperatures under general anesthesia. However, noninvasive imaging techniques are required to ascertain this because invasive brain temperature measurements can cause unintended temperature changes by inserting the temperature sensors into the brain or by performing the surgical operations. In this study, we employed in vivo magnetic resonance thermometry to observe the brain temperatures of patients under general anesthesia using the proton resonance frequency shift method. The rectal temperature was also recorded using a fiber optic thermometer during the MR thermometry to compare with the brain temperature changes. When the rectal temperature decreased by 1.4 ± 0.5 °C (mean ± standard deviation), the brain temperature (white matter) decreased by 4.8 ± 0.5 °C. Furthermore, a difference in the temperature reduction of the different types of brain tissue was observed; the reduction in the temperature of white matter exceeded that of gray matter mainly due to the distribution of blood vessels in the gray matter. We also analyzed and interpreted the core temperature changes with the body conditioning scores of subjects to see how the body weight affected the temperature changes.

Experimental study on microwave absorption properties of HMA containing copper slag

In order to enhance the microwave absorption efficiency of asphalt mixture, copper slag (CS) was used to partially replace natural aggregates in the hot mix asphalt (HMA). The effect was analyzed on heating rate, crack healing properties and mechanical performance of asphalt concrete. A fiber optic thermometer was employed to test the internal temperature of the specimen and heating rate at different heights in the mixture cylinder. Also, the surface temperature was recorded by the infrared thermometer. The effects of copper slag content, heating power and aging of the mix were investigated on the healing performance of the mixture through semicircle three-point bending tests. It was concluded that adding CS aggregates can significantly enhance microwave absorption properties and improve the heating rate of asphalt concrete. And, the heating power played an essential role in the heating rate and induced healing efficiency. The aggravation of aging degree had a negative impact on the healing efficiency. The incorporation of copper slag was also helpful for improving the mechanical properties of the mixture. Overall, the use of copper slag as aggregate in asphalt mixture is a good option when adopting microwave-induced heating technology to repair and maintain pavements.

Ultrahigh‐Resolution Optical Fiber Thermometer Based on Microcavity Opto‐Mechanical Oscillation

High‐resolution temperature measurement is nerve‐wracking obstruction for precise characterization of many physical, chemical, and biological processes. To solve this problem, a novel microcavity–optomechanical–oscillation‐based thermometer is proposed. The microcavity serving as a link parametrically couples the mechanical resonator and optical resonator in the same structure and provides a natural and highly sensitive temperature transduction mechanism and ultrahigh‐resolution optical demodulation. The mathematical model of geometrical parameters, mechanics, and material properties for temperature response mechanism is established and verified experimentally. The proposed thermometer has a thermal sensitivity of 11 300 Hz °C−1 and an ultrahigh‐temperature resolution of 1 × 10−4 °C, to the best of one's knowledge, which is the highest temperature resolution with a silica cavity.

Electromagnetic immune phosphor-tipped fibre-optic thermometers

Calibration traceability can be broken where there are significant, unquantified uncertainties. Thermometry in harsh environments using electrical sensors, such as thermocouples or resistance thermometers, can be unpredictably affected by electro-magnetic sources. For this application, phosphor based temperature sensors with fibre-optic connection have been made following two different approaches—phosphor decay time changes and phosphor emission spectral changes—and tested by bombardment with high energy electrons and by measurements in large magnetic fields. Both sets of tests showed good immunity to exposure, and with magnetic field tests significantly better than a thermocouple. Phosphor thermometry therefore has potential to retain traceability in situations where conventional sensors might fail.

Dosimetry of Microelectrodes Array Chips for Electrophysiological Studies Under Simultaneous Radio Frequency Exposures

Studying the response of neuronal networks to radio frequency (RF) signals requires the use of a specific device capable of accessing and simultaneously recording neuronal activity during electromagnetic fields (EMF) exposure. In this study, a microelectrode array (MEA) that records the spontaneous activity of neurons is coupled to an open transverse electromagnetic (TEM) cell that propagates EMF. We characterize this system both numerically and experimentally at 1.8 GHz. Two MEA versions were compared, for the first time, to determine the impact of their design dissimilarities on the response to EMF. Macroscopic and microscopic measurements using, respectively, a fiber-optic probe and a temperature-dependent fluorescent dye (Rhodamine-B) were carried out. Results indicate that one MEA shows more stability toward the changes of the surrounding environment compared to the other MEA. Using a fiber-optic thermometer, the measured specific absorption rate (SAR) probe value in the center of the more stable MEA was 5.5 ± 2.3 W/kg. Using a Rhod-B microdosimetry technique, the measured SAR value at the level of the MEA electrodes was 7.0 ± 1.04 W/kg. SAR values are normalized per 1 W incident power. Due to the additional metallic planes and a smaller chip aperture, this new recording chip is steadier in terms of SAR and temperature stability allowing high exposure homogeneity as required during biological experiments. A typical neuronal activity recording under EMF exposure is reported.

Electromagnetic immune phosphor-tipped fibre-optic thermometers

Abstract Calibration traceability can be broken where there are significant, unquantified uncertainties. Thermometry in harsh environments using electrical sensors, such as thermocouples or resistance thermometers, can be unpredictably affected by electro-magnetic sources. For this application, phosphor based temperature sensors with fibre-optic connection have been made following two different approaches – phosphor decay time changes and phosphor emission spectral changes – and tested by bombardment with high energy electrons and by measurements in large magnetic fields. Both sets of tests showed good immunity to exposure, and with magnetic field tests significantly better than a thermocouple. Phosphor thermometry therefore has potential to retain traceability in situations where conventional sensors might fail.

Optical fiber amplifier and thermometer assisted point-of-care biosensor for detection of cancerous exosomes

Developing a simple, reliable and sensitive point-of-care testing (POCT) biosensor for cancerous exosomes detection is crucial to early cancer diagnosis and prognosis. Herein, a colorimetric and photothermal POCT biosensor was demonstrated based on rolling circle amplification (RCA) mediated 2,2'-azinobis-(3-ethylbenzthiazoline-6-sulphonate) (ABTS)‑H2O2 system for sensitive detection of cancerous exosomes. In the presence of target exosomes, RCA could be triggered and produced multiple units that hybridized to horseradish peroxidase (HRP) modified DNA probes. Colorless ABTS would be converted by HRP into the oxidized form with strong near-infrared absorbance, enabling colorimetric and photothermal detection of exosomes. Then, colorimetric and photothermal responses were recorded by optical fiber amplifier and forehead thermometer, respectively, enabling hand-held detection. Moreover, EpCAM aptamer was used as biorecognition element for exosomes secreted by MCF-7 breast cancer cells so that the point-of-care biosensor exhibited excellent specificity. Furthermore, the point-of-care biosensor could effectively detect the cancerous exosomes in 30% fetal bovine serum with lots of normal exosomes. Moreover, the biosensor could avoid the influence of the external environment, including surrounding light and temperature. These results suggest that the proposed strategy has great potential as a powerful tool for POCT application of exosomes in future diagnosis.

ZnO–SrAl2O4:Eu Nanocomposite-Based Optical Sensors for Luminescence Thermometry

Conventional thermometers fail to operate in a variety of medical procedures due to the harsh and sensitive environments required for such applications, and therefore, the development of optical fiber thermometers has gained significant attention. In this study, a ZnO–SrAl2O4:Eu (ZnO–SAO:Eu) nanocomposite has been synthesized by using a CO2 laser, which showed enhanced optical properties and a dynamic range in comparison with the crystalline ones. XRD, EDAX, SEM, and PL spectroscopy investigated the crystalline and optical properties of precursors, and the final nanostructure, and the findings were in agreement with references. Further analysis of the PL spectra in a 0–100 °C range suggests that the optical properties of the ZnO–SAO:Eu nanocomposite show a linear behavior toward temperature alterations. Considering this inter-relation and measuring the decay time for various frequencies helped us calibrate the temperature based on phase angle shift alterations. The curve obtained at 30 Hz frequency exhibits the highest linearity and accuracy (0.33%) due to its relatively high phase shift (60 °C) in the studied temperature range. The fabricated sensor exhibited great sensitivity and repeatability while maintaining an unprecedented structure. Finally, the thermometer’s applicability for future industries was tested by measuring the interior temperature of a dead muscle tissue as it was being heated by a diode laser and it was accompanied by remarkable results. This achievement could make this device a promising addition to the drug delivery science and industry as it could aid the study and optimization of medications that increase the targeted tissues temperature and therefore can be employed in treating tumors that are formed in organic tissues.

Design, construction and traceable calibration of a phosphor-based fibre-optic thermometer from 0 °C to 650 °C

Measurement traceability, in which there is a documented chain of calibration links from a measurement back to a primary realisation of a unit, is vital for achieving the smallest uncertainty in metrology. A sensor that can provide a traceable link in harsh environments may be advantageous even if its uncertainty is larger than that of typical calibrated devices. A phosphor-based thermometer that has optical rather than electrical connections has been built and then calibrated in terms of the International Temperature Scale of 1990. Its standard uncertainty ranges from 0.5 °C at 0 °C to 2 °C at 650 °C. While this uncertainty cannot match what is possible with thermocouples or resistance thermometers, the optical basis of the sensor means it can be used in situations where electrical connections are precluded.

A Simple and High‐Accuracy PID‐Based Temperature Control System for Magnetic Hyperthermia Using Fiber Optic Thermometer

Magnetic hyperthermia is very promising cancer therapy in which heating temperature is expected to be a key determinant for its success. Herein, we present a simple, real‐time, and high‐accuracy proportional‐integral‐derivative‐based temperature control system for magnetic hyperthermia using widely‐used induction heater and fiber optic thermometer. Our in vitro result shows that the temperature of clinically‐approved Resovist® (0.5 ml) was accurately controlled with very small overshoot (e.g., 45.0 ± 0.07 °C and 55.0 ± 0.11°C for low‐ and high‐temperature magnetic hyperthermia). Our system has the potential to be used for magnetic hyperthermia either alone or together with other cancer treatment modalities for basic and clinical studies. © 2021 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.