Thermometry Method Research Articles

Development of a murine laser interstitial thermotherapy system.

The objective of this study was to develop a murine system for the delivery of laser interstitial thermotherapy (LITT) with probe-based thermometry as a model for human glioblastoma treatment to investigate thermal diffusion in heterogeneous brain tissue. First, the tissue heating properties were characterized using a diode-pumped solid-state near-infrared laser in a homogeneous tissue model. The laser was adapted for use with a repurposed stereotactic surgery frame utilizing a micro laser probe and Hamilton syringe. The authors designed and manufactured a stereotactic frame attachment to work as a temperature probe stabilizer. Application of this novel design was used as a precise method for real-time thermometry at known distances from the thermal ablative center mass during murine LITT studies. Temperature measurements were achieved during LITT that verified the direct thermometry capability of the system without the need for MR-based thermal monitoring. Application of multiple stereotactic design iterations led to an accurately reproducible surgical laser ablation procedure. Histological staining confirmed precise thermal ablation and controllable lesion size based on time and temperature control. Treatment of a syngeneic intracranial glioma model highly resistant to conventional therapy resulted in a modest survival benefit. The authors have successfully developed a murine model system of LITT with direct in situ thermometry for investigation into the effects of thermal ablation and combinatorial treatments in murine brain tumor models.

Microwave-hydrothermal synthesis, near ultraviolet/infrared-excited green fluorescence and ratiometric thermometry of Er3+-activated iodate phosphors

Fluorescence intensity ratio (FIR) technique has been a promising non-contact thermometry method owing to the characteristics of rapid response and exceptional resolution. In this study, a new iodate phosphor NaYI4O12:Er3+ (NYIO:Er3+) is synthesized via a microwave-assisted hydrothermal method. It exhibits bright green emission under 380 and 980 nm excitations. The power-dependent upconversion and Er3+ content-dependent downshifting performances are investigated. Excited by 380 nm, the temperature-dependent FIR originating from thermally coupled levels of Er3+ are discussed in detail. The resulting material displays outstanding temperature sensing properties across the temperature range of 298–523 K. The absolute and relative sensitivities can reach the maximum values of 0.51 × 10−2 K−1 and 1.3 % K−1, separately. Meanwhile, the reliability and repeatability of the temperature sensing characteristics are verified. The result demonstrates that the Er3+-activated iodate phosphor NaYI4O12:Er3+ is a promising candidate in non-contact optical thermometry domain.

Experimental study on surface temperature and emissivity of rotating turbine blades of a micro turbojet engine

The temperature of the rotating turbine blades of a turbojet engine must be known to assess the combustion state and improve turbine blade quality. Obtaining online temperature measurements of high-speed rotating turbine blades in high-temperature gas flow remains challenging. A multispectral radiation thermometry method without emissivity assumption is proposed to measure the temperature of high-speed rotating turbine blades of a micro turbojet engine. The relative radiative intensity is calculated by accounting for smooth changes in the wavelength using the moving narrowband method to determine the influence of emissivity on multispectral radiation thermometry results. The method’s performance in measuring the surface temperature of high-speed rotating objects is tested. The wavelength range of 970 nm to 1700 nm is selected because the radiation from gases is weaker in comparison to the radiation emitted by solid surfaces within this band. The spectral radiation of the turbine blade surface is measured at three rotational speeds: 38,000 r/min, 48,000 r/min, and 58,000 r/min. The results show that, unlike thermocouples that measure the temperature of the hot gas flow near the blade, multispectral radiation thermometry provides the average surface temperature with high consistency (with a deviation smaller than 50 K). Multispectral radiation thermometry can be applied to measure the surface temperature and emissivity of high-speed rotating objects, such as the blades of turbojet engines.

Response to “Comment on ‘Fast data processing method for multispectral radiation thermometry based on Euclidean distance optimization’”

Response to “Comment on ‘Fast data processing method for multispectral radiation thermometry based on Euclidean distance optimization’”

Real-time non-invasive control of ultrasound hyperthermia using high-frequency ultrasonic backscattered energy in ex vivo tissue and in vivo animal studies

Objective.A reliable, calibrated, non-invasive thermometry method is essential for thermal therapies to monitor and control the treatment. Ultrasound (US) is an effective thermometry modality due to its relatively high sensitivity to temperature changes, and fast data acquisition and processing capabilities.Approach.In this work, the change in backscattered energy (CBE) was used to control the tissue temperature non-invasively using a real-time proportional-integral-derivative (PID) controller. A clinical high-frequency US scanner was used to acquire radio-frequency echo data fromex vivoporcine tissue samples andin vivomice hind leg tissue while the tissue was treated with mild hyperthermia by a focused US applicator. The PID controller maintained the focal temperature at approximately 40 °C for about 4 min.Main results.The results show that the US thermometry based on CBE estimated by a high-frequency US scanner can produce 2D temperature maps of a localized heating region and to estimate the focal temperature during mild hyperthermia treatments. The CBE estimated temperature varied by an average of ±0.85 °C and ±0.97 °C, compared to a calibrated thermocouple, inex vivoandin vivostudies, respectively. The mean absolute deviations of CBE thermometry during the controlled hyperthermia treatment were ±0.45 °C and ±0.54 °C inex vivoandin vivo,respectively.Significance.It is concluded that non-invasive US thermometry via backscattered energies at high frequencies can be used for real-time monitoring and control of hyperthermia treatments with acceptable accuracy. This provides a foundation for an US mediated drug delivery system.

Comment on "Fast data processing method for multispectral radiation thermometry based on Euclidean distance optimization"

Comment on "Fast data processing method for multispectral radiation thermometry based on Euclidean distance optimization"

Measurement and advanced data post-processing of proton resonance frequency shift in 7 T MRI to obtain local temperature in a tissue-mimicking phantom

Abstract The radio-frequency (RF) transmit power deposition in tissue during magnetic resonance imaging (MRI) at ultra-high fields, i.e. B 0 ≥ 7 T, is a major challenge for pulse sequences requesting large flip angles. The absorbed RF energy can pose safety risk to patients as it is rising temperature in the tissue. The temperature can be accessed using MRI itself via the proton-resonance frequency (PRF) shift technique, which at low B 0 has been shown a valid MR thermometry method. In this paper, we explore the applicability of the PRF method to the assessment of local temperature in 7 T MRI procedures. To this end, we built a phantom filled with a material presenting electrical conductivity and permittivity close to muscle tissue. Tubes filled with oil were placed nearby the phantom to observe the time dependent B 0 drift. MRI phase images were acquired by gradient-echo (GRE) sequences at time points between spin-echo sequences with large flip angle allowing for a continuous assessment of the temperature during a 114 min RF-heating experiment. All acquired phase images were post-processed with attention to the time dependent instability of B 0, and, in addition, to potential spatial and temporal phase discontinuities, known as wraps. In this paper, we present a strategy to analyze and to unfold these phase wraps for large measurement fields and long acquisition times. It is shown that the PRF shift method is beneficial for the assessment of temperature at 7 T MRI. The temperature maps for axial and coronal planes display a temperature increase of approximately 3.5 °C during the time of the RF-heating experiment. Overall it is shown that B 0-drift correction and, importantly, the spatio-temporal unwrapping are an indispensable part of post-processing.

Experimental Study of a Temperature Field in a Shut-in Well in Relation to Determining Behind-the-Casing Flow Using Active Thermometry

Abstract —This paper presents results of experimental studies of a thermal field in the barrel of a shut-in (no fluid movement in the casing) well in relation to determining a behind-the-casing upward flow using the method of active thermometry. The studies are carried out using the physical model of a well that is a vertically located steel pipe with a system of externally attached copper tubes simulating a behind-the-casing flow. The pipe contains a local heating section, above which a temperature probe is located to record thermal disturbance from the heating section. The effect of free convection in a fluid on the temperature field in the pipe during and after heating is described. It is revealed that there are high-frequency temperature oscillations on sensors that record the temperature of the inner surface (wall) of the pipe and fluid above the heating area, whose value reaches higher than 2 °C and decreases when the distance to the heating region becomes longer. There is an empirical relationship that relates the time of arrival of the temperature disturbance front associated with free convection and the distance to the pipe heating region. Azimuthal temperature distribution curves on the inner wall of the pipe above the heating section are constructed in the absence and presence of a behind-the-casing flow. Qualitative criteria have been obtained indicating the presence of an azimuthally localized behind-the-casing flow (sector flow) of fluid based on the azimuthal temperature distribution analysis.

Diagnostics of the technical condition of wells drilled through freshwater horizons using active thermometry

Relevance. Recently, ESG (Environment, Social, Governance) principles have been given an important role in the agenda of oil and gas companies – this is an actively developing global trend in the modern business environment. One of its key aspects is a responsible attitude to the environment, increasing the priority of solving environmental problems arising from the extraction of hydrocarbons. A significant environmental problem is, in particular, pollution of freshwater horizons during oil production due to their poor-quality insulation during well cementing. At the same time, in the space of the well behind the casing, there is a flow of borehole fluid to freshwater horizons, which has a negative impact on the environmental situation in this region. In this regard, monitoring the technical condition of wells crossing freshwater horizons is an important and urgent task. Object. An operational well drilled through freshwater horizon, in which geophysical studies are carried out by the method of active thermometry – local heating of the casing section is carried out and the dynamics of the temperature field in it is studied. Aim. To identify qualitative patterns and obtain quantitative estimates of the effect of the fluid flow in the space behind the casing (column space) on the temperature field in the casing. Methods. Numerical mathematical modeling of thermal and hydrodynamic processes in a well using the software package Ansys Fluent (ANSYS Academic Research CFD license, agreement with Bashkir State University dated 06/15/2020). Results. The authors have studied the influence of a plane-parallel horizontal fluid flow of the freshwater horizon on the azimuthal temperature distribution of the casing string during induction heating. It is shown that in the case of leakiness of the cement ring in the interval of the freshwater horizon, an inhomogeneity of the azimuthal temperature distribution of the column is observed, reaching a value of few more K. The authors carried out the simulation of induction heating in the well with liquid column flow to the interval of the freshwater horizon. It is shown that the sign indicating the overflow is the occurrence of a temperature disturbance area vertically above the induction heating interval with a length of more than 1 m. In general, the results of the performed studies show the informativeness of the active thermometry method in relation to the diagnosis of the technical condition of wells drilled through freshwater horizons.

Estimation of Infrared Stellar Flux Based on Star Catalogs with I-GWO for Stellar Calibration

As on-orbit space cameras evolve toward larger apertures, wider fields of view, and deeper cryogenic environments, achieving absolute radiometric calibration using an all-optical path blackbody reference source in orbit becomes increasingly challenging. Consequently, stars have emerged as a novel in-orbit standard source. However, due to differences in camera bands, directly obtaining the stellar radiance flux corresponding to specific camera bands is not feasible. In order to address this challenge, we propose a method for estimating radiance flux based on the MSX star catalog, which integrates a dual-band thermometry method with an improved grey wolf optimization (I-GWO) algorithm. In an experiment, we analyzed 351 stars with temperatures ranging from 4000 to 7000 K. The results indicate that our method achieved a temperature estimation accuracy of less than 10% for 83.5% of the stars, with an average estimation error of 5.82%. Compared with previous methods based on star catalogs, our approach significantly enhanced the estimation accuracy by 75.4%, improved algorithm stability by 91.3%, and reduced the computation time to only 3% of that required by other methods. Moreover, the on-orbit star calibration error using our stellar radiance flux estimation method remained within 5%. This study effectively leveraged the extensive data available in star catalogs, providing substantial support for the development of an infrared star calibration network, which holds significant value for the in-orbit calibration of large-aperture cameras. Future research will explore the potential applicability of this method across different spectral bands.

Development of a micro-infrared thermometry method for surface temperature distribution and variation of millimeter particle during high-temperature reaction

Temperature strongly affects the conversion efficiency, local reactivity, and particle stabilization of the reactions, particularly at high temperature. This study integrated infrared thermography with a high-temperature hot stage reactor to develop a methodology of continuous temperature measurement for a single particle reaction at high temperatures. The external optical transmission transmittance and temperature field core were corrected, and the relationship between the measured temperature (Tr) and true temperature (T0) was obtained by adjusting the sample emissivity. Sample temperature with known emissivity at elevated temperature was measured with 1% deviation. The instantaneous temperature measurement for the gasification process was carried out and the overall emissivities of coal particles were corrected. Temperature distribution and variation on the coal particle surface during the gasification process were further obtained and consistent with the previous research results. The proposed online temperature measurement method provides a new approach for gaining insights into particle reaction states.

Geochemical Thermometry of Ore-Bearing Gabbronorites from the Apophisis of the Yoko-Dovyren Massif: Composition, Amount of Olivine, and Conditions of Sulphide Saturation in the Parental Magma

The temperature and compositional parameters of the parental magma of the ore-bearing apophysis DV10 from the Yoko-Dovyren massif are estimated based on the results of thermodynamic modeling the equilibrium crystallization of melts of 24 samples, following the method of geochemical thermometry. Thermometric calculations were carried out using the COMAGMAT-5.3 program with a step of 0.5 mol. % to a maximum degree of crystallization 75–85% under oxygen fugacity controlled by the QFM buffer. The model order of mineral crystallization corresponds to the sequence: olivine (Ol) + + Cr-Al spinel (Spl) → plagioclase (Pl) → high-Ca pyroxene (Cpx) → orthopyroxene (Opx). Silicate-sulfide immiscibility was modeled to occur mostlybefore the onset of plagioclase crystallization, being consistent with sulfide saturation of the parental magma. The results of calculations demonstrate the convergence and intersection of the model liquid lines of descent at temperatures of about 1185°C. When applied to the average composition of the DV10 apophysis, this temperature indicates the existence of a suspension of the original crystals (52.1 wt. % cumulus olivine (Fo83.6), 2.3 wt. % plagioclase (An79.7), 0.24% clinopyroxene (Mg# 88.8), 1 wt. % aluminochromite (Cr# 0.62)) and about 0.2% sulfide liquid in a moderately magnesian melt (53.6 wt. % SiO2, 7.4 wt. % MgO). At that the solubility of sulfide sulfur (SCSS) was estimated to be 0.083 wt. %. This heterogeneous system had a viscosity of 4.71 log. units (Pa · s) and an integral density of 2929 kg/m3. Such rheological properties do not contradict the possibility of the migration and emplacement of the protocumulus mush from the main Dovyren chamber. However, a more probable scenario includes a localized accumulation of olivine in the trough-like part of the DV10 subchamber, which preceded or occurred in parallel to the accumulation of segregated sulfides.

A novel optical thermometry strategy: Based on the combined effects of red-shift charge transfer band and thermal coupling

The non-contact temperature measurement method based on the fluorescence intensity ratio of thermally coupled energy levels has emerged as a focal point of research in recent years due to its characteristics of short response time, suitability for extreme environments, and high sensitivity. The enhancement of relative sensitivity (Sr) is a key objective in refining ratio-metric optical thermometry. However, the Sr is limited by the thermometry strategies. Regarding excitation and monitoring methods, ratio-metric temperature measurement strategies typically adopt two distinct approaches: single-excitation dual-emission (S-D), and dual-excitation single-emission (D-S). In this study, we developed a dual-excitation dual-emission (D-D) thermometry strategy that theoretically and experimentally demonstrates higher Sr and reduced temperature uncertainty (δT). This advancement was achieved by analyzing thermal coupling energy levels (TCELs) and the red-shift charge transfer band (CTB) properties. YVO4:Er3+ was selected for experimental validation due to its pronounced thermal coupling and red-shift CTB effects. The experimental results show that the Sr(D-D) equal to the sum of Sr(S-D) and Sr(D-S), and 1/δT(D-D) equal to the sum of 1/δT(S-D) and 1/δT(D-S), which well verifies the theoretical expectations. Thus, the D-D strategy emerges as a novel and effective method for ratio-metric thermometry, promising enhanced precision in temperature measurements.

Radiometric thermometry of point targets based on dual-band infrared imaging

The observation area of a point target, which is usually inaccessible, is a necessary condition when utilizing the conventional single-band infrared radiometric thermometry method, as the image gray level inevitably undergoes dispersion. Otherwise, significant errors will be generated, seriously affecting the applicability of infrared radiometric thermometry for distant point targets in the external field. To address the above issue, the infrared radiometric thermometry method for point targets has been researched. A point target radiometric thermometry method based on dual-band infrared imaging is proposed, which can effectively measure radiance and temperature when the area of the point target is unknown. The experimental results show that, compared with conventional single-band algorithms, the proposed dual-band point target thermometry algorithm has a maximum error of 11.18°C under the condition of unknown area, which can meet the needs of infrared radiometric thermometry of point targets at long distances in the external field.

Multispectral Thermometry Method Based on Optimisation Ideas.

Multispectral thermometry is based on the law of blackbody radiation and is widely used in engineering practice today. Temperature values can be inferred from radiation intensity and multiple sets of wavelengths. Multispectral thermometry eliminates the requirements for single-spectral and spectral similarity, which are associated with two-colour thermometry. In the process of multispectral temperature inversion, the solution of spectral emissivity and multispectral data processing can be seen as the keys to accurate thermometry. At present, spectral emissivity is most commonly estimated using assumption models. When an assumption model closely matches an actual situation, the inversion of the temperature and the accuracy of spectral emissivity are both very high; however, when the two are not closely matched, the inversion result is very different from the actual situation. Assumption models of spectral emissivity exhibit drawbacks when used for thermometry of a complex material, or any material whose properties dynamically change during a combustion process. To address the above problems, in the present study, we developed a multispectral thermometry method based on optimisation ideas. This method involves analysing connections between measured temperatures of each channel in a multispectral temperature inversion process; it also makes use of correlations between multispectral signals at different temperatures. In short, we established a multivariate temperature difference correlation function based on the principles of multispectral radiometric thermometry, using information correlations between data for each channel in a temperature inversion process. We then established a high-precision thermometry model by optimising the correlation function and correcting any measurement errors. This method simplifies the modelling process so that it becomes an optimisation problem of the temperature difference function. This also removes the need to assume the relationships between spectral emissivity and other physical quantities, simplifying the process of multispectral thermometry. Finally, this involves correction of the spectral data so that any impact of measurement error on the thermometry is reduced. In order to verify the feasibility and reliability of the method, a simple eight-channel multispectral thermometry device was used for experimental validation, in which the temperature emitted from a blackbody furnace was identified as the standard value. In addition, spectral data from the 468-603 nm band were calibrated within a temperature range of 1923.15-2273.15 K, resulting in multispectral thermometry based on optimisation principles with an error rate of around 0.3% and a temperature calculation time of less than 3 s. The achieved level of inversion accuracy was better than that obtained using either a secondary measurement method (SMM) or a neural network method, and the calculation speed achieved was considerably faster than that obtained using the SMM method.

Unraveling High Thermal Conductivity with In-Plane Anisotropy Observed in Suspended SiP2.

The anisotropic thermal transport properties of low-symmetry two-dimensional materials play an important role in understanding heat dissipation and optimizing thermal management in integrated devices. Examples of efficient energy dissipation and enhanced power sustainability have been demonstrated in nanodevices based on materials with anisotropic thermal transport properties. However, the exploration of materials with high thermal conductivity and strong in-plane anisotropy remains challenging. Herein, we demonstrate the observation of anisotropic in-plane thermal conductivities of few-layer SiP2 based on the micro-Raman thermometry method. For suspended SiP2 nanoflake, the thermal conductivity parallel to P-P chain direction (κ∥b) can reach 131 W m-1 K-1 and perpendicular to P-P chain direction (κ⊥b) is 89 W m-1 K-1 at room temperature, resulting in a significant anisotropic ratio (κ∥b/κ⊥b) of 1.47. Note that such a large anisotropic ratio mainly results from the higher phonon group velocity along the P-P chain direction. We also found that the thermal conductivity can be effectively modulated by increasing the SiP2 thickness, reaching a value as high as 202 W m-1 K-1 (120 W m-1 K-1) for κ∥b (κ⊥b) at 111 nm thickness, which is the highest among layered anisotropic phosphide materials. Notably, the anisotropic ratio always remains at a high level between 1.47 and 1.68, regardless of the variation of SiP2 thickness. Our observation provides a new platform to verify the fundamental theory of thermal transport and a crucial guidance for designing efficient thermal management schemes of anisotropic electronic devices.

Absolute temperature estimation using thermal strain imaging

The objective of this study is to present a new thermometry method, based on thermal strain imaging, to estimate the absolute temperature using ultrasound. Unlike the conventional method presented in previous studies, this method does not require knowledge of the initial temperature or of speed of sound. The method was tested in simulations and experimentally. Simulations were performed at different temperatures (from 20 to 90 °C), using k-wave. Then, experimental measurements were performed in Zerdine phantom samples at different temperature (from 23 to 88 °C). A linear array transducer, with a 12-angle plane wave imaging sequence, was used to acquire the thermal strain images and to derive the temperature at the focus. To control the temperature during the measurements, a thermocouple was used. Both simulations and experiments showed a good estimation of the temperatures. The new ultrasound-based method is a promising technique to estimate and monitor temperature during thermal ablation.

Multi-spectral radiation thermometry based on the reconstructed spectral emissivity model

With the aim of solving the problem of detecting the true temperature of objects using multi-spectral radiation thermometry, this paper proposes a multi-spectral radiation thermometry method based on the reconstructed spectral emissivity model. Compared with traditional hypothetical spectral emissivity models, this model is a reconstruction emissivity model based on actual measured brightness and known wavelength quantities, which can improve the characterization of the real emissivity state of the measured object and not be affected by any hypothetical conditions or artificial preset parameters. In order to verify the effectiveness of the proposed method for detecting the temperature of real problems, a total of eight typical spectral emissivity models, spectral data of Si3N4 ceramics and ZrO2 ceramics, and measurement data of rocket motor casings are selected for experiments. The experimental results indicate that the true temperature calculated by the proposed method has a relative error of less than 1 %, and the calculation time is kept at the millisecond level, which meets the real-time multi-spectral temperature measurement requirements.

Laser cooling ytterbium doped silica by 67 K from ambient temperature.

Laser cooling of a 5 cm long, 1 mm diameter ytterbium doped (6.56×1025 ions/m3) silica rod by 67 K from room temperature was achieved. For the pump source, a 100 W level ytterbium fiber amplifier was constructed along with a 1032 nm fiber Bragg grating seed laser. Experiments were done in vacuum and monitored with the non-contact differential luminescence thermometry method. Direct measurements of the absorption spectrum as a function of temperature were made, to avoid any possible ambiguities from site-selectivity and deviations from McCumber theory at low temperature. This allowed direct computation of the cooling efficiency versus temperature at the pump wavelength, permitting an estimated heat lift of 1.42 W/m as the sample cooled from ambient temperature to an absolute temperature of 229 K.

Fast data processing method for multispectral radiation thermometry based on Euclidean distance optimization.

This study presents a fast and accurate data processing method for multispectral radiation thermometry that can accurately measure the true temperature of steel materials without requiring a priori emissivity model. The method generates a temperature matrix by inputting emissivity values at different wavelengths and selects a reference vector from the matrix. Then, it rearranges the temperature matrices at other wavelengths and calculates the Euclidean distance between each column element of the rearranged matrix and the reference vector. The method uses an unconstrained optimization technique to minimize the Euclidean distance and obtain the true temperature and emissivity of the object simultaneously. We evaluate the performance of the method by simulation and experiment in the response band of 1.4 ∼ 2.5 µm and temperature range of 873 ∼ 1173 K. The simulation results indicate that the relative error of the inverted temperature is within 0.229%, and the average computation time is less than 112.301 ms. The experimental results show that the maximum temperature error during the measurement process is 0.813%. Our method provides a feasible and efficient solution for real-time temperature measurement of steel materials.