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Microscopic lattice vibration images of the E2(high) mode (E2H) and another mode of A1(LO) (A1L) or the higher energy branch of LO‐phonon−plasmon coupling mode (LOPC+) in a Ga0.95In0.05N film on a GaN template are obtained by Raman scattering spectroscopy using a 325 nm laser. The increase in temperature by increasing the laser power is obtained from the decrease in the energy of E2H and the theoretical formula comprising two terms based on the mode energy variation of the bulk material and the thermal strain effect. Using the obtained temperature and the energy shift of the LOPC+, the mapping images of the temperature and electron density in the x–y plane are simultaneously obtained. This image provides the spatial variation of photoluminescence (PL) emission efficiency, given as PL intensity per electron. This method enables the quantitative discussion on photo‐emission efficiency even in the regions of low or high carrier density affected by carrier transport. In the investigated area, a region with a lower PL efficiency is found despite a higher electron density and lower temperature increase than the surrounding region. This imaging analysis is feasible in integrating the carrier and thermal energy transports and recombination processes in carrier dynamics study. [ABSTRACT FROM AUTHOR]

Cellular temperature affects every biochemical reaction, underscoring its critical role in cellular functions. In neurons, temperature not only modulates neurotransmission but is also a key determinant of neurodegenerative diseases. Considering that the brain consumes a disproportionately high amount of energy relative to its weight, neural circuits likely generate a lot of heat, which can increase cytosolic temperature. However, the changes in temperature within neurons and the mechanisms of heat generation during neural excitation remain unclear. In this study, we achieved simultaneous imaging of Ca2+ and temperature using the genetically encoded indicators, B-GECO and B-gTEMP. We then compared the spatiotemporal distributions of Ca2+ responses and temperature. Following neural excitation induced by veratridine, an activator of the voltage-gated Na+ channel, we observed an approximately 2 °C increase in cytosolic temperature occurring 30 s after the Ca2+ response. The temperature elevation was observed in the non-nuclear region, while Ca2+ increased throughout the cell body. Moreover, this temperature increase was suppressed under Ca2+-free conditions and by inhibitors of ATP synthesis. These results indicate that Ca2+-induced upregulation of energy metabolism serves as the heat source during neural excitation. • Simultaneous imaging of Ca2+ and temperature in neurons was achieved. • Veratridine-induced excitation of neurons heated the cytosol by approximately 2 °C. • The temperature increase was delayed by 30 s after the Ca2+ response. • Inhibition of ATP synthesis suppressed the temperature rise during neural excitation. [ABSTRACT FROM AUTHOR]

Tunable diode laser absorption spectroscopy (TDLAS) tomography is a well-established combustion diagnostic technique for imaging 2-D cross-sectional distributions of critical flow-field parameters. As two key metrics in TDLAS tomography, reconstruction accuracy and efficiency are generally traded off to satisfy either the requirement of high-fidelity image retrieval or rapid tomographic data inversion. In this article, a novel quality-hierarchical temperature imaging network for TDLAS tomography is developed based on stacked long short-term memory (LSTM). From limited line-of-sight TDLAS measurements, this network outputs two reconstructed temperature images, i.e., a coarse-quality image and a fine-quality image, with different numbers of network layers and consequently different computational costs. The coarse-quality image provides more timely temperature reconstruction, which can satisfy real-time dynamic monitoring of turbulence–chemistry interactions with a temporal resolution of tens of kilo frames per second. In contrast, the fine-quality image, which can be stored and utilized for offline analysis and diagnosis, further details the temperature reconstruction with more accurate features. Both numerical stimulation and lab-scale experiment validated the accuracy-efficiency tradeoff achieved by the proposed quality-hierarchical temperature imaging network. [ABSTRACT FROM AUTHOR]

Fluorescent hydrophilic polymeric nanoparticle for ratiometric real-time sensing of the temperature of virus-infected cell. [Display omitted] Temperature is a key indicator of infection and disease, however, it is difficult to measure at a cellular level. Nanoparticles are applied to measure the cellular temperature, and enhancement of the stability and reliability of the signal and higher biocompatibility are demanded. We have developed fluorescent polymeric nanoparticles loaded with temperature-sensitive units (as rhodamine B) and internal reference units (as coumarin) for imaging and ratiometric sensing of the cellular temperature in the physiological range. The fluorescence signal of the nanoparticles was stable in the bio-environment and the ratiometric sensing strategy could overcome the concentration effect of nanoparticles. The nanoparticles were endocytosed by cells and partially presented in mitochondria. The fluorescence intensity ratio of rhodamine B and coumarin using nanoparticles showed good linear correlations in buffer solutions, cell suspensions, and imaging of living cells. Using the fluorescent polymeric nanoparticles, the change of temperature of cells during influenza virus infection could be individually monitored. [ABSTRACT FROM AUTHOR]

As an in situ combustion diagnostic tool, tunable diode laser absorption spectroscopy (TDLAS) tomography has been widely used for imaging 2-D temperature distributions in reactive flows. Compared with the computational tomographic algorithms, convolutional neural networks (CNNs) have been proved to be more robust and accurate for image reconstruction, particularly in the case of limited access of laser beams in the region of interest (RoI). In practice, the flame in the RoI that requires to be reconstructed with the good spatial resolution is commonly surrounded by low-temperature background. Although the background is not of high interest, spectroscopic absorption still exists due to heat dissipation and gas convection. Therefore, we propose a pseudoinversed CNN (PI-CNN) for hierarchical temperature imaging that: 1) uses efficiently the training and learning resources for temperature imaging in the RoI with good spatial resolution and 2) reconstructs the less spatially resolved background temperature by adequately addressing the integrity of the spectroscopic absorption model. In comparison with the traditional CNN, the newly introduced pseudoinversion of the RoI sensitivity matrix is more penetrating for revealing the inherent correlation between the projection data and the RoI to be reconstructed, thus prioritizing the temperature imaging in the RoI with high accuracy and high computational efficiency. In this article, the proposed algorithm was validated by both numerical simulation and lab-scale experiment, indicating good agreement between the phantoms and the high-fidelity reconstructions. [ABSTRACT FROM AUTHOR]

Tunable diode laser absorption spectroscopy (TDLAS) tomography has been widely used for in situ combustion diagnostics, yielding images of both species concentration and temperature. The temperature image is generally obtained from the reconstructed absorbance distributions for two spectral transitions, i.e., two-line thermometry. However, the inherently ill-posed nature of tomographic data inversion leads to noise in each of the reconstructed absorbance distributions. These noise effects propagate into the absorbance ratio and generate artifacts in the retrieved temperature image. To address this problem, we have developed a novel algorithm, which we call Relative Entropy Tomographic RecOnstruction (RETRO), for TDLAS tomography. A relative entropy regularization is introduced for high-fidelity temperature image retrieval from jointly reconstructed two-line absorbance distributions. We have carried out numerical simulations and proof-of-concept experiments to validate the proposed algorithm. Compared with the well-established simultaneous algebraic reconstruction technique (SART), the RETRO algorithm significantly improves the quality of the tomographic temperature images, exhibiting excellent robustness against TDLAS tomographic measurement noise. RETRO offers great potential for industrial field applications of TDLAS tomography, where it is common for measurements to be performed in very harsh environments. [ABSTRACT FROM AUTHOR]

Purpose: To reduce temperature errors due to water motion in transcranial MR‐guided focused ultrasound (tcMRgFUS) ablation. Theory and Methods: In tcMRgFUS, water is circulated in the transducer bowl around the patient's head for acoustic coupling and heat removal. The water moves during sonications that are monitored by MR thermometry, which causes it to alias into the brain and create temperature errors. To reduce these errors, a two‐dimensional excitation pulse was implemented in a gradient‐recalled echo thermometry sequence. The pulse suppresses water signal by selectively exciting the brain only, which reduces the imaging FOV. Improvements in temperature precision compared to the conventional full‐FOV scan were evaluated in healthy subject scans outside the tcMRgFUS system, gel phantom scans in the system with heating, and in 2×‐accelerated head phantom scans in the system without heating. Results: In vivo temperature precision (standard deviation of temperature errors) outside the tcMRgFUS system was improved 43% on average, due to the longer TR and TE of the reduced‐FOV sequence. In the phantom heating experiments, the hot spot was less distorted in the reduced‐FOV scans, and background temperature precision was improved 59% on average. In the accelerated head phantom temperature reconstructions, temperature precision was improved 89% using the reduced‐FOV sequence. Conclusions: Reduced‐FOV temperature imaging alleviates temperature errors due to water bath motion in tcMRgFUS, and enables accelerated temperature mapping with greater precision. [ABSTRACT FROM AUTHOR]

Purpose: To increase volume coverage in real‐time MR thermometry for transcranial MR‐guided focused ultrasound (tcMRgFUS) ablation, without multiple receive coils. Theory and Methods: Multiband excitation and incoherent blipped‐controlled aliasing were implemented in a 2DFT pulse sequence used clinically for tcMRgFUS, and an extended k‐space hybrid reconstruction was developed that recovers slice‐separated temperature maps assuming that heating is focal, given slice‐separated pretreatment images. Simulations were performed to characterize slice leakage, the number of slices that can be simultaneously imaged with low‐temperature error, and robustness across random slice‐phase k‐space permutations. In vivo experiments were performed using a single receive coil without heating to measure temperature precision, and gel phantom FUS experiments were performed to test the method with heating and with a water bath. Results: Simulations showed that with large hot spots and identical magnitude images on each slice, up to three slices can be simultaneously imaged with less than 1∘C temperature root‐mean‐square error. They also showed that hot spots do not alias coherently between slices, and that an average 86% of random slice‐phase k‐space permutations yielded less than 1∘C temperature error. Temperature precision was not degraded compared to single‐slice imaging in the in vivo SMS scans, and the gel phantom SMS temperature maps closely tracked single‐slice temperature in the hot spot, with no coherent aliasing to other slices. Conclusions: Incoherent controlled aliasing SMS enables accurate reconstruction of focal heating maps from two or three slices simultaneously, using a single receive coil and a sparsity‐promoting temperature reconstruction. [ABSTRACT FROM AUTHOR]

We introduce a measurement concept using seeded thermographic phosphor particles, which achieves high spatial resolution and rejection of surface induced signals, and is thereby applicable to resolve two-dimensional temperature distribution in sub-millimeter thermal boundary layers. Unlike previous implementations of ratiometric phosphor thermometry in fluid flows, which is based on the division of two spectrally or temporally separated images of the luminescence from groups of seeded particles, here we treat the individual phosphor particles as independent temperature detectors positioned at the discrete particle locations. 2D rotated Gaussian functions are fitted to each particle image as to integrate particle signals in the two frames for ratio-based thermometry and to position the particles with sub-pixel resolution (< 10 μ m). In addition, the fitting method allows to separate the luminescence signal of the imaged particles from interfering signals with a low spatial frequency, for example from surface reflection or re-scattering of luminescence light. After assessing the spatial resolution, and the robustness of the temperature measurements against high levels of re-scattered signals, near-wall measurements are demonstrated. The ability to finely resolve the temperature distribution within a 500 μ m thin thermal boundary layer is validated against the laminar Prandtl–Blasius equation. As the thermometry counterpart and complement to Particle Tracking Velocimetry, this technique allows to probe the fine details of heat transfer in boundary layers. • New 2D thermometry for gas flows with spatial resolution below 10 microns. • Individual phosphor particle images are fitted to yield temperature and position. • Fitting method rejects signals from surface and multiply scattered light. • Temperature profile in 500-micron laminar boundary layer validated against theory. [ABSTRACT FROM AUTHOR]

Fluorescence anisotropy, a technique to study the folding state of proteins or affinity of ligands, is used in this present work as a temperature sensor, to measure the microfluidic temperature field, by adding fluorophore in the liquid. Fluorescein was used as a temperature-sensing probe, while glycerol–aq. ammonia solution was used as a working fluid. Fluorescence anisotropy of fluorescein was measured by varying various parameters. Apart from this, a comparison of fluorescence anisotropy and fluorescence intensity is also performed to demonstrate the validity of anisotropy to be applied in a microfluidic field with non-uniform liquid thickness. Viscosity dependence and temperature dependence on the anisotropy are also clarified; the results indicate an appropriate selection of relation between molecule size and viscosity is important to obtain a large temperature coefficient in anisotropy. Furthermore, a practical calibration procedure of the apparatus constant is proposed. In addition, the potential of temperature imaging is confirmed by the measurement of temperature distribution under focused laser heating.

Abstract Simultaneously calibrated, non-linear two-line atomic fluorescence (SC-nTLAF) thermometry for application in turbulent sooting flames has been developed to increase the precision of single-shot, planar measurements of gas temperature. The technique has been demonstrated in both steady and turbulent sooting flames, showing good agreements with previous optical measurements. The SC-nTLAF involves imaging simultaneously laser-induced fluorescence (LIF) of atomic indium in both the target flame and a non-sooting calibration flame for which the temperature distribution is known. The LIF intensities from the reference flame enable correction for fluctuations, not only in the laser power, but also in the laser mode. The resulting precision was found to be ±67 K and ±75 K (based on one standard deviation) in the rich and oxidizing regions of a steady sooting flame for which the measured temperature was 1610 K and 1854 K, respectively, with a spatial resolution of 550 × 550 µm2. This corresponds to a relative precision of ∼ 4.1%. The resulting precision in the single-shot temperature images for a well-characterized, lifted ethylene jet diffusion flame (fuel jet Reynolds number = 10,000) compares favorably with previously reported data obtained with shifted-vibrational coherent anti-Stokes Raman spectroscopy (CARS), together with increased spatial resolution. The planar imaging also provides more details of the temperature distribution, particularly in the flame brush region, which offers potential for measurement of more parameters, such as gradients and spatial corrections. The new calibration method has also achieved a significant time-saving in both data collection and processing, which is an estimated total of ∼ 60%–70% compared with conventional nTLAF. [ABSTRACT FROM AUTHOR]

This paper quantitatively investigates the spatial and temperature resolutions of magnetic nanoparticle (MNP) temperature imaging with a multiline phantom filled with MNPs. The multiline phantom in total consists of seven lines with different distances between two adjacent lines. A scanning magnetic particle spectrometer is used to measure the spatial distributions of the MNP harmonics for MNP concentration and temperature imaging, whereas an iterative deconvolution method is used to improve the spatial resolution. A modulation transfer function calculated from the MNP concentration image is used to quantitatively present the spatial resolution, whereas the standard deviation of the measured temperatures is used to quantitatively present the temperature resolution. The spatial resolution is about 4 mm while the temperature resolution is about 1.0 K without deconvolution. With increasing the number of the iterative loops in the deconvolution, the spatial resolution is improved to 2 mm while the temperature resolution is worsened to about 9.6 K due to deconvolution-based oscillation.

Volumetric thermometry with fine spatiotemporal resolution is desirable to monitor MR-guided focused ultrasound (MRgFUS) procedures in the brain, but requires some form of accelerated imaging. Accelerated MR temperature imaging methods have been developed that undersample k-space and leverage signal correlations over time to suppress the resulting undersampling artifacts. However, in transcranial MRgFUS treatments, the water bath surrounding the skull creates signal variations that do not follow those correlations, leading to temperature errors in the brain due to signal aliasing. Methods: To eliminate temperature errors due to the water bath, a spatially-segmented iterative reconstruction method was developed. The method fits a k-space hybrid signal model to reconstruct temperature changes in the brain, and a conventional MR signal model in the water bath. It was evaluated using single-channel 2DFT Cartesian, golden angle radial, and spiral data from gel phantom heating, and in vivo 8-channel 2DFT data from a FUS thalamotomy. Water bath signal intensity in phantom heating images was scaled between 0-100% to investigate its effect on temperature error. Temperature reconstructions of retrospectively undersampled data were performed using the spatially-segmented method, and compared to conventional whole-image k-space hybrid (phantom) and SENSE (in vivo) reconstructions. Results: At 100% water bath signal intensity, 3×-undersampled spatially-segmented temperature reconstruction error was nearly 5-fold lower than the whole-image k-space hybrid method. Temperature root-mean square error in the hot spot was reduced on average by 27× (2DFT), 5× (radial), and 12× (spiral) using the proposed method. It reduced in vivo error 2× in the brain for all acceleration factors, and between 2× and 3× in the temperature hot spot for 2-4× undersampling compared to SENSE. Conclusions: Separate reconstruction of brain and water bath signals enables accelerated MR temperature imaging during MRgFUS procedures with low errors due to undersampling using Cartesian and non-Cartesian trajectories. The spatially-segmented method benefits from multiple coils, and reconstructs temperature with lower error compared to measurements from SENSE-reconstructed images. The acceleration can be applied to increase volumetric coverage and spatiotemporal resolution. [ABSTRACT FROM AUTHOR]

Purpose This study aims to accelerate MR temperature imaging using the proton resonance frequency (PRF) shift method for real time temperature monitoring during thermal ablation. Materials and methods The proposed method estimates temperature changes from undersampled k-space with a fully sampled center. This proposed algorithm is based on the hybrid multi-baseline and referenceless treatment image model and can be seen as an extension of the conventional k-space-based hybrid thermometry. The parameters of hybrid model are acquired by utilizing information from low resolution images which are obtained from fully-sampled centers of k-space. Registration is used to correct temperature errors due to the displacement of the subject. Phantom heating simulations, motion simulations, phantom heating and in-vivo experiments were performed to investigate the efficiency of the proposed method. SPIRiT and the conventional k-space estimation reconstruction thermometry were implemented for comparison using the same sampling pattern. Results The phantom heating simulations showed that the proposed method results in lower RMSEs than the conventional k-space hybrid thermometry and SPIRiT at various reduction factors tested. The motion simulations indicated the robustness of the proposed method to displacement of the subject. Phantom heating experiment further demonstrated the ability of the method to reconstruct temperature maps with less computation time and higher accuracy (RMSEs lower than 0.4 °C) at a net reduction factor of 3.5 in the presence of large noise caused by a microwave needle. In-vivo experiments validated the feasibility of the proposed method to estimate temperature changes from undersampled k-space (net reduction factor 4.3) in presence of respiratory motion and complicated anatomical structure, while reducing computation time as much as 10-fold compared with the conventional k-space method. Conclusion The proposed method accelerates the PRF-shift MR thermometry and provides more accurate temperature maps in presence of motion with relatively short computation time, which may make real time imaging for MR-guided microwave ablation possible. [ABSTRACT FROM AUTHOR]

• Quantitative temperature visualization is realized using narrowband MPI. • Temperature dependence of phase lag of 3rd harmonic is employed for temperature imaging. • Verification measurements are performed with magnetic particle spectroscopy. • The measured temperature has a systematic deviation of 0.9 °C and standard deviation of 0.13 °C. Magnetic Particle Imaging (MPI) is a very promising imaging modality for disease theranostics. It allows quantitative visualization of magnetic nanoparticles (MNPs) by utilizing their non-linear response to an alternating magnetic field. In this study, we propose a new approach for the additional quantitative imaging of temperature with single harmonic-based narrowband MPI via measuring the phase lag of the 3rd harmonic of MNP response. Temperature dependent phase lag is measured and calibrated with both magnetic particle spectroscopy and MPI systems. Afterwards, phantom experiments are performed for quantitative temperature imaging with MPI. Experimental results demonstrate the feasibility of the proposed approach for temperature imaging with a systematic deviation of 0.9 °C and a standard deviation of 0.13 °C. We believe that the proposed approach will provide a novel tool for non-invasive and quantitative temperature imaging with applications to biomedicine. [ABSTRACT FROM AUTHOR]

Purpose To reconstruct proton resonance frequency-shift temperature maps free of chemical shift distortions. Theory and Methods Tissue heating created by thermal therapies such as focused ultrasound surgery results in a change in proton resonance frequency that causes geometric distortions in the image and calculated temperature maps, in the same manner as other chemical shift and off-resonance distortions if left uncorrected. We propose an online-compatible algorithm to correct these distortions in 2DFT and echo-planar imaging acquisitions, which is based on a k-space signal model that accounts for proton resonance frequency change-induced phase shifts both up to and during the readout. The method was evaluated with simulations, gel phantoms, and in vivo temperature maps from brain, soft tissue tumor, and uterine fibroid focused ultrasound surgery treatments. Results Without chemical shift correction, peak temperature and thermal dose measurements were spatially offset by approximately 1 mm in vivo. Spatial shifts increased as readout bandwidth decreased, as shown by up to 4-fold greater temperature hot spot asymmetry in uncorrected temperature maps. In most cases, the computation times to correct maps at peak heat were less than 10 ms, without parallelization. Conclusion Heat-induced proton resonance frequency changes create chemical shift distortions in temperature maps resulting from MR-guided focused ultrasound surgery ablations, but the distortions can be corrected using an online-compatible algorithm. Magn Reson Med 76:172-182, 2016. © 2015 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Purpose Intermolecular multiple quantum coherences (iMQCs) are a source of MR contrast with applications including temperature imaging, anisotropy mapping, and brown fat imaging. Because all applications are limited by signal-to-noise ratio (SNR), we developed a pulse sequence that detects intermolecular zero quantum coherences with improved SNR. Methods A previously developed pulse sequence that detects iMQCs, HOMOGENIZED with off resonance transfer (HOT), was modified with a multi-spin echo spatial encoding scheme (MSE-HOT). MSE-HOT uses a series of refocusing pulses to generate a stack of images that are averaged in postprocessing for higher SNR. MSE-HOT performance was quantified by measuring its temperature accuracy and precision during hyperthermia of ex vivo red bone marrow samples. Results MSE-HOT yielded a three-fold improvement in temperature precision relative to previous pulse sequences. Sources of improved precision were 1) echo averaging and 2) suppression of J-coupling in the methylene protons of fat. MSE-HOT measured temperature change with an accuracy of 0.6°C. Conclusion MSE-HOT improved the temperature accuracy and precision of HOT to a level that is sufficient for hyperthermia of bone marrow. Magn Reson Med 75:1958-1966, 2016. © 2015 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Purpose Acceleration of magnetic resonance (MR) thermometry is desirable for several applications of MR-guided focused ultrasound, such as those requiring greater volume coverage, higher spatial resolution, or higher frame rates. Methods We propose and validate a constrained reconstruction method that estimates focal temperature changes directly from k-space without spatial or temporal regularization. A model comprising fully-sampled baseline images is fit to undersampled k-space data, which removes aliased temperature maps from the solution space. Reconstructed temperature maps are compared to maps reconstructed using parallel imaging (iterative self-consistent parallel imaging reconstruction [SPIRiT]) and conventional hybrid thermometry, and temporally constrained reconstruction thermometry. Results Temporal step response simulations demonstrate finer temporal resolution and lower error in 4×-undersampled radial k-space reconstructions compared to temporally constrained reconstruction. Simulations show that the k-space method can achieve higher accelerations with multiple receive coils. Phantom heating experiments further demonstrate the algorithm's advantage over reconstructions relying on parallel imaging alone to overcome undersampling artifacts. In vivo model error comparisons show the algorithm achieves low temperature error at higher acceleration factors (up to 32× with a radial trajectory) than compared reconstructions. Conclusion High acceleration factors can be achieved using the proposed temperature reconstruction algorithm, without sacrificing temporal resolution or accuracy. Magn Reson Med 73:1914-1925, 2015. © 2014 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

We present a numerical study demonstrating the simultaneous reconstruction of the temperature, species concentration, and pressure of molecular water vapor, by tomographic means, from near-infrared laser absorption measurements over beam paths transecting the gaseous region. The synthetic measurement data is predicted from a set of randomized distributions of the reconstructed variables using spectroscopic theory and the HITRAN parameter database. Design optimization geometric orientation of the beams is performed to maximize reconstruction accuracy. [ABSTRACT FROM PUBLISHER]

Experimental evidence shows that nanosecond pulsed electric fields (nsPEF) trigger apoptosis in skin tumors. We have postulated that the energy delivered by nsPEF is insufficient to impart significant heating to the treated tissue. Here we use both direct measurements and theoretical modeling of the Joule heating in order to validate this assumption. For the temperature measurement, thermo-sensitive liquid crystals (TLC) were used to determine the surface temperature while a micro-thermocouple (made from 30 μm wires) was used for measuring the temperature inside the tissue. The calculation of the temperature distribution used an asymptotic approach with the repeated calculation of the electric field, Joule heating and heat transfer, and the subsequent readjustment of the electrical tissue conductivity. This yields a temperature distribution both in space and time. It can be shown that for the measured increase in temperature an unexpectedly high electrical conductivity of the tissue would be required, which was indeed found by using voltage and current monitoring during the experiment. Using impedance measurements within t after = 50 μs after the pulse revealed a fast decline of the high conductivity state when the electric field ceases. The experimentally measured high conductance of a skin fold (mouse) between plate electrodes was about 5 times higher than those of the maximally expected conductance due to fully electroporated membrane structures ( G max / G electroporated ) ≈ 5. Fully electroporated membrane structure assumes that 100% of the membranes are conductive which is estimated from an impedance measurement at 10 MHz where membranes are capacitively shorted. Since the temperature rise in B-16 mouse melanoma tumors due to equally spaced ( Δt = 2 s) 300 ns-pulses with E = 40 kV/cm usually does not exceed ΔΤ = 3 K at all parts of the skin fold between the electrodes, a hyperthermic effect on the tissue can be excluded. [ABSTRACT FROM AUTHOR]

Abstract: High-speed laser induced fluorescence (LIF) thermometry is combined with particle image velocimetry (PIV) to measure the temporal evolution of the spatial unburned gas temperature distribution in a motored spark-ignition (SI) optical engine. Single-line excitation of toluene and subsequent two-color emission detection is employed for LIF thermometry. Precision uncertainty is assessed pixel-wise and found to be ±5K at 295K and ±29K at 550K, but decreases by 34% (i.e., ±19K at 550K) when spatially averaging the LIF signal over a 10×10pixel2 region. The polytropic temperature relation is used to correlate LIF ratio with temperature to calibrate the in-cylinder gas temperature measurements. Instantaneous temperature images and temperature PDFs show homogeneous temperature distribution during compression, while significant temperature inhomogeneities from entrained colder gases are captured during early expansion. Simultaneously acquired PIV and LIF images illustrate the evolution of the cold gas distribution during expansion. The images presented reveal the capability of high-speed toluene-LIF thermometry combined with PIV in an engine to capture the 2D temperature distribution and track structures of colder temperatures. [Copyright &y& Elsevier]

Abstract: Direct-injection (DI) concepts with spray-guided mixture formation are promising methods to increase the efficiency of spark ignition (SI) engines. The fuel and temperature distribution determines evaporation and ignition behavior. However, the resulting mixture and temperature are not homogeneous through the combustion chamber. Furthermore, it is strongly affected by the fuel evaporation properties, which are different for modern biofuels compared to gasoline. The present paper demonstrates the procedure and the capability of two-line excitation LIF based on 3-pentanone for accurate planar temperature determination in DISI-sprays at late injection timing conditions. The jet temperature profiles were determined for the gasoline surrogate fuel iso-octane and the biogenic component ethanol, which have a significant difference in their heat of evaporation. The spray of a 6-hole solenoid-injector in an optically accessible combustion test rig is analyzed by quasi-simultaneous excitation by two different excimer lasers. The signals are recorded with one double-shutter ICCD-camera. From the signal ratio of the images the temperature field in the fuel spray can be calculated. The tracer is calibrated with an enhanced high temperature calibration cell for temperatures up to 700K and pressures up to 1MPa, which are relevant for the studied conditions. The postprocessing strategy is optimized regarding high accuracy and precision. The fuel spray behavior is evaluated at different positions in the spray and times showing larger evaporation cooling in the jet of maximum 141K for ethanol. For a comparison of the ensemble averaged results a CFD-spray model was set up under the same boundary conditions showing very similar trends. The temperature images yielded a single-shot precision of approximately 5.6% and inaccuracies of 3.8% making this technique capable for model improvements and validation. [Copyright &y& Elsevier]

Abstract: The development of accurate and non-invasive temperature imaging techniques has a wide variety of applications in fields such as medicine, chemistry and materials science. Accurate detection of temperature both in phantoms and in vivo can be obtained using iMQCs (intermolecular multiple quantum coherences), as demonstrated in a recent paper . This paper describes the underlying theory of iMQC temperature detection, as well as extensions of that work allowing not only for imaging of absolute temperature but also for imaging of analyte concentrations through chemically-selective spin density imaging. [Copyright &y& Elsevier]

Abstract: This paper presents a method of imaging temperature distributions of sub-millimeter-thick water using a near-infrared camera and optical narrow-bandpass filter. The principle is based on the temperature dependence of the ν 1 + ν 3 absorption band of water. Temperature images are constructed by measuring the absorbance of water at the wavelength of 1412nm through the filter for all pixels of the camera. From calibration measurements on 0.5-mm thick water at temperatures from 26.0°C to 40.0°C, the temperature coefficient was 6.3×10−4 K−1 and the standard deviation of absorbance was 1.9×10−4. Thermal diffusion in 0.5-mm thick water caused by a thin heating wire was visualized with this method. The obtained images were verified against temperature distributions calculated by solving a two-dimensional thermal conduction model. This method would be useful for temperature measurement applications and control of aqueous solutions in microchips. [Copyright &y& Elsevier]

Abstract: The present study is concerned with investigating temperature evolution during weld heating phase in a particular device. Experimental results are presented as a guide to theoretical calculations. The main theoretical item is an attempt to solve the heat equation by considering the evolution of the source term inside electrically heated zone. Empirical variations of both thermal and electrical conductivities are treated and involved in the model. [Copyright &y& Elsevier]

• A comprehensive compilation of articles presenting the design and validation of contrast agents to be used with ratiometric approaches in MRI is presented. • The principles of ratiometric imaging in MRI and its benefits are introduced. • The rationale behind designed probes is discussed. • The feasibility for translation and use of this kind of methodologies and probes in the clinic are analysed. Magnetic Resonance Imaging (MRI) is a powerful imaging tool that combined with the use of contrast agents (CA) provides meaningful and crucial information both in the research and clinical settings. In recent years, strides have been taken towards the development of new CAs with enhanced capabilities (specificity, responsiveness, multimodality...) to better diagnose and monitor physiological and pathological conditions in the body. Despite recent development, there are still challenges in the use of MRI to quantify specific functional or metabolic processes. The application of a ratiometric approach, in which images are acquired from the same sample using two different MR acquisitions, has potential to greatly improve the utility of MRI. In order to make this ratiometric approach work, a new generation of ratiometric probes are being developed which will be discussed in this review, classifying them based on the biological parameter under study as well as on the ratiometric analysis approach. Finally, the advantages and feasibility of using this methodology in a routine way will also be discussed. [ABSTRACT FROM AUTHOR]

Abstract: Radiofrequency ablation is the most common minimally invasive therapy used in the United States to treat hepatocellular carcinoma and liver metastases. The ability to perform real-time temperature imaging while a patient is undergoing ablation therapy may help reduce the high recurrence rates following ablation therapy. Ultrasound echo signals undergo time shifts with increasing temperature due to sound speed and thermal expansion, which are tracked using both 1D cross correlation and 2D block matching based speckle tracking methods. In this paper, we present a quantitative evaluation of the accuracy and precision of temperature estimation using the above algorithms on both simulated and experimental data. A finite element analysis simulation of radiofrequency ablation of hepatic tissue was developed. Finite element analysis provides a method to obtain the exact temperature distribution along with a mapping of the tissue displacement due to thermal expansion. These local displacement maps were combined with the displacement due to speed of sound changes and utilized to generate ultrasound radiofrequency frames at specified time increments over the entire ablation procedure. These echo signals provide an ideal test-bed to evaluate the performance of both speckle tracking methods, since the estimated temperature results can be compared directly to the exact finite element solution. Our results indicate that the 1D cross-correlation (CC) method underestimates the cumulative displacement by 0.20mm, while the underestimation with 2D block matching (BM) is about 0.14mm after 360s of ablation. The 1D method also overestimates the size of the ablated region by 5.4% when compared to 2.4% with the 2D method after 720s of ablation. Hence 2D block matching provides better tracking of temperature variations when compared to the 1D cross-correlation method over the entire duration of the ablation procedure. In addition, results obtained using 1D cross-correlation diverge from the ideal finite element results after 7min of ablation and for temperatures greater than 65°C. In a similar manner, experimental results presented using a tissue-mimicking phantom also demonstrate that the maximum percent difference with 2D block matching was 5%, when compared to 31% with the 1D method over the 700s heating duration on the phantom. [Copyright &y& Elsevier]

Abstract: Ultrasound backscattered from tissue has previously been shown theoretically and experimentally to change predictably with temperature in the hyperthermia range, i.e., 37°C to 45°C, motivating use of the change in backscattered ultrasonic energy (CBE) for ultrasonic thermometry. Our earlier theoretical model predicts that CBE from an individual scatterer will be monotonic with temperature, with, e.g., positive change for lipid-based scatterers and negative for aqueous-based scatterers. Experimental results have previously confirmed the presence of these positive and negative changes in one-dimensional ultrasonic signals and in two-dimensional images acquired from in vitro bovine, porcine and turkey tissues. In order to investigate CBE for populations of scatterers, we have developed an ultrasonic image simulation model, including temperature dependence for individual scatterers based on predictions from our theoretical model. CBE computed from images simulated for populations of randomly distributed scatterers behaves similarly to experimental results, with monotonic variation for individual pixel measurements and for image regions. Effects on CBE of scatterer type and distribution, size of the image region and signal-to-noise ratio have been examined. This model also provides the basis for future work regarding significant issues relevant to temperature imaging based on ultrasonic CBE such as effects of motion on CBE, limitations of motion-compensation techniques and accuracy of temperature estimation, including tradeoffs between temperature accuracy and available spatial resolution. (E-mail: jasont@wustl.edu) [Copyright &y& Elsevier]

Abstract: Inductively coupled plasma (ICP) sources typically used for trace elemental determination and speciation were investigated with infrared (IR) thermography to obtain spatially resolved torch temperature distributions. Infrared thermographic imaging is an excellent tool for the monitoring of temperatures in a fast and non-destructive way. This paper presents the first application of IR thermography to inductively coupled plasma torches and the possibility to investigate temperatures and thermal patterns while the ICP is operating and despite background emission from the plasma itself. A fast and easy method is presented for the determination of temperature distributions and stress features within ICP torches. Two different ICP operating torches were studied: a commercially available Fassel-type ICP unit with 14 L min−1 total Ar consumption and a SHIP torch with the unusually low Ar flow of 0.6 L min−1. Spatially resolved infrared images of both torches were obtained and laterally resolved temperature profiles were extracted. After temperature-resolved calibration of the emissivity (between 0.5 and 0.35 at 873–1323 K) and transmission (20% between 3.75 and 4.02 μm) of the fused quartz used in the torch construction, an image correction was applied. Inhomogeneous temperature distributions with locally defined stress areas in the conventional Fassel-type torch were revealed. As a general trend, it was found that the SHIP torch exhibited higher temperatures (T max =1580 K) than the conventional torch (T max =730 K). In the former case, torch sites with efficient and inefficient cooling were discovered and the external flow of cooling air (24–48 m s−1) was identified as the limiting factor. [Copyright &y& Elsevier]

Abstract: Continuous radio-frequency (rf) irradiation during decoupling and spin-lock periods in NMR pulse sequences may lead to undesired sample heating. Heat-sensitive samples can suffer damage from the sudden temperature rise which cannot be adequately compensated by the temperature control system. Moreover, as the heating is spatially inhomogeneous, higher temperature increases can arise locally than are indicated by the average increase detected by the temperature controller. In this work we present a technique that allows measurement of a real-time 2D-image of the temperature distribution inside an NMR sample during an experiment involving rf-heating. NMR imaging methods have previously been used to project the temperature distribution inside an NMR sample onto a single spatial axis or to acquire steady-state 2D- temperature distributions. The real-time 2D-temperature profiles obtained with our procedure provide much more detailed data. Our results show, that not only inhomogeneous heating but also inhomogeneous sample cooling contribute to the build-up of temperature gradients across the sample. The technique can be used to visualize rf-heating in order to protect sensitive samples and to experimentally test new coil geometries or to guide probehead design. [Copyright &y& Elsevier]

Spherical nanoparticles with a gold outer shell and silica core can be tuned to absorb near-infrared light of a specific wavelength. These nanoparticles have the potential to enhance the treatment efficacy of laser-induced thermal therapy (LITT). In order to enhance both the potential efficacy and safety of such procedures, accurate methods of treatment planning are needed to predict the temperature distribution associated with treatment application. In this work, the standard diffusion approximation was used to model the laser fluence in phantoms containing different concentrations of nanoparticles, and the temperature distribution within the phantom was simulated in three-dimensions using the finite element technique. Magnetic resonance temperature imaging was used to visualize the spatiotemporal distribution of the temperature in the phantoms. In most cases, excellent correlation is demonstrated between the simulations and the experiment (<3.0% mean error observed). This has significant implications for the treatment planning of LITT treatments using gold-silica nanoshells. [ABSTRACT FROM AUTHOR]

Abstract: Our challenge was to design and implement a dedicated temperature imaging feedback control system to guide and assist in a thermal liver ablation procedure in a double-donut 0.5T open MR scanner. This system has near-real-time feedback capability based on a newly developed “self-referenced” temperature imaging method using “moving-slab” and complex-field-fitting techniques. Two phantom validation studies and one ex vivo experiment were performed to compare the newly developed self-referenced method with the conventional subtraction method and evaluate the ability of the feedback control system in the same MR scanner. The near-real-time feedback system was achieved by integrating the following primary functions: (1) imaging of the moving organ temperature; (2) on-line needle tip tracking; (3) automatic turn-on/off the heating devices; (4) a Windows operating system-based novel user-interfaces. In the first part of the validation studies, microwave heating was applied in an agar phantom using a fast spoiled gradient recalled echo in a steady state sequence. In the second part of the validation and ex vivo study, target visualization, treatment planning and monitoring, and temperature and thermal dose visualization with the graphical user interface of the thermal ablation software were demonstrated. Furthermore, MR imaging with the “self-referenced” temperature imaging method has the ability to localize the hot spot in the heated region and measure temperature elevation during the experiment. In conclusion, we have demonstrated an interactively controllable feedback control system that offers a new method for the guidance of liver thermal ablation procedures, as well as improving the ability to assist ablation procedures in an open MR scanner. [Copyright &y& Elsevier]

Continuous, real-time, 3D temperature mapping during a hyperthermic procedure may provide (i) enhanced safety by visualizing temperature maps in and around the treated region, (ii) improved efficiency by adapting local energy deposition with feedback coupling algorithms and (iii) therapy end-points based on the accumulated thermal dose. Non-invasive mapping of temperature changes can be achieved with MRI and may be based on temperature dependent MRI parameters. The excellent linearity of the temperature dependency of the proton resonance frequency (PRF) and its near-independence with respect to tissue type make the PRF-based methods the preferred choice for many applications, in particular at mid- to-high field strength (≥0.5&ThickSpace; T ). The PRF methods employ RF-spoiled gradient echo imaging methods and incorporate fat suppression techniques for most organs. A standard deviation of less than 1°C, for a temporal resolution below 1&ThickSpace;s and a spatial resolution of &nvsim;2&ThickSpace;mm is feasible for immobile tissues. Special attention is paid to methods for reducing artifacts in MR temperature mapping caused by intra-scan and inter-scan motion and motion and temperature-induced susceptibility effects in mobile tissues. Real-time image processing and visualization techniques, together with accelerated MRI acquisition techniques, are described because of their potential for therapy guidance. [ABSTRACT FROM AUTHOR]

Abstract: The safe, clean, and reliable operation of combustion devices depends to a large degree on the exact control of the fuel/air mixing process prior to ignition. Therefore, quantitative measurement techniques that characterize the state of the fresh gas mixture are crucial in modern combustion science and engineering. This paper presents the fundamental concepts for how to devise and apply quantitative measurement techniques for studies of fuel concentration, temperature, and fuel/air ratio in practical combustion systems, with some emphasis on internal combustion engines. The paper does not attempt to provide a full literature review of quantitative imaging diagnostics for practical combustion devices; rather it focuses on explaining the concepts and illustrating these with selected examples. These examples focus on application to primarily gaseous situations. The photophysics of organic molecules is presented in an overview followed by discussions on specific details of the temperature-, pressure-, and mixture-dependence of the laser-induced fluorescence strength of aliphatic ketones, like acetone and 3-pentanone, and toluene. Models that describe the fluorescence are discussed and evaluated with respect to their functionality. Examples for quantitative applications are categorized in order of increased complexity. These examples include simple mixing experiments under isothermal and isobaric conditions, fuel/air mixing in engines, temperature measurements, and mixing studies where fuel and oxygen concentrations vary. A brief summary is given on measurements of fuel concentrations in multiphase systems, such as laser‐induced exciplex spectroscopy. Potentially adverse effects that added tracers might have on mixture formation, combustion, and the faithful representation of the base fuel distribution are discussed. Finally, a brief section describes alternative techniques to tracer-based measurements that allow studies of fuel/air mixing processes in practical devices. The paper concludes with a section that addresses key issues that remain as challenges for continued research towards the improvement of quantitative, tracer-based LIF measurements. [Copyright &y& Elsevier]

Fluorescence anisotropy, a technique to study the folding state of proteins or affinity of ligands, is used in this present work as a temperature sensor, to measure the microfluidic temperature field, by adding fluorophore in the liquid. Fluorescein was used as a temperature-sensing probe, while glycerol–aq. ammonia solution was used as a working fluid. Fluorescence anisotropy of fluorescein was measured by varying various parameters. Apart from this, a comparison of fluorescence anisotropy and fluorescence intensity is also performed to demonstrate the validity of anisotropy to be applied in a microfluidic field with non-uniform liquid thickness. Viscosity dependence and temperature dependence on the anisotropy are also clarified; the results indicate an appropriate selection of relation between molecule size and viscosity is important to obtain a large temperature coefficient in anisotropy. Furthermore, a practical calibration procedure of the apparatus constant is proposed. In addition, the potential of temperature imaging is confirmed by the measurement of temperature distribution under focused laser heating. [ABSTRACT FROM AUTHOR]

Drebrin E is a regulatory protein of intracellular force produced by actomyosin complexes, that is, myosin molecular motors interacting with actin filaments. The expression level of drebrin E in nerve cells decreases as the animal grows, suggesting its pivotal but unclarified role in neuronal development. Here, by applying the microscopic heat pulse method to actomyosin motility assay, the regulatory mechanism is examined from the room temperature up to 37 °C without a thermal denaturing of proteins. We show that the inhibition of actomyosin motility by drebrin E is eliminated immediately and reversibly during heating and depends on drebrin E concentration. The direct observation of quantum dot-labeled drebrin E implies its stable binding to actin filaments during the heat-induced sliding. Our results suggest that drebrin E allosterically modifies the actin filament structure to regulate cooperatively the actomyosin activity at the maintained in vivo body temperature.

• A near-infrared imaging method is used for temperature measurement.. • Induction heating of micro-magnetic particle layers is performed in a fluidic channel. • Temperature images of water near the layers are acquired under different heating conditions. • The heat generation rates of the layers are determined. This paper presents an experimental method for measuring the water temperature near micro-magnetic particle (MMP) layers in a fluidic channel under induction heating. This method is based on the temperature dependence of the spectrum of the ν 1 + ν 3 absorption band of water in the near-infrared (NIR) region. The absorbance images at the wavelength of 1412 nm, which is the most temperature-sensitive wavelength in the band, were obtained through a U-shaped channel with an optical path length of 1 mm using a narrow-bandpass filter and an NIR camera. An MMP layer was formed on the inner surface of the channel by an external strong permanent magnet and then heated inductively by applying a 760-kHz magnetic field. The temperature distribution of water was found to depend on the heating time, heating power level, and MMP layer thickness (0.5, 0.6, and 1.0 mm). The maximum increase in temperature near the MMP layer was approximately 5 °C, and the temperature resolution was 0.2 °C. A numerical simulation was used to verify the measured temperature profiles then apply the residual fitting method to determine the heat generation rates (HGRs) of the MMPs. The HGRs were independent of the heating time, and varied consistently with the heating power level. This method is useful for the quantitative understanding and control of temperature fields in applications that use MMPs for chemical reactions and cell/tissue therapy. [ABSTRACT FROM AUTHOR]

• High relative sensitivities were obtained for different temperature sensing modes. • A temperature sensing scheme based on time-resolved technique was proposed. • Temperature imaging of micro circuit with high sensitivity and resolution was realized. Motivated from increasing demands of non-contact temperature sensing, here Mn2+ doped Zn 2 GeO 4 (ZGO) phosphor is produced to explore the temperature dependencies of its optical characteristics. Temperature dependencies of emission intensity and luminescence decay lifetime of Mn2+ in the range from 250 K to 420 K are investigated. The maximum relative sensitivities achieved are 4.5% K−1 and 4.6% K−1 for temperature sensing modes of emission intensity and decay lifetime, respectively. In order to realize temperature imaging, a temperature sensing scheme is employed based on time-resolved technique with the help of an intensified charge coupled device (ICCD) and a fluorescent microscope, where the luminescence integral intensities ratio of obtained images for two time segments is calibrated to measure the temperature. A maximum relative sensitivity of 12.2% K−1 is achieved and the best temperature resolution is about 0.68 K. Employing the temperature imaging system we built, the temperature distribution of micro circuit on a printed circuit board (PCB) has been monitored with high temperature and spatial resolution. The results may offer a significant advance in the development of temperature visualization for precise distributions and change of temperature field. [ABSTRACT FROM AUTHOR]

A composite film material that combines CsPbBr 3 perovskite nanocrystals with a Hyflon AD 60 fluoropolymer was developed and utilized for high-resolution optical temperature imaging. It exhibited bright luminescence and, most importantly, long-term stability in an aqueous medium. CsPbBr 3 nanocrystal-Hyflon films immersed in aqueous solutions showed stable luminescence over at least 4 months and exhibited a fully reversible pronounced temperature sensitivity of 1.2% K -1 between 20 and 80 °C. They were incorporated into a digital microfluidic (electrowetting on dielectric) platform and were used for spatially resolved temperature measurements during droplet movements. Thermal mapping with a CsPbBr 3 nanocrystal-Hyflon sensing layer in a room temperature environment (22.0 °C) revealed an increase in local temperatures of up to 40.2 °C upon voltage-driven droplet manipulations in a digital microfluidic system, corresponding to a local temperature change of up to 18.2 °C.

This paper quantitatively investigates the spatial and temperature resolutions of magnetic nanoparticle (MNP) temperature imaging with a multiline phantom filled with MNPs. The multiline phantom in total consists of seven lines with different distances between two adjacent lines. A scanning magnetic particle spectrometer is used to measure the spatial distributions of the MNP harmonics for MNP concentration and temperature imaging, whereas an iterative deconvolution method is used to improve the spatial resolution. A modulation transfer function calculated from the MNP concentration image is used to quantitatively present the spatial resolution, whereas the standard deviation of the measured temperatures is used to quantitatively present the temperature resolution. The spatial resolution is about 4 mm while the temperature resolution is about 1.0 K without deconvolution. With increasing the number of the iterative loops in the deconvolution, the spatial resolution is improved to 2 mm while the temperature resolution is worsened to about 9.6 K due to deconvolution-based oscillation. [ABSTRACT FROM AUTHOR]