Non-invasive Temperature Measurement Research Articles

Comparison of Frequently Used Fever Measurement Methods: Which One is the Best?

Abstract Objective Peripheral measurement sites and methods used to determine core body temperature were investigated, as there is still debate about which noninvasive core body temperature measurement method is the most valuable and accurate for each age group. Methods Children aged 1 to 36 months were included in the study. The temperature was measured from the forehead (noncontact cutaneous), temporal artery (TA), axilla, and rectum. The rectal measurement was accepted as the reference measurement. A rectal temperature of ≥38.3°C was defined as fever. Results The noncontact cutaneous, axillary, and TA measurements were 1.2, 1.1, and 0.7°C lower than rectal measurements, respectively (p < 0.001, <0.001, <0.001). The TA and noncontact cutaneous measurements demonstrated a moderate positive correlation with rectal measurements, whereas a strong positive correlation was seen between the axillary and rectal measurements. A cutaneous temperature of 37.8°C was found to have a positive predictive value (PPV) of 100%, negative predictive value (NPV) of 81%, sensitivity of 34%, and specificity of 100% for detecting fever. The respective values were 80, 79.4, 23.5, and 98% for an axillary temperature of 37.5°C, and 90, 86.2, 52.9, and 98% for a TA temperature of 38°C. Conclusion The commonly used fever measurement methods have high PPV and NPV and specificity but low sensitivity.

Photoacoustic thermal-strain measurement towards noninvasive and accurate temperature mapping in photothermal therapy

Photothermal therapy is a promising tumor treatment approach that selectively eliminates cancer cells while assuring the survival of normal cells. It transforms light energy into thermal energy, making it gentle, targeted, and devoid of radiation. However, the efficacy of treatment is hampered by the absence of accurate and noninvasive temperature measurement method in the therapy. Therefore, there is a pressing demand for a noninvasive temperature measurement method that is real-time and accurate. This article presents one such attempt based on thermal strain photoacoustic (PA) temperature measurement. The method was first modelled, and a circular array-based photoacoustic photothermal system was developed. Experiments with Indian ink as tumor simulants suggest that the temperature monitoring in this work achieves a precision of down to 0.3 °C. Furthermore, it is possible to accomplish real-time temperature imaging, providing accurate two-dimensional temperature mapping for photothermal therapy. Experiments were also conducted on human fingers and nude mice, validating promising potentials of the proposed method for practical implementations.

Noninvasive Temperature Measurements in Tissue-Simulating Phantoms Using a Solid-State Near-Infrared Sensor.

The monitoring of body temperature is a recent addition to the plethora of parameters provided by wellness and fitness wearable devices. Current wearable temperature measurements are made at the skin surface, a measurement that is impacted by the ambient environment of the individual. The use of near-infrared spectroscopy provides the potential for a measurement below the epidermal layer of skin, thereby having the potential advantage of being more reflective of physiological conditions. The feasibility of noninvasive temperature measurements is demonstrated by using an in vitro model designed to mimic the near-infrared spectra of skin. A miniaturizable solid-state laser-diode-based near-infrared spectrometer was used to collect diffuse reflectance spectra for a set of seven tissue phantoms composed of different amounts of water, gelatin, and Intralipid. Temperatures were varied between 20-24 °C while collecting these spectra. Two types of partial least squares (PLS) calibration models were developed to evaluate the analytical utility of this approach. In both cases, the collected spectra were used without pre-processing and the number of latent variables was the only optimized parameter. The first approach involved splitting the whole dataset into separate calibration and prediction subsets for which a single optimized PLS model was developed. For this first case, the coefficient of determination (R2) is 0.95 and the standard error of prediction (SEP) is 0.22 °C for temperature predictions. The second strategy used a leave-one-phantom-out methodology that resulted in seven PLS models, each predicting the temperatures for all spectra in the held-out phantom. For this set of phantom-specific predicted temperatures, R2 and SEP values range from 0.67-0.99 and 0.19-0.65 °C, respectively. The stability and reproducibility of the sample-to-spectrometer interface are identified as major sources of spectral variance within and between phantoms. Overall, results from this in vitro study justify the development of future in vivo measurement technologies for applications as wearables for continuous, real-time monitoring of body temperature for both healthy and ill individuals.

Analytical Analysis of Factors Affecting the Accuracy of a Dual-Heat Flux Core Body Temperature Sensor.

Non-invasive core body temperature (CBT) measurements using temperature and heat-flux have become popular in health, sports, work safety, and general well-being applications. This research aimed to evaluate two commonly used sensor designs: those that combine heat flux and temperature sensors, and those with four temperature sensors. We used analytical methods, particularly uncertainty analysis calculus and Monte Carlo simulations, to analyse measurement accuracy, which depends on the accuracy of the temperature and flux sensors, mechanical construction parameters (such as heat transfer coefficient), ambient air temperature, and CBT values. The results show the relationship between the accuracy of each measurement method variant and various sensor parameters, indicating their suitability for different scenarios. All measurement variants showed unstable behaviour around the point where ambient temperature equals CBT. The ratio of the heat transfer coefficients of the dual-heat flux (DHF) sensor's channels impacts the CBT estimation uncertainty. An analysis of the individual components of uncertainty in CBT estimates reveals that the accuracy of temperature sensors significantly impacts the overall uncertainty of the CBT measurement. We also calculated the theoretical limits of measurement uncertainty, which varied depending on the method variant and could be as low as 0.05 °C.

Measurement the 3D temperature distribution in the combustion zone using acoustic tomography and nolinear wavefont tracing

A non-invasive temperature measurement method in three dimensions is proposed to reconstruct the three-dimensional temperature. It relies on the use of nonlinear acoustic travel-time tomography, which incorporates acoustic path tracing, Gaussian kernel function, and modified Tikhonov regularization. Sound signals can be distorted due to large average temperature gradients and oscillatory release of heat in the combustion region. The effective acoustic signal is extracted based on spectral subtraction to evaluate the sound propagation time under distorted signals. The analysis of experimental errors indicates that the proposed acoustic pyrometry method has an average relative error of less than 15% compared to the time-averaged temperature measured by thermocouples. This result verifies the efficacy of the method when it comes to accurately reconstructing the temperature field in the combustion area. The reduction in error is attributed to the consideration of acoustic ray tracing within the proposed method.

Rapid quantitative PCR equipment using photothermal conversion of Au nanoshell

The emergence of infectious diseases worldwide necessitates rapid and precise diagnostics. Using gold nanoshells in the PCR mix, we harnessed their unique photothermal properties in the near-infrared regime to attain efficient heating, reaching ideal photothermal PCR cycle temperature profile. Our photothermal PCR method expedited DNA amplification while retaining its detection sensitivity. Combining photothermal quantitative PCR with real-time fluorometry and non-invasive temperature measurement, we could amplify the target DNA within just 25 min, with a minimum detectable DNA amount of 50 picograms. This innovation in photothermal qPCR, leveraging the photothermal properties of gold nanoshells, will pave the way for immediate point-of-care diagnostics of nucleic acid biomarkers.

Real-time temperature monitoring technology for dynamic combustion processes using dual-probe femtosecond CARS

We propose a fast responsive and non-invasive optical temperature measurement method which can be used to monitor the temperature of air-fed flames in real time. This method is based on femtosecond time-resolved coherent anti-Stokes Raman spectroscopy (fs-CARS). Two probe pulses with different wavelengths are employed in the CARS system to generate two CARS signals, and the intensity ratio of the two CARS signals has a definite numerical relationship with temperature and therefore can be used to rapidly measure the flame temperature. The temperature of methane/air swirl flames was monitored by the dual-probe fs-CARS thermometry with a sampling rate of 100 Hz. For the steady swirl flame, the measured average temperature in the inner recirculation zone is 1551 K with a standard deviation of 3.7%. While, at a higher methane/air equivalent ratio of 0.74, the flame cannot remain steady, and the temperature frequently jumps from around 1700 K to 2000 K, causing the vortex to expand and break. A significant advantage of the dual-probe fs-CARS thermometry is that the temperature of the flame can be obtained immediately during the measurement without any post-processing. Therefore, this method is a potential candidate for accurately monitoring the real-time temperature of turbulent combustion.

Non-invasive temperature measurement in fixed bed reactors using RFID technology

Measuring axial temperature profiles in fixed bed reactors is essential for an optimal and safe operation. Typically, thermocouples are used which influence the bed structure - especially in arrangements with a low ratio between tube and particle diameter - and thus local transport phenomena and reaction rates. In this publication, Radio-Frequency Identification (RFID) tags are used for temperature measurement in fixed beds without disturbing the bed structure. Therefore, the temperature is compared in a tubular fixed bed (▪) of ceramic rings (▪) measured with RFID tags and thermocouples at similar axial positions at different temperature levels 20<T<140▪. By integrating an RFID tag into a particle using 3D printing, the disturbance of the fixed bed by the measurement device can be even completely avoided. It is shown that the overall values of temperature and the dynamic measurement with RFID tags is comparable to measurements using thermocouples. However, significant measurement gaps can occur, especially with unfavorable antenna-tag alignment or small antenna spacing. As a summary, it is possible to measure temperature in fixed bed reactors using RFID technology without requiring direct access and thus disturbing the bed structure. Finally, current shortcomings of RFID are discussed, and research needs presented.

Feasibility analysis of applying non-invasive core body temperature measurement in sleep research

Core body temperature (CBT) emerges as a pivotal physiological marker in sleep research, and the commonly employed invasive CBT measurements significantly disrupt the sleep process itself. Non-invasive CBT measurement offers a viable solution to this challenge but lack validation. In this sleep study, simultaneous invasive and non-invasive measurements of CBT were conducted on 14 subjects. Ingestible capsule was chosen to represent invasive measurement, while external GreenTeg patch was selected as representative device for non-invasive measurement. Quantitative comparisons of two measurements were conducted from four perspectives: correlation, consistency, difference, and stability, and results indicated: (1) A significant correlation was observed between two real-time measurements, and correlation became stronger as ambient temperature decreased. (2) Consistency of most data group can be acceptable as most of them fell within the 95% agreement range. (3) Non-invasive instrument exhibited substantial error for unstable core temperature, yet displayed relatively small error for stable core temperature. (4) Stability of difference between two measurements was poor during 64.3% of the time intervals, and this performance deteriorated further in unstable state. In summary, existing non-invasive measurement can serve as a reference for sleep research, but caution is warranted when applying it to real-time and unstable analyses. Additionally, feasibility of algorithm optimization makes the future of non-invasive measurements promising.

Quantitative Microscale Thermometry in Droplets Loaded with Gold Nanoparticles.

Gold nanoparticles (AuNPs) are increasingly used for their thermoplasmonic properties, i.e., their ability to convert light energy into heat through plasmon resonance. However, measuring temperature gradients generated at the microscale by assemblies of AuNPs remains challenging, especially for random 3D distributions of AuNPs. Here, we introduce a label-free thermometry approach, combining quantitative wavefront microscopy and numerical simulations, to infer the heating power dissipated by a 3D model system consisting of emulsion microdroplets loaded with AuNPs. This approach gives access to the temperature reached in the droplets under laser irradiation without the need for extrinsic calibration. This versatile thermometry method is promising for noninvasive temperature measurements in various 3D microsystems involving AuNPs as colloidal heat sources, including photothermal drug delivery systems.

A multi-mode self-referenced optical thermometer based on low-doped YVO4: Eu3+ phosphor

In recent years, the continued development of optical thermometry has become a hot topic of interest for researchers, due to its advantages of non-contact and non-invasive temperature measurement. The optical thermometry is based on the different photophysical properties or changes in luminescent parameters of luminescent materials to reflect temperature. Further, the development of multi-mode optical thermometers can effectively expand the practical application rang of the temperature measurements. Here, we monitored various temperature sensitive luminescence characteristics of YVO4: Eu3+ phosphor by testing its temperature-dependent photoluminescence (PL) spectra, photoluminescence excitation (PLE) spectra, and luminescence decay curves. We successfully realized a multi-mode optical thermometer based on the luminescence intensity ratio, absorption intensity ratio, the thermally induced behavior of the charge transfer band, and luminescent transition probability (A) of the host material. Different temperature measurement strategies were evaluated and compared in terms of relative sensitivity (Sr) and temperature uncertainty (ΔT). Notably, the Sr of the rarely used temperature measurement strategy based on the A of host luminescence was the optimal among the studied strategies with 2.03% K−1, corresponding to a ΔT of 0.5 K. The results suggest that YVO4: Eu3+ phosphor has potential applications in self-referential optical thermometry.

Self-monitored Nd-doped MoSe2 nanosheets with near-infrared luminescent sensing for photothermal therapy

The acquisition of real-time temperature monitoring during photothermal therapy is significant to prevent unnecessary damage to healthy tissues. However, owing to complexity and diverse factors in microenvironment of cells, there still remain considerable challenges in achieving noninvasive temperature measurement and manipulation in therapeutic process. Herein, biocompatible Nd-doped MoSe2 nanosheets have been developed on the premise of excellent photothermal effect, which manifest desirable photoluminescence and distinct temperature self-monitored capability in near-infrared I and II bio-windows. Based on thermally coupled energy levels of Nd ions, the real-time monitoring on temperature changes in intracellular environment can be realized which provide instant temperature feedbacks to avoid side effects from hyperthermia. Exclusive of detrimental elements such as F and Pb, the objective nanosheets manifest satisfactory biosafety and can induce effective tumor ablation under near-infrared irradiation with photothermal conversion efficiency up to 40.8%, providing an innovative vision for developing more precisely and safely photothermal approaches.

Noninvasive measurement of temperature for simulated tissue based on piezoelectric micromachined ultrasonic transducers

This paper reports a noninvasive measurement of temperature for simulated tissue based on an AlN piezoelectric micromachined ultrasonic transducer array. Polydimethylsiloxane and a built-in heating plate are used to simulate the thermal therapy of human tissue. Based on time-of-flight (ToF) from the simulated tissue surface to the heating plate surface and corresponding temperature data, the piecewise linear fitting method is used to fit the ToF-temperature curve, and its sensitivity is (below 50 °C) and (from 50 °C to 65 °C). The average error of real-time temperature measurements is 0.58 °C for temperatures below 65 °C. The proposed method can provide a good solution for temperature detection during thermal therapy.

Multi-Wavelength Photoacoustic Temperature Feedback Based Photothermal Therapy Method and System.

Photothermal therapy (PTT) is a new type of tumor treatment technology that is noninvasive, repeatable, and does not involve radiation. Owing to the lack of real-time and accurate noninvasive temperature measurement technology in current PTT surgical procedures, empirical and open-loop treatment laser power control mode inevitably leads to overtreatment. Thermal radiation causes irreversible damage to normal tissue around cancer tissue and seriously affects the therapeutic effect of PTT and other therapies conducted at the same time. Therefore, real-time measurement and control of the temperature and thermal damage of the therapeutic target are critical to the success of PTT. To improve the accuracy and safety of PTT, we propose a multi-wavelength photoacoustic (PA) temperature feedback based PTT method and system. PA thermometry information at different wavelengths is mutually corrected, and the therapeutic light dose is regulated in real time to accurately control the treatment temperature. The experimental results on the swine blood sample confirm that the proposed method can realize real-time temperature measurement and control of the target area with an accuracy of 0.56 °C and 0.68 °C, demonstrating its good prospects for application.

Proposal of a Skin Temperature Measurement System Based on Digital Thermometers

The representation of temperature measurement methods is worldwide, as is the number of industries that use them. Their utilization allows one to assess the object’s temperature relatively accurately and further according to the defined dependencies to evaluate its condition. In the medical sector, non-invasive temperature measurement methods are increasingly gaining ground. In our work, we focus on the design of a system for measuring skin temperature using digital DS18B20 thermometers. The technical design consists of the mechanical design of the sensor housing based on the requirements of healthcare professionals, the design of a 1-wire bus active pull-up driver with improved features, and the user software, allowing for the future implementation in various, not necessarily medical environments. The main contribution lies in optimizing the hardware design concerning the components’ parameters and surge protection. In the medical field, the aim was to compare changes in skin temperature in the shoulder region depending on the type of muscle contraction during static and dynamic components of movement and to record the thermal work of the muscle during activity in real-time. We experimented by applying temperature sensors to the deltoid muscle of the dominant limb in a temperature environment of 25.76 °C. In the experimental measurements, we demonstrated that during the three selected muscle work movements, there was a temperature change in the respective regions of the deltoid muscle for each of the three, which the temperature sensors could capture. Our results were statistically significant when comparing the baseline values, and the highest temperature reached. The level of significance α ⩽ 0.05 and a low percentage of errors were valid.

Noninvasive measurement of subcutaneous temperature using active antenna and high gain low noise microwave radiometer

ABSTRACT This paper presents a radiometric thermometer for non-invasive measurement of the internal body temperature. The proposed radiometric thermometer designed in 1.575 GHz band consists of a near-field probe and a high gain Dick radiometer. A phantom based on Agar material was developed to emulate the real tissue of skin and muscle for experiments. The measured results show that the active probe antenna provides additional 12.5 dB gain with noise figure less than 1dB, and the radiometer has a system gain of 50 dB and total noise figure of 1.738 dB at 1.575 GHz. The output voltage measured by the proposed 1.575 GHz microwave radiometer is 2.994 V when the water temperature is set to 25 °C, while it is 3.129 V when the water temperature is set to 80 °C. The study demonstrates that using the active probe connected to the radiometer can identify temperature difference of the body.

Highly thermally stable upconversion in copper(II)-doped LiYF4:Yb,Er microcrystals toward ultrahigh temperature (micro)thermometers

Lanthanide-based optical ratiometric thermometer is a promising temperature detecting tool for noninvasive temperature measurements. However, owing to the thermal quenching of upconversion luminescence (UCL), the traditional temperature sensing range is limited to less than 600 K. In this work, highly thermally stable UCL is observed through introduced appropriate Cu 2+ ions into LiYF 4 :Yb/Er (20/2 mol%) microcrystals (MCs) and on which are further used for temperature sensing applications. As gradually increases the doping of Cu 2+ ions, the octahedron morphology of LiYF 4 MCs with smooth surfaces gradually aggregates smaller particles on their surface forming diamond-like micro-clusters. Based on the single-particle spectroscopy technique, the temperature-dependent UCL properties were systematically investigated and demonstrated. Doping of Cu 2+ ions can efficiently adjust and enhance the UCL in the LiYF 4 :Yb/Er (20/2 mol%) MCs. The UCL thermal quenching temperature is less than ~670 K for Cu 2+ -free MCs. In contrast, the quenching temperature extends to as high as ~870 K when doping with 2 mol% Cu 2+ ions. Furthermore, these highly thermal stable MCs are utilized to detect the temperature in a wide temperature ranging from 298 K to 873 K. A maximum relative sensitivity ( S r ) of 1.23%K −1 at 298 K is obtained and temperature uncertainty δ T < 0.091 K is determined under the measured temperature for the 2 mol% Cu 2+ -doped MCs. The highly thermally stable UCL properties and excellent thermometer performance of these MCs, particularly conducted at single-particle spectroscopy technique, can be potentially applied to micro-scale thermometers. • Cu 2+ ions manipulate the morphology and size of LiYF 4 :Yb 3+ /Er 3+ microcrystals. • Appropriate Cu 2+ ions improve the upconversion luminescence thermostability. • High-temperature thermometers achieved at single-particle spectroscopy technique.

A pilot study of agreement between noninvasive thermometers and the core temperature of postoperative cardiothoracic surgical patients

ObjectiveReliable and accurate temperature assessment is fundamental for clinical monitoring; noninvasive thermometers of various designs are widely used in intensive care units, sometimes without a specific assessment of their suitability and interchangeability. This study evaluated agreement of four noninvasive thermometers with a pulmonary artery catheter temperature. MethodsThis prospective method comparison study was conducted in an Australian adult intensive care unit. One hundred postoperative adult cardiothoracic surgery patients who had a pulmonary artery catheter (Edwards Lifescience) in situ were identified. The temperature reading from the pulmonary artery catheter was compared to contemporaneous measurements returned by four different thermometers—temporal Artery (TA, Technimed), Per Axilla (Axilla, Welch Allyn), Tympanic (Tymp, Covidien), and the NexTemp® (NEXT, Medical Indicators [used per axilla]). The time required to obtain each noninvasive temperature measurement was recorded. ResultsAgreements between each noninvasive temperature and the pulmonary artery catheter standard were assessed using summary statistics and the Bland–Altman method comparison approach. A clinically acceptable maximum difference from the standard was defined as ±0.5 °C. Temperature agreement with the pulmonary artery standard (mean difference °C [95% limits of agreement °C]) was greatest for Tymp (−0.20 [−0.92 to 0.52]), intermediate for AXILLA (−0.37 [−1.3 to 0.59]) and NEXT (−0.71 [−1.7 to 0.27]), and least for TA (−0.60 [−2.0 to 0.81]). The proportion of measurements within ±0.5 °C of the standard were TYMP (81%), AXILLA (63%), TA (45%), and NEXT (30%). The time to obtain measurements varied, with the Tymp and TA estimates immediate, the AXILLA a mean of 40 s (standard deviation = 11 s), while NEXT results were at the manufacturer-recommended 3-min point. ConclusionsTympanic thermometers showed closest agreement with the pulmonary artery standard. Deviations by more than 0.5 °C from that standard were relatively common with all noninvasive devices.

Experimental study on the accuracy of non-invasive temperature measurement by magnetic resonance in microwave ablation.

This study aimed to explore the accuracy of non-invasive temperature measurement based on proton resonance frequency (PRF) phase subtraction in microwave ablation (MWA). The signal change of the agar phantom during the ablation process was monitored by the gradient echo sequence under 1.5 T superconducting magnetic resonance imagining (MRI), and the temperature change was converted by the phase subtraction method of the PRF, which was compared with the temperature measured using an optical fiber. SPSS software version 22.0 was used for data processing, and the independent sample t-test was used for comparative analysis. P < 0.05 indicated statistical significance. The maximum error between the MRI temperature measurement and the standard value was 3.61°C, whereas the minimum and average errors were 0.01°C and 1.19°C ± 0.78°C, respectively. The temperature measurement technology, which is based on the PRF phase method, has good accuracy in MRI-guided MWA.

Mild-temperature photothermal treatment method and system based on photoacoustic temperature measurement and control

As a non-invasive technology for tumor treatment, photothermal therapy (PTT) is increasingly applied during clinical treatment. However, due to the lack of non-invasive temperature measurement methods, excessive therapeutic light dose will damage the healthy tissue around the lesion. Monitoring and control the therapy temperature during PTT application is necessary to ensure effective therapy while minimizing thermal damage to adjacent tissue. In order to ensure that the therapy temperature in PTT is stable in the mild range (below 43 °C), it is necessary to design a mild-temperature PTT method and system that can detect and control the temperature in real-time. A mild-temperature photothermal treatment method and system based on photoacoustic temperature measurement and control is proposed in this paper. On the basis of reference temperature, the relative temperature change is measured based on the photoacoustic information, and the treatment temperature of the target area is precisely controlled in real time using the closed-loop temperature control algorithm. Based on the experimental results of agar-based phantoms and pig liver tissue, the proposed system can achieve temperature imaging in real time, and the control steady-state error and overshoot are 0.62 °C and 0.3 % respectively. The results show that our method has the potential for accurate temperature monitoring and closed-loop temperature control during PTT.