Non-invasive Temperature Measurement Research Articles

Development of Body-Tissue Temperature-Control Transducer.

The aim of this study was to develop a transducer for non-invasive temperature measurement in deeper tissue layers during tissue cooling. Simulation of the temperature field distribution in human tissues and the transducer were done, and the influence of transducer structure and material properties were studied. Using simulation results, the experimental transducer was designed for temperature measurement in deeper tissue layers during cooling. The temperature measurements with the needle thermometer and the transducer were well correlated at both before tissue cooling r = 0.723 and after cooling r = 0.945, and the temperature difference was no more than ±0.2 °C.

Investigating the subjective cooling effect of eyelid cleansing gel on eyelid and ocular surface temperature

PurposeTo investigate if the application of Blephagel, an eyelid cleansing gel, causes subjective and/or objective cooling effects by measuring ocular symptomology and temperature. MethodsTwenty-five healthy subjects underwent baseline non-invasive temperature measurements on the closed upper eyelid (centrally, nasally, and temporally) and ocular surface temperature (OST) on both eyes using an infrared camera. A standard application of Blephagel was then applied to the closed upper eyelid and eyelashes with a sterile cotton-wool to one eye selected at random. Temperature measures were then repeated on both eyes after 30–60, 120–150, and 180–210 s. At each interval, subjects rated the comfort and any cooling sensation of each eye on a 0–10 scale. ResultsAfter application of the gel, there was a significant difference in temperature at all locations on the eyelid between the test and control eyes over time (F = 9.322, p < 0.001). Post hoc analysis revealed this was significant from 30 to 60 s interval (36.3 ± 1.1 °C versus 37.2 ± 0.7 °C; p < 0.001) and the 120–150 s interval (36.8 ± 0.8 °C versus 37.2 ± 0.6 °C; p < 0.001). There was no significant variation between the OST locations over time (F = 3.350, p = 0.07). With respect to symptoms, there was a significant increase in cooling sensation in the test eye compared to the control eye over time (F = 10.438, p < 0.001), that remained throughout the experiment. ConclusionsBlephagel produces a reduction in temperature of the eyelids that is accompanied with a subjective cooling sensation.

Modern fertility awareness methods: wrist wearables capture the changes in temperature associated with the menstrual cycle.

Core and peripheral body temperatures are affected by changes in reproductive hormones during the menstrual cycle. Women worldwide use the basal body temperature (BBT) method to aid and prevent conception. However, prior research suggests that taking one’s daily temperature can prove inconvenient and subject to environmental factors. We investigate whether a more automatic, non-invasive temperature measurement system can detect changes in temperature across the menstrual cycle. We examined how wrist skin temperature (WST), measured with wearable sensors, correlates with urinary tests of ovulation and may serve as a new method of fertility tracking. One hundred and thirty-six eumenorrheic, non-pregnant women participated in an observational study. Participants wore WST biosensors during sleep and reported their daily activities. An at-home luteinizing hormone (LH) test was used to confirm ovulation. WST was recorded across 437 cycles (mean cycles/participant = 3.21, S.D. = 2.25). We tested the relationship between the fertile window and WST temperature shifts, using the BBT three-over-six rule. A sustained 3-day temperature shift was observed in 357/437 cycles (82%), with the lowest cycle temperature occurring in the fertile window 41% of the time. Most temporal shifts (307/357, 86%) occurred on ovulation day (OV) or later. The average early-luteal phase temperature was 0.33°C higher than in the fertile window. Menstrual cycle changes in WST were impervious to lifestyle factors, like having sex, alcohol, or eating prior to bed, that, in prior work, have been shown to obfuscate BBT readings. Although currently costlier than BBT, the present study suggests that WST could be a promising, convenient parameter for future multiparameter fertility awareness methods.

Thermal Imaging as a Noncontact Inline Process Analytical Tool for Product Temperature Monitoring during Continuous Freeze-Drying of Unit Doses.

Freeze-drying is a well-established technique to improve the stability of biopharmaceuticals which are unstable in aqueous solution. To obtain an elegant dried product appearance, the temperature at the moving sublimation interface Ti should be kept below the critical product temperature Ti,crit during primary drying. The static temperature sensors applied in batch freeze-drying provide unreliable Ti data due to their invasive character. In addition, these sensors are incompatible with the continuous freeze-drying concept based on spinning of the vials during freezing, leading to a thin product layer spread over the entire inner vial wall. During continuous freeze-drying, the sublimation front moves from the inner side of the vial toward the glass wall, offering the unique opportunity to monitor Ti via noncontact inline thermal imaging. Via Fourier's law of thermal conduction, the temperature gradient over the vial wall and ice layer was quantified, which allowed the exact measurement of Ti during the entire primary drying step. On the basis of the obtained thermal images, the infrared (IR) energy transfer was computed via the Stefan-Boltzmann law and the dried product mass transfer resistance ( Rp) profile was obtained. This procedure allows the determination of the optimal dynamic IR heater temperature profile for the continuous freeze-drying of any product. In addition, the end point of primary drying was detected via thermal imaging and confirmed by inline near-infrared (NIR) spectroscopy. Both applications show that thermal imaging is a suitable and promising process analytical tool for noninvasive temperature measurements during continuous freeze-drying, with the potential for inline process monitoring and control.

A non-invasive measurement of tongue surface temperature

Oral temperature, tongue specifically, is a key factor affecting oral sensation and perception of food flavour and texture. It is therefore very important to know how the tongue temperature is affected by food consumption. Unfortunately, traditional methods such as clinical thermometers and thermocouples for oral temperature measurement are not most applicable during food oral consumption due to its invasive nature and interference with food. In this study, infrared thermal (IRT) imager was investigated for its feasibility for the measurement of tongue surface temperature. The IRT technique was firstly calibrated using a digital thermometer (DT). The technique was then used to measure tongue surface temperature after tongue was stimulated by (1) water rinsing at different temperatures (0–45 °C); and (2) treated with capsaicin solutions (5, 10, and 20 ppm). For both cases, tongue surface temperature showed significant changes as a result of the physical and chemical stimulation. Results confirm that IRT is feasible for tongue temperature measurement and could be a useful supporting tool in future for the study of food oral processing and sensory perception.

Introduction of Clinical Practice Guidelines for Emergency Patients

A hospital emergency department is unique among medical environments, with risks of medical errors often higher than in other medical units. Previous studies have confirmed that establishing comprehensive clinical practice guidelines in the emergency department reduces medical costs and improves patient safety and satisfaction. Furthermore, having these guidelines positively influences and significantly impacts the work of emergency care professionals. This article addresses the current assessment and treatment of common emergency care, including non-invasive temperature measurements, oxygenated monitoring during procedural sedation and analgesia, postural differences and vital signs monitoring, and difficulties in peripheral vein placement. Further, this article introduces the recommendations of the Emergency Nurses Association on the empirical level and in terms of the clinical application of these practices in order to help emergency staffs develop domestic and local emergency clinical care guidelines in order to reduce the incidence of medical malpractice and improve care quality and patient satisfaction.

(Invited) Analytical Methods for Understanding Multiscale Thermal Transport in Li-Ion Batteries Towards Improved Safety and Performance

Li-ion cells are widely used for electrochemical energy storage and conversion in applications such as consumer electronics, transportation, grid storage, etc. Multiple transport processes such as ionic, electronic and thermal transport occur simultaneously in a Li-ion cell, and interact with each other through a number of mechanisms at multiple length scales. This considerable complexity makes it imperative to carry out a careful, analytical investigation of these transport processes for optimizing performance and ensuring safety. This presentation will summarize ongoing research on analytical modeling of heat transfer in Li-ion cells with the overarching of improving safety and performance of electrochemical devices and systems. The governing energy conservation equation in a Li-ion cell is solved in a variety of scenarios to help better understand the nature of heat transfer in the cell. Specifically the effect of temperature-dependent, exothermic decomposition processes is examined. It is shown that such processes can lead to a thermal runaway situation wherein the cell temperature becomes unbounded. It is shown whether thermal runaway occurs or not depends on the value of a specific non-dimensional parameter called the thermal runaway number which captures the contributions of three different thermal processes that combine to determine the thermal fate of the cell. This treatment offers a potential mechanism to monitor the health of a cell and proactively take measures to prevent thermal runaway before it is too late. Further, analytical modeling of temperature distribution with a cell is carried out in order to develop a method for non-invasively determining the core temperature of a cell. This is important because a direct measurement of the core temperature is not possible in most cases due to lack of physical access to the cell core. An analytical model for the temperature distribution in the cell is developed using the method of undetermined parameters. This shows that the core temperature of a cell undergoing any arbitrary process can be determined through appropriate time and space integrals of the outside temperature of the cell, combined with certain other thermal parameters. This has enabled an experimental method for non-invasive core temperature measurement of a Li-ion cell based on infrared thermography of its outside surface. These results indicate, for example, that the core temperature of the cell may be hundreds of degrees Celsius greater than the measured outside temperature during a thermal runaway event. Given that the thermal fate of the cell is ultimately governed by its peak temperature, which occurs at its core, this is an important insight into the thermal state of a cell undergoing, or close to thermal runaway. In addition to improving the understanding of fundamental heat transfer processes in a Li-ion cell, the analytical modeling work described here also forms the basis for novel techniques for measurement of critical processes and properties, thereby contributing towards improved overall safety and performance of the cell.

Characterization and Corrections for Clamp-On Fluid Temperature Measurements in Turbulent Flows

A clamp-on measurement system for flexible and accurate fluid temperature measurements for turbulent flows with Reynolds numbers higher than 30,000 is presented in this paper. This noninvasive system can be deployed without interference with the fluid flow while delivering the high accuracies necessary for performance and acceptance testing for power plants in terms of measurement accuracy and position. The system is experimentally validated in the fluid flow of a solar thermal parabolic trough collector test bench, equipped with built-in sensors as reference. Its applicability under industrial conditions is demonstrated at the 50 MWel AndaSol-3 parabolic trough solar power plant in Spain. A function based on large experimental data correcting the temperature gradient between the measured clamp-on sensor and actual fluid temperature is developed, achieving an uncertainty below ±0.7 K (2σ) for fluid temperatures up to 400 °C. In addition, the experimental results are used to validate a numerical model. Based on the results of this model, a general dimensionless correction function for a wider range of application scenarios is derived. The clamp-on system, together with the dimensionless correction function, supports numerous combinations of fluids, pipe materials, insulations, geometries, and operation conditions and should be useful in a variety of industrial applications of the power and chemical industry where temporal noninvasive fluid temperature measurement is needed with good accuracy. The comparison of the general dimensionless correction function with measurement data indicates a measurement uncertainty below 1 K (2σ).

Non-invasive Measurement of Water Temperature by a Combined Method of Ultrasound and Laser

Non-invasive Measurement of Water Temperature by a Combined Method of Ultrasound and Laser

Position adjustment method and distance estimation method of magnetic field supply and detection unit for magnetic hyperthermia

In magnetic hyperthermia, the temperature and localization of a ferromagnetic implant in a tumor region is vital in determining the effectiveness of therapeutic heating. We have developed a noninvasive wireless temperature measurement method by utilizing the magnetic permeability property of a ferromagnetic implant with low Curie temperature (FILCT) that varies with the temperature. In clinical settings, when the FILCT is injected into a tumor region, the position of the FILCT is expected to deviate from the central axis of the heating coil (drive coil). When it deviates, the magnetic flux density applied to the FILCT decreases, thus causing difficulty in detecting the temperature of FILCT via a pickup coil and heating of the FILCT at a constant treatment temperature. Therefore, to adjust the magnetic field supply and detection (MFSD) unit to be directly above the FILCT, we propose a position adjustment method by referring to three voltages induced in three pickup coils symmetrically installed inside the drive coil. By using the average value of the three voltages, we also propose a method to estimate the distance between the MFSD unit and the FILCT, which is required for wireless thermometry and determination of the optimal energy applied. The proposed methods are experimentally examined by a verification system.

Agreement of Axillary and Auricular Temperature with Rectal Temperature in Systemically Healthy Dogs Undergoing Surgery.

Obtaining a patient's temperature is an important part of a patient's physical examination. As human medicine transitions to noninvasive temperature measurements, so does veterinary medicine. Historically, temperature measurement has been obtained from rectal readings; however, alternative methods, such as axillary and auricular temperatures, are increasing in popularity. The purpose of the study was to compare these alternative techniques to the gold standard of rectal temperature. Temperatures were obtained three ways for each patient: rectal, axillary, and auricular. Results indicated a positive linear relationship between rectal and axillary temperatures (bivariate correlation coefficient [r] = 0.65, P < .001) and axillary and auricular temperatures (r = 0.55, P < .001). Agreement was strongest between rectal and auricular temperatures (r = 0.80, P < .001). The average discrepancy between axillary and rectal temperature was 1.2°C [2.1°F] with the highest difference being 4.0°C [7.3°F]. The average discrepancy between auricular and rectal temperature was 0.6°C [1.2°F] with the highest difference being 2.2°C [4.1°F]. Despite auricular temperatures having stronger agreement, Bland-Altman Limits of Agreement testing revealed that it was a poor predictor of rectal temperature. Based on these results, axillary and auricular temperatures should not be substituted for rectal temperature.

Smartphone-Based Thermal Imaging: A New Modality for Tissue Temperature Measurement in Hand and Upper Extremity Surgeries.

Smartphone-based thermal imaging (SBTI) allows noninvasive temperature measurements. Its validity compared with a conventional infrared probe temperature scanner (IPTS) has not been studied. This study compares temperature measurements between the 2 technologies on human participants. Bilateral index finger temperature measurements were obtained on 30 healthy participants using IPTS and SBTI devices. Dominant versus nondominant sides (side-to-side difference) and individual side measurements between the 2 methods were compared for repeatability (precision) and agreement. A total of 23 female and 7 male participants were tested. Based on nonoverlapping confidence intervals (CIs), intraclass correlation coefficient of repeatability was higher for SBTI than for IPTS measurements in side-to-side differences: 0.97 (95% CI, 0.96-0.99) versus 0.89 (95% CI, 0.82-0.95). The SBTI method recorded higher side-to-side difference and individual side measurements: 0.56°C (limits of agreement [LOA], -1.09°C to 2.20°C) and 2.64°C (LOA, 0.96°C-4.32°C), respectively. In addition to higher precision, SBTI offers added benefits of instantaneous acquisition of the temperature map of the entire hand, allowing quick comparisons of the uninjured and injured fingers. SBTI measurements consistently yielded higher temperature readings in the side-to-side difference as well as individual measurements. This suggested that both devices are not interchangeable for absolute temperature comparisons but are interchangeable in monitoring the changes in temperatures. This study suggests the potential for SBTI devices to be used in the clinical settings and may be of special benefit in telemedicine.

Validity and reliability of the myTemp ingestible temperature capsule

ObjectivesAn accurate and non-invasive measurement of core body temperature (Tc) is of great importance to quantify exercise-induced increases in Tc in athletes or to assess changes in Tc in patient populations. The use of ingestible gastrointestinal telemetric temperature capsules is widely accepted as a surrogate marker for Tc, but widespread implementation is lacking due to the high costs of these disposable capsules. A new and cheaper temperature capsule system (i.e. myTemp) was recently introduced. The aim of present study is to determine the validity and test–retest reliability of the myTemp system. DesignEx-vivo experimental study. MethodsFifteen ingestible temperature capsules (myTemp, Nijmegen, Netherlands) were tested in a highly temperature controlled water bath, in which the water temperature gradually increased from 34°C to 44°C. The study protocol was performed twice for each temperature capsule. ResultsMean difference between myTemp temperature and water bath temperature was −0.001±0.005°C (Limit of Agreement (LOA): ±0.011°C) during Trial 1 (p=0.11) and −0.001±0.006°C (LOA: ±0.012°C) during Trial 2 (p=0.039). Furthermore, an Intraclass Correlation Coefficient (ICC) of 1.00 was found for both trials. A systematic difference between Trials 1 and 2 of 0.004±0.008°C (LOA: ±0.015°C) was found (p<0.001), whereas the ICC between both trials was 1.00 and the standard error of measurement was 0.005°C. ConclusionsAlthough we found a systematic bias for the sensitivity (−0.001°C) and reliability (0.004°C), these values can be considered insignificant from a physiological and clinical perspective. Thus, the myTemp ingestible temperature capsule is a valid technique to measure (water) temperature under controlled circumstances.

A microwave radiometer for deep noninvasive diagnostics of thermal fields inside a biological object

A microwave radiometer for a wavelength of 10.5 cm with a frequency band of received signals of 200 MHz is described. It allows one to perform remote noninvasive temperature measurements deep in a biological object. The use of a modified null–reception method as the basis of the instrument operation made it possible to reduce the influence of the reflectance at the location of the contact between an applicator antenna and a body on the measurement accuracy and increase the dynamic characteristics during mapping of a biological object. At a storage signal time of 1 s, the measurement accuracy was 0.047 K. The output–signal changes were within 0.1 K when the reflectance was varied from 0.1 to 0.5.

Non-Invasive Monitoring of Temperature in the Heart Hypo- and Hyperthermia with Cardiopulmonary Bypass

Background. The implementation of the method of non-invasive control of heart temperature based on the model of heat exchange in the myocardium during extracorporeal circulation is considered. Objective. The purpose of the research is the use of numerical simulation methods in the MSC Sinda system to estimate the temperature gradient that is observed on the surface of the myocardium during hypo- and hyperthermia in the conditions of artificial circulation. Methods. To obtain the original data in the cardiopulmonary bypass loop temperature sensor system in arterial, venous, and cardioplegic lines is used. When assessing the temperature gradient applied of thermal diagnostics methods and analysis of thermograp in the infrared spectrum that allow getting data for the simulation of heat transfer process between the myocardium and coronary vessels in the MSC Sinda system. Results. As a result of numerical modeling 2D-model of heat exchange in the myocardium was proposed and the comparative analysis of thermal images of open heart with hypo- and hyperthermia with cardiopulmonary bypass was carried out. Carrying out non-invasive temperature measurement and simulation results of heat transfer on the surface of the myocardium allow more accurately adjust the speed of warming (hyperthermia) of venous blood in the heat exchanger. Conclusions. The simulation results allow supplementing the qualitative indications of system sensors for cardiopulmonary bypass. Application of thermal diagnostics methods and imaging analysis of thermograms for the monitoring of venous return temperature cardiopulmonary bypass circuit that allows you to adjust the flow of blood to the hollow veins with using venous occlusion line change with the clamp or a special device.

Non-invasive measurement of internal temperature of a cylindrical Li-ion cell during high-rate discharge

Li-ion cells are a technologically important class of devices for electrochemical energy storage and conversion. Overheating of a Li-ion cell during operation is undesirable as it directly affects performance and safety. Although a number of methods have been used for temperature measurement in Li-ion cells, there is a lack of non-invasive techniques to determine the peak temperature at the core of the cell. Measuring only the outside surface temperature, while straightforward, is not sufficient since the core temperature may be much higher. This paper presents non-invasive measurement of the core temperature of a Li-ion cell using a recently developed technique that utilizes space and time integrals of the measured temperature field at the outside surface. The surface temperature field of an operating Li-ion cell is measured using infrared thermography at multiple discharge rates up to 10C, using which, the core temperature is predicted as a function of time. In each case, there is excellent agreement throughout the discharge period between the predicted core temperature and measurements from a thermocouple embedded at the core of the cell. These measurements quantify the temperature gradient within the cell, which is particularly high at large discharge rates. The non-invasive core measurement methods described here may contribute towards performance optimization and improved safety of Li-ion cells.

Noninvasive temperature measurements of RLIF and nPIT in DI water flow microchannels

Abstract Experiments were performed herein to examine the near-wall water flow/thermal characteristics and bulk flow behavior in a 20 mm long microchannel with a height of 45 μm (thermal) and a width of 200 μm, through the noninvasive optical measuring techniques of nPIT and RLIF. The corresponding streamwise wall temperature distribution (45 μm channel) was measured. It was found that at Re = 2, the flow can be fully developed thermally. In addition, both the local heat transfer coefficient and the corresponding Nusselt number were obtained via the RLIF and traditional thermocouple measurements. When compared to the results of previous studies our results are in good agreement.

Effects of tissue susceptibility on brain temperature mapping

A method for mapping of temperature over a large volume of the brain using volumetric proton MR spectroscopic imaging has been implemented and applied to 150 normal subjects. Magnetic susceptibility-induced frequency shifts in gray- and white-matter regions were measured and included as a correction in the temperature mapping calculation. Additional sources of magnetic susceptibility variations of the individual metabolite resonance frequencies were also observed that reflect the cellular-level organization of the brain metabolites, with the most notable differences being attributed to changes of the N-Acetylaspartate resonance frequency that reflect the intra-axonal distribution and orientation of the white-matter tracts with respect to the applied magnetic field. These metabolite-specific susceptibility effects are also shown to change with age. Results indicate no change of apparent brain temperature with age from 18 to 84 years old, with a trend for increased brain temperature throughout the cerebrum in females relative for males on the order of 0.1°C; slightly increased temperatures in the left hemisphere relative to the right; and a lower temperature of 0.3°C in the cerebellum relative to that of cerebral white-matter. This study presents a novel acquisition method for noninvasive measurement of brain temperature that is of potential value for diagnostic purposes and treatment monitoring, while also demonstrating limitations of the measurement due to the confounding effects of tissue susceptibility variations.

Hypothermia in Adult ICUs: Changing Incidence But Persistent Risk Factor for Mortality.

This study examined whether hypothermia (< 36.0°C) incidence among critically ill patients varied over time, the determinants of change, and the associated risk for ICU mortality. Interrupted time series analysis among adults admitted to ICUs in Calgary, Canada over 8.5 years. Changes in the incidence of hypothermia within the first 24 hours of ICU admission were modelled using segmented regression. Among 15,291 first admissions to ICU, hypothermia incidence decreased from 29% to 21% during the study period. Implementation of a new temporal artery thermometer (TAT) was associated with the majority of the decrease in incidence (10%; 95% CI 7.1-13%; P < .0001). However, subgroup analysis revealed important differences between medical and surgical patients. Hypothermia incidence decreased among surgical patients before TAT implementation (0.4% per quarter, 95% CI 0.1-0.7%, P = .009), but not after, whereas in medical patients, the incidence increased after (1.0% per quarter, 95% CI 0.6-1.4%, P < .0001) but not before TAT implementation. Segmented logistic regression suggested that increases in the proportion of patients with non-traumatic neurologic admission diagnoses were associated with hypothermia incidence among medical patients, whereas there was no measurable clinical factor associated with the observed time trends among surgical patients. Hypothermia at ICU admission was independently associated with ICU mortality in medical and surgical patients throughout the entire study. The incidence of hypothermia at ICU admission was dependent on medical versus surgical status, and the method of non-invasive temperature measurement, but was persistently associated with ICU mortality.

Nanosecond-resolved temperature measurements using magnetic nanoparticles.

Instantaneous and noninvasive temperature measurements are important when laser thermotherapy or welding is performed. A noninvasive nanosecond-resolved magnetic nanoparticle (MNP) temperature measurement system is described in which a transient change in temperature causes an instantaneous change in the magnetic susceptibilities of the MNPs. These transient changes in the magnetic susceptibilities are rapidly recorded using a wideband magnetic measurement system with an upper frequency limit of 0.5 GHz. The Langevin function (the thermodynamic model characterizing the MNP magnetization process) is used to obtain the temperature information. Experiments showed that the MNP DC magnetization temperature-measurement system can detect a 14.4 ns laser pulse at least. This method of measuring temperature is likely to be useful for acquiring the internal temperatures of materials irradiated with lasers, as well as in other areas of research.