Tissue Temperature Changes Research Articles

Diode Laser Light Scattering and Temperature Changes Due to Anesthesia Injection in Bovine Tongue Mucosa.

Background and objective: Diode lasers are used in periodontal therapy. Parameters such as wavelength and application mode can affect the laser/tissue interactions, quality of incision, and final outcomes. This study set out to assess the temperature changes in tissue when diode lasers are used for incisions on tissues injected with local anesthetics. Materials and methods: Incisions were made on the surface of bovine tongue parallel to the tongue axis (ex vivo). The tissue was divided into three groups (lidocaine, saline, and a control group with no infiltration). Irradiation was performed with 810 and 980 nm diode lasers. Trials were further divided using noninitiated and initiated tips. A microprobe thermocouple was placed to evaluate the temperature changes. Linear mixed-model with Tukey adjustment was used to make comparisons and p < 0.05 was denoted as statistically significant. Results: The overall group comparisons reveal that the control group mean rise in temperature is lower than both the lidocaine group (p < 0.0001) and the saline group (p < 0.0001). When combining the data in and across each group, the average temperature rise that occurred for incisions made with initiated tips was significantly lower than incisions made with noninitiated tips (p < 0.0001). Combining the data of tip initiation shows that incisions made with a 980 nm laser produced lower temperature changes, than incisions made with an 810 nm laser (p < 0.0001). Conclusions: Infiltration of water-based liquids, such as local anesthetics or saline, causes an increase in tissue temperature during irradiation, especially when noninitiated tips are used. In addition, temperature significantly rises with the use of the 810 compared with the 980 nm diode laser. Therefore, to avoid photothermal damage to the tissue, the use of initiated tips is encouraged and local anesthetics in conjunction with 810 nm diode lasers should be minimized.

A three-dimensional model of transient bioheat transfer in the lower extremity during cryotherapy.

The purpose of this research was to create a computational model of the human thigh undergoing cryotherapy. The tissue temperatures were measured for five cold pack temperatures of -8°C, -4°C, 0°C, 4°C, and 8°C in addition to six different time intervals of cold application and ice removal. The depth of cold penetration and duration of local tissue cooling were investigated at 10 points during 30 min of application and 7 h of post-application. The model was created in CATIA, using a mid-axial cut of the human thigh MRI without pathology. After validation by the available clinical data, this research applied the finite-volume discretization method to solve bioheat transfer equations. A 16°C decrease in the cold pack temperature reduced the tissue temperatures located 1 and 2 cm below the fat by almost 3.34°C and 1.4°C, respectively, after 30 min of cold application. It took the tissues 10-15 min to start cooling down, and the temperature reached its plateau after 100 min. Thirty minutes of cold application declined the superficial tissue and deep tissue temperatures near the bone by 22.59°C and 0.48°C, respectively. Intense cryotherapy led to an insignificant change in the deep tissue temperature at 2 cm and deeper below the fat tissue. After ice removal, tissues continued cooling down for about 8 min until 40 min, depending on the tissue depth. This study proposed a 100-min cold therapy with 10 min of ice removal to optimize tissue cooling.

Lytic Release of Cellular ATP: Physiological Relevance and Therapeutic Applications.

The lytic release of ATP due to cell and tissue injury constitutes an important source of extracellular nucleotides and may have physiological and pathophysiological roles by triggering purinergic signalling pathways. In the lungs, extracellular ATP can have protective effects by stimulating surfactant and mucus secretion. However, excessive extracellular ATP levels, such as observed in ventilator-induced lung injury, act as a danger-associated signal that activates NLRP3 inflammasome contributing to lung damage. Here, we discuss examples of lytic release that we have identified in our studies using real-time luciferin-luciferase luminescence imaging of extracellular ATP. In alveolar A549 cells, hypotonic shock-induced ATP release shows rapid lytic and slow-rising non-lytic components. Lytic release originates from the lysis of single fragile cells that could be seen as distinct spikes of ATP-dependent luminescence, but under physiological conditions, its contribution is minimal <1% of total release. By contrast, ATP release from red blood cells results primarily from hemolysis, a physiological mechanism contributing to the regulation of local blood flow in response to tissue hypoxia, mechanical stimulation and temperature changes. Lytic release of cellular ATP may have therapeutic applications, as exemplified by the use of ultrasound and microbubble-stimulated release for enhancing cancer immunotherapy in vivo.

Ocular surface temperature differences in glaucoma.

Accumulating evidence suggests that neuroinflammation and immune response are part of the sequence of pathological events leading to optic nerve damage in glaucoma. Changes in tissue temperature due to inflammation can be measured by thermographic imaging. We investigated the ocular surface temperature (OST) profile of glaucomatous eyes to better understand the pathophysiology of these conditions. Subjects diagnosed with glaucoma (primary open angle glaucoma [POAG] or pseudo exfoliation glaucoma [PXFG]) treated at the Sam Rothberg Glaucoma Center (11/2019-11/2020.) were recruited. Healthy subjects with no ocular disease served as controls. The Therm-App thermal imaging camera was used for OST acquisition. Room and body temperatures were recorded, and the mean temperatures of the medial cantus, lateral cantus, and cornea were calculated with image processing software. Thermographic images were obtained from 52 subjects (52 eyes: 25 POAG and 27 PXFG) and 66 controls (66 eyes). Eyes with glaucoma had a significantly higher OST compared to controls (mean 0.9 ± 0.3°C, p < 0.005). The difference between the two groups remained significant after adjustment for age, sex, intraocular pressure (IOP) and room and body temperatures. Lens status and topical IOP-lowering medication did not significantly affect OST. A subgroup analysis revealed that the OST was higher among eyes with POAG compared to eyes with PXFG, but not significantly. Differences in the OST between glaucomatous and normal eyes strengthens current thinking that inflammation affects the pathophysiology of glaucoma. Longitudinal studies are warranted to establish the prognostic value of thermographic evaluations in these patients.

Gene Expression Analysis of Environmental Temperature and High-Fat Diet-Induced Changes in Mouse Supraclavicular Brown Adipose Tissue.

Obesity, a dysregulation of adipose tissue, is a major health risk factor associated with many diseases. Brown adipose tissue (BAT)-mediated thermogenesis can potentially regulate energy expenditure, making it an attractive therapeutic target to combat obesity. Here, we characterize the effects of cold exposure, thermoneutrality, and high-fat diet (HFD) feeding on mouse supraclavicular BAT (scBAT) morphology and BAT-associated gene expression compared to other adipose depots, including the interscapular BAT (iBAT). scBAT was as sensitive to cold induced thermogenesis as iBAT and showed reduced thermogenic effect under thermoneutrality. While both scBAT and iBAT are sensitive to cold, the expression of genes involved in nutrient processing is different. The scBAT also showed less depot weight gain and more single-lipid adipocytes, while the expression of BAT thermogenic genes, such as Ucp1, remained similar or increased more under our HFD feeding regime at ambient and thermoneutral temperatures than iBAT. Together, these findings show that, in addition to its anatomical resemblance to human scBAT, mouse scBAT possesses thermogenic features distinct from those of other adipose depots. Lastly, this study also characterizes a previously unknown mouse deep neck BAT (dnBAT) depot that exhibits similar thermogenic characteristics as scBAT under cold exposure and thermoneutrality.

Skin Viability and Microvascular Function Under Localised Applications of Heat and Pressure

Soft tissue pressure injuries are localised injuries to surface and deep tissue, caused by sustained compression of skin and muscle between a bony area of the body, and for example, a hospital mattress or medical device. Prolonged cell deformation is known to reduce the structural integrity of the cell cytoskeleton, leading to cascade of cell death, inflammation, oedema and oxidative stress, factors that are likely exacerbated by inadequate blood flow and oxygen delivery. Numerous secondary factors are thought to accelerate this cascade, including systemic hypoxia and changes in tissue temperature. By examining the responses of various skin viability markers, both during and after the application of temperature and pressure stimuli, the present study aims to expand understanding of the secondary factors affecting pressure ulcer onset and progression. In the present study, a custom skin deformation device, with an area of 33cm2, was used to apply a combination of pressures (6, 20 and 40mmHg) and temperatures (23, 33, 38°C) at the sacrum of four healthy volunteers (data collection ongoing). A laser doppler flowmetry probe, embedded into the skin deformation device, was used to measure baseline skin blood flow, skin blood flow under pressure, and reactive hyperaemia (RH) on pressure release. All measurements were calculated as a percentage of heat-induced maximal cutaneous vascular conductance (%CVCmax). Changes in stratum corneum and epidermal hydration were calculated using the difference in tissue electrical capacitance (corneometry) measurements before and after skin deformation. The results indicated a significant difference in loaded skin blood flow between the pressures of 6-20mmHg (p=0.045), and 6-40mmHg (p=0.018), decreasing from 30.5 ± 9.1 %CVCmax to 21.8 ± 9.0 %CVCmax and 17.5 ± 6.7 %CVCmax respectively. Furthermore, there was a significant increase (p=0.030) from 16.9 ± 8.2 %CVCmax to 29.8 ± 5.4 %CVCmax in loaded skin blood flow, between the temperatures of 28-38°C. Finally, blood flow saw a significant (p=0.005) increase on pressure release, from a loaded average of 19.7 ± 8.2 %CVCmax to an unloaded average of 29.0 ± 12.0 %CVCmax, however there was no significant effect of pressure level or temperature on reactive hyperemia. Changes in stratum corneum hydration between 28-33°C (p=0.044), and 28-38°C (p=0.019), increased from 20.8 ± 11.3% to 38.8 ± 12.7% and 48.5 ± 15.5% respectively. Differing pressures and temperatures had no significant effect on epidermal hydration. Initial indications from the present study suggest low local tissue temperature reduces tissue blood flow under pressure, thereby potentially reducing oxygen transport to, and metabolites away from, areas of loaded tissue. However, increased local temperature results in greater moisture accumulation on the surface layer of the cutaneous tissues, potentially resulting in a lower structural integrity. On balance, a neutral skin temperature may be best to balance the harmful effects pressure on tissue viability, but further investigation is required to fully understand the influence of temperature on each aspect of the pressure injury cascade, including cell cytoskeleton integrity, inflammation, and oedema, as well as blood flow dynamics, oxygen delivery, cell metabolism and oxidative stress.

Temperature Change from Diode Lasers in Oral Mucosa: An Ex Vivo Study.

Objective: The aim of this ex vivo study was to assess the mean temperature change deep in tissue during diode laser (980 vs. 810 nm) irradiation using continuous and pulsed laser and initiated versus noninitiated tips. Background data: Previous studies have determined thermal effects of diode lasers on tissue damage but have yet to compare the incision qualities of 980 versus 810 nm diode lasers. Further studies need to be done to determine the efficiency of diode lasers to create a safer protocol for clinicians. Methods: Ninety-six incisions of 20 mm length were made in three bovine tongues using diode lasers (980 and 810 nm). Both continuous and pulsed modes were tested with initiated (using blue articulating paper) and noninitiated glass fibers (n = 12 per group). Thermocouples attached to LabChart® software were used to measure mean temperature changes. Mean, standard deviations, and p values were conducted for each group to test the statistical significance (p < 0.05). Results: Quality of incisions were better using the initiated tips for both laser wavelengths. Pulsed mode with 810 nm diode laser produced the least mean temperature change in tissue. Overall, both pulsed and continuous mode showed similar thermal effects on tissue. Conclusions: Within the limitations of this study, noninitiated tips are responsible for diffuse irradiation in tissue and are associated with tissue temperature increase during surgery. Low incision quality was observed using noninitiated tips. The temperature changes seem to be dependent on the laser wavelength and are higher for 980 nm compared with 810 nm pulsed diode laser.

Noninvasive calibrated tissue temperature estimation using backscattered energy of acoustic harmonics

PurposeA real-time and non-invasive thermometry technique is essential in thermal therapies to monitor and control the treatment. Ultrasound is an attractive thermometry modality due to its relatively high sensitivity to change in temperature and fast data acquisition and processing capabilities. A temperature-sensitive acoustic parameter is required for ultrasound thermometry in order to track the changes in that parameter during the treatment. Currently, the main ultrasound thermometry methods are based on variation in the attenuation coefficient, the change in backscattered energy of the signal (CBE), the backscattered radio-frequency (RF) echo-shift due to change in the speed of sound and thermal expansion of the medium, and change in the amplitudes of the acoustic harmonics. In this work, an ultrasound thermometry method based on second harmonic CBE (CBEh2) and combined fundamental and second harmonic CBE (CBEcomb) is used to produce 2D temperature maps, detect localized heated region generated by low intensity focused ultrasound (LIFU), and control temperature in the heated region. Materials and methodsEx vivo pork muscle tissue samples were exposed to localized LIFU heating source and 2D temperature maps were produced from the RF data acquired by a 4.2 MHz linear array probe using a Verasonics Vantage™ ultrasound scanner (Verasonics Inc., Redmond, WA) after the exposure. Calibrated needle thermocouples were also placed in the ex vivo tissue sample close to the LIFU focal zone for temperature calibration purposes. The estimated temperature maps were the established echo-shift technique. A tissue motion compensation algorithm was also used to reduce the susceptibility to motion artifacts. Results2D temperature maps were generated using CBE of acoustic harmonic and echo-shift techniques. The results show a direct correlation between the CBE of acoustic harmonics and focal tissue temperature for a range of temperatures from 37 °C (baseline) to 47 °C. ConclusionsThe findings of this study show that the CBE of acoustic harmonics technique can be used to noninvasively estimate temperature change in tissue in the hyperthermia temperature range.

Temperature and current flow effects of different electrode placement in shoulder capacitive-resistive electric transfer applications: a cadaveric study

BackgroundImpingement syndrome is currently estimated to represent 60% of all shoulder pain disorders. Capacitive-Resistive electric transfer therapy is aimed to provoke temperature and current flow changes in superficial and deep tissues. This in vitro study has evaluated the variation of temperature and current flow in the shoulder tissues during two different areas of application of the movable capacitive-resistive electric transfer electrode.MethodsA cross-sectional study designed, five fresh cryopreserved cadavers (10 shoulders) were included in this study. Four interventions (capacitive and resistive modes; low- and high-power) were performed for 5 min each by a diathermy “T-Plus” device in two shoulder regions: postero-superior and antero-lateral. Supraspinatus tendon, glenohumeral capsule and superficial temperatures were recorded at 1-min intervals and 5 min after treatment.ResultsA statistically significant difference was found only for the superficial area and time interaction, with high power-resistive application at the postero-superior shoulder area (P< 0.035). All the applications showed a 5 min after treatment temperature increase compared with the basal data, in all the application points. Superficial temperature in the high power-resistive application showed the greatest percent increase (42.93% ± 22.58), followed by the temperature in the tendon area with the same high power-resistive application (22.97% ± 14.70). The high power-resistive application showed the greatest percent of temperature increase in the applications, reaching 65.9% ± 22.96 at 5-min at the superficial level, and 32% ± 24.25 at 4-min at the level of the supraspinatus tendon. At the capsule level, high power-resistive was also the application that showed the greatest percent of increase, with 21.52% ± 16.16. The application with the lowest percent of temperature increase was the low power-capacitive, with a mean value of 4.86% at supraspinatus tendon level and 7.47% at capsular level.ConclusionThe shoulder postero-superior or antero-lateral areas of application of capacitive-resistive electric transfer did not cause statistically significant differences in the temperature changes in either supraspinatus tendon or glenohumeral capsule tissues in cadaveric samples. The high power-resistive application in the postero-superior area significantly increased superficial temperature compared with the same application in the antero-lateral position area.

Thermal and Current Flow Effects of a Capacitive-Resistive Electric Transfer Application Protocol on Chronic Elbow Tendinopathy. A Cadaveric Study.

Lateral elbow tendinopathy, or “tennis elbow,” is a pathology that affects around 1.3% of the general population. Capacitive–resistive electric transfer therapy aims to provoke temperature and current flow changes in superficial and deep tissues. The aim of this in vitro study was to analyze the thermal behavior and transmission of electric current on the superficial and deep tissues of the elbow during the application of different modalities of a capacitive–resistive electric transfer treatment protocol for chronic elbow tendinopathy. A cross-sectional study was designed; five fresh cryopreserved cadavers (10 elbows) were included in this study. A 30 min intervention was performed based on a protocol commonly used in clinics for the treatment of chronic lateral elbow tendinopathy by diathermy using the “T-Plus.” Common extensor tendon, radiohumeral capsule, and superficial temperatures were registered after each application for the duration of the 30 min treatment protocol. During all applications, we observed a current flow of over 0.03 A. The protocol showed a statistically significant increase in superficial temperature by 24% (5.02°) (p < 0.005), the common extensor tendon by 19.7% (4.36°) (p < 0.007), and the radiohumeral joint capsule by 17.5% (3.41°) (p < 0.005) at the end of the 30 min protocol compared with the baseline temperature. The different applications of the protocol showed specific effects on the temperature and current flow in the common extensor tendon and radiohumeral capsule. All applications of the protocol produced a current flow that is associated with the generation of cell proliferation. These results strengthen the hypothesis of cell proliferation and thermal changes in deep and distal structures. More studies are needed to confirm these results.

Multivariate Regression Between Hounsfield Unit Shift, Tissue Temperature, and Tissue Contraction: A Feasibility Study of Computed Tomography Thermometry

This study aims to determine the relationship between Hounsfield Unit shift ( $\Delta {\mathrm{ HU}}$ ), tissue temperature change ( $\Delta T$ ), and tissue’s relative cross-sectional area change ( $\Delta A$ ) of ex vivo bovine liver tissues. The fresh bovine livers ( $n = 3$ ) were heated from 21 °C to 100 °C within 24 min using a custom-made ceramic hot plate and left for cooling to room temperature (~70 min). HU and tissue temperature measurement were obtained at 3-min intervals during the experiment. After that, the cross-sectional tissue area changes, and $\Delta A$ was calculated. Finally, a multivariate linear regression analysis was performed to determine the relationship between $\Delta {\mathrm{ HU}}$ , $\Delta T$ , and $\Delta A$ . The results were compared with that of the conventional $\Delta {\mathrm{ HU}}$ - $\Delta T$ linear model. Tissues that underwent a larger thermal dose experienced a higher degree of tissue contraction, an irreversible process that contributed to the non-linear behavior in the $\Delta {\mathrm{ HU}}$ - $\Delta T$ characteristic curve. This finding was in agreement with the histological test, in which the tissues nearer to the heat source had higher cell counts than those farther away. A phenomenological equation for $\Delta {\mathrm{ HU}}$ in the function of $\Delta T$ and $\Delta A$ shows better regression with the experimental data ( $R^{2} \in $ [0.838, 0.977]) than the conventional $\Delta {\mathrm{ HU}}$ - $\Delta T$ linear model. This finding indicates that tissue contraction is an important parameter to be considered in the development of CT thermometry. The $\Delta {\mathrm{ HU}}$ - $\Delta T$ - $\Delta A$ characteristic equation presented in this work offers accurate estimation of tissue temperature based on the HU change and magnitude of tissue contraction during a CT-guided thermal ablation procedure.

Optimizing Impedance Change Measurement During Radiofrequency Ablation Enables More Accurate Characterization of Lesion Formation.

This study sought to determine whether a novel impedance thermal imaging system (ITIS) provides an impedance measurement that is better correlated with lesion dimensions than circuit impedance during radiofrequency (RF) ablation. A 5- to 10-Ω impedance drop is clinically used to corroborate an effective RF ablation lesion. However, the contribution of local tissue heating to circuit impedance change is small and dependent on the local environment of the catheter and placement of the grounding patch. ITIS uses ablation catheter and skin electrodes to perform 4-terminal impedance measurements with separate voltage sensing and current injection electrode pairs. Seven sheep underwent endocardial ventricular irrigated RF ablation at 40W for 60 s. ITIS impedance and circuit impedance were both measured throughout ablation. When the sheep were sacrificed, ablation lesions were cut along their long axis; the depth, width, and surface area of the cut surface were measured. A total of 68 RF ablations were performed, with a median depth of 3.5mm (interquartile range [IQR]: 2.1 to 4.9mm), width of 8.3mm (IQR: 5.7 to 10.8mm), and surface area of 23.8mm2 (IQR: 9.3 to 43.0mm2). ITIS impedance change had good correlation with lesion depth, width, and surface area (R=0.76, R=0.87, and R=0.87, respectively); and superior to circuit impedance for lesion depth, width, and surface area (p=0.0018, p=0.0004, and p=0.0001, respectively). By optimizing the current path and using 4-terminal impedance measurement during RF ablation, the contribution of tissue temperature changes to measured impedance is better standardized to provide a more reliable measure than conventional ablation circuit impedance.

Contrast therapy: Tissue heating and cooling properties within the equine distal limb.

Rehabilitation of tendon injuries in horses often involves cryotherapy to reduce inflammation and occasionally tissue heating to increase collagen extensibility. The application of alternating cold and hot (ie contrast therapy) is widely used in human physical therapy; however, its utility in equine rehabilitation is largely unknown. The objectives of this study were to (a) assess if the equipment could achieve therapeutic tissue temperatures (<15 and >40°C) at different tissue depths relative to the digital flexor tendons and (b) evaluate the time-temperature profiles during serial heating and cooling cycles using a contrast therapy device. In vivo experiment. In 4 adult horses with normal forelimb digital flexor tendons, fine-wire temperature probes were placed superficially on the skin and implanted subcutaneously, deep to the superficial digital flexor tendon (SDFT) and deep to the deep digital flexor tendon (DDFT). Temperatures were recorded over three complete thermal (hot-cold) cycles. Minimum and maximum temperatures were recorded and the rate of temperature changes and the areas underneath the time-temperature curves (ie thermal load) were calculated. Minimum and maximum tissue temperatures (°C) included: superficial skin [12.6±1.0; 42.4±2.4], subcutaneous tissues [14.1±0.8; 42.3±2.2], deep to the SDFT [15.6±0.8; 41.7±2.6] and deep to DDFT [25.1±2.0; 38.0±3.5]. An initial rapid rate of tissue temperature change between 3.2 and 4.3°C/min occurred within tissues to the depth of the DDFT. Tissue thermal loads during heating ranged from 255 to 607°C*second and from 309 to 780°C*second during tissue cooling, with the lower values noted deep to the DDFT. Unknown clinical efficacy in diseased tissues. The applied contrast therapy was consistently able to induce cooling and heating of tissues to the depth of the DDFT.

Comparison of Soft Tissue Thermal Changes Induced by Three Types of Diode Lasers at 810, 940, and 980nm Wavelengths

Background and AimDiode laser is a great choice for soft tissue surgery. The diode laser is partially absorbed by hard dental tissues, making it safe for soft tissue surgery. This study aimed to compare the tissue thermal changes induced by three types of diode lasers at 810, 940, and 980nm wavelengths.Materials and MethodsIn this in-vitro experimental study, using a diode laser device (continuous mode with a 400μm fiber tip) at each of the 810, 940, and 980nm wavelengths and powers of 1, 2, and 3W in contact mode, incisions with the length of 2cm were made on pieces of meat over a period of 10 seconds. The primary and secondary temperatures were measured using a thermocouple. Data were analyzed using two-way analysis of variance (ANOVA).ResultsTissue temperature changes induced by diode laser at 810nm/3W were significantly greater than that of 2W power. These changes were higher with 2W of power compared to 1W (P<0.05). Temperature changes induced by diode laser at 940nm/2 and 3W were significantly greater than that of 1W power (P<0.05). Temperature changes induced by diode laser at 980nm/3W were significantly greater than that of 2W power. Tissue temperature changes were higher with 2W of power compared to 1W (P<0.05).ConclusionDiode laser (continuous mode with a 400µm fiber tip) at 3W of power and 980nm wavelength caused the highest rate of thermal changes. The 810nm diode laser with the power of 1W caused the slightest heat changes in the soft tissue.

Accurate and Real-Time Temperature Monitoring during MR Imaging Guided PTT.

Photothermal therapy (PTT) is an efficient approach for cancer treatment. However, accurately monitoring the spatial distribution of photothermal transducing agents (PTAs) and mapping the real-time temperature change in tumor and peritumoral normal tissue remain a huge challenge. Here, we propose an innovative strategy to integrate T1-MRI for precisely tracking PTAs with magnetic resonance temperature imaging (MRTI) for real-time monitoring temperature change in vivo during PTT. NaBiF4: Gd@PDA@PEG nanomaterials were synthesized with favorable T1-weighted performance to target tumor and localize PTAs. The extremely weak susceptibility (1.04 × 10-6 emu g-1 Oe1-) of NaBiF4: Gd@PDA@PEG interferes with the local phase marginally, which maintains the capability of MRTI to dynamically record real-time temperature change in tumor and peritumoral normal tissue. The time resolution is 19 s per frame, and the detection precision of temperature change is approximately 0.1 K. The approach achieving PTT guided by multimode MRI holds significant potential for the clinical application.

Modeling on Metabolic Rate and Thermoregulation in Three Layered Human Skin during Carpentering, Swimming and Marathon

Metabolisms play a vital role in thermoregulation in the human body. The metabolic rate varies with the activity levels and has different behaviors in nature depending on the physical activities of the person. During the activity, metabolic rate increases rapidly at the beginning and then increases slowly to become almost constant after a certain time. So, its behavior is as logistics in nature. The high metabolic rate during activity causes the increase of body core temperature up to 39˚C [1] [2]. The logistic model of metabolic rate is used to re-model Pennes’ bioheat equation for the study of temperature distribution in three layered human dermal parts during carpentering, swimming and marathon. The finite element method is used to obtain the solution of the model equation. The results demonstrate that there is a significant change in tissue temperature due to sweating and ambient temperature variations.

Energy analysis of PDT using thermography during the treatment of basal cell carcinoma.

The changes in tissue temperature of basal cell carcinoma lesions were investigated during photodynamic therapy in order to better understand the effects and mechanisms of PDT in tissue. In this study, the monitoring of 40 lesions of basal cell carcinoma was performed during photodynamic therapy. The lesion region becomes thermally evident throughout the procedure, and there is an improved contrast of the lesion edges after the end of the irradiation. The comparison between thermal and fluorescence images showed a correlation between the PpIX evidenced through widefield fluorescence and the temperature gradient of the thermal images after the procedure, indicating that thermography is a potential diagnostic tool to evaluate the selective response of PDT. A model was created to calculate the amount of light energy converted to heat, tissue damage, and other energy transfer processes involved in the PDT. Using this model, it was shown that most of the energy conversion was in photodynamic action (48.7% and 48.3%, in first and second session, respectively), followed by the energy ratio attributable to blood perfusion (37.2%). This is evidence that photodynamic therapy does not generate a significant thermal component, an important aspect of the study of its mechanisms.

Optimization of an artificial neural network to estimate laser ablation efficiency

The use of fiber laser in surgery has many advantages due to its small size, efficiency, operation in continuous and pulse mode and easy coupling to fiber optics for various applications. Laser surgery requires very precise control on laser parameters, and imprecision can cause unacceptable damages during operation, particularly in neurosurgical applications. There have been many experimental studies looking to optimize laser parameters to control laser thermal therapy. In this study, we propose an artificial neural network method (ANN) to predict laser ablation damage as a function of laser parameters and temperature. The purpose of this study was to investigate the performance of artificial neural networks to predict the ablation efficiency of a 1940 nm thulium fiber laser on ovine brain tissue. Twelve experimental data were used to train an ANN model. Tissue type (cortical/subcortical), laser mode, laser power, laser energy, time, temperature and temperature change were used as inputs for the ANN and the ablation efficiency (ablated area/total thermally altered area) was the output of the model. Four untrained data were used to validate the ANN prediction ability after finding correlation between the ANN inputs and output. Experimental and predicted data were compared to find the accuracy of the model. Moreover, optimum laser mode (continuous/pulse) selection was also studied. Five different machine learning methods were used for laser mode selection, and the results were compared. Our results showed that prediction for the ablation efficiency of an ANN is lower than 15% and 87.5% classification accuracy was obtained for optimum laser mode selection.

Relative Tissue Oxygenation and Temperature Changes for Detecting Early Upper Extremity Skin Ischemia.

The authors' purpose was to determine whether there are reliable noninvasive methods of assessing upper extremity ischemia regardless of skin pigmentation. The authors conducted a study of healthy subjects classified based on skin pigmentation using the Fitzpatrick scale, the von Luschan color scale, and self-described race (two Hispanics, three Caucasians, and four African Americans). A surface temperature probe and a near-infrared spectroscopy monitor were placed on the posterior interosseous artery skin territory. Temporary upper limb ischemia was induced by tourniquet insufflation. Readings from both devices were taken at baseline and every 15 seconds for a total of 10 minutes of ischemia. During tourniquet insufflation, the authors found a reliable decrease in tissue oxygenation measured by near-infrared spectroscopy in all subjects and no significant change in temperature readings for any subjects. There was an average decrease of 19 percent in tissue oxygenation using near-infrared spectroscopy, with measurements on average starting at 77 percent and ending at 57 percent. There was no significant difference in the change in near-infrared spectroscopy oxygenation between participants with Fitzpatrick skin types 3, 4, and 5 or when participants were grouped into Fitzpatrick skin type less than or equal to 3 versus greater than 3, or when grouped into Fitzpatrick skin type less than or equal to 4 versus greater than 4. There was also no significant difference in participants grouped into von Luschan scores less than or equal to 20 versus greater than 20. In this healthy subjects study, near-infrared spectroscopy rapidly identified ischemia in all cases, whereas skin surface temperature did not. Near-infrared spectroscopy may be a reliable way of noninvasively monitoring for ischemia regardless of skin pigmentation degree. CLINICAL QUESTION/LEVEL OF EVIDENCE:: Diagnostic, IV.

Effects of 1-MHz Ultrasound on Epaxial Muscle Temperature in Horses.

Objective: The purpose of this study was to examine the tissue temperature changes that occur at various depths during 1.0-MHz ultrasound (US) treatments of the epaxial muscles in horses.Animals: Ten healthy adult mares with no lameness or orthopedic disease weighing between 465 and 576 kg were studied.Procedures: Two 1.0 MHz US treatments, one at an intensity of 1.0 W/cm2 and one at 2.0 W/cm2, were administered to the epaxial region. Needle thermistors were inserted in the epaxial muscles below the skin surface at depths of 1.0, 3.0, and 5.0 cm, directly under the US treatment area. Depths were verified with diagnostic ultrasound. Both intensities of US treatment were performed on each horse over a 20 cm2 area for 10 min using a sound head with an effective radiating area of 10 cm2. Treatments were administered in random order. Tissue temperature was measured before, during, and for an additional 10 min after the end of US treatment. Mean temperatures for each time point, location, and intensity was recorded at 30 s intervals. A mixed model analysis of variance (ANOVA) with repeated measures was used to test for differences in these means. Individual differences in the means was tested for by a Least Significant Difference (LSD) mean separation test.Results: At the completion of the 10 min US treatment, the temperature rise at an intensity of 1.0 W/cm2 was 1.55°C at the 1.0 cm depth, 1.18°C at 3.0 cm depth, and 1.29°C at 5.0 cm depth. At an intensity of 2.0 W/cm2, temperatures rose 2.48°C at the 1.0 cm depth, 1.24°C at 3.0 cm depth, and 1.95°C at 5.0 cm depth.Conclusion and Clinical Importance: The main findings of the study is that use of therapeutic ultrasound with a 1.0 MHz US for 10 min in horse's epaxial muscles when clipped creates the greatest heat at 1.0 cm. The heat in the tissues at 5 cm depth is more than at 3 cm depth.