Assessment Of Thermal Damage Research Articles

Assessment of Thermal Damage During Skin Tumor Treatment Using Thermal Wave Model: A Realistic Approach

In this study, a three-layered skin tissue has been modeled to assess the heat transfer characteristics in laser skin tumor–tissue interaction. A finite-volume-based two-dimensional numerical bioheat transfer model has been put together to study the damage prediction of healthy tissues by considering both Fourier and non-Fourier laws. The combination of the bioheat transfer equation with Fourier law forms the parabolic equation (Pennes model) and with the non-Fourier equation forms the hyperbolic equation (thermal wave model). In this paper, the laser source is provided on the outer layer of the skin to dismantle the undesired tumor region exemplified as inhomogeneity (tumor) present in the intermediate layer. Heat input through the laser source is on until it reaches the tumor-killing criteria. The heat transport equation has been discretized by the finite volume method (FVM). The finite-volume-based numerical model is developed in such a way that the non-Fourier model predictions can be obtained through conventional Fourier-based solver. The central difference scheme is adopted for discretizing the spatial derivative terms. An implicit scheme is applied to treat the transient terms in the model. For few cases of the hyperbolic problems, certain limitation for a chosen implicit scheme has also been addressed in this paper. The results are validated with the existing literatures. The evaluated results are based on both the Fourier and the non-Fourier model, to investigate the temperature distribution and thermal damage by ensuring irreversible thermal damage in the whole tumor region placed in the dermis layer. Thermal damage of the healthy tissue is found to be more in the time scale of the thermal wave model.

Comparing two Uterine Manipulators During Total Laparoscopic Hysterectomy: A Randomized Controlled Trial

Study ObjectiveTo compare 2 different types of uterine manipulators (i.e., tight fitting vs loose fitting) used for total laparoscopic hysterectomy (TLH). DesignA randomized controlled trial. The primary end points were time for colpotomy, time from skin incision to detachment of the uterus, and histologic assessment of thermal damage to the vagina (Canadian Task Force classification I). SettingA university teaching hospital. PatientsAll consecutive women scheduled for TLH from May 2014 to December 2015. Patients were excluded if pregnancy or malignancy was suspected or uterine size exceeded 20 weeks' gestation. InterventionsPatients were randomized to undergo TLH with 1 of the following uterine manipulators: (1) Colpo-Probe Vaginal Fornix Delineator (Cooper Surgical, Inc, Trumbull, CT) or (2) Hohl manipulator (KARL STORZ AG, Tuttlingen, Germany). Measurements and Main ResultsA total of 91 patients, 49 in the Hohl manipulator group and 42 in the Colpo-Probe group, were included in the final analysis. There was no difference in patient characteristics, uterine weight, or estimated blood loss. The median time for insertion of the manipulator (2 minutes [interquartile range (IQR), 2–5 minutes] vs 6 minutes [IQR, 5–7], p < .001), the median time from skin incision to detachment of the uterus (55 minutes [IQR, 41–70] vs 65 minutes [IQR, 58–79], p = .004), and the median time for colpotomy (7 minutes [IQR, 5–10] vs 12 [IQR, 8–17], p < .001) were shorter with the Hohl manipulator. Thermal damage to the vagina varied greatly and ranged from 32 μm to 5232 μm but was not significantly different between groups (median maximum thermal damage = 1043 μm [IQR, 682–1934] vs 1522 μm [IQR, 884–2144], p = .211). ConclusionUse of the Hohl manipulator results in a shorter operative time from skin incision to detachment of the uterus during TLH. Although the colpotomy time is shorter using the Hohl manipulator, this did not translate to less thermal damage to the vaginal cuff. Further studies comparing uterine manipulators are warranted to find the optimal instrument for ease of surgery and decreased thermal spread.

Histological Assessment of Thermal Damage in the Brain Following Infrared Neural Stimulation

Infrared neural stimulation (INS) is a novel technique for modulating neural function. Its advantages over electrical stimulation include high spatial specificity, lack of electrical artifact and contact-free stimulation. INS acts via a rapid, focal increase in temperature. However, in order to become a viable experimental and therapeutic tool, the safety of INS must be demonstrated. Our aim was to determine the upper limit for the radiant exposure of INS in the brain without causing damage, using an INS sequence previously shown to induce both behavioral and electrophysiological effects in rodents and non-human primates. We stimulated the brains of anesthetized rodents and two squirrel monkeys using an infrared laser, depositing radiant energies from 0.3 to 0.9 J/cm2 per pulse in 0.5 s-long 200 Hz trains. At the end of the experiment, the animals were euthanized, perfused and the brains processed using standard histological techniques. Radiant exposures greater than or equal to 0.4 J/cm2 resulted in identifiable lesions in brain sections. The lesions had a shape of a parabola and could further be subdivided into three concentric zones based on the type of damage observed. The thermal damage threshold following our INS paradigm was between 0.3 and 0.4 J/cm2 per pulse. This value is lower than the one found previously in peripheral nerve. The differences are likely due to the structure of the INS sequence itself, particularly the repetition rate. The results warrant further modeling and experimental work in order to delimit the INS parameter space that is both safe and effective.

Expression of heat shock proteins 70 and 47 in tissues following short-pulse laser irradiation: Assessment of thermal damage and healing

In order to develop effective laser-based therapeutics, the extent of laser-induced damage must be quantified for given laser parameters. Therefore, we want to determine the spatiotemporal expression patterns of heat shock proteins, both to understand the roles of heat shock proteins in laser-induced tissue damage and repair and to develop heat shock proteins as tools to illustrate the extent of laser-induced damage and wound healing following irradiation. We exposed anesthetized mice to the focused beam of a short-pulse Nd:YAG laser (1064nm; 200ns pulsewidth) for 15s, while measuring temperature distribution in the skin using an infrared thermal camera. Following irradiation, we examined expression of HSP47 and HSP70 over time (0–24h) as indicators of the heat shock response and recovery from damage in the laser-irradiated region. Expression patterns of HSP70 and HSP47 as detected by immunohistochemistry and confocal microscopy delineate the extent of damage and the process of healing in tissue. Both HSP70 and HSP47 were expressed in dermis and epidermis following laser irradiation, and the spatial and temporal changes in HSP expression patterns define the laser-induced thermal damage zone and the process of healing in tissues. HSP70 may define biochemically the thermal damage zone in which cells are targeted for destruction, and HSP47 may illustrate the process of recovery from thermally induced damage. Studying the effects of different laser parameters on the expression of HSPs will allow development of effective laser therapies that provide accurate and precise tissue ablation and may promote rapid wound healing following laser-based surgery.

Transportation of Liquefied Gases: Assessing the Risk of Thermal Damage to Roadside Infrastructure from a Road Tank “Bleve”

An assessment of risk posed by a road transportation of liquefied gases to roadside property is considered. The attention is focussed on an estimation of the probability of thermal damage to a roadside object. Such damage can be caused by a boiling-liquid expanding-vapour explosion (BLEVE) of a road tank. It is suggested to estimate this probability by a combined application of stochastic simulation and deterministic models used to predict a thermal effect of a BLEVE fireball. A development of a fragility function expressing the probability of ignition of the roadside object is discussed. The fragility function is integrated into the simulation-based procedure of an estimation of the thermal damage probability. The approach proposed in this study is illustrated by an example which considers an assessment of thermal damage to a reservoir built in the vicinity of a road used for transportation of liquefied gases.

Assessment of Thermal Damage for Railway Wheel of Long-Term Running

The railway wheel in long-term running had experienced the wheel damage due to fatigue crack and shelling. The damaged wheel in railway vehicle would cause a poor ride comfort, a rise in the maintenance cost and even fracture of the wheel, which then leads to a tremendous social and economical cost. It is necessary to evaluate long-term damage of railway wheel in order to ensure the safety of wheel. To evaluate the damage for railway wheels, the measurements for the replication of wheel surface and residual stress of railway wheel using x-ray diffraction system were carried out. The result shows that the residual stress of wheel is depend on the running distance and thermal gradient during brake application also that the replication test can be applied in new evaluation method of wheel damage.

Experimental study of thermal degradation in ferritic Cr–Ni alloy steel plates using nonlinear Lamb waves

The thermal degradation in ferritic Cr–Ni alloy steel plates is measured using the nonlinear effect of Lamb wave propagation. Experiments were carried out to introduce controlled levels of thermal damage to determine the nonlinear response of Lamb waves. A “mountain-shape” change in the normalized acoustic nonlinearity of Lamb wave versus the level of thermal degradation in the specimens has been observed. The variation in the measured acoustic nonlinearity reveals, based on metallographic studies, that the normalized acoustic nonlinearity increases due to the second phase precipitates in the early stage and it decreases as a combined result of dislocation change and micro-void initiation in the material. The results show a potential application of the nonlinear Lamb waves for the quantitative assessment of thermal damage in metallic plates or pipes.

Thresholds for thermal damage to normal tissues: An update

The purpose of this review is to summarise a literature survey on thermal thresholds for tissue damage. This review covers published literature for the consecutive years from 2002–2009. The first review on this subject was published in 2003. It included an extensive discussion of how to use thermal dosimetric principles to normalise all time-temperature data histories to a common format. This review utilises those same principles to address sensitivity of a variety of tissues, but with particular emphasis on brain and testis. The review includes new data on tissues that were not included in the original review. Several important observations have come from this review. First, a large proportion of the papers examined for this review were discarded because time–temperature history at the site of thermal damage assessment was not recorded. It is strongly recommended that future research on this subject include such data. Second, very little data is available examining chronic consequences of thermal exposure. On a related point, the time of assessment of damage after exposure is critically important for assessing whether damage is transient or permanent. Additionally, virtually no data are available for repeated thermal exposures which may occur in certain recreational or occupational activities. For purposes of regulatory guidelines, both acute and lasting effects of thermal damage should be considered.

Thermal Damage Assessment of Novel Bipolar Forceps in a Sheep Model of Spinal Surgery

Heat transfer from bipolar tips to adjacent tissue presents a risk of thermal injury during spine surgery. The present study was designed to determine wither bipolar forceps using a novel heat pipe thermal regulation technology resulted in decreased collateral thermal injury of adjacent tissue compared with traditional bipolar forceps (control). Eight sheep underwent multilevel laminectomy and controlled bipolar coagulation of the dorsal spinal dura mater at multiple levels using forceps with or without heat pipe technology (24 spinal segments tested; heat pipe, n=11; non-heat pipe, n=11; sham, n=2). The severity (range, 1-5) and size of thermal injury to the spinal cord resulting from forceps with vs without heat pipe were assessed via histological analysis at 8 days postoperatively. Macroscopic occlusion of the pial vein underlying the segment of epidural coagulation occurred at surgery in 64% of segments (7 of 11) coagulated with control forceps but did not occur in any segments coagulated with heat pipe forceps (P<.005). The mean width (0.58+/-0.58 vs 1.4+/-0.77 mm; P<.05) and cross-sectional area of unintended thermal injury (1.2+/-1.7 vs 4.9+/-3.2 mm2; P<.05) were decreased in segments treated with heat pipe forceps compared with control. The severity of thermal injury was decreased in segments coagulated with (median, grade 1) vs without (median, grade 3) heat pipe forceps (P<.05). Bipolar forceps that incorporate heat pipe technology limited thermal spread and reduced the extent of unintended injury to the spinal cord and collateral vessels.

Assessment of Thermal Damage in Hybrid Fiber-Reinforced Concrete

Three-point bending tests on high-strength concrete specimens after exposure to high temperatures are presented, with a detailed evaluation of process zone size. The variables considered for the high-strength concrete were the types of fiber reinforcement: steel microfibers, polypropylene microfibers, and a hybrid combination of steel and polypropylene microfibers. Both virgin (no heat related damage) and heat treated specimens were tested by conducting experiments at ambient conditions approximately one month after exposure to the high temperature. For both undamaged and heat treated specimens, acoustic emission monitoring and high-resolution interferometric measurements were used to characterize the evolution of the finite size of the process zone as a function of the applied load. The size and shape of the localized damage zone due to prepeak microcracking are two of the significant factors influencing the strength of quasibrittle materials, i.e., the structural scaling. This paper reveals that the material ductility increases with the thermal damage, which is explained by the increase in the fracture process zone size. As a consequence, a correct interpretation of the experimental data requires an identification of fracture parameters through indirect methods.

In-situ Fatigue Damage Investigations in Welded Metallic Components by Infrared Techniques

Abstract The paper reviews the state of the art of thermal damage assessment in metals and proposes a specialized form of lock-in thermography as an efficient tool for the quantification of early fatigue damage phenomena in welded steel structures in the regime of mid- to high-cycle fatigue. It can be proved that advanced thermographic techniques are sensitive to early damage phenomena in the weld toe. They provide a new experimental mean for in-situ investigation of early inhomogeneous fatigue damage phenomena as mesoplasticity and fatigue cracks. The results demonstrate that non-contacting full field temperature measurements using highly sensitive infrared technology can be applied successfully to detect localized fatigue damage at around 10 % to 20 % of the total fatigue lifetime of the tested specimens. The applied method is based on the separation of thermoelastic and thermoplastic temperature effects which cause characteristic local temperature signatures. In contrast to other well-known approaches—as, e.g., measuring the rise of mean temperature during fatigue loading—the applied method offers a very high spatial resolution and resolves extremely localized phenomena. The methodology can be applied to monitor the fatigue process during conventional fatigue testing. The additional effort for the specimen preparation and the installation of the testing setup is minimal.

Non-Fourier Heat Conduction Effect on Laser-Induced Thermal Damage in Biological Tissues

To ensure personal safety and improve treatment efficiency in laser medical applications, one of the most important issues is to understand and accurately assess laser-induced thermal damage to biological tissues. Biological tissues generally consist of nonhomogeneous inner structures, in which heat flux equilibrates to the imposed temperature gradient via a relaxation phenomenon characterized by a thermal relaxation time. Therefore, it is naturally expected that assessment of thermal damage to tissues could be inaccurate when a classical bioheat conduction model is employed. However, little attention has been given to studying the impact of the bioheat non-Fourier effect. In this article, a thermal wave model of bioheat transfer, together with a seven-flux model for light propagation and a rate process equation for tissue damage, is presented to investigate thermal damage in biological tissues. It is shown that the thermal damage assessed with the thermal wave bioheat model may differ significantly from that assessed with the classical bioheat model. Without including the bioheat non-Fourier effect, the assessment of thermal damage to biological tissue may not be reliable.

Applying nonlinear resonant ultrasound spectroscopy to improving thermal damage assessment in concrete

Nonlinear resonant ultrasound spectroscopy (NRUS) consists of evaluating one or more resonant frequency peak shifts while increasing excitation amplitude. NRUS exhibits high sensitivity to global damage in a large group of materials. Most studies conducted to date are aimed at interrogating the mechanical damage influence on the nonlinear response, applying bending, or longitudinal modes. The sensitivity of NRUS using longitudinal modes and the comparison of the results with a classical linear method to monitor progressive thermal damage (isotropic) of concrete are studied in this paper. In addition, feasibility and sensitivity of applying shear modes for the NRUS method are explored.

Improved staining method for determining the extent of thermal damage to cells

Enzyme histochemical stains of frozen sections have been used by investigators to assess thermal damage. The assessment of thermal damage to cells in lipid-rich tissues such as subcutaneous tissue and sebaceous glands can be difficult due to the quality of frozen sections of such tissues. The purpose of this study is to develop an improved method for this type of evaluation. Thick frozen sections of thermally damaged pig and human skin were stained for lactate dehydrogenase. The sections were fixed in formalin and processed for paraffin-embedded sections. The sections showed well-defined localization of the enzymatic deposits as well as preservation of the tissue architecture. The paraffin-embedded lactate dehydrogenase stained sections provide improved evaluation of thermally damaged tissues, particularly the lipid rich tissues.

In Vivo Assessment of Radio Frequency Induced Thermal Damage of Kidney Using Optical Spectroscopy

Radio frequency ablation is a promising modality for treating small renal tumors. Several studies have been published showing its efficacy. A major drawback in the current management of renal tumors with radio frequency ablation is the lack of an effective modality to accurately monitor the progress of the ablation zone in real-time fashion. Previous studies have demonstrated the feasibility of using optical spectroscopy to assess tissue thermal damage, especially in hepatic lesions. We examined the feasibility of this technology in the setting of renal radio frequency ablation. A portable spectroscopic system was used to acquire in vivo fluorescence and diffuse reflectance spectra from porcine renal tissue undergoing radio frequency ablation in real-time fashion with simultaneous temperature recordings. Fluorescence and diffuse reflectance spectral data were then correlated with various degrees of thermal damage and temperature recordings. The most noticeable change in fluorescence characteristics of renal tissue resulting from thermal coagulation was a strong decrease in fluorescence intensity between 400 and 550 nm. When fully coagulated, a significant increase in diffuse reflectance intensity was observed between 500 and 800 nm. Optical spectroscopy, specifically fluorescence and diffuse reflectance spectroscopy, differs significantly in porcine renal tissues with varying degrees of thermal damage from radio frequency ablation in an in vivo setting. Future clinical studies with sufficient sample size are required to validate the potential of these findings. Optical diagnostics may prove to be a rapid, noninvasive, low cost option for monitoring the tumor response to radio frequency based ablative techniques. It may be integrated into future radio frequency ablation probes.

Real-time spectroscopic assessment of thermal damage: implications for radiofrequency ablation.

Radiofrequency ablation (RFA) is an evolving technology used to treat unresectable liver tumors. Currently, there is no accurate method to determine RFA margins in real-time during the procedure. We hypothesized that a fiber-optic based spectroscopic monitoring system could detect thermal damage from RFA in real-time. Fluorescence (F) and diffuse reflectance (Rd) spectra were continuously acquired from within the expected ablation zone during canine hepatic RFA using a fiber-optic microinterrogation probe (MIP). The F and Rd spectral feedback were continuously monitored and ablations were stopped based on changes in spectra alone. After each ablation, the MIP tract was marked with India ink and the ablation zone was excised. The relationship of the MIP to the zone of ablation was examined grossly and microscopically. F and Rd spectral changes occurred in three characteristic phases as the ablation zone progresses past the MIP. Phase 1 indicates minimal deviation from normal lives. Phase 2 occurs as the MIP lies within the hemorrhagic zone of the ablated tissue. Phase 3 correlates with complete tissue coagulation. The absolute magnitude of spectral change correlates with the gross and histologic degree of thermal damage. Optical spectroscopy is a technology that allows real-time detection of thermal tissue damage. In this study, both F and Rd spectroscopy accurately defined the advancing hemorrhagic edge of the zone of ablation and the central coagulation zone. These results suggest that F and Rd spectroscopy can be used to create a real-time feedback system to accurately define RFA margins.

Diode laser-induced thermal damage evaluation on the retina with a liposome dye system.

The aim of the study was to evaluate the feasibility of retinal thermal damage assessment in a rabbit eye model by using laser-induced release of liposome-encapsulated dye. After anesthesia, thermosensitive liposomes (DiStearoyl Phosphatidyl Choline: DSPC) loaded with 5,6-carboxyfluorescein were injected intravenously to pigmented rabbits. Retinal photocoagulations were performed with a 810nm diode laser (P=100-400 mW, laser spot=500 microm, 1s) (OcuLight, IRIS Medical Instruments, Mountain View, CA). Fluorescence measurements in the area of the laser exposures were then realized with a digitized angiograph (CF-60UVi, Canon-Europe, The Netherlands; OcuLab, Life Science Resources, UK). Fluorescent spots were observed for power ranging from 100 +/- 5 mW to 400 +/- 5 mW. The fluorescence intensity increased linearly with the power and reached a plateau at 280 +/- 5 mW. The fluorescence intensity was correlated to the maximum temperature at the center of the laser spot with a linear increase from 42 +/- 3 degrees C to 65 +/- 3 degrees C. These results are in agreement with our two previous studies with DSPC liposomes for temperature measurements in a tissue model and then in a vascular model. This preliminary study demonstrates the possibility of a laser-induced release of liposome-encapsulated dye for a quantification of diode laser induced thermal damage in ophthalmology. Such a method could be useful for a real-time monitoring of laser photocoagulation for conditions such as choroidal neovascular membranes when a precise thermal damage is required near the foveolar area.

Thermal damage assessment of blood vessels in a hamster skin flap model by fluorescence measurement of a liposome-dye system.

The present study was undertaken to evaluate the feasibility of thermal damage assessment of blood vessels by using laser-induced release of liposome-encapsulated dye. Experiments were performed in a hamster skin flap model. Laser irradiation was achieved with a 300 microm fiber connected to a 805 nm diode laser (power = 0.8W, spot diameter = 1.3 mm and pulse exposure time lasting from 1 to 6 s) after potentiation using a specific indocyanine green (ICG) formulation (water and oil emulsion). Liposomes-encapsulated carboxyfluorescein were prepared by the sonication procedure. Carboxyfluorescein (5,6-CF) was loaded at high concentration (100 mM) in order to quench its fluorescence. The measurements were performed after i.v. injection of DSPC liposomes (1.5 ml) and lasted 40 min. Fluorescence emission was measured with an ultra high sensitivity intensified camera. Three different shapes of fluorescent spots were identified depending on target (blood vessel or skin) and energy deposition in tissue: (i) intravascular fluorescence, (ii) transient low fluorescence circular spot, and (iii) persistent high intense fluorescence spot. These images are correlated with histological data. Real-time fluorescence imaging seems to be a good tool to estimate in a non-invasive manner the thermal damage induced by a diode laser combined with ICG potentiation.

Assessment of thermal damage in precooled CO 2 laser wounds using biological markers

Precooling of the tissues was investigated as a possible means of reducing the thermal damage during CO 2 laser surgery of the oral mucosa. Standard wounds 5 mm long were created with the CO 2 laser, with and without precooling, or the scalpel on the dorsum of tongues. Tissue damage was evaluated by studying changes in mast cells and in the activity of lactate (LDH) and succinate (SDH) dehydrogenase. Cooled unoperated tongues acted as controls. The area of thermal damage, indicated by loss of SDH activity, was significantly smaller in precooled tissues (p < 0.001). Although a similar pattern was detected using LDH, the difference was not significant. At both 0 and 6 h normal mast cell numbers were significantly different between groups (p < 0.02). Furthermore, at 0 time, there were significant differences in the numbers of degranulated mast cells between surgical treatment groups (p = 0.001), although not at 6 h. Total numbers of mast cells (normal and degranulated) did not differ between treatment groups or between 0 and 6 h sampling times. Positive significant correlations were observed between the cross-sectional areas and widths of non-reactive succinate and lactate dehydrogenase and the number of degranulated mast cells around the laser wounds. Analysis of the data demonstrated that (i) uncooled laser wounds but not precooled laser wounds were associated significantly with greater levels of immediate mast cell degranulation than scalpel wounds (p = 0.03); (ii) areas and widths of non-reactive SDH and LDH were larger in non-cooled laser wounds than in precooled ones; (iii) precooling of tissues prior to laser treatment significantly decreased the level of mast cell degranulation immediately after surgery (p = 0.03). These results indicate that tissue damage in CO 2 laser surgery may be reduced by the precooling of tissue, thus improving the quality and results of treatment.

The use of dansyl lysine to assess heat damage and thermotolerance of normal tissues

The fraction of cells excluding the fluorescent dye dansyl lysine has previously been shown to correlate well with heat-induced cell killing in a variety of mammalian cell lines and in murine tumors in vivo. Here we evaluate the usefulness of dansyl lysine as a probe for assessment of thermal damage and for measuring the kinetics of thermotolerance development and decay in murine normal tissues. Skin cells were heated in vivo with an initial treatment of 44°C for 20 min by local radiofrequency. Bone marrow cells were heated at 42.5°C for 20 min by whole body water bath immersion. Cell suspensions were prepared, heated in vitro for various lengths of time at 44°C (skin) or 43°C (bone marrow), and scored for the fraction of dansyl lysine-excluding cells. Skin and bone marrow cells expressed maximum thermotolerence by 8 and 6 hr, respectively and returned to normal heat sensitivity by 48 and 146 hr, respectively. The assay was not useful with skeletal muscle and liver, as we were not successful in obtaining viable, dansyl lysine-excluding cells from these tissues. Also, in our hands red blood cells, normal human leukocytes, mouse spleen and thymus cells all failed to stain dansyl lysine even after extreme heating. Dansyl lysine staining, particularly when combined with flow cytometry analysis, has been shown to be a useful method for assessing thermal damage and thermotolerance relatively rapidly in all tumor systems tested to date, and, as shown here, may possess utility in measuring similar endpoints for certain nonclonogenic normal tissues.