Laser-induced Temperature Changes Research Articles

Laser induced temperature changes on the outer surface of titanium dental implants—an in vitro study

Laser induced temperature changes on the outer surface of titanium dental implants—an in vitro study

A temperature model for laser lithotripsy

ObjectiveTo derive and validate a mathematical model to predict laser-induced temperature changes in a kidney during kidney stone treatment.MethodsA simplified mathematical model to predict temperature change in the kidney for any given renal volume, irrigation flow rate, irrigation fluid temperature, and laser power was derived. We validated our model with matched in vitro experiments.ResultsExcellent agreement between the mathematical model predictions and laboratory data was obtained.ConclusionThe model obviates the need for repeated experimental validation. The model predicts scenarios where risk of renal tissue damage is high. With real-time knowledge of flow rate, irrigating fluid temperature and laser usage, safety warning levels could be predicted. Meanwhile, clinicians should be aware of the potential risk from thermal injury and take measures to reduce the risk, such as using room temperature irrigation fluid and judicious laser use.

Temporal and spatial temperature modelling for understanding pulsed laser induced solution based nanomanufacturing

Recently, pulsed lasers have demonstrated great potential in targeted synthesis in solution based nanomanufacturing, realizing high precision and accuracy in space, time and energy input. The unique temperature history induced by pulsed lasers is indispensable to understand the related fundamentals and to realize the precision control of deposition. In this study a heat transfer model was developed and applied to predict the temporal evolution and the spatial distribution of pulsed laser induced temperature change across the reaction sites. Chemically deposited ZnO crystals were studied as an example, showing the relationships among laser parameters and heating conditions, and deposited crystal characteristics. Peak temperature and heat accumulation induced by pulsed laser were found to affect deposited crystal number density and size. The nucleation number density distribution was found to be correlated with the spatial temperature distribution and inversely proportional to the crystal size. The presented heat transfer model is a crucial tool to understand crystallization fundamentals and it is essential for facilitating pulsed laser as a new tool for research, design, manufacturing and control.

Enhanced green fluorescent protein in optofluidic Fabry-Perot microcavity to detect laser induced temperature changes in a bacterial culture

Thermal therapy using laser sources can be used in combination with other cancer therapies to eliminate tumors. However, high precision temperature control is required to avoid damage in healthy surrounding tissues. Therefore, in order to detect laser induced temperature changes, we have used the fluorescence signal of the enhanced Green Fluorescent Protein (eGFP) over-expressed in an E. coli bacterial culture. For that purpose, the bacteria expressing eGFP are injected in a Fabry-Perot (FP) optofluidic planar microcavity. In order to locally heat the bacterial culture, external infrared or ultraviolet lasers were used. Shifts in the wavelengths of the resonant FP modes are used to determine the temperature increase as a function of the heating laser pump power. Laser induced local temperature increments up to 6–7 °C were measured. These results show a relatively easy way to measure laser induced local temperature changes using a FP microcavity and using eGFP as a molecular probe instead of external nanoparticles, which could damage/alter the cell. Therefore, we believe that this approach can be of interest for the study of thermal effects in laser induced thermal therapies.

Rod-shaped NaY(MoO4)2:Sm3+/Yb3+ nanoheaters for photothermal conversion: Influence of doping concentration and excitation power density

Thermal effect of rare earth (RE) ions doped nanoparticles under near-infrared light irradiation has been underestimated, because main interest and efforts still fall into the distinctive up-converting luminescence property of these particles. In this work, we demonstrate an approach to convert 980nm light energy to heat energy via a designed nanoheater which is Sm3+/Yb3+ codoped NaY(MoO4)2 nanorods derived from a microwave-assisted hydrothermal reaction. To inspect the photothermal conversion effect of the nanoheaters, Er3+/Yb3+ codoped NaY(MoO4)2 nanorods are prepared via the same synthesis route. A convenient strategy, in which NaY(MoO4)2:Er3+/Yb3+ nanorods are used as nanothermometer, is proposed to monitor the laser-induced temperature change of the nanoheaters by mixing a small amount of nanothermometer with nanoheater. The influence of Sm3+/Yb3+ concentrations and excitation power density on the final temperature of the nanoheaters is studied. It is found that when Yb3+ concentration is fixed to be 10mol%, the influence of increasing Sm3+ concentration on the photothermal conversion effect is limited; but when Sm3+ is fixed to be 5mol%, the photothermal conversion is enhanced greatly with the increase of Yb3+ concentration. In addition, the temperature for all the NaY(MoO4)2:Sm3+/Yb3+ nanoheaters after laser irradiation is linearly dependent on the excitation power density. In order to examine the photothermal conversion effect of the nanoheater in liquid media, the PVP (polyvinyl pyrrolidone) solution is used for accommodating the nanoheaters, and effective photothermal conversion is observed.

Nanoscale Measurement of Laser-Induced Temperature Rise and Field Evaporation Effects in CdTe and GaN

The measurement of laser-induced temperature change and its influence on the field evaporation behavior in nanoscale CdTe and GaN specimens was assessed through systematic studies using laser pulsed atom probe tomography. For CdTe, the laser was shown to induce a linear thermal response in the material. Using the determined relationships, a phase map of the field evaporation behavior was created. This shows that at high base temperatures, high laser energies, or low fields, significant Cd sublimation occurs, leading to apparently Te-rich measured compositions. In contrast, the highest fields result in simultaneous evaporation of multiple Te species, leading to apparently Cd-rich measured compositions. For GaN, increasing laser energy reduced the applied bias necessary for a given detection rate, whereas base temperature changes produced no significant effect on the evaporation behavior, indicative of a largely athermal evaporation mechanism. Similarly, the laser energy and bias affected the measured compo...

Temperature-dependent nonlinear phonon behavior in high-density carbon nanotube thin films

We report the temperature-dependent Raman spectra for high-density single-walled carbon nanotube thin films. We show that the position of the main Raman mode (G) softens as the temperature increases and is nonlinear in the range of 70–270 K. This effect is explained by optical phonon decay. In the linear regime, the first-order temperature coefficient (χT) equals −0.02 cm−1/K, which is lower than for any other carbon nanotubes. Importantly, we found that local laser-induced temperature change shows a nonlinear trend as a function of global temperature with a minimum at 270 K. Our results contribute to understand the thermal properties of carbon nanotube thin films that could be applied, for example, in photovoltaic or thermoelectric devices.

Microscopic Heat Pulses Induce Ca2+-Independent Contraction of Cardiomyocytes

Laser irradiation has developed into a novel technique of non-invasive stimulation in cardiac and neural tissues. However, physical parameters for the laser irradiation-induced cardiac contractions have not been clarified, because various physicochemical reactions, such as photochemical and photothermal effects, are triggered in this process. Here we studied the effects of laser-induced local temperature changes on the functions of isolated cardiomyocytes. We demonstrated previously that a microscopic heat pulse (ΔT = 0.2°C for 2 sec) induces a Ca2+ burst in cancer cells (HeLa cells) at a body temperature (Tseeb et al., HFSP J., 2009), with the mechanism similar to that of rapid cooling contracture in skeletal and cardiac muscles. In the present study, we generated microscopic heat pulses by focusing infrared laser light in extracellular solution near adult rat cardiomyocytes. We found that a microscopic heat pulse (ΔT = 5°C for 0.5 sec) induces contractions at basal temperature of 36°C. At 25°C, larger ΔT was required to induce contractions. When 2.5 Hz heat pulses were repeatedly applied, we observed oscillatory contractions of cardiomyocytes. Different from contractions induced by electric stimulation, Ca2+ transients were not detected during the contraction. Likewise, heat pulses induced contractions of skinned cardiomyocytes in Ca2+-free solution in the presence of ATP. These results demonstrate that heat pulses can regulate cardiac contractions without any involvement of Ca2+ dynamics, by directly activating the actomyosin interaction. Hence, our microheating technique may be useful for stimulating the beating of failing hearts without causing abnormal Ca2+ dynamics.

Laser recovery of machining damage under curved silicon surface

Nano-second pulsed laser irradiation was used to recover machining-induced damage under curved surfaces of single-crystal silicon. Microstructural changes of silicon due to laser irradiation were characterized by cross-sectional transmission electron microscopy and laser micro-Raman spectroscopy. The recoverable damage depth was predicted by finite element modeling of laser-induced temperature change in the workpiece material. Slanted irradiation experiments were performed and the critical surface inclination angle for complete recovery was experimentally obtained. The results demonstrate that atomic-level subsurface integrity and nanometric surface roughness can be achieved on large-curvature silicon surfaces, such as the surfaces of toroidally shaped wafer edges.

Abstract No. 120: Near-infrared laser-induced temperature changes mediated by systemically administered hollow gold nanoshells and intra-tumor laser fiber

Abstract No. 120: Near-infrared laser-induced temperature changes mediated by systemically administered hollow gold nanoshells and intra-tumor laser fiber

Precision, all-optical measurement of external quantum efficiency in semiconductors

External quantum efficiency of semiconductor photonic devices is directly measured by wavelength-dependent laser-induced temperature change (scanning laser calorimetry) with very high accuracy. Maximum efficiency is attained at an optimum photo-excitation level that can be determined with an independent measurement of power-dependent temperature or power-dependent photoluminescence. Time-resolved photoluminescence lifetime and power-dependent photoluminescence measurements are used to evaluate unprocessed heterostructures for critical performance parameters. The crucial importance of parasitic background absorption is discussed.

Monitoring annealing via CO_2 laser heating of defect populations on fused silica surfaces using photoluminescence microscopy

Photoluminescence (PL) microscopy and spectroscopy under 266 nm and 355 nm laser excitation are explored as a means of monitoring defect populations in laser-modified sites on the surface of fused silica and their subsequent response to heating to different temperatures via exposure to a CO(2) laser beam. Laser-induced temperature changes were estimated using an analytic solution to the heat flow equation and compared to changes in the PL emission intensity. The results indicate that the defect concentrations decrease significantly with increasing CO(2) laser exposure and are nearly eliminated when the peak surface temperature exceeds the softening point of fused silica (approximately 1900K), suggesting that this method might be suitable for in situ monitoring of repair of defective sites in fused silica optical components.

Model of laser-induced temperature changes in solid-state optical refrigerators

We present an efficient and numerically stable method to calculate time-dependent, laser-induced temperature distributions in solids and provide a detailed description of the computational procedure and its implementation. This study combines the two-dimensional heat equation with laser-induced heat generation and temperature-dependent luminescence. The time-dependent optical response of a system is obtained numerically by the Crank–Nicolson method. This general model is applied to the specific case of optical refrigeration in ytterbium (Yb3+) doped fluorozirconate glass (ZBLAN). The laser-induced temperature change upon optical pumping and the respective transient luminescence response are calculated and compared to experimental data. The model successfully predicts the zero-crossing temperature, the net quantum efficiency, and the functional shape of the transients. We find that the laser-cooling transients have a fast and a slow component that are determined by the excited-state lifetime of the lumines...

Measurement of solid-state optical refrigeration by two-band differential luminescence thermometry

We present a non-contact optical technique for the measurement of laser-induced temperature changes in solids. Two-band differential luminescence thermometry (TBDLT) achieves a sensitivity of 7 mK and enables a precise measurement of the net quantum efficiency of optical refrigerator materials. The TBDLT detects internal temperature changes by decoupling surface and bulk heating effects via time-resolved luminescence spectroscopy. Several Yb 3+ -doped fluorozirconate (ZrF4‐BaF2‐LaF3‐AlF3‐NaF‐InF3, ZBLANI) glasses fabricated from precursors of varying purity and by different processes are analyzed in detail. A net quantum efficiency of 97.39±0.01% at 238 K (at a pump wavelength of 1020.5 nm) is found for a ZBLANI:1% Yb3+ lasercooling sample produced from metal fluoride precursors that were purified by chelate-assisted solvent extraction and dried in hydrofluoric gas. In comparison, a ZBLANI:1% Yb 3+ sample produced from commercialgrade metal fluoride precursors showed pronounced laser-induced heating that is indicative of a substantially higher impurity concentration. The TBDLT enables rapid and sensitive benchmarking of laser-cooling materials and provides critical feedback to the development and optimization of high-performance optical cryocooler materials. © 2010 Optical Society of America OCIS codes: 160.5690, 300.2530, 300.6430.

D123 流体の局所的温度変化を利用した光学的物質移動技術に関する研究(表面張力・電気浸透流)

A novel technique of non-instructive microflow control with laser-induced temperature change is described in this paper. In microscale, the scale effect in heat and mass transfer appears and phenomenon is governed by properties of fluids or devices. Generation of local distribution of property have a potential to control flow behavior in microfluids. Absorption of focused laser beam causes local temperature distribution and results in the properties change. We have developed an experimental system to induce local temperature rise in microchannel flow and to measure the velocity profile simultaneously. Velocity measurement is performed by micro-PIV (particle image velocimetry) technique. During the laser irradiation, flow velocity around the hot spot increases by approximately 15%. It is found that the principal factor of the velocity variation of microflow is the temperature dependence of liquid viscosity. Validity of the laser-induced viscosity distribution for liquid flow in microfluidic device is confirmed both experimentally and numerically.

Laser-induced temperature changes in dentine.

The purpose of this work is to study the temperature rise and potential thermal damage caused during ablation of human dentine using a super pulsed carbon dioxide laser of 9.6-microm wavelength, equipped with a water-cooling spray and scanner system. There have been no reports on thermal effects of super pulsed CO2 laser of 9.6 microm wavelength on human dentine recently. Two different types of samples were investigated to yield data most consistent with a typical clinical situation. Human dentine slices and crown segments were studied at a drilling depth of 1.0 +/- 0.1 mm and 2.5 +/- 0.5 mm, respectively. A control group treated with a conventional hand piece was compared to four laser groups with settings varying from 2 to 8 W. In the laser group demonstrating the highest elevation in temperature of the four studied, dentine slices lased at 2 W for 15 sec showed a mean temperature rise of less than 1.68 degrees C at an ablation rate of 0.86 +/- 0.08 mm. Conventional drilling with a comparable ablation rate of 0.76 +/- 0.59 mm resulted in a mean rise of 2.87 degrees C. The laser groups of crown segments revealed a constant decrease in temperature. SEM observations were lacking the typical morphological changes seen in earlier studies, specifically extensive melting, charring or cracking. A maximum rise of mean temperature to 1.68 degrees C in closest vicinity to the pulpal chamber and the morphological unaltered dentine surfaces demonstrate the safe and tissue preserving character of the superpulsed 9.6 microm CO2 laser. The laser caused an even lower temperature rise than conventional drilling. Moreover, the laser showed acceptable efficacy with ablation rates that did not significantly differ from the conventional dental drill.

7086 In-vivo real-time mr-monitoring of endoscopic laser application in the porcine colon.

Background: Magnetic resonance (MR) imaging is uniquely sensitive to temperature changes. This preliminary study assessed the feasibility of real-time MR-monitoring of the endoscopic laser application in an interventional scanner. Methods: The procedures were performed with a MRcompatible endoscope (XGIF-MR30C, Olympus, Tokyo, Japan) in two domestic pigs in an interventional 0.5 Tesla MR-system (Signa SP, General Electric Medical, Schenectady, NY, USA) with a 56 cm gap permitting vertical access to the animal. Both the endoscopic view and the MR-images were simultaneously visible on two liquid crystal monitors within the scanner. An external circular balloon filled with gadolinium rendered the endoscope tip visible for MR-imaging. A 10 meter long 365 μm bare laser fiber connected to a Nd:YAG laser located outside the scanner room was inserted through the accessory channel of the endoscope. Laser applications were performed in the rectum (n=5) and the transverse colon (n=1) with energy outputs ranging between 1200 and 1950 Joules delivered at a power of 5 Watts during 4 to 6.5 minutes. The laser induced temperature changes were visualized using a color-coded subtraction technique based on amplitude alterations of T1-weighted gradient echo sequences enabling an image update every 3 seconds in a single axial, sagittal or coronal plane. The animals were sacrificed and the macroscopic coagulation sizes were compared with the lesion sizes seen at real-time MR.Results: The endoscope did not cause any artifacts at continuous MR-imaging. The sizes of the macroscopic coagulation zones of the laser induced lesions were correctly predicted by the color-coded MR-images in a 5 mm lesion in the transverse colon and two 10 mm and 15 mm lesions in the rectum. One lesion was underestimated (5 mm instead of 15 mm) by MR. The lack of a visible pre-treatment lesion inherent with the healthy animal model complicated the accurate MR-localization of the intended laser application sites. This resulted in the failed MR-delineation of two 10 mm laser lesions. Conclusion: Real-time MR-monitoring of endoscopic laser application in an interventional scanner is feasible. This new technique may allow future safe and predictable destruction of gastrointestinal tumors with fewer treatment sessions.

Effect of irradiation with a low-intensity diode laser on the metabolism of equine articular cartilage in vitro

Abstract Objective To determine whether irradiation with a low-intensity diode laser, which produces radiation at a wavelength of 810 nm, will induce nonthermal enhancement of chondrocyte metabolism. Sample Population 144 grossly normal articular cartilage expiants aseptically harvested from the femoral condyles of 6 adult horses. Procedure Treated cartilage expiants were irradiated with a diode laser at 1 of 7 fluence levels that ranged from 8 to 1,600 J/cm2. Expiants were incubated for 24 or 72 hours, labeled for 24 hours with [35S]Na2SO4, and assayed for newly synthesized sulfated glycosaminoglycan (GAG; measured incorporation of 35SO4) and endogenous GAG, chondroitin 6-sulfate (CS), and keratan sulfate (KS) content, using a dimethylmethylene blue assay. Laser-induced temperature changes were measured during irradiation with a diode laser and a neodymiumyttrium aluminum garnet (Nd:YAG) laser, which produces radiation at a wavelength of 1,064 nm, using conditions that were reported in previous studies to increase explant metabolism. Results After incubation for 24 or 72 hours, rate of 35SO4 uptake or endogenous GAG, CS, or KS content in irradiated expiants was not significantly different than in nonirradiated expiants. Cartilage temperature increased < 4.75 C during diode laser application. Cartilage temperature increased 5 to 12 C during Nd:YAG laser application. Conclusions Minimal thermal increases in cartilage expiants with use of a low-intensity diode laser resulted in no change in proteoglycan metabolism of chondrocytes. An increase in tissue temperature over a narrow range with use of a Nd:YAG laser may have contributed to the metabolic alteration of chondrocytes reported in previous studies. (Am J Vet Res 1998;59:1613-1618)

Imaging temperature changes in an interventional 0.5 T magnet: in-vitro results.

To evaluate the ability of monitoring laser induced temperature changes in an open, interventional 0.5 T magnet, adopting fast T1-weighted sequences. A fast gradient echo- (FGRE) and a fast spoiled gradient echo-sequence (FSPGR), both enabling an image update every 2.5 s, were investigated for their ability to visualize laser tissue effects at 5 Watt. Laser induced temperature was fluorooptically measured and correlated with signal intensity (SI) changes depicted by magnetic resonance imaging (MRI). MRI-lesions were compared with macroscopic findings. SI changes on FGRE images appeared as early as 15 s following the onset of laser application and were significantly more pronounced than those seen on FSPGR images (p < .0001). A correlation of r = 0.94 (FGRE) and r = 0.92 (FSPGR) between temperature and SI loss was established. Owing to a steeper slope, the FGRE sequence was considered more sensitive to temperature changes. The areas of macroscopic tissue change correlated with those of SI loss, but lesion size was generally underestimated by MRI. Laser monitoring is possible with rapid image updates in a midfield (0.5 T) interventional MRI environment using fast gradient echo sequence designs.

Theory of acoustic-surface-wave detection of radiative absorption

A new technique is presented to study surface absorption properties by utilizing the interaction of a radiatively heated surface region with an acoustic-surface-wave probe. Surface-wave phase changes are induced by the absorption of 10.6-μm laser radiation. A detailed theory is presented to describe the thermal-acoustic interaction under the condition that the laser-induced temperature change is uniform within the acoustic-wave penetration depth. Where the theory is applicable, calculations in which there are no free parameters agree with quantitative phase-change measurements on yx α-quartz and yz lithium niobate. Phase-change dispersion measurements are shown which indicate a sensitivity to the depth dependence of the absorbed radiation and the resulting temperature distribution.