Needle Thermocouples Research Articles

Laser‐induced photothermal ablation of equine dermal melanoma

SummaryBackgroundEquine dermal melanoma is a skin tumour most commonly seen in grey horses. Most grey horses will develop at least one tumour if they live long enough. Dermal melanoma and dermal melanomatosis are histologically identical, but dermal melanoma can present as either isolated single or multiple discreet lesions, while dermal melanomatosis presents as multiple coalescing lesions. These tumours are slow growing and have a predilection for the base of the tail, perineum, prepuce, parotid salivary gland and commissures of the lips. This report describes 980‐nm diode laser photothermal ablation as a non‐invasive treatment for equine dermal melanoma.ObjectivesTo report the results of a series of horses that underwent laser photothermal ablation of equine dermal melanomas with a 980‐nm diode therapy laser.Study designRetrospective case series.MethodsHorses were sedated for a standing procedure and restrained in stocks. A thermocouple needle was inserted deep to/into each lesion and the laser was applied either in contact or non‐contact fashion at 4–6 watts until a temperature of 50°C was reached. Masses that were significantly thicker than 1 cm had thermocouple needles placed at multiple levels. After 1 month, treatment sites were re‐evaluated. Lesions in which the planned treatment and follow‐up were completed were included.ResultsFifty‐one individual melanomas in seven horses were included. Fifty lesions were classified as ‘Complete Response’ (CR). One thicker lesion had a ‘Partial Response’ (PR) but there was CR to the depth that temperature was reached.Main limitationsOnly tumours approximating 1 cm in thickness are practical.ConclusionsLaser photothermal ablation using a 980‐nm therapy laser is a practical, non‐invasive and readily available modality for treating smaller equine dermal melanomas. Thickness rather than surface area is the main limitation for a single application.

Comprehensive Evaluation of the BeShape One Device: Assessing Thermal Safety in Noninvasive Body Contouring Using Advanced Techniques.

This study aims to assess the thermal safety profile of the BeShape One Device, a noninvasive, high-intensity, non-focused ultrasound device designed for reducing waist circumference. This device possesses several features that distinguish it from other commercial ultrasound-based fat reduction devices. The study focuses on evaluating temperature-related physiological changes through thermal safety analysis and histopathology in a swine model. The study utilized three types of applicators-active, demo, and modified-to comprehensively assess the device's impact on various skin layers. Five female Large White X Landrace swine were involved in the study, and the BeShape One Device was applied to designated treatment sites using a specific treatment protocol. The assessment included clinical observations, skin reaction evaluations, gross pathology, histopathological analyses, and advanced temperature measurement techniques, including needle thermocouples, thermal cameras, COMSOL modeling, and CEM43 analysis. Clinical observations indicated the animals' overall well-being throughout the study. Skin reactions, including erythema, edema, bruising, and crust formation, were temporary and resolved over time. Gross pathology revealed no treatment-related pathologies, except for a discoloration related to a tattoo procedure. Histopathological analyses at 30 and 90 days posttreatment demonstrated an absence of heat-related lesions in skin layers. Needle thermocouples and thermal camera measurements supported the device's ability to maintain consistent thermal homogeneity. COMSOL modeling and CEM43 analysis predicted no thermal damage to the skin, confirming the safety of the BeShape One Device. Under the experimental conditions, the BeShape One Device demonstrated a favorable safety profile. Clinically and histopathologically, no adverse effects were observed. The device's ability to achieve thermal homogeneity in skin layers was validated through advanced temperature measurement techniques. COMSOL modeling and CEM43 analysis further supported the conclusion that the device is safe, making it a promising option for noninvasive body contouring procedures.

Controlled Hyperthermia With High-Intensity Focused Ultrasound and Ultrasound Contrast Agent Microbubbles in Porcine Liver.

The objective of this work was to study microbubble-enhanced temperature elevation with high-intensity focused ultrasound (HIFU) at different acoustic pressures and under image guidance. The microbubbles were administered with either local or vascular injections (that mimic systemic injections) in perfused and non-perfused ex vivo porcine liver under ultrasound image guidance. Porcine liver was insonified for 30 s with a single-element HIFU transducer (0.9 MHz, 0.413 ms, 82% duty cycle, focal pressures of 0.6-3.5 MPa). Contrast microbubbles were injected either locally or through the vasculature. A needle thermocouple at the focus measured temperature elevation. Diagnostic ultrasound (Philips iU22, C5-1 probe) guided placement of the thermocouple and delivery of microbubbles and monitored the procedure in real time. At lower acoustic pressures (0.6 and 1.2 MPa) in non-perfused liver, inertial cavitation of the injected microbubbles led to greater temperatures at the focus compared with HIFU-only treatments. At higher pressures (2.4 and 3.5 MPa) native inertial cavitation in the tissue (without injecting microbubbles) resulted in temperature elevations similar to those after injecting microbubbles. The heated area was larger when using microbubbles at all pressures. In the presence of perfusion, only local injections provided a sufficiently high concentration of microbubbles necessary for significant temperature enhancement. Local injections of microbubbles provide a higher concentration of microbubbles in a smaller area, avoiding acoustic shadowing, and can lead to higher temperature elevation at lower pressures and increase the size of the heated area at all pressures.

Novel temperature test method for aroma and filter materials

AbstractA good aromatherapy experience of an incense stick with filter material depended heavily on the barrier effect of the filter material particles and the comfort temperature of the aroma. The lack of accurate methods to determine the aroma temperature greatly hindered the quality control and product development of aromatherapy. In this study, a novel method was proposed to measure the temperature of the filter material and aroma with an negative temperature coefficient thermistor and a needle thermocouple. The experimental results showed that the measurement accuracy of this method was up to ±0.01°C, and the surface temperature distribution of the filter media and the extracted aroma temperature can be obtained quickly and accurately. It was found that under the two different heating methods, the aroma temperature produced by heating non-combustion was significantly higher than that produced by the non-flaming combustion. Different aroma delivery intervals also had significant effects on the aroma. This paper showed that this novel method could contribute to quality evaluation of filter sticks for aromatherapy products.

Does the Novel Thulium Fiber Laser Have a Higher Risk of Urothelial Thermal Injury than the Conventional Holmium Laser in an In Vitro Study?

Introduction and Objective: The novel thulium fiber laser (TFL) has been shown to break stones more rapidly than the holmium:YAG laser (HL). However, some evidence suggests that the TFL generates more heat. The purpose of this study is to compare ureteral temperatures generated by these lasers during ureteroscopic laser lithotripsy in a benchtop model. Methods: A 1-cm BegoStone was manually impacted in the proximal ureter of a three-dimensional printed kidney-ureter model and submerged in 35.5°C saline. Lithotripsy was performed using a 7.6F flexible ureteroscope and a 200 μm laser fiber without a ureteral access sheath. The Dornier 30 W HL, Olympus 100 W HL, and Olympus 60 W TFL were compared. A needle thermocouple to measure temperature was inserted 2 mm from the laser tip. Irrigation was maintained at 35 cc/minute at room temperature using the Thermedx FluidSmart System. Intraluminal temperature was continuously recorded for 60 seconds of laser activation. Five trials were performed for each of four different power settings: 3.6, 10, 20, and 30 W. Analysis of variance and Mann-Whitney U tests were performed with p < 0.05 considered significant. Results: Intraureteral fluid temperature increased as laser power settings increased for all lasers (p < 0.05). The TFL generated higher average ureteral fluid temperatures than the Dornier and Empower HL at all power settings tested (p < 0.001). The maximum temperature for the TFL was higher than the Dornier and Empower HL at all power settings tested (p < 0.001), except at 20 W with the Empower HL. At 30 W, the TFL exceeded 43°C, the threshold for tissue damage. Conclusions: The TFL generated more heat at all settings tested. Supraphysiologic ureteral temperatures may be generated with extended use at high energy settings and low irrigation rates. Understanding the heat generation properties of both lasers could help improve the safety of ureteroscopic laser lithotripsy.

Design of an apparatus for low-temperature processing of meat delicacies

Culinary meat products, in particular, delicacies, account for a significant share of the diet in many countries of the world, predetermining the need to introduce innovative solutions for the production of products of a wide range of use with original taste properties. A structure of the device for low-temperature processing of meat delicacies involving the heating of the working surface with a flexible film resistive electric heater of radiative type has been developed. Temperature control is carried out with a needle thermocouple. That makes it possible to cool the delicacy to 25...30 °C by autonomous fans during the conversion of secondary thermal energy by Peltier elements. It was established that the low voltage at the temperature of 70...80 °C is 4...6 W, and, at 25...30 °C, it is, respectively, 1.5...3 W. A comparative analysis has been performed of the heat treatment of meat delicacy in the traditional way and in the developed apparatus upon reaching 71...75 °C inside the product. The temperature for a traditional machine, after 5 minutes of processing, is 15...17 °C at the contact surface and 8 °C at the center. For the model structure, the temperature of the contact surface is 7...8 °C, and 4...5 °C in the center. After 25 minutes of processing in the traditional way, the temperature in the center was 17...18 °C, in the near-wall layers ‒ 60 °C. In the model structure, 8...9 °C, at a temperature of the near-wall layers of 25 °C. The temperature difference from the center to the near-wall layer, depending on the processing time in the traditional way, ranges from 10 to 50 °C, and, in the model apparatus, from 4 to 24 °C. The model device provides a uniform heat supply under conditions of achievement of 71…75 °C in the center of a product with a reduction of specific cost by 2.6 times in comparison with a traditional technique. The ham prepared in the developed apparatus is characterized by uniform coloration, juiciness, and natural original taste

MP65-03 DOES THE NOVEL THULIUM LASER GENERATE MORE HEAT THAN THE CONVENTIONAL HOLMIUM LASER?

You have accessJournal of UrologyStone Disease: Surgical Therapy V (MP65)1 Sep 2021MP65-03 DOES THE NOVEL THULIUM LASER GENERATE MORE HEAT THAN THE CONVENTIONAL HOLMIUM LASER? Joshua D. Belle, Nathaniel Srikureja, Natalie Chen, Mohamed Keheila, Akin S. Amasyali, Jenna Lee, Mohammad Hajiha, and D. Duane Baldwin Joshua D. BelleJoshua D. Belle More articles by this author , Nathaniel SrikurejaNathaniel Srikureja More articles by this author , Natalie ChenNatalie Chen More articles by this author , Mohamed KeheilaMohamed Keheila More articles by this author , Akin S. AmasyaliAkin S. Amasyali More articles by this author , Jenna LeeJenna Lee More articles by this author , Mohammad HajihaMohammad Hajiha More articles by this author , and D. Duane BaldwinD. Duane Baldwin More articles by this author View All Author Informationhttps://doi.org/10.1097/JU.0000000000002105.03AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookLinked InTwitterEmail Abstract INTRODUCTION AND OBJECTIVE: The novel thulium fiber laser (TFL) has been shown to break stones more rapidly than the traditional holmium:YAG laser (HL). However, some evidence suggests that the TFL may generate comparatively more heat. The purpose of this study is to compare ureteral temperatures generated by these lasers during flexible ureteroscopic laser lithotripsy in a benchtop model. METHODS: A 1-cm BegoStone (CaOx monohydrate consistency) was manually impacted in the proximal ureter of a 3D printed kidney-ureter model and submerged in 35°C saline. Lithotripsy was performed with a flexible ureteroscope and a 200 μm laser fiber without a ureteral access sheath. Three lasers were compared (Dornier 30W HL, Olympus 100W HL, and Olympus 60W TFL). A needle thermocouple to measure temperature was inserted 2 mm from the laser tip. Irrigation was maintained at 35cc/min at room temperature using the Thermedx FluidSmart System. Intraluminal temperature was continuously recorded for 60 seconds of laser activation. Time was given between each trial for the intraureteral fluid to return to room temperature. 5 trials were performed for each of 4 different power settings: 3.6, 10, 20, and 30 Watts. ANOVA and Mann-Whitney U tests were performed, with p<0.05 considered significant. RESULTS: Intraureteral fluid temperature increased as laser power settings increased for all lasers trialed (p<0.05, table 1). The TFL produced significantly higher temperatures at both 3.6W (26.36°C vs. 24.57°C (Dornier) and 23.23°C (Empower); p<0.05) and 30W (41.76°C vs. 37.28°C (Empower); p<0.05). There was no difference in intraureteral temperature between lasers at the 10W and 20W settings. At 30W, the TFL generated supraphysiologic intraluminal temperature. CONCLUSIONS: The TFL generated significantly more heat at both the 3.6W and 30W settings. Supraphysiologic ureteral temperatures may be generated by the TFL with extended use at high energy settings and low irrigation rates. Understanding the heat generation properties of both the Holmium and Thulium lasers during ureteroscopy could help improve the safety of ureteroscopic laser lithotripsy. Source of Funding: None © 2021 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 206Issue Supplement 3September 2021Page: e1119-e1119 Advertisement Copyright & Permissions© 2021 by American Urological Association Education and Research, Inc.MetricsAuthor Information Joshua D. Belle More articles by this author Nathaniel Srikureja More articles by this author Natalie Chen More articles by this author Mohamed Keheila More articles by this author Akin S. Amasyali More articles by this author Jenna Lee More articles by this author Mohammad Hajiha More articles by this author D. Duane Baldwin More articles by this author Expand All Advertisement Loading ...

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.

Testicular hyperthermia reduces testosterone concentrations and alters gene expression in testes of Nelore bulls

Increased testicular temperature reduces sperm motility, morphology and fertility. Our objectives were to characterize effects of testicular hyperthermia (scrotal insulation) on acute testosterone concentrations and gene expression in Bos indicus testes. Nelore bulls (n = 20), ∼27 mo of age, 375 kg, scrotal circumference >31 cm, with ≥30% motile sperm, were allocated into four groups (n = 5/group): non-insulated (Control) and insulation removed after 12, 24, or 48 h. Immediately after insulation, intratesticular temperatures (needle thermocouples) were coolest in Control bulls and warmest in 48-h bulls (mean ± SEM, 35.28 ± 0.31 vs 38.62 ± 0.57 °C, P < 0.05). Bulls were castrated and testes recovered. Testicular testosterone concentrations were higher in Control versus 48-h bulls (3119 ± 973.3 and 295.5 ± 122.8 ng/g of tissue, respectively, P < 0.05). Total RNA was extracted, reverse transcribed and RT-qPCR done. For STAR, mRNA abundance decreased from Control to 48 h (1.14 + 0.32 vs 0.32 + 0.5, P < 0.05). For BCL2, expression decreased from Control to 24 h (1.00 + 0.07 vs 0.70 + 0.12, P < 0.05), but then rebounded. In addition, GPX1 had a 70% increase (P < 0.05) at 48 h, whereas HSP70 had a 34-fold increase (P < 0.05) at 12 h and 2- and 14-fold increases (P < 0.05) at 24 and 48 h, respectively. HSF1, BAX, P53 and CASP 8 remained unchanged. Downregulation of STAR, critical in androgen production, was consistent with reduced testosterone concentrations, whereas increased GPX1 enhanced testicular antioxidative capability. Huge increases in HSP70 conferred protection again apoptosis and cell destruction, whereas reduced BCL2 promoted apoptosis. These findings provided novel insights into acute tissue responses (testosterone and gene activity) to testicular hyperthermia in B. indicus bulls.

X-ray phase contrast imaging of Vitis spp. buds shows freezing pattern and correlation between volume and cold hardiness

Grapevine (Vitis spp.) buds must survive winter temperatures in order to resume growth when suitable conditions return in spring. They do so by developing cold hardiness through deep supercooling, but the mechanistic process of supercooling in buds remains largely unknown. Here we use synchrotron X-ray phase contrast imaging to study cold hardiness-related characteristics of V. amurensis, V. riparia, and V. vinifera buds: time-resolved 2D imaging was used to visualize freezing; and microtomography was used to evaluate morphological changes during deacclimation. Bud cold hardiness was determined (low temperature exotherms; LTEs) using needle thermocouples during 2D imaging as buds were cooled with a N2 gas cryostream. Resolution in 2D imaging did not allow for ice crystal identification, but freezing was assessed by movement of tissues coinciding with LTE values. Freezing was observed to propagate from the center of the bud toward the outer bud scales. The freezing events observed lasted several minutes. Additionally, loss of supercooling ability appears to be correlated with increases in bud tissue volume during the process of deacclimation, but major increases in volume occur after most of the supercooling ability is lost, suggesting growth resumption processes are limited by deacclimation state.

An Algorithm of Mathematical Modeling of Laser-Induced Indirect Thermotherapy of a Baker’s Cyst

Abstract—A thermophysical model of heat transfer from a liquid heated by radiation into biological tissues with a cyst of an individual picture of temperature fields, which takes the parameters of laser radiation, as well as the individual thermodynamic and morphometric characteristics of the object of exposure and its syntopy, into account, is proposed. The model is designed for algorithmization of performance of laser-induced indirect thermotherapy of cavity tumors. A comparison was made between the theoretical prediction of the dynamics of temperature changes in the wall of a Baker’s cyst and the experimental data obtained using a thin needle thermocouple placed through a needle in the center of a cyst filled with liquid, whose dimensions had been previously determined by magnetic resonance imaging. It was shown that at the heat transfer coefficient of 3000 W/(m2 K) the proposed model described the heating of the cyst contents due to heat transfer from its inner wall accurately.

Image-Guided High Intensity Focused Ultrasound System for Large Animal Nerve Ablation Studies.

High intensity focused ultrasound (HIFU) is a form of thermal ablation technique, which can treat a variety of medical afflictions. One promising therapeutic use is the permanent destruction of nerves non-invasively in patients with severe spasticity or certain types of pain (e.g., phantom limb pain). To this end, HIFU requires ultrasound guidance, which allows the non-invasive, target-specific deposition of thermal energy to the targeted nerve, thereby blocking axonal conduction. In this paper, a composite system comprising both ultrasound-imaging and HIFU therapy was developed and used to induce localized non-invasive nerve blockage in an in vivo large animal study. Five pigs were used with the femoral nerve as the target. Calibrated needle thermocouples inserted at the target site were employed to monitor the target tissue temperature. The degree of nerve blockage was assessed by measuring compound action potential (CAP) signal with a clinical nerve electrophysiology system before and after HIFU exposures. An average CAP signal amplitude reduction of 49% of baseline with a standard deviation of 9% was observed after 20–30 min post exposure. These results demonstrate the feasibility of the proposed ultrasound-guided HIFU modality as a potential non-invasive nerve ablation method.

Quantitative ultrasound imaging to monitor in vivo high-intensity ultrasound treatment

The success of any minimally invasive treatment procedure can be enhanced significantly if combined with a robust noninvasive quantitative imaging modality. Quantitative ultrasound (QUS) imaging has been widely investigated for monitoring various treatment responses such as chemotherapy and thermal therapy. Previously we have shown the feasibility of using spectral based quantitative ultrasound parameters to monitor high-intensity focused ultrasound (HIFU) treatment of in situ tumors [Ultrasonic Imaging, 2014]. In the present study we examined the use the various QUS parameters to monitor HIFU treatment of an in vivo mouse mammary adenocarcinoma model. Spectral parameters in terms of the backscatter coefficient, integrated backscattered energy, attenuation coefficient, and effective scatterer size and concentration were estimated from radiofrequency signals during the treatment. The characteristic of each parameter was compared to the temperature profile recorded by needle thermocouple inserted into the tumor a few millimeters away from the focal zone of the intersecting HIFU and the imaging transducer beams. The changes in the QUS parameters during the HIFU treatment followed similar trends observed in the temperature readings recorded from the thermocouple. These results suggest that QUS techniques have the potential to be used for non-invasive monitoring of HIFU exposure.

Approaches for modelling interstitial ultrasound ablation of tumours within or adjacent to bone: Theoretical and experimental evaluations

Purpose: The objectives of this study were to develop numerical models of interstitial ultrasound ablation of tumours within or adjacent to bone, to evaluate model performance through theoretical analysis, and to validate the models and approximations used through comparison to experiments. Methods: 3D transient biothermal and acoustic finite element models were developed, employing four approximations of 7-MHz ultrasound propagation at bone/soft tissue interfaces. The various approximations considered or excluded reflection, refraction, angle-dependence of transmission coefficients, shear mode conversion, and volumetric heat deposition. Simulations were performed for parametric and comparative studies. Experiments within ex vivo tissues and phantoms were performed to validate the models by comparison to simulations. Temperature measurements were conducted using needle thermocouples or magnetic resonance temperature imaging (MRTI). Finite element models representing heterogeneous tissue geometries were created based on segmented MR images. Results: High ultrasound absorption at bone/soft tissue interfaces increased the volumes of target tissue that could be ablated. Models using simplified approximations produced temperature profiles closely matching both more comprehensive models and experimental results, with good agreement between 3D calculations and MRTI. The correlation coefficients between simulated and measured temperature profiles in phantoms ranged from 0.852 to 0.967 (p-value < 0.01) for the four models. Conclusions: Models using approximations of interstitial ultrasound energy deposition around bone/soft tissue interfaces produced temperature distributions in close agreement with comprehensive simulations and experimental measurements. These models may be applied to accurately predict temperatures produced by interstitial ultrasound ablation of tumours near and within bone, with applications toward treatment planning.

Calibration of Ultrasound Backscatter Temperature Imaging for High-Intensity Focused Ultrasound Treatment Planning

High-intensity focused ultrasound (HIFU) is rapidly gaining acceptance as a non-invasive method for soft tissue tumor ablation, but improvements in the methods of treatment delivery, planning and monitoring are still required. Backscatter temperature imaging (BTI) uses ultrasound to visualize heating-induced echo strain and may be used to indicate the position of the HIFU focal region using low-power “sub-lesioning” exposure. The technique may also provide a quantitative tool for assessing the efficacy of treatment delivery if apparent strain measurements can be related to the underlying temperature rise. To obtain temperature estimates from strain measurements, the relationship between these variables has to be either measured or otherwise assumed from previous calibrations in similar tissues. This article describes experimental measurements aimed at deriving the relationship between temperature rise and apparent strain in the laboratory environment using both ex vivo bovine liver tissue samples and normothermically perfused porcine livers. A BTI algorithm was applied to radiofrequency ultrasound echo data acquired from a clinical ultrasound scanner (Z.One, Zonare Medical Systems, Mountain View, CA, USA) where the imaging probe was aligned with the focal region of a HIFU transducer. Temperature measurements were obtained using needle thermocouples implanted in the liver tissue. A series of “non-ablative” HIFU exposures giving peak temperatures below 10°C were made in three separate ex vivo bovine livers, yielding an average strain/temperature coefficient of 0.126 ± 0.088 percentage strain per degree Celsius. In the perfused porcine livers at a starting temperature of 38°C (normal body temperature) the strain/temperature coefficients were found to be 0.040 ± 0.029 percentage strain per degree Celsius. The uncertainty in these results is directly linked to the precision of the strain measurement, as well as the naturally occurring variance between different tissue samples, indicating that BTI may lack the accuracy required to be implemented successfully in practice as a quantitative treatment planning technique at a sub-lesioning exposure level. This is because, to be of use in treatment planning, temperature-rise estimates may require an accuracy greater (<10%) than that offered by BTI measurement. BTI may, however, still play a role in ensuring the correct positioning of the focal region and as a treatment monitoring modality capable of detecting an increased rate of heating in tissue after HIFU ablation.

Effect of warm compress application on tissue temperature in healthy dogs

To measure the effect of warm compress application on tissue temperature in healthy dogs. 10 healthy mixed-breed dogs. Dogs were sedated with hydromorphone (0.1 mg/kg, IV) and diazepam (0.25 mg/kg, IV). Three 24-gauge thermocouple needles were inserted to a depth of 0.5 cm (superficial), 1.0 cm (middle), and 1.5 cm (deep) into a shaved, lumbar, epaxial region to measure tissue temperature. Warm (47°C) compresses were applied with gravity dependence for periods of 5, 10, and 20 minutes. Tissue temperature was recorded before compress application and at intervals for up to 80 minutes after application. Control data were collected while dogs received identical sedation but with no warm compress. Mean temperature associated with 5 minutes of heat application at the superficial, middle, and deep depths was significantly increased, compared with the control temperature. Application for 10 minutes significantly increased the temperature at all depths, compared with 5 minutes of application. Mean temperature associated with 20 minutes of application was not different at the superficial or middle depths, compared with 10 minutes of application. Temperature at the deep depth associated with 10 minutes of application was significantly higher, compared with 20 minutes of application, but all temperature increases at this depth were minimal. Results suggested that application of a warm compress should be performed for 10 minutes. Changes in temperature at a tissue depth of 1.5 cm were minimal or not detected. The optimal compress temperature to achieve therapeutic benefits was not determined.

Effect of cold compress application on tissue temperature in healthy dogs

To measure the effect of cold compress application on tissue temperature in healthy dogs. 10 healthy mixed-breed dogs. Dogs were sedated with hydromorphone (0.1 mg/kg, IV) and diazepam (0.25 mg/kg, IV). Three 24-gauge thermocouple needles were inserted to a depth of 0.5 (superficial), 1.0 (middle), and 1.5 (deep) cm into a shaved, lumbar, epaxial region to measure tissue temperature. Cold (-16.8°C) compresses were applied with gravity dependence for periods of 5, 10, and 20 minutes. Tissue temperature was recorded before compress application and at intervals for up to 80 minutes after application. Control data were collected while dogs received identical sedation but with no cold compress. Mean temperature associated with 5 minutes of application at the superficial depth was significantly decreased, compared with control temperatures. Application for 10 and 20 minutes significantly reduced the temperature at all depths, compared with controls and 5 minutes of application. Twenty minutes of application significantly decreased temperature at only the middle depth, compared with 10 minutes of application. With this method of cold treatment, increasing application time from 10 to 20 minutes caused a further significant temperature change at only the middle tissue depth; however, for maximal cooling, the minimum time of application should be 20 minutes. Possible changes in tissue temperature and adverse effects of application > 20 minutes require further evaluation.

The numerical analysis and measurements of temperature profile in fat tissue during neodymium-doped yttrium aluminum garnet laser irradiation for laser-assisted lipolysis

The purpose of the study is to investigate the temperature profile of fat tissue during neodymium-doped yttrium aluminum garnet laser irradiation (1064, 1320, and 1444 nm wavelengths) for laser-assisted lipolysis. The numerical analysis was performed to assess the wavelength dependence of the temperature distribution in fat tissue. For the internal temperature profile measurements, a cannula was placed in the middle of fat tissue for laser irradiation, and two hypodermic thermocouple needles were placed at 2 and 5 mm apart from the cannula. For surface temperature measurements, an infrared camera was placed at the surface of fat tissue. The highest temperature with the least thermal expansion in fat tissue was observed in the 1444 nm wavelength both on the numerical analysis and on the experimental results. Therefore, the 1444 nm wavelength provided the highest thermal confinement with the least thermal damage in surrounding tissue as compared with the other two laser wavelengths, 1064 and 1320 nm.

HIFU-Induced Cavitation and Heating in Ex Vivo Porcine Subcutaneous Fat

The present study is motivated by the fact that there are no published studies quantifying cavitation activity and heating induced by ultrasound in adipose tissue and that there are currently no reliable techniques for monitoring successful deposition of ultrasound energy in fat in real time. High-intensity focused ultrasound (HIFU) exposures were performed in excised porcine fat at four different frequencies (0.5, 1.1, 1.6 and 3.4 MHz) over a range of pressure amplitudes and exposure durations. The transmission losses arising from reflection at the skin interface and attenuation through skin and fat were quantified at all frequencies using an embedded needle hydrophone. A 15 MHz passive cavitation detector (PCD) coaxial to the HIFU transducer was used to capture acoustic emissions emanating from the focus during HIFU exposures, while the focal temperature rise was measured using minimally invasive needle thermocouples. Repeatable temperature rises in excess of 10°C could be readily instigated across all four frequencies for acoustic intensities (Ispta) in excess of 50 W/cm 2 within the first 2 s of exposure. Even though cavitation could not be initiated at 1.1, 1.6 and 3.4 MHz over the in situ peak rarefactional ( p -) pressure range 0–3 MPa explored in the present study, inertial cavitation activity was always initiated at 0.5 MHz for pressures greater than 1.6 MPa ( p -) and was found to enhance focal heat deposition. A good correlation was identified between the energy of broadband emissions detected by the PCD and the focal temperature rise at 0.5 MHz, particularly for short 2 s exposures, which could be exploited as a tool for noninvasive monitoring of successful treatment delivery. (E-mail: zoe.kyriakou@eng.ox.ac.uk)

Exploitation of cavitation‐enhanced heating for release of doxorubicin from thermosensitve liposomes by therapeutic ultrasound.

The systemic toxicity of current chemotherapeutic treatments motivates the investigation of targeted delivery techniques to restrict the action of drugs to the tumor region. ThermoDox© copyright (Celsion Corporation) consists of doxorubicin, a common anticancer agent, encapsulated within thermally sensitive liposomes designed to release their contents above 39 °C. Activation of such an agent with the use of HIFU, which can generate localized heating non‐invasively, potentially combines the benefits of targeted chemotherapy and hyperthermia while minimizing undesirable systemic side‐effects. ThermoDox© release was investigated and optimized in a novel cell‐embedding, tissue‐mimicking material. The material was exposed to 1.1 MHz HIFU using a range of clinically relevant pressure amplitudes, duty cycles, and exposure durations to identify optimal insonation conditions for complete doxorubicin release, resulting in cell death that is solely due to drug activity. The corresponding temperature profiles were mapped throughout the focal region using embedded needle thermocouples. Drug release and cell viability were quantified using fluorescent microscopy and cell luminescence, respectively. Optimal conditions for drug release only due to the thermal effects of HIFU, with and without cavitation, were identified and cell death only due to drug release was achieved, demonstrating the potential for safe and effective targeted drug release by HIFU‐induced hyperthermia.