Measurement of SAR-induced temperature increase in a phantom and in vivo with comparison to numerical simulation

Introduction The quantification of heating effects during exposure to ultrasound is usually based on laboratory experiments in water and is assessed using extrapolated parameters such as the thermal index. In our study, we have measured the temperature increase directly in a simulator of the maternal–fetal environment, the ‘ISUOG Phantom’, using clinically relevant ultrasound scanners, transducers and exposure conditions. Methods The study was carried out using an instrumented phantom designed to represent the pregnant maternal abdomen and which enabled temperature recordings at positions in tissue mimics which represented the skin surface, sub-surface, amniotic fluid and fetal bone interface. We tested four different transducers on a commercial diagnostic scanner. The effects of scan duration, presence of a circulating fluid, pre-set and power were recorded. Results The highest temperature increase was always at the transducer–skin interface, where temperature increases between 1.4°C and 9.5°C were observed; lower temperature rises, between 0.1°C and 1.0°C, were observed deeper in tissue and at the bone interface. Doppler modes generated the highest temperature increases. Most of the heating occurred in the first 3 minutes of exposure, with the presence of a circulating fluid having a limited effect. The power setting affected the maximum temperature increase proportionally, with peak temperature increasing from 4.3°C to 6.7°C when power was increased from 63% to 100%. Conclusions Although this phantom provides a crude mimic of the in vivo conditions, the overall results showed good repeatability and agreement with previously published experiments. All studies showed that the temperature rises observed fell within the recommendations of international regulatory bodies. However, it is important that the operator should be aware of factors affecting the temperature increase.

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Computational Study on the Effects of Peripheral Vessel Network on Blood Flow in the Arterial Circle of Willis

ASME 2007 Summer Bioengineering Conference ◽

10.1115/sbc2007-176706 ◽

2007 ◽

Author(s):

Shigefumi Tokuda ◽

Takeshi Unemura ◽

Marie Oshima

Keyword(s):

Numerical Simulation ◽

Blood Flow ◽

Boundary Conditions ◽

Vascular System ◽

Computational Study ◽

Circulatory System ◽

Biological Data ◽

Patient Specific ◽

Peripheral Vessel

Cerebrovascular disorder such as subarachnoid hemorrhage (SAH) is 3rd position of the cause of death in Japan [1]. Its initiation and growth are reported to depend on hemodynamic factors, particularly on wall shear stress or blood pressure induced by blood flow. In order to investigate the information on the hemodynamic quantities in the cerebral vascular system, the authors have been developing a computational tool using patient-specific modeling and numerical simulation [2]. In order to achieve an in vivo simulation of living organisms, it is important to apply appropriate physiological conditions such as physical properties, models, and boundary conditions. Generally, the numerical simulation using a patient-specific model is conducted for a localized region near the research target. Although the analysis region is only a part of the circulatory system, the simulation has to include the effects from the entire circulatory system. Many studies have carried out to derive the boundary conditions to model in vivo environment [3–5]. However, it is not easy to obtain the biological data of cerebral arteries due to head capsule.

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Intraosseous Temperature Change during Installation of Dental Implants with Two Different Surfaces and Different Drilling Protocols: An In Vivo Study in Sheep

Journal of Clinical Medicine ◽

10.3390/jcm8081198 ◽

2019 ◽

Vol 8 (8) ◽

pp. 1198 ◽

Cited By ~ 4

Author(s):

Michele Stocchero ◽

Yohei Jinno ◽

Marco Toia ◽

Marianne Ahmad ◽

Evaggelia Papia ◽

...

Keyword(s):

Temperature Increase ◽

Element Model ◽

Multiple Regression Model ◽

Metatarsal Bone ◽

Area Fraction ◽

Bone Area ◽

Implant Surface ◽

Bone Necrosis ◽

Bone To Implant Contact

Background: The intraosseous temperature during implant installation has never been evaluated in an in vivo controlled setup. The aims were to investigate the influence of a drilling protocol and implant surface on the intraosseous temperature during implant installation, to evaluate the influence of temperature increase on osseointegration and to calculate the heat distribution in cortical bone. Methods: Forty Brånemark implants were installed into the metatarsal bone of Finnish Dorset crossbred sheep according to two different drilling protocols (undersized/non-undersized) and two surfaces (moderately rough/turned). The intraosseous temperature was recorded, and Finite Element Model (FEM) was generated to understand the thermal behavior. Non-decalcified histology was carried out after five weeks of healing. The following osseointegration parameters were calculated: Bone-to-implant contact (BIC), Bone Area Fraction Occupancy (BAFO), and Bone Area Fraction Occupancy up to 1.5 mm (BA1.5). A multiple regression model was used to identify the influencing variables on the histomorphometric parameters. Results: The temperature was affected by the drilling protocol, while no influence was demonstrated by the implant surface. BIC was positively influenced by the undersized drilling protocol and rough surface, BAFO was negatively influenced by the temperature rise, and BA1.5 was negatively influenced by the undersized drilling protocol. FEM showed that the temperature at the implant interface might exceed the limit for bone necrosis. Conclusion: The intraosseous temperature is greatly increased by an undersized drilling protocol but not from the implant surface. The temperature increase negatively affects the bone healing in the proximity of the implant. The undersized drilling protocol for Brånemark implant systems increases the amount of bone at the interface, but it negatively impacts the bone far from the implant.

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Numerical simulation of the in vivo fluorescence in plants

Mathematics and Computers in Simulation ◽

10.1016/0378-4754(95)00114-x ◽

1996 ◽

Vol 42 (2-3) ◽

pp. 245-253 ◽

Cited By ~ 20

Author(s):

Alexandrina D. Stirbet ◽

Reto J. Strasser

Keyword(s):

Numerical Simulation ◽

In Vivo Fluorescence

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Thermal Distribution of Ultrasound Waves in Prostate Tumor: Comparison of Computational Modeling with In Vivo Experiments

ISRN Biomathematics ◽

10.1155/2013/428659 ◽

2013 ◽

Vol 2013 ◽

pp. 1-4 ◽

Cited By ~ 6

Author(s):

Forough Jafarian Dehkordi ◽

Ali Shakeri-Zadeh ◽

Samideh Khoei ◽

Hossein Ghadiri ◽

Mohammad-Bagher Shiran

Keyword(s):

Computer Simulation ◽

Temperature Rise ◽

Temperature Increase ◽

Ultrasound Irradiation ◽

Prostate Tumor ◽

Great Promise ◽

Distribution Profile ◽

Thermal Distribution ◽

In Vivo Experiments

Ultrasound irradiation to a certain site of the body affects the efficacy of drug delivery through changes in the permeability of cell membrane. Temperature increase in irradiated area may be affected by frequency, intensity, period of ultrasound, and blood perfusion. The aim of present study is to use computer simulation and offer an appropriate model for thermal distribution profile in prostate tumor. Moreover, computer model was validated by in vivo experiments. Method. Computer simulation was performed with COMSOL software. Experiments were carried out on prostate tumor induced in nude mice (DU145 cell line originated from human prostate cancer) at frequency of 3 MHz and intensities of 0.3, 0.5, and 1 w/cm2 for 300 seconds. Results. Computer simulations showed a temperature rise of the tumor for the applied intensities of 0.3, 0.5 and 1 w/cm2 of 0.8, 0.9, and 1.1°C, respectively. The experimental data carried out at the same frequency demonstrated that temperature increase was 0.5, 0.9, and 1.4°C for the above intensities. It was noticed that temperature rise was very sharp for the first few seconds of ultrasound irradiation and then increased moderately. Conclusion. Obtained data holds great promise to develop a model which is able to predict temperature distribution profile in vivo condition.

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Numerical and Experimental Simulations as Symbiotic Tools for Solving Complex Biothermal Problems

Journal of Medical Devices ◽

10.1115/1.3443759 ◽

2010 ◽

Vol 4 (2) ◽

Cited By ~ 1

Author(s):

Ephraim Sparrow ◽

John Abraham ◽

Yilmaz Bayazit ◽

Ryan Lovik ◽

Dianna Smith

Keyword(s):

Numerical Simulation ◽

Medical Devices ◽

Skin Surface ◽

Time Dependent ◽

Safety Issues ◽

Finite Element Software ◽

Simulation Time

In the design of medical devices, the use of numerical simulation, either with or without complementary experimentation, may lead to a more competent product. The experimentation in question may either be performed in vitro or in vivo. This paper conveys a case study in which the two methodologies, numerical simulation and in vitro experimentation used in tandem, enabled the evaluation of safety issues related to a heat-generating implant. The numerical simulation was implemented by means of ANSYS finite-element software employed in the transient mode. The experimental work provided information necessary for the execution of the simulation and, therefore, was performed as the first phase of the research. The implant is of the type that is equipped with a short-lived battery that requires intermittent recharging. The recharging is accomplished by means of an antenna that is externally mounted on the skin surface. The antenna is the primary of a transformer, and the implant contains the secondary of the transformer. During the recharging period of the battery, heat is generated in both the antenna and the implant. By the symbiotic use of the experimental results and the numerical simulation, time-dependent temperatures were determined in the tissue that is situated in the neighborhood of the implant and the antenna. These temperatures were evaluated from the standpoint of possible tissue damage.

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