RF-INDUCED TEMPERATURE INCREASE IN A STRATIFIED MODEL OF THE SKIN FOR PLANE-WAVE EXPOSURE AT 6–100 GHZ

Abstract This study assesses the maximum temperature increase induced by exposure to electromagnetic fields between 6 and 100 GHz using a stratified model of the skin with four or five layers under plane wave incidence. The skin model distinguishes the stratum corneum (SC) and the viable epidermis as the outermost layers of the skin. The analysis identifies the tissue layer structures that minimize reflection and maximize the temperature increase induced by the electromagnetic field. The maximum observed temperature increase is 0.4°C for exposure at the present power density limit for the general population of 10 W m −2 . This result is more than twice as high as the findings reported in a previous study. The reasons for this difference are identified as impedance matching effects in the SC and less conservative thermal parameters. Modeling the skin as homogeneous dermis tissue can underestimate the induced temperature increase by more than a factor of three.

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Evaluation of the soft tissue thermal index and the maximum temperature increase for homogeneous and layered tissues

IEEE 1992 Ultrasonics Symposium Proceedings ◽

10.1109/ultsym.1992.275849 ◽

2003 ◽

Author(s):

D.S. Ellis ◽

W.D. O'Brien

Keyword(s):

Soft Tissue ◽

Temperature Increase ◽

Maximum Temperature ◽

Thermal Index

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An automated and minimally invasive tool harvests viable epidermis capable of cellular outgrowth using a bench skin model

Journal of Applied Bioinformatics & Computational Biology ◽

10.4172/2329-9533.c1.002 ◽

2015 ◽

Vol 04 (03) ◽

Author(s):

Sandra N Osborne

Keyword(s):

Minimally Invasive ◽

Skin Model ◽

Viable Epidermis

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Assessment of Effects of Laser Light Combining Three Wavelengths (450, 520 and 640 nm) on Temperature Increase and Depth of Tissue Lesions in an Ex Vivo Study

Materials ◽

10.3390/ma13235340 ◽

2020 ◽

Vol 13 (23) ◽

pp. 5340

Author(s):

Kamil Jurczyszyn ◽

Witold Trzeciakowski ◽

Zdzisław Woźniak ◽

Piotr Ziółkowski ◽

Mateusz Trafalski

Keyword(s):

Duty Cycle ◽

Temperature Increase ◽

Ex Vivo ◽

Visible Spectrum ◽

Maximum Temperature ◽

Lesion Depth ◽

Single Beam ◽

Duty Cycles ◽

Rate Of Increase

Background: Lasers are widely used in medicine in soft and hard tissue surgeries and biostimulation. Studies found in literature typically compare the effects of single-wavelength lasers on tissues or cell cultures. In our study, we used a diode laser capable of emitting three components of visible light (640 nm, red; 520 nm, green; 450 nm, blue) and combining them in a single beam. The aim of the study was to assess the effects of laser radiation in the visible spectrum on tissue in vitro, depending on the wavelength and pulse width. Methods: All irradiations were performed using the same output power (1.5 W). We used various duty cycles: 10, 50, 80 and 100% with 100 Hz frequency. Maximum superficial temperature, rate of temperature increase and lesion depth were investigated. Results: Maximum superficial temperature was observed for 450 + 520 nm irradiation (100% duty cycle). The highest rate of increase of temperature was noted for 450 + 520 nm (100% duty cycle). Maximum lesion depth was observed in case of three-wavelength irradiation (450 + 520 + 640 nm) for 100, 80 and 50% duty cycles. Conclusions: The synergistic effect of two-wavelength (450 + 520 nm) irradiation was observed in case of maximum temperature measurement. The deepest depth of lesion was noted after three-wavelength irradiation (450 + 520 + 640 nm).

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In vitro characterisation of ultrasound-induced heating effects in the mother and fetus: A clinical perspective

Ultrasound ◽

10.1177/1742271x20953197 ◽

2020 ◽

pp. 1742271X2095319

Author(s):

Stephanie F Smith ◽

Piero Miloro ◽

Richard Axell ◽

Gail ter Haar ◽

Christoph Lees

Keyword(s):

Temperature Increase ◽

Skin Surface ◽

Maximum Temperature ◽

Factors Affecting ◽

Bone Interface ◽

Heating Effects ◽

Power Setting ◽

Lower Temperature

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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LOW-FREQUENCY ACOUSTIC SCATTERING BY AN INHOMOGENEOUS MEDIUM

Mathematical Models and Methods in Applied Sciences ◽

10.1142/s0218202505000881 ◽

2005 ◽

Vol 15 (10) ◽

pp. 1459-1468 ◽

Cited By ~ 1

Author(s):

GEORGE VENKOV

Keyword(s):

Refractive Index ◽

Plane Wave ◽

Inhomogeneous Medium ◽

Acoustic Waves ◽

Spherical Wave ◽

Low Frequency ◽

Far Field ◽

Scattering Medium ◽

Wave Incidence ◽

Plane Wave Incidence

This paper deals with the scattering of time-harmonic acoustic waves by inhomogeneous medium. We study the problem to recover the near and the far field using a priori information about the refractive index and the support of inhomogeneity. The incident spherical wave is modified in such a way as to recover the plane wave incidence when the source point approaches infinity. Applying the low-frequency expansions, the scattering medium problem is reduced to a sequence of potential problems for the approximation coefficients in the presence of a monopole singularity located at the source of incidence. Complete expansions for the integral representation formula in the near field as well as for the scattering amplitude in the far field are provided. The method is applied to the case of a spherical region of inhomogeneity and a radial dependent refractive index. As the point singularity tends to infinity, the relative results recover the scattering medium problem for plane wave incidence.

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