Dielectric properties of mammalian brain tissue between 1 and 18 GHz

Steel, Moscow; Sheppard, R J

doi:10.1088/0031-9155/30/7/001

Cited by 17 publications

(6 citation statements)

References 12 publications

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“…The IT’IS data on white matter, grey matter and cerebellum permittivity originate from Gabriel [ 20 ]. The values for brain tissues in the frequency range from 500 MHz to 18 GHz in Gabriel [ 20 ] were compiled from the literature already published at that time (i.e., before 1996): rabbit specimen at 37 °C [ 31 ] (white and grey matter), mouse specimen at 37 °C [ 32 ] (grey matter), rat specimen in vivo at 32 °C [ 33 ] (grey matter), feline specimen in vivo at 36 °C [ 33 ] (grey matter), canine specimen in situ at 36 °C [ 34 ] (white and grey matter), canine specimen at 20 °C [ 35 ] (white and grey matter), feline specimen in vivo at 33 °C [ 36 ] (white and grey matter), canine specimen at 37 °C [ 37 ] (white and grey matter), as well as from her own measurement results.…”

Section: Discussionmentioning

confidence: 99%

Complex Permittivity of Ex-Vivo Human, Bovine and Porcine Brain Tissues in the Microwave Frequency Range

et al. 2022

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Accurate knowledge about the dielectric properties of biological tissues in the microwave frequency range may lead to advancement of biomedical applications based on microwave technology. However, the published data are very scarce, especially for human brain tissues. The aim of this work was to measure and report the complex permittivity of brain white matter, grey matter and cerebellum. Complex permittivity was measured on human, bovine and porcine brain tissues in the microwave frequency range from 0.5 to 18 GHz using an open-ended coaxial probe. The results present a valuable addition to the available data on the brain tissue complex permittivity. Some noticeable variations between the results lead to several conclusions. Complex permittivity variation within the same tissue type of the individual species was comparable to interspecies variation. The difference was prominent between human brains obtained from autopsies, while bovine brains obtained from healthy animals showed very similar complex permittivity. We hypothesize that the difference might have been caused by the basic pathologies of the patients, where the associated therapies could have affected the brain water content. We also examined the effect of excised tissue degradation on its complex permittivity over the course of three days, and the results suggest the gradual dehydration of the samples.

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Section: Discussionmentioning

confidence: 99%

Complex Permittivity of Ex-Vivo Human, Bovine and Porcine Brain Tissues in the Microwave Frequency Range

et al. 2022

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“…There have been a number of prior studies in the microwave and millimeter-wave bands on the dielectric properties of brain tissue [53][54][55][56], tissue and head modeling [57][58][59][60] and RF energy exposure modeling [61][62][63][64][65][66][67][68]. Here, we study simultaneously the effects of beam penetration, absorption and thermal diffusion in brain tissue through realtime temperature measurements during the irradiation.…”

Section: Introduction To This Studymentioning

confidence: 99%

Absorption of 5G Radiation in Brain Tissue as a Function of Frequency, Power and Time

Gültekin

Siegel

2020

IEEE Access

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The rapid release of 5G wireless communications networks has spurred renewed concerns regarding the interactions of higher radiofrequency (RF) radiation with living species. We examine RF exposure and absorption in ex vivo bovine brain tissue and a brain simulating gel at three frequencies: 1.9 GHz, 4 GHz and 39 GHz that are relevant to current (4G), and upcoming (5G) spectra. We introduce a highly sensitive thermal method for the assessment of radiation exposure, and derive experimentally, accurate relations between the temperature rise (ΔT), specific absorption rate (SAR) and the incident power density (F), and tabulate the coefficients, ΔT/ΔF and Δ(SAR)/ΔF, as a function of frequency, depth and time. This new method provides both ΔT and SAR applicable to the frequency range below and above 6 GHz as shown at 1.9, 4 and 39 GHz, and demonstrates the most sensitive experimental assessment of brain tissue exposure to millimeter-wave radiation to date, with a detection limit of 1 mW. We examine the beam penetration, absorption and thermal diffusion at representative 4G and 5G frequencies and show that the RF heating increases rapidly with frequency due to decreasing RF source wavelength and increasing power density with the same incident power and exposure time. We also show the temperature effects of continuous wave, rapid pulse sequences and single pulses with varying pulse duration, and we employ electromagnetic modeling to map the field distributions in the tissue. Finally, using this new methodology, we measure the thermal diffusivity of ex vivo bovine brain tissue experimentally.

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“…A survey of the literature showed that most of the research on dielectric properties on biological samples was done on nonliving tissue. Regarding brain tissue, which is of special interest for the exposure of the human head from modern handheld communication devices, most of this work was done in vitro on various animal tissues Thurai et al, 1984;Steel and Sheppard, 1985;Surowiec et al, 1986a;Xu et al, 1987;Gabriel et al, 1996]. In vivo measurements of the dielectric properties of brain tissue were reported by Stuchly et al [1981], Kraszewski et al [1982], and Burdette et al [1986] using cats, dogs, and rats as test animals.…”

Section: Introductionmentioning

confidence: 99%

Dielectric properties of porcine brain tissue in the transition from life to death at frequencies from 800 to 1900 MHz

Schmid

Neubauer

Illievich

et al. 2003

Bioelectromagnetics

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Ten experiments on pigs were performed to investigate possible postmortem changes of the dielectric properties of brain gray matter in the frequency range of 800-1900 MHz. After keeping the animals in stable anaesthesia for at least 45 min, they were euthanatised by an intravenous injection of hypertonic potassium chloride (KCl), causing cardiac arrest within 3 min. Measurements of the dielectric properties were performed repeatedly from at least 45 min prior to death to 18 h after euthanasia. The anaesthesia regimen was chosen to minimize influence on brain tissue characteristics such as brain water content, intracranial blood volume, and cerebral blood flow. The data showed a decline of mean gray matter equivalent conductivity of about 15% at 900 MHz and about 11% at 1800 MHz within the first hour after death. The decline in permittivity was less pronounced (about 3-4%) and almost frequency independent. The results indicate that in vitro measurements of dielectric properties of brain tissue underestimate equivalent conductivity as well as permittivity of living tissue. These changes may affect the generally accepted data of dielectric properties of brain tissue widely used in RF dosimetry.

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Dielectric properties of mammalian brain tissue between 1 and 18 GHz

Cited by 17 publications

References 12 publications

Complex Permittivity of Ex-Vivo Human, Bovine and Porcine Brain Tissues in the Microwave Frequency Range

Complex Permittivity of Ex-Vivo Human, Bovine and Porcine Brain Tissues in the Microwave Frequency Range

Absorption of 5G Radiation in Brain Tissue as a Function of Frequency, Power and Time

Dielectric properties of porcine brain tissue in the transition from life to death at frequencies from 800 to 1900 MHz

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