Dielectric properties of ocular tissues in the supercooled and frozen states

Gabriel, Camelia; Grant, E H

doi:10.1088/0031-9155/30/9/009

Cited by 12 publications

(4 citation statements)

References 20 publications

(16 reference statements)

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“…Conditions such as temperature and viability also affect skin dielectric properties; for example, lowering skin temperature has been reported to decrease conductivity. Necrotic or excised tissues are reported to have different conductivity and permittivity compared with healthy in vivo tissues due to changes in cell membrane integrity and extracellular water content (Gabriel and Grant 1985, Pethig 1987, Kyber et al 1992, Marzec and Wachal 1999, Martinsen et al 2000, Grimnes and Martinsen 2010. These causes of variability in skin properties emphasize the need to be aware of the application for which the measurements are being performed, make sure that the measurement conditions resemble those imposed by the application, and pay close attention to sample composition.…”

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confidence: 99%

The dielectric properties of skin and their influence on the delivery of tumor treating fields to the torso: a study combining in vivo measurements with numerical simulations

Hershkovich¹,

Urman²,

Yesharim³

et al. 2019

Phys. Med. Biol.

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The study of the dielectric properties of tissues plays a key role in understanding the interaction between electromagnetic energy and the human body, for safety assessments of human exposure to electromagnetic fields, as well as for numerous biomedical applications such as tumor treating fields (TTFields). TTFields are low-intensity alternating electric fields in the 100–500 kHz frequency range, which have an antimitotic effect on cancerous cells. TTFields are delivered to the body through pairs of transducer arrays placed on a patient’s skin in close proximity to the tumor. Therefore, it is essential to understand how the skin’s dielectric properties affect TTFields delivery in clinical settings. In this paper, we present a study combining in vivo measurements with numerical simulations that elucidate how different layers of the skin influence TTFields distribution in the body. The dielectric properties of the skin were measured on volunteers using a setup that ensured skin conditions resembled those when TTFields are delivered to patients. The measured properties were incorporated into a realistic human computational phantom and delivery of TTFields to the phantom’s abdomen was simulated. The total impedance of the simulated model was within the mid-range of impedance values measured in patients with pancreatic cancer treated with TTFields. A computational study investigating model sensitivity to the dielectric properties of the skin and subcutaneous adipose tissue (SAT) showed that when skin conductivity increased above a threshold value, the total impedance of the model was largely insensitive to changes in the conductivity of these tissues. Furthermore, for a given current, the field intensity within the internal organs was mostly unaffected by skin properties but was highly sensitive to the conductivity of the organ itself. This study provides a new insight into the role of skin in determining the distribution of TTFields within the body.

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confidence: 99%

The dielectric properties of skin and their influence on the delivery of tumor treating fields to the torso: a study combining in vivo measurements with numerical simulations

Hershkovich¹,

Urman²,

Yesharim³

et al. 2019

Phys. Med. Biol.

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“…The data on normal tissues are summarised by Schwan and Foster (1980) and Stuchly and Stuchly (1980a). More recent data have been reported by Schwartz and Mealing (1985), Smith and Foster (1989, Surowiec et a1 (1989, Gabriel andGrant (1985), Gabriel et a1 (1983), Nightingale et a1 (1983), Kraszewski et a1 (1982), Stoy et a1 (1982), Stuchly et a1 (1982a, c, 1981) and Brady et a1 (1981). Data on neoplastic tissues are rare and moreover mostly taken from excised tumour tissue (Schepps and Foster 1980, Foster and Schepps 1981, Rogers et a1 1983 al 1984).…”

Section: Introductionmentioning

confidence: 88%

Dielectric properties of CO-γ-irradiated and microwave-heated rat tumour and skin measured in vivo between 0.2 and 2.4 GHz

Zywietz¹,

Knöchel²

1986

Phys. Med. Biol.

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The dielectric properties of a rat tumour (rhabdomyosarcoma R1H), skin and muscle were measured in vivo with an open-ended coaxial line and a computer-controlled system based on a network analyser. The permittivity of the tumour R1H and of the normal tissues in anaesthetised rats was determined at frequencies between 0.2 and 2.4 GHz. No significant differences were observed either between rat tumour and muscle or between normal and 15 Gy irradiated rat tumour and skin. However, after a hyperthermia treatment at 43 degrees C for 60 min the dielectric properties, especially of the rat skin, changed due to the hyperthermic induced oedema which is related to an increase in tissue water content. The process of the oedema modifies the dielectric properties of the skin to a higher degree than those of the tumour.

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“…One problem with interpreting unambiguously these kinds of data is that the small dispersion tends to become overshadowed by the Maxwell-Wagner and counterion dispersion regions occurring at lower fre- [Gabriel and Grant, 1985], is to freeze the material and thus significantly reduce the conductivity. This method then causes considerable reduction in the amplitudes of the low frequency dispersions arising from the properties of the macromolecule itself and allows any subsidiary dispersion to be resolved much more clearly.…”

Section: Origin Of the Dispersionsmentioning

confidence: 99%