In vitro dielectric properties of human tissues at radiofrequencies

Abstract

In vitro permittivity measurements of excised human liver, spleen, kidney and cardiac muscle at frequencies from 10 kHz to 100 MHz are described. An end-of-the-line capacitive sensor and a computer-controlled network analyser HP 3577 were employed. The results were compared with human data reported by other investigators as well as with the animal (cat) data obtained earlier in this laboratory. It was found that the conductivity of most of the human tissues tested was significantly higher than that of the animal tissues for the test frequencies. The dielectric constants for human kidney and spleen are higher than the corresponding animal (cat) tissues at frequencies from 10 kHz to approximately 1 MHz and at around 100 MHz. However, the values for liver do not differ significantly between the two species in the same frequency range.

Investigation of the effect of dehydration on tissue dielectric properties in ex vivo measurements

“…In one of the most comprehensive studies, Gabriel et al (1996) reported the dielectric properties of a large number of biological tissues including freshly excised bovine and porcine tissue, human autopsy material, and human skin and tongue over a frequency range of 10 Hz-20 GHz. Dielectric data for various human and animal tissues reported in other studies (Foster et al 1979, Surowiec et al 1987, Peyman et al 2001, Schmid et al 2003, Lazebnik et al 2006, Abdilla et al 2013, Sasaki et al 2014 align with the data presented in (Gabriel et al 1996), which is widely used in electromagnetic modeling and assessment of specific absorption rate. Stuchly et al (1982) studied inter-species differences in dielectric properties of skeletal muscle, brain cortex, spleen, and liver tissue between 0.1 and 10 GHz, and reported a very small difference (within system uncertainty) between the same tissues of different species, which led researchers to believe that the data from animal studies can be generalized and used for human tissue modeling.…”

Tumor ablation at low frequencies for preferential tumor heating: Initial ex-vivo tissue studies

“…Several previous studies have shown that tumor tissue has lower measured electrical resistivity than normal tissue in the radiofrequency range, and that this difference in resistivity becomes more pronounced at even lower frequencies ( Fig. 1 intro) [2][3][4][5]. A previous modeling study that utilized the frequency-dependent electrical resistivity values from Fig.…”

“…Several previous studies have investigated the electrical properties of different cancer tissues over a wide frequency range (from 1 kHz to 100 MHz) [2][3][4][5], and have found that the electrical resistivity of tumor tissue is significantly lower than normal tissue, with a more pronounced difference at lower frequencies. An example of this trend is shown graphically in Fig.…”

Design of Magneto-Inductive Magnetic Resonance Imaging Catheters

“…If these waves are resonant, the result may be rapid heating [13][14][15][16]. Unfortunately, the conductors are often closely surrounded by tissue, whose dielectric constant is high at standard clinical frequencies (63.85 MHz for 1 H MRI at 1.5 T) [17], so the resonant length is short. Development of decoupling methods to control spurious resonances is more difficult for long conductors.…”