The dielectric properties of biological tissues: II. Measurements in the frequency range 10 Hz to 20 GHz

Gabriel, Sami; Lau, R W M; Gabriel, Camelia

doi:10.1088/0031-9155/41/11/002

Cited by 3,663 publications

(2,587 citation statements)

References 8 publications

Supporting

Mentioning

2,461

Contrasting

Unclassified

Order By: Relevance

“…aThe permittivity (conductivity) ratio is (permittivity (conductivity) of newborn tissue)/( permittivity (conductivity) of adult tissue) at 130 MHz as reported by Peyman et al 18.bNewborn tissue permittivity (conductivity) values are the adult values (from References 20, 21, 22) multiplied by the appropriate ratio.cDensity values provided by Helmholtz Zentrum München.…”

Section: Methodsmentioning

confidence: 99%

See 1 more Smart Citation

Specific absorption rate in neonates undergoing magnetic resonance procedures at 1.5 T and 3 T

et al. 2015

View full text Add to dashboard Cite

MRI is finding increased clinical use in neonatal populations; the extent to which electromagnetic models used for quantification of specific absorption rate (SAR) by commercial MRI scanners accurately reflect this alternative scenario is unclear. This study investigates how SAR predictions relating to adults can be related to neonates under differing conditions when imaged using 1.5 T and 3 T MRI scanners. Electromagnetic simulations were produced in neonatal subjects of different sizes and positions within a generic MRI body transmit device operating at both 64 MHz and 128 MHz, corresponding to 1.5 T and 3 T MRI scanners, respectively. An adult model was also simulated, as was a spherical salt‐water phantom, which was also used in a calorimetry experiment. The SAR in neonatal subjects was found to be less than that experienced in an adult in all scenarios; however, the overestimation factor was variable. For example a 3 T body scan resulting in local 10 g SAR of 10.1 W kg−1 in an adult would deposit 2.6 W kg−1 in a neonate: an approximately fourfold difference. The SAR experienced by neonatal subjects undergoing MRI is lower than that in adults in equivalent situations. If the safety of such procedures is assessed using adult‐appropriate models then the result is a conservative estimate. © 2015 The Authors. NMR in Biomedicine published by John Wiley & Sons, Ltd.

show abstract

Section: Methodsmentioning

confidence: 99%

“…Newborn tissue permittivity (conductivity) values are the adult values (from References 20, 21, 22) multiplied by the appropriate ratio.…”

Section: Methodsmentioning

confidence: 99%

Specific absorption rate in neonates undergoing magnetic resonance procedures at 1.5 T and 3 T

et al. 2015

View full text Add to dashboard Cite

show abstract

“…The wall of the blood vessel was modelled as a layer with a thickness of 1 mm and the tumour tissue as a homogeneous material surrounding the vessel wall. Both regions were assigned an electric conductivity of 0.3 S m À1 , which is an average value of reported bulk electric conductivities of soft tissues (including epithelial and tumour tissues) that range from 0.1 to 0.5 S m À1 (Geddes and Barker, 1967;Duck, 1990;Gabriel et al, 1996). The distribution of the electric potential was derived analytically by solving the Laplace equation in cylindrical coordinates with the boundary conditions of homogeneity of the electric field far from the vessel, boundedness and continuity of the electric potential, and continuity of the electric current density (Kotnik et al, 1997;Kotnik and Miklavcic, 2000).…”

Section: Mathematical Model Of Electric Field Distribution In and Aromentioning

confidence: 99%

“…The plot shows the ratio between the local electric field (E) along the line a and the external field to which the tissue is exposed (E 0 ), for three different orientations of the vessel with respect to the field (901 -solid, 601 -dashed, 301 -dotted). The conductivities of the tissues and the blood are taken from the literature (Hirsch et al, 1950;Duck 1990;Gabriel et al, 1996). In the capillary, a somewhat lower serum content (and therefore conductivity) is assumed due to the erythrocytes filling most of the volume in the thin passages.…”

Section: Mathematical Model Of Electric Field Distribution In and Aromentioning

confidence: 99%

Vascular disrupting action of electroporation and electrochemotherapy with bleomycin in murine sarcoma

et al. 2008

View full text Add to dashboard Cite

Electrochemotherapy has a direct cytotoxic effect on tumour cells, and presumably, a vascular disrupting effect. In this study, on the basis of the prediction of the mathematical model, histological evaluation and physiological measurements of the tumours were carried out to confirm that electroporation and electrochemotherapy of tumours have a vascular disrupting action. In the study, SA-1 solid subcutaneous sarcoma tumours in A/J mice were treated by bleomycin (BLM) given intravenously (1 mg kg À1 ), application of electric pulses (8 pulses, 1040 V, 100 ms, 1 Hz) or a combination of both -electrochemotherapy. The vascular effect was determined by laser Doppler flowmetry, power Doppler ultrasonographic imaging and Patent blue staining. The extent of tumour hypoxia was determined immunohistochemically by hypoxia marker pimonidazole and partial pressure of oxygen (pO 2 ) in tumours by electron paramagnetic resonance oximetry. Electrochemotherapy with BLM induced good antitumour effect with 22 days, tumour growth delay and 38% tumour cures. The application of electric pulses to the tumours induced instant but transient tumour blood flow reduction (for 70%) that was recovered in 24 h. During this tumour blood flow reduction, we determined an increase in hypoxic tumour area for up to 30%, which was also reflected in reduced tumour oxygenation (for 70%). According to the described mathematical model, endothelial cells lining in tumour blood vessels are exposed to a B40% higher electric field than the surrounding tumour cells, and therefore easily electroporated, allowing access of high BLM concentration to the cytosol. Consequently, electrochemotherapy has, besides the immediate vascular disrupting action, also a delayed one (after 24 h), as a consequence of endothelial cell swelling and apoptosis demonstrated by extensive tumour necrosis, tumour hypoxia, prolonged reduction of tumour blood flow and significant tumour growth delay, and tumour cures. Our results demonstrate that in addition to the well-established direct cytotoxic effect on tumour cells, electrochemotherapy also has an indirect vascular disrupting action resulting altogether in extensive tumour cell necrosis leading to complete regression of tumours.

show abstract

“…We got the electrical conductivity values and their changes during electroporation from literature and experiments, as well as the electric field values above which tissues are permeabilized. [4][5][6][7][15][16][17][18]25,26 However, getting these values was a difficult task, due to the lack of measurements in this field.…”

Section: Parameters Of the Numerical Modelmentioning

confidence: 99%

A Numerical Model of Skin Electropermeabilization Based on In Vivo Experiments

2007

View full text Add to dashboard Cite

Abstract-As an alternative to viral methods that are controversial because of their safety issues, chemical and physical methods have been developed to enhance gene expression in tissues. Reversible increase of the cell membrane permeability caused by the electric field-electroporation-is currently one of the most efficient and simple nonviral methods of gene transfer. We performed a series of in vivo experiments, delivering plasmids to rat skin using external plate electrodes. The experiments showed that skin layers below stratum corneum can be permeabilized in this way. In order to study the course of skin tissue permeabilization by means of electric pulses, a numerical model using the finite element method was made. The model is based on the tissue-electrode geometry and electric pulses used in our in vivo experiments. We took into account the layered structure of skin and changes of its bulk electrical properties during electroporation, as observed in the in vivo experiments. We were using tissue conductivity values found in literature and experimentally determined electric field threshold values needed for tissue permeabilization. The results obtained with the model are in good agreement with the in vivo results of gene transfection in rat skin. With the model presented we used the available data to explain the mechanism of the tissue electropermeabilization propagation beyond the initial conditions dictated by the tissue initial conductivities, thus contributing to a more in-depth understanding of this process. Such a model can be used to optimize and develop electrodes and pulse parameters.

show abstract

The dielectric properties of biological tissues: II. Measurements in the frequency range 10 Hz to 20 GHz

Cited by 3,663 publications

References 8 publications

Specific absorption rate in neonates undergoing magnetic resonance procedures at 1.5 T and 3 T

Specific absorption rate in neonates undergoing magnetic resonance procedures at 1.5 T and 3 T

Vascular disrupting action of electroporation and electrochemotherapy with bleomycin in murine sarcoma

A Numerical Model of Skin Electropermeabilization Based on In Vivo Experiments

Contact Info

Product

Resources

About