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Power density, field intensity, and carrier frequency determinants of RF‐energy‐lnduced calcium‐ion efflux from brain tissue
Author(s) -
Joines William T.,
Blackman Carl F.
Publication year - 1980
Publication title -
bioelectromagnetics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.435
H-Index - 81
eISSN - 1521-186X
pISSN - 0197-8462
DOI - 10.1002/bem.2250010303
Subject(s) - efflux , calcium , intensity (physics) , power density , brain tissue , ion , field (mathematics) , materials science , field intensity , power (physics) , biophysics , physics , chemistry , nuclear magnetic resonance , optics , biomedical engineering , medicine , biology , biochemistry , quantum mechanics , mathematics , pure mathematics , metallurgy
Abstract To explain a carrier frequency dependence reported for radiofrequency (RF)‐induced calcium‐ion efflux from brain tissue, a chick‐brain hemisphere bathed in buffer solution is modeled as a sphere within the uniform field of the incident electromagnetic wave. Calculations on a spherical model show that the average electric‐field intensity within the sample remains the same at different carrier frequencies if the incident power density (P i ) is adjusted by an amount that compensates for the change in complex permittivity (ϵ r * ) and the change of wavelength, as a function of carrier frequency. The resulting formula for transforming P i is seen to follow the pattern of both positive and negative demonstrations of calcium‐ion efflux that have been observed at carrier frequencies of 50, 147, and 450 MHz. Indeed, all results obtained at these three frequencies, when related by P i 's that produce the same average electric‐field intensity within the sample, are seen to be in agreement; no prediction is contradicted by an experiment.