RF hyperthermia using conductive nanoparticles

H. Michael Gach, Arvind Balachandrasekaran, Tejas Nair

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review

3 Scopus citations

Abstract

Specific absorption rate (SAR) heating using radiofrequency (RF) waves is affected by the RF frequency and amplitude, and the conductivity of the tissue. Recently, conductive nanoparticles were demonstrated to induce hyperthermia in vitro and in vivo upon irradiation with an external 13.56 MHz RF field. The addition of conductive nanoparticles was assumed to increase the tissue conductivity and SAR. However, no quantitative studies have been performed that characterize the conductivities of biocompatible colloids or tissues containing nanoparticles, and relate the conductivity to SAR. The complex permittivities were measured for colloids containing single-wall carbon nanotubes (SWCNTs) in normal saline with 0.32% w/v Pluronic F108 nonionic surfactant. The carbon concentrations of the colloids ranged from 0 to 88 mM. The permittivities were measured using a dielectric probe and RF network analyzer for RF frequencies from 200 MHz to 3 GHz. The nonionic surfactant was added to the colloids to minimize flocculation of the nanotubes during the RF heating experiments. The results were compared with prior measurements of colloids containing 0.02% Pluronic F108. The dielectric and conductivity of the 0.02% Pluronic colloids rose linearly with carbon concentration but the 0.32% Pluronic colloids varied from linearity. Based on the permittivity results, selected colloid samples were placed inside a Bruker 7T/20 magnetic resonance (MR) imaging (MRI) system and irradiated at 300 MHz using a high duty cycle RF pulse sequence. The temperature changes were measured directly using fiber-optic thermometers and indirectly using MR thermometry and spectroscopy. Temperature changes were consistent with the colloid conductivities.

Original languageEnglish
Title of host publicationPhotonic Therapeutics and Diagnostics VI
DOIs
StatePublished - Dec 1 2010
EventPhotonic Therapeutics and Diagnostics VI - San Francisco, CA, United States
Duration: Jan 23 2010Jan 25 2010

Publication series

NameProgress in Biomedical Optics and Imaging - Proceedings of SPIE
Volume7548
ISSN (Print)1605-7422

Conference

ConferencePhotonic Therapeutics and Diagnostics VI
Country/TerritoryUnited States
CitySan Francisco, CA
Period01/23/1001/25/10

Keywords

  • RF
  • carbon nanotubes
  • electrical conductivity
  • hyperthermia
  • permittivity
  • saline
  • specific absorption rate

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