Time-multiplexed two-channel capacitive radiofrequency hyperthermia with nanoparticle mediation.
BACKGROUND
Capacitive radiofrequency (RF) hyperthermia suffers from excessive temperature rise near the electrodes and poorly localized heat transfer to the deep-seated tumor region even though it is known to have potential to cure ill-conditioned tumors. To better localize heat transfer to the deep-seated target region in which electrical conductivity is elevated by nanoparticle mediation, two-channel capacitive RF heating has been tried on a phantom.


METHODS
We made a tissue-mimicking phantom consisting of two compartments, a tumor-tissue-mimicking insert against uniform background agarose. The tumor-tissue-mimicking insert was made to have higher electrical conductivity than the normal-tissue-mimicking background by applying magnetic nanoparticle suspension to the insert. Two electrode pairs were attached on the phantom surface by equal-angle separation to apply RF electric field to the phantom. To better localize heat transfer to the tumor-tissue-mimicking insert, RF power with a frequency of 26 MHz was delivered to the two channels in a time-multiplexed way. To monitor the temperature rise inside the phantom, MR thermometry was performed at a 3T MRI intermittently during the RF heating. Finite-difference-time-domain (FDTD) electromagnetic and thermal simulations on the phantom model were also performed to verify the experimental results.


RESULTS
As compared to the one-channel RF heating, the two-channel RF heating with time-multiplexed driving improved the spatial localization of heat transfer to the tumor-tissue-mimicking region in both the simulation and experiment. The two-channel RF heating also reduced the temperature rise near the electrodes significantly.


CONCLUSIONS
Time-multiplexed two-channel capacitive RF heating has the capability to better localize heat transfer to the nanoparticle-mediated tumor region which has higher electrical conductivity than the background normal tissues.
Department of Biomedical Engineering, Kyung Hee University, Yongin-si, Gyeonggi, 446-701, Korea. kspace0802@naver.com.
Ki Soo
KS
Kim
Department of Biomedical Engineering, Kyung Hee University, Yongin-si, Gyeonggi, 446-701, Korea. theasdwmove@gmail.com.
Daniel
D
Hernandez
Department of Biomedical Engineering, Kyung Hee University, Yongin-si, Gyeonggi, 446-701, Korea. sylee01@khu.ac.kr.
Soo Yeol
SY
Lee
D025802:Electric Capacitance; D004553:Electric Conductivity; D004566:Electrodes; D006979:Hyperthermia, Induced / Q000009:adverse effects / Q000295:instrumentation / Q000379:methods*; D008279:Magnetic Resonance Imaging; D053758:Nanoparticles; D009369:Neoplasms / Q000628:therapy; D019047:Phantoms, Imaging; D011846:Radio Waves / Q000009:adverse effects; D000078702:Radiofrequency Therapy; D062125:Thermometry