A 2 1/4-turn spiral antenna for catheter cardiac ablation

Gu, Zeji; Rappaport, Carey M.; Wang, P.J.; VanderBrink, Brian A.

doi:10.1109/10.804576

Cited by 26 publications

(8 citation statements)

References 5 publications

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“…Notably, looped designs operating in the axial mode have been described for cardiac ablation, while helices have been proposed for microwave-assisted angioplasty 49, 63. Single and multi-loop designs have also been tested for microwave ablation in the liver 64…”

Section: Microwave Ablation Technologymentioning

confidence: 99%

Microwave Tissue Ablation: Biophysics, Technology, and Applications

Brace

2010

Crit Rev Biomed Eng

272

214

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Microwave ablation is an emerging treatment option for many cancers, cardiac arrhythmias and other medical conditions. During treatment, microwaves are applied directly to tissues to produce rapid temperature elevations sufficient to produce immediate coagulative necrosis. The engineering design criteria for each application differ, with individual consideration for factors such as desired ablation zone size, treatment duration, and procedural invasiveness. Recent technological developments in applicator cooling, power control and system optimization for specific applications promise to increase the utilization of microwave ablation in the future. This article will review the basic biophysics of microwave tissue heating, provide an overview of the design and operation of current equipment, and outline areas for future research for microwave ablation.

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Section: Microwave Ablation Technologymentioning

confidence: 99%

Microwave Tissue Ablation: Biophysics, Technology, and Applications

Brace

2010

Crit Rev Biomed Eng

272

214

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“…6,7,10,12,[17][18][19][20]23,27,33,35,39 In addition, studies have been conducted on the effects of implantable chips placed on the retina, cardiac muscle, and other structures within the body. 4,8,15,16,26,30,34,37 However, much less has been done on the consequences of wirelessly powering devices within the skull 14,31 . In this work, a 2-D numerical model with approximations to 3D was developed and implemented to provide an analysis of the SAR values and temperature changes in the cortical tissue surrounding the implanted and electromagnetically-excited BMI chip(s).…”

Section: Introductionmentioning

confidence: 98%

Electromagnetic Power Absorption and Temperature Changes due to Brain Machine Interface Operation

2007

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To fully understand neural function, chronic neural recordings must be made simultaneously from 10s or 100s of neurons. To accomplish this goal, several groups are developing brain machine interfaces. For these devices to be viable for chronic human use, it is likely that they will need to be operated and powered externally via a radiofrequency (RF) source. However, RF exposure can result in tissue heating and is regulated by the FDA/FCC. This paper provides an initial estimate of the amount of tissue heating and specific absorption rate (SAR) associated with the operation of a brain-machine interface (BMI). The operation of a brain machine interface was evaluated in an 18-tissue anatomically detailed human head mesh using simulations of electromagnetics and bio-heat phenomena. The simulations were conducted with a single chip, as well as with eight chips, placed on the surface of the human brain and each powered at four frequencies (13.6 MHz, 1.0 GHz, 2.4 GHz, and 5.8 GHz). The simulated chips consist of a wire antenna on a silicon chip covered by a Teflon dura patch. SAR values were calculated using the finite-difference time-domain method and used to predict peak temperature changes caused by electromagnetic absorption in the head using two-dimensional bio-heat equation. Results due to SAR alone show increased heating at higher frequencies, with a peak temperature change at 5.8 GHz of approximately 0.018 degrees C in the single-chip configuration and 0.06 degrees C in the eight-chip configuration with 10 mW of power absorption (in the human head) per chip. In addition, temperature elevations due to power dissipation in the chip(s) were studied. Results show that for the neural tissue, maximum temperature rises of 3.34 degrees C in the single-chip configuration and 7.72 degrees C in the eight-chip configuration were observed for 10 mW dissipation in each chip. Finally, the maximum power dissipation allowable in each chip before a 1.0 degrees C temperature increase (most stringent standards as denoted in the FDA guidelines) is exceeded in the head was simulated and found to be 2.92 mW in the single-chip configuration and 1.25 mW in the eight-chip configuration. As thermal heating due to SAR was insignificant, this study suggests that wireless electromagnetics, i.e., RF may be a viable option for powering, and communicating with brain machine interfaces for clinical applications.

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“…Thus, these two currents will excite fields that constructively interfere along the axis of the loop and cancel outside the loop. For a loop positioned on a planar tissue surface, this modest focusing yields an enhanced electric field and, hence, increased power deposition at depth within the tissue 37,38 .…”

Section: Wide Aperture Catheter Antennasmentioning

confidence: 99%

Cardiac tissue ablation with catheter-based microwave heating

Rappaport

2004

International Journal of Hyperthermia

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The common condition of atrial fibrillation is often treated by cutting diseased cardiac tissue to disrupt abnormal electrical conduction pathways. Heating abnormal tissue with electromagnetic power provides a minimally invasive surgical alternative to treat these cardiac arrhythmias. Radio frequency ablation has become the method of choice of many physicians. Recently, microwave power has also been shown to have great therapeutic benefit in medical treatment requiring precise heating of biological tissue. Since microwave power tends to be deposited throughout the volume of biological media, microwave heating offers advantages over other heating modalities that tend to heat primarily the contacting surface. It is also possible to heat a deeper volume of tissue with more precise control using microwaves than with purely thermal conduction or RF electrode heating. Microwave Cardiac Ablation (MCA) is used to treat heart tissue that allows abnormal electrical conduction by heating it to the point of inactivation. Microwave antennas that fit within catheter systems can be positioned close to diseased tissue. Specialized antenna designs that unfurl from the catheter within the heart can then radiate specifically shaped fields, which overcome problems such as excessive surface heating at the contact point. The state of the art in MCA is reviewed in this paper and a novel catheter-based unfurling wide aperture antenna is described. This antenna consists of the centre conductor of a coaxial line, shaped into a spiral and insulated from blood and tissue by a non-conductive fluid filled balloon. Initially stretched straight inside a catheter for transluminal guiding, once in place at the cardiac target, the coiled spiral antenna is advanced into the inflated balloon. Power is applied in the range of 50-150 W at the reserved industrial, scientific and medical (ISM) frequency of 915 MHz for 30-90 s to create an irreversible lesion. The antenna is then retracted back into the catheter for removal. Simulated and experimental measurements on phantoms, in vitro animal organ tissue and living animals have shown that these microwave applicators deliver the intended therapeutic lesions that are both wider and deeper than those generated by RF ablation or other recently reported microwave applicators.

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A 2 1/4-turn spiral antenna for catheter cardiac ablation

Cited by 26 publications

References 5 publications

Microwave Tissue Ablation: Biophysics, Technology, and Applications

Microwave Tissue Ablation: Biophysics, Technology, and Applications

Electromagnetic Power Absorption and Temperature Changes due to Brain Machine Interface Operation

Cardiac tissue ablation with catheter-based microwave heating

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