Two 27 MHz Simple Inductive Loops, as Hyperthermia Treatment Applicators: Theoretical Analysis and Development.

Kouloulias V, Karanasiou I, Koutsoupidou M, Matsopoulos G, Kouvaris J, Uzunoglu N - Comput Math Methods Med (2015)

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fig7: (a) Numerical and simulation results for the normalized SAR values in relation to the depth for the trace of two antennas with radii 7 cm and 9 cm placed over a dielectric semi-infinite space and a cube, respectively. (b) Simulation results for the normalized SAR values in relation to the depth for the trace of the two antennas placed over a cylinder modeled with skin, fat, muscle, and bone.
Mentions: Following that, numerical code executions have been realized and the results for the SAR distribution are presented for two different current loops with radii 7 cm and 9 cm. For the theoretical analysis the circular current source has been considered infinitely thin as at 27 MHz the free space wavelength is 11.1 m and thus much larger than the antenna's thickness. The dielectric properties, used for the computations, were εr = 113 and σ = 0.62 Si/m representing soft tissues [13]. In Figure 6 normalized values for SAR in relation to the horizontal distance from the antenna center along OX semiaxis are depicted. The results are given for three different depths, 0 cm, 2 cm, and 4 cm, when the radius of the antenna is 7 cm and 9 cm and is placed 1 cm above the dielectric. In Figure 7(a) the penetration of the radiation in relation to the depth is depicted for the field created by the loop antennas with radii 7 and 9 cm. Finally, in Figure 8 SAR distribution in relation to depth, for the central level (XY) of the antenna, is depicted, when the antenna radii are 7 cm and 9 cm.

Bottom Line: The specific absorption rate (SAR) distributions were estimated from the respective local phantom temperature measurements.Comparisons of the theoretical, simulation, and experimental studies showed satisfying agreement.The penetration depth was measured theoretically and experimentally in the range of 2-3.5 cm.

View Article: PubMed Central - PubMed

Affiliation: 2nd Department of Radiology, ATTIKON University Hospital, Medical School, University of Athens, Rimini 1, Haidari, 124 64 Athens, Greece ; Microwave and Fiber Optics Laboratory, School of Electrical and Computer Engineering, Institute of Communication and Computer Systems, National Technical University of Athens, Heroon Polytechniou 9, 15780 Zografou, Greece ; 1st Department of Radiology, Aretaieion University Hospital, Medical School, University of Athens, Vassilissis Sofias 76, 115 28 Athens, Greece.

ABSTRACT

Background: Deep heating is still the main subject for research in hyperthermia treatment.

Aim: The purpose of this study was to develop and analyze a simple loop as a heating applicator.

Methods: The performance of two 27 MHz inductive loop antennas as potential applicators in hyperthermia treatment was studied theoretically as well as experimentally in phantoms. Two inductive loop antennas with radii 7 cm and 9 cm were designed, simulated, and constructed. The theoretical analysis was performed by using Green's function and Bessel's function technique. Experiments were performed with phantoms radiated by the aforementioned loop antennas.

Results: The specific absorption rate (SAR) distributions were estimated from the respective local phantom temperature measurements. Comparisons of the theoretical, simulation, and experimental studies showed satisfying agreement. The penetration depth was measured theoretically and experimentally in the range of 2-3.5 cm.

Conclusion: The theoretical and experimental analysis showed that current loops are efficient in the case where the peripheral heating of spherical tumor formation located at 2-3.5 cm depth is required.

No MeSH data available.

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