Numerical and experimental assessments of focused microwave thermotherapy system at 925 MHz

Abstract

This work investigated three-dimensional (3D) focused microwave thermotherapy (FMT) at 925 MHz for a human tissue mimicking phantom using the time reversal (TR) principle for musculoskeletal disorders. We verified the proposed TR algorithm by evaluating the possibility of 3D beam focusing through simulations and experiments. The simulation, along with the electromagnetic and thermal analyses of the human tissue mimicking phantom model, was conducted by employing the Sim4Life commercial tool. Experimental validation was conducted on the developed FMT system using a fabricated human tissue mimicking phantom. A truncated threshold method was proposed to reduce the unwanted hot spots in a normal tissue region, wherein a beam was appropriately focused on a target position. The validation results of the simulation and experiments obtained by utilizing the proposed TR algorithm were shown to be acceptable. Effective beam focusing at the desired position of the phantom could be achieved. K E Y W O R D S beam focusing, microwave thermal therapy, musculoskeletal disorder, Sim4Life, time reversal | 851 KIM et al.

Time‐reversal microwave focusing using multistatic data

“…Microwaves technique uses heat generated by transmitting microwaves from external transmitters outside the human body and focusing the microwave energy on the lesion [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17]. Therefore, microwave focusing is important.…”

“…However, the focusing parameter extraction algorithms based on optimization require considerable processing time. Another widely used estimation algorithm for focusing parameter extraction algorithm is the time-reversal (TR) focusing algorithm [7][8][9][10][11][12][13][14][15][16][17]. The principle of the TR focusing algorithm is that microwaves are transmitted from a virtual transmitter at the focusing target position to external receivers.…”

“…When the received waves are time-reversed and retransmitted, they are focused on the target position. The received waves are obtained using the finite-difference time-domain (FDTD) method, and the magnitude and phase of the time-reversed wave are extracted as the focusing parameters [11][12][13][14]. However, when an FDTD-based TR focusing algorithm is used, reanalysis is necessary to obtain the focusing parameters if the focusing target position changes.…”

“…Treatments using microwaves have been widely investigated because of problems such as radiation exposure when radiation is used and bone impenetrability when ultrasound is used [1, 2]. Microwaves technique uses heat generated by transmitting microwaves from external transmitters outside the human body and focusing the microwave energy on the lesion [3–17]. Therefore, microwave focusing is important.…”