Ověření proveditelnosti mikrovlnného monitorování regionální hypertermie

Abstract

Microwave hyperthermia is a cancer supplementary treatment that has been researched for over two decades, as it has proven to improve the cancer treatment process significantly. This thesis aimed to study non-invasive temperature monitoring during hyperthermia in the pelvic region using Microwave Imaging technology at a frequency of 1 GHz. The feasibility of imaging the temperature changes in the heated tissue by detecting small changes in the dielectric properties, relative permittivity εr and equivalent conductivity σ, in the area was tested numerically and experimentally. In the software, COMSOL Multiphysics were developed multiple numerical simulations with different configurations of UWB antennas and a muscle phantom. The inverse-scattering problem was solved using a distorted Born Approximation (DBA) algorithm with a truncated singular values decomposition (TSVD). Additionally, noise was introduced to replicate the environment of the experiment. With 80 dB of noise, the numerical simulation reconstructions detected a temperature resolution of 1.55 °C, an accuracy of 97.64 % and a localisation error of 1.4 mm. Following was designed the first prototype of the experimental setup, which included a plexiglass tank with the UWB antennas attached to it, a vector network analyser (VNA) with a 24-port switching matrix and a liquid muscle phantom. The preliminary experimental reconstructions were unsuccessful, but after additional noise level measurement and matching medium (MM) testing, it was established that with proper stabilisation of the system and a different matching medium with dielectric properties ɛr = 40 and σ = 0.7 S/m, differential Microwave Imaging for temperature monitoring in the pelvic region with the proposed prototype is possible.

Microwave hyperthermia is a cancer supplementary treatment that has been researched for over two decades, as it has proven to improve the cancer treatment process significantly. This thesis aimed to study non-invasive temperature monitoring during hyperthermia in the pelvic region using Microwave Imaging technology at a frequency of 1 GHz. The feasibility of imaging the temperature changes in the heated tissue by detecting small changes in the dielectric properties, relative permittivity εr and equivalent conductivity σ, in the area was tested numerically and experimentally. In the software, COMSOL Multiphysics were developed multiple numerical simulations with different configurations of UWB antennas and a muscle phantom. The inverse-scattering problem was solved using a distorted Born Approximation (DBA) algorithm with a truncated singular values decomposition (TSVD). Additionally, noise was introduced to replicate the environment of the experiment. With 80 dB of noise, the numerical simulation reconstructions detected a temperature resolution of 1.55 °C, an accuracy of 97.64 % and a localisation error of 1.4 mm. Following was designed the first prototype of the experimental setup, which included a plexiglass tank with the UWB antennas attached to it, a vector network analyser (VNA) with a 24-port switching matrix and a liquid muscle phantom. The preliminary experimental reconstructions were unsuccessful, but after additional noise level measurement and matching medium (MM) testing, it was established that with proper stabilisation of the system and a different matching medium with dielectric properties ɛr = 40 and σ = 0.7 S/m, differential Microwave Imaging for temperature monitoring in the pelvic region with the proposed prototype is possible.