Towards a microwave hyperthermia system for head and neck tumors
Licentiate thesis, 2016
Hyperthermia has shown the ability to enhance the performance of radiotherapy
and chemotherapy in many clinical trials. The incidence of increased tissue toxicity
as a result of high radiotherapy dose, made hyperthermia as a safe method
in combination with radiotherapy to enhance the treatment outcome. Although
many clinical studies have shown the effectiveness of hyperthermia for treatment
of head-and-neck (H&N) cancer, presence of large vessels, tissue transitions and
critical tissues in head and neck pose therapeutic challenges for treatment of advanced
tumors in this region. Moreover the application of hyperthermia to deep
seated tumors in H&N region requires suitable heating equipment which was not
available until recently.
In this thesis, an ultra wideband antenna has been designed, evaluated and built
to act as the radiating element of microwave hyperthermia applicator. The time
reversal focusing technique is used to target electromagnetic energy to the tumor.
This focusing method is implemented by a 3D finite difference time domain based
code for tumor models in head and neck.
The single antenna element is a modified bow-tie antenna with wideband characteristic
over 430-1000 MHz and small size. The antenna size has been reduced
considerably by immersion in a conical shape water bolus, while maintaining the
radiation characteristics in the presence of human phantom. The specific shape
and size of water container, wideband matching network between coaxial port
and feeding elements of the bow-tie and addition of low-permittivity dielectric
material to the bow-tie radiating arms are the other influential factors on final
performance of the antenna.
The focusing ability of 3D time reversal technique was analyzed using tumor
models in head and neck region of an anthropomorphic phantom. Two hyperthermia
applicators were designed and used, one for the head and one for the neck.
The 3D models of Head&Neck phantom together with phased array applicators
were modeled in two electromagnetic solvers, CST microwave studio and an inhouse
developed FDTD-based code.
Keywords: microwave hyperthermia, time reversal, wideband antenna, treatment
planning, head and neck tumors.
head and neck tumors.
treat- ment planning
Room EA, Hörsalsvägen 11, Campus Johanneberg
Opponent: Dr. Petra Kok, Academic Medical Center, University of Amsterdam, Netherlands