Experimental Evaluation of a Microwave Imaging System for Muscle Rupture Detection

Licentiate thesis, 2023

Injuries to the hamstring muscles are one of the most common injuries in
sports such as football, sprinting, and running. Imaging plays a key role
in diagnosing and managing athletes with muscle injuries, and particularly
magnetic resonance imaging is usually required to diagnose muscle ruptures.
Unfortunately, this imaging modality is both costly and availability is limited.
The aim of this work is to explore the possibility of using a microwave imaging
system to aid in the diagnosis of a muscle rupture and eventually supplement
or perhaps even replace current imaging modalities. A microwave based imaging
system could help improve availability and bring the cost down leading to
improved and more accurate diagnostics.
The microwave imaging system consist of several antennas placed on a semi
circular array. The antennas consists of monopole antennas and a lossy (conductive)
gel. The lossy gel serves the purpose of reducing the effects of signals
taking undesired paths outside the body under test and improves the image
quality. In this work, different gels were manufactured and evaluated in imaging
experiments. The results show that the lossy gels can effectively reduce
the undesired signals, resulting in significantly more stable and repeatable image
reconstructions. The results were consistent in several different imaging
experiments with targets of different size and location.
Furthermore, a software defined radio (SDR) board was explored and benchmarked
against a high-performance Vector Network Analyzer (VNA) with the
purpose to assess whether it could be used as a low-cost and compact alternative
for the measurements. The measurements showed good repeatability
and accuracy for a transmission loss up to 70 dB, with the option to adapt
the system gain to handle even higher transmission losses in specific channels