Microwave medicals

Abstract

Researchers at the University of Queensland, Australia, have published results suggesting microwave imaging could be used to detect even early-stage lung tumours. This imaging would also be suitable for frequent monitoring as it doesn't involve ionising radiation and can be made portable for small clinic and even home use for a range of diseases. The authors working with the test setup for the microwave imaging system in the lab at the University of Queensland There is currently great interest in building portable microwave imaging systems as safe, low-cost and reliable diagnostic tools for medical applications. This is because microwave-based diagnostic systems use non-ionising radiation and are non-invasive so they can be used frequently as a monitoring tool. “By virtue of being low-cost and portable, microwave diagnostic systems will provide a technology platform that is easy to use and offers a significant complement to the existing diagnostic technologies, such as MRI and X-rays. In contrast to the current tools that are only available in major medical centres, microwave-based systems can be deployed in ambulances, rural clinics, and doctors’ offices. They could also be used as a self-monitoring tool for healthcare at home leading to a huge reduction in healthcare costs,” explained Queensland team member Ali Zamani. “Lung cancer is the number one cancer killer in the world. Unfortunately, there is no fully reliable and accepted screening tool for the early detection of lung cancer. The significant difference in the dielectric properties between cancerous and healthy lung tissues at microwave frequencies motivated us to investigate the feasibility of building a microwave imaging tool for early-stage lung cancer detection.” The difficulty with using a microwave approach for lung cancer detection is that the human torso also contains different healthy tissues with a wide range of dielectric properties, making microwave signal propagation and penetration complex, and introducing signal clutter. The resulting signals need to be processed to remove this clutter. The complexity and the sheer size of the torso mean that the results of traditional microwave imaging algorithms are very slow to process, and inaccurate. In addition, strong reflections, especially from the outer layers of the torso tissues, mask cancerous tissue signals. To address these problems, the Queensland team's algorithms process the signals in the frequency domain to remove the effect of the clutter, while at the same time a field intensity enhancement factor is used to enhance the signals from abnormal tissues for more accurate tumour detection. As well as developing new algorithms for this system the team have created a compact, unidirectional wideband three-dimensional slot-rotated antenna, working at the 1.5-3 GHz frequency band and integrated it into the imaging platform. In this issue of Electronics Letters the team report results from using their system to image an artificial torso phantom with an emulated lung cancer. Running off a laptop, the results show that their system can detect smaller abnormalities than previous approaches; detecting an emulated cancer only two cubic centimetres in size. The microwave group at the University of Queensland is now looking to gain the proper ethical clearances to proceed with human trials of this approach. They expect human trials to introduce several new challenges, including the effect of normal body movements like heartbeat and breathing, and for this reason they plan to use a three-dimensional multi-static scanning system so that the whole torso can be scanned and imaged in a fraction of a second. The imaging results for the torso phantom containing an emulated lung tumour In addition to this work, the group has been active in building portable microwave imaging systems for medical applications including detection of strokes, brain tumours, heart failure and pulmonary oedema. They currently have ethical approval for human trials on the early detection of strokes, and congestive heart failure. Looking ahead the authors see this imaging technology becoming commonplace and freeing medical imaging from being confined to major medical establishments. “In the next decade, microwave imaging systems are likely to become a reliable diagnostic tool for many medical applications. Those tools will also be available as a monitoring tool, not only in major clinical centres but also at home for self-monitoring.”