Editor’s message: Microwave imaging advances

Abstract

Since visual representations are more efficient in transmitting ideas, usually, plots are preferred over tables, schemes as a complement of text descriptions and pictures as evidence in a sense of “An image is worth a thousand words.” Picturing the visible light world seems to be the easiest of all, but it depends on the details that we wish to capture; the resolution is limited by the light wavelength and our eyes are also part of the optical system. Interaction wave-matter can lead to wave transmission, absorption, and reflection, as energetic beams hitting a sample can produce secondary electrons, backscattered electrons, x-rays, or heat, which can be detected for constructing with electronic devices an image that we can see. An important application of high energy radiation is for industrial testing and analysis, such as welding cords inspection and search of cracks inside materials. The attractiveness of these techniques, considered as non-destructive in that field, is that they make it possible to see inside the samples. In the same manner, not invasive medical diagnosis is of the same interest for clinical applications, and even more, the patients, who prefer to avoid surgeries. However, ionizing radiation is hazardous for us and there is no way that it can be considered as not invasive. Certainly, concerns in medicine, regarding the exposition of patients to these radiation forms either for diagnosis or treatment purposes has increased significative since R€ ontgen discovered the x-rays to visualize, with radiography, the inside of the body, so that nowadays, the development of techniques for reducing the risks are in progress. Decreasing the doses with more sensitive devices and changing to lower energy radiation sources, such as in soft x-rays, microwaves, and RF, are among the possibilities. Insistence on claims usually presented on the internet about microwave hazards for healthy, forces to cast comments about that in terms of safety. For instance, the report entitled “Review of Published Literature between 2008 and 2018 of Relevance to Radiofrequency Radiation and Cancer” published by the FDA U.S. Food & Drug, Center for Devices and Radiological Health, in February 2020, indicates that there is insufficient evidence to support a causal association between RFR exposure and tumorigenesis. Moreover, despite the complaints against mobile phones (RFR), according to the World Bank, there were in 2019, 8196 million mobile phone subscriptions worldwide, about 1 per habitant, so that there is evidence of a certain population level of confidence. Microwave imaging is not new; more than 30 years of research have produced advances in impedance imaging with some resolution problems, antennas with good stability of the directionality, confirmation of differences between healthy and cancerous breast tissues, comparisons with images obtained by other techniques; thermography, and tomography. However, it seems that the most noticeable application is in the pathology of bones, lungs, and more in breast imaging. It must be considered that effectiveness in the construction of images is as important as safety, and that is the reason microwaves are not a direct substitute for x-rays, and the