Biomedical imaging systems based on the use of microwaves operating up to 10 GHz received a lot of interest over the last years, particularly for breast cancer detection, as well as for brain imaging in stroke, lung cancer, skin lesions, and bone fracturing. For the former application, both tomographic and confocal system prototypes have been developed, and some have undergone clinical trials. An emerging field of investigation is also that of millimeter-wave imaging, where shorter wavelengths can be exploited to achieve improved spatial resolution.

Microwave imaging is based on the existence of differences in terms of dielectric properties among different biological tissues and can offer several important advantages as compared to other diagnostic techniques, in that it does not involve ionizing radiation, it is noninvasive, and it has potentially low cost. The development of a microwave imaging system is a complex task that requires merging competencies from the fields of medicine, bioengineering, electromagnetic fields, antenna, and system design. Some of the key aspects in this process include the dielectric characterization of ex vivo/in vivo tissues, as well as materials for the development of tissue-mimicking phantoms, electromagnetic simulations with realistic numerical models, the design of conformal antenna arrays, the study of effective signal processing techniques, and high-quality image formation methods.

Despite the significant potential of microwave imaging for medical applications, full clinical acceptance of the technology has been limited, and further improvements in technology are necessary to address clinical and commercial challenges.

This special issue aims to bring together contributions from researchers working in the field of micro/millimeter-waves for medical imaging applications, in order to outline the current state-of-the-art and highlight the emerging trends and challenges in this field, ranging from methodological aspects to in vivo testing. Both original research and review papers are thus invited to contribute.

Potential topics include but are not limited to the following:

• Microwave/millimeter-wave imaging systems and antenna design for diagnostic applications and cancer detection
• Experimental and numerical modelling of microwave/millimeter-wave imaging systems and/or their components
• Image reconstruction, beamforming, signal, and image processing techniques
• Microwave tomography and radar imaging
• Dielectric characterization of biological tissues
• Tissue-mimicking phantom design, fabrication, and material characterization