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Article Nanotechnology-supported THz medical imaging

Nanotechnology is one of the newest fields of technology and science that has attracted the attention of the scientific community, since it is believed to possess the potential to entirely change our everyday life as we know it up to now. It is quite complicated to identify the origins of nanotechnology; however, no-one can deny the fact that the inspiring lecture of R. Feynman (29 December 1959) “There is plenty of room at the bottom” is the keystone to the field of nanotechnology 1. This talk was so amazing for its time that many believe that it represented the birth of the new scientific field of nanotechnology.

Not only are the origins of nanotechnology complicated, but also the definition of the term ‘nanotechnology’ is not as straightforward as it sounds since the field is very recent and there are many conflicting opinions. The first part of the words nanotechnology and nanoscience, the word nano, comes from the Greek word ‘nannos’, which means a very short man 2 and indicates that we are referring to the technology and science that deal with the physical phenomena/technology in the nanoscale. Generally, we call nanotechnology the manipulation and study of the properties of objects that are, in at least one of their dimensions, smaller than 100 nm.

The importance of nanotechnology is the fact that on the nanometre scale, dimensions of materials are essential to characterise their properties 3. At such dimensions, materials possess new physical properties or exhibit new physical phenomena. At such small dimensions, the properties of matter are completely different from what we have been taught and new uncommon properties are observed 4. The new properties arise from the fact that at these dimensions the surface area per volume is increased and the material properties obey the rules of quantum mechanics and not the classical physics of the macroscopic scale 5. Therefore, nanotechnology has not only to do with small dimensions, but also with new novel physical properties 2.

The emerging applications of nanotechnology are so powerful that many scientists believe that it has the potential to radically change the world as we know it and some of them are even wondering whether nanotechnology can push forward the next 'nano-industrial revolution’ 6, 7. One area that has been very promising is the application of nanotechnology to medicine 5, the so-called nanomedicine. Through the developing field of nanomedicine, nanotechnology and medicine come together so that existing therapies and medical techniques can be improved 8. Due to its significance for humans, nanomedicine has become one of the most crucial branches of nanoscience. It is considered to be the great challenge of medicine of the 21 st century, mainly in three key areas: diagnosis, treatment and regenerative medicine 9.

A scientific and technological area with so many expectations will inevitably also positively affect the field of medical imaging and radiology. The field of medical imaging is very broad and since the discovery of X-rays, many non-invasive imaging modalities have been invented. Each modality presents its unique characteristics and its intrinsic limitations, and there are differences in their ionising or non-ionising nature, sensitivity, resolution, complexity, time of data acquisition, physical principles, performance conditions, provided information and of course the financial costs. Although the field of medical imaging has a quite long history, new innovative imaging modalities emerge in order to reduce the limitations and expand the capabilities of the existing modalities 10. Unfortunately a ‘perfect and ideal’ imaging modality has not yet been developed and the existing modalities are characterised by different limitations. According to Boulaiz et al. , an ideal imaging modality should have a non-invasive nature, high sensitivity and the ability to provide information on cell survival, function and localisation.

An area that attracts the interest of researchers is the use of non-invasive and non-ionising radiation for medical-imaging purposes. It has been stated that there is a revolution in non-invasive imaging modalities 11 and imaging modalities that do not use ionising radiation minimise patient’s risks, enable imaging repeatability and in many cases are non-invasive and reduce patient’s suffering. According to Wallace et al. 12 there is a gap between microscopy and medical imaging and consequently current efforts are focusing on developing non-ionising modalities that can fill this gap. One of the most recent and attractive modalities that satisfy these requirements is Terahertz (THz) imaging .

THz radiation, also called ‘sub-millimetre radiation’ or ‘T-rays’, is generally defined as the frequency range from 100 GHz to 10 THz 17 and is actually the gap between the infrared (IR) and microwaves 13( Figure 1). This region of the electromagnetic spectrum remained unexplored for many years since there were not appropriate sources (electronic or optical) 18 available, although the characteristics of this radiation are unique and there are a number of potential applications. The development of ultra-short optical pulse lasers and the growth of semiconductor microfabrication techniques pushed for the expansion of THz radiation technology .

Ashraf Alattar if you are looking for medical applications of THz radiation, you should keep on mind that it is strongly absorbed by water. Our organisms are mostly made of water so now everything seems to indicate that it is suitable for testing the surface of the body and not to replace X-rays.

Melania Deresz .....

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