  Purpose: The terahertz (THz) medical imaging is a promising noninvasive
technique for monitoring the skin's conditions, early detection of the human
skin cancer, and recovery from burns and wounds. It can be applied for
visualization of healing process directly through clinical dressings and
restorative ointments, minimizing the frequency of dressing changes. The THz
imaging technique is cost effective, as compared to the magnetic resonance
method. Our aim was to develop an approach capable of providing better image
resolution than the commercially available THz imaging cameras. Approach: The
terahertz-to-infrared (THz-to-IR) converters can visualize the human skin
cancer by converting the latter's specific contrast patterns recognizable in
THz radiation range into IR patterns, detectable by a standard IR imaging
camera. At the core of suggested THz-to-IR converters are flat matrices
transparent both in the THz range to be visualized and in the operating range
of the IR camera; these matrices contain embedded metal nanoparticles, which,
when irradiated with THz rays, convert the energy of THz photons into heat and
become nanosources of IR radiation detectable by an IR camera. Results: The
ways of creating the simplest converter, as well as a more complex converter
with wider capabilities, are considered. The first converter is a gelatin
matrix with gold 8.5 nm diameter nanoparticles, the second is a polystyrene
matrix with 2 nm diameter nanoparticles from copper-nickel MONEL (c) alloy 404.
Conclusions: An approach with a THz-to-IR converter equipped with an IR camera
is promising in that it could provide a better image of oncological pathology
than the commercially available THz imaging cameras do.
