Effects of window index and thickness on hydration sensitivity and probing depth of THz imaging systems

Electromagnetic modeling predicts that dielectric substrate windows placed above a tissue of interest alter the hydration sensitivity of reflective THz imaging systems. Furthermore, interference effects between layers (the window with the skin layers) cause the window´s optical path length to change the depth probed by the imaging system. A pulsed THz imaging system operating at ~ 500 GHz was used to image a burn wound in a rat model, with thin mylar (12 μm) and quartz (500 mm) windows examined. Imaging occurred over five hour period, with windows exchanged every 13 minutes. Large differences in contrast between the windows was observed, and the two sets of images reveal different hydration maps distal to the burn, suggestive that the dielectric window successfully probed a different depth than the mylar window.