Horizontal-scanning attenuated total reflection terahertz imaging for biological tissues.

Terahertz wave is a potential tool for biological tissues due to its noninvasiveness and high sensitivity to water. Attenuated total reflection (ATR) with the characteristics of high sensitivity and nondestruction has been applied for THz imaging. We aim to develop an imaging methodology to facilitate practical application of THz ATR imaging. We have demonstrated a horizontally scanning THz continuous wave ATR imaging system. The effective imaging area was as large as the prism imaging surface by optimizing the ATR prism, and the influence of secondary reflection can be well avoided. By taking the image resolution and stability of this system into consideration, the incident angle to the prism bottom was chosen to be 30 deg. The image resolution of this system can be up to 400 and in horizontal and vertical directions, respectively. Furthermore, U87-glioma regions of mice brain tissues with different sizes and C6-glioma regions of rat brain tissues with relatively large size can be differentiated clearly from normal brain tissues by this imaging system. The volume and location of the tumor region shown in the THz images are similar to those visualized macroscopically in the corresponding visual and H&E-stained images. We indicate terahertz horizontal-scanning ATR imaging technique with large effective imaging area, and high resolution could be used as an alternative method for label-free and high-sensitivity imaging of biological tissues.