High-resolution polarimetric THz imaging for biomedical applications

We present a novel millimeter-wave to terahertz-frequency polarimetric imaging system utilizing diagonal-horn output port of a vector network analyzer and an off-axis parabolic mirror focusing the signal onto the specimen through a low-loss, high-index hyper-hemispherical silicon lens. The proposed system is capable of producing reflection images of formalin-fixed paraffin-embedded tissue samples with 3.4-times improved resolution, compared to commercially available free-space imaging systems. Due to the polarization purity of diagonal horn antennas, the proposed system also exhibits excellent polarization purity. As such, elongated morphological and biochemical features in tissue samples can be resolved for the first time with unprecedented resolution. In particular, the proposed technique is used to study the axon demyelization effects in human brain tissues due to Alzheimer's disease.