In this study, we propose a THz computed tomography (CT) method based on phase contrast, which retrieves the phase shift information at each data point through a phase modulation technique using a Mach-Zehnder interferometer with a continuous wave (CW) source. The THz CT is based on first-generation CT, which acquires a set of projections by translational and rotational scans using a thin beam. From the phase-shift projections, we reconstruct a spatial distribution of refractive indices in a cross section of interest. We constructed a preliminary system using a highly coherent CW THz source with a frequency of 0.54 THz to prove the concept and performed an imaging experiment using phantoms to investigate its imaging features such as artifact-immune imaging, quantitative measurement, and selective detection.

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-We propose a novel computed tomography (CT) imaging method based on phase-contrast using a continuous wave (CW) THz source with a frequency of 0.54 THz. The system acquires phase-shift by phase modulation technique using Mach-Zehnder interferometer at each data point, and collects projections of the phase-shift from multiple directions over 360 degrees to finally reconstruct a spatial distribution of refractive index. We construct a preliminary system for proof of the concept, and perform an imaging experiment using a polystyrene foam phantom. It was shown that the THz-CT produces an artifact-free and quantitative reconstruction at a spatial resolution of a few mm.