Accelerated gradient restarted FISTA-TV algorithm for 3D terahertz transmission tomography

Terahertz computed tomography (THz-CT) is a non-destructive technique for characterizing the external and internal structures of complex samples. In this research, a 2.5 THz continuous-wave THz-CT system integrating a quantum cascade laser and a high-speed focal plane array detector was developed. To enhance reconstruction quality under sparse projection conditions, we proposed a fast iterative shrinkage-thresholding algorithm with total variation regularization (FISTA-TV). Comparative experiments demonstrated that FISTA-TV outperformed conventional methods by effectively suppressing noise and streak artifacts while preserving edge sharpness and internal structures. This superiority was quantitatively verified by metrics, including Laplacian variance, mean gradient magnitude, and entropy, which indicated enhanced edge sharpness and reduced noise. These results demonstrate the feasibility of FISTA-TV for high-quality THz-CT imaging under limited-angle conditions and its potential in non-destructive inspection of polymeric components and pharmaceutical preparations.