Propagation beam consideration for 3D THz computed tomography

Abstract

In this paper, a model of the beam propagation is developed according to the physical properties of THz waves used in THz computed tomography (CT) scan imaging. This model is first included in an acquisition simulator to observe and estimate the impact of the Gaussian beam intensity profile on the projection sets. Second, the model is introduced in several inversion methods as a convolution filter to perform efficient tomographic reconstructions of simulated and real acquired objects. Results obtained with three reconstruction methods (BFP, SART and OSEM) are compared to the techniques proposed in this paper. We will demonstrate an increase of the overall quality and accuracy of the 3D reconstructions.

Terahertz radiation for tomographic inspection

“…19 Mathematically, this process is given in two dimensions by the following optimization of the Radon transform: 19 Mathematically, this process is given in two dimensions by the following optimization of the Radon transform:…”

Towards a 3D material characterization using dual-energy THz tomography

“…whereR t s (i) is the expected photon counts computed from µ t s , S(s) are the radiographs in the subset s, β is a sensitivity parameter for the penalization part, Φ (·) and Φ (·) are respectively the first and second derivative of the potential function Φ(·), N (j) denotes the neighbourhood of pixel j and y jk is a weight factor (usually inverse proportional to the distance between voxels j and k).R t s is modelled by:R where I0 (blank calibration scan) and bg (background noise) are determined experimentally, wij is a weight coefficient defining the voxel j contribution on the detector i and G is the THz Gaussian beam propagation model as defined in [3] (where denotes the convolution operator). A main iteration t is completed when all subsets have been processed.…”

“…In the field of non-destructive testing, Terahertz (THz) tomography is a recent imaging technique allowing 3D inspection of soft materials [1], [2], [3]. Several radiographs are acquired around the sample at different viewing angles.…”

A modified algebraic reconstruction technique taking refraction into account with an application in terahertz tomography

“…Some publications consider these effects by adaptations. In [29], Recur et al presented a filtered backprojection and adapted iterative methods (SART, OSEM) for 3D THz CT, which considers the intensity distribution of THz rays (Gaussian beam). Mukherjee et al only regard cylindric objects, but take Fresnel reflection losses and beam steering losses into account, see [23].…”