Most of the modules for the reconstructor block are incorporated into the ScannerTemplate as they depend mainly on the type of scanner geometry chosen for simulation. A special feature of DEBISim is the use of FreeCT_wFBP package for fast reconstruction of X-ray projections for Spiral CBCT scanners. Besides, the 3D reconstruction can be performed using 3D SIRT but it is much slower than the former method.
The module houses a library of functions that assist in executing 3D image reconstruction for Spiral Cone Beam CT scanners. The library of functions, which is used internally in the DEBISim pipeline, is essentially a Python wrapper for the FreeCT_wFBP CUDA library for 3D CT reconstruction [1].
FreeCT_wFBP is an open-source CUDA-based implementation of the weight filtered back-projection (wFBP) algorithm by Stierstofer et al. [2], which performs 3D reconstruction of X-ray images from CT projection data obtained from Spiral Cone Beam CT scanners with curved rectangular detector panels and a helical motion path for data acquisition. The CUDA implementation allows strong parallelization of the reconstruction operation allowing fast reconstruction of large image volumes.
[1]. J . Hoffman, S. Young, F. Noo, M. McNitt-Gray, “Technical Note: FreeCT_wFBP: A robust, efficient, open-source implementation of weighted filtered backprojection for helical, fan-beam CT,” Med. Phys., vol. 43, no. 3, pp. 1411-1420, Feb. 2016.
[2]. K. Stierstorfer, A. Rauscher, J. Boese, H. Bruder, S. Schaller, and T. Flohr, “Weighted FBP—a simple approximate 3D FBP algorithm for multislice spiral CT with good dose usage for arbitrary pitch,” Phys. Med. Biol., vol. 49, no. 11, pp. 2209–2218, Jun.2004.