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. 2018 May 25:6:47-52.
doi: 10.1016/j.phro.2018.05.004. eCollection 2018 Apr.

VOXSI: A voxelized single- and dual-energy CT scenario generator for quantitative imaging

Brent van der Heyden  1 , Lotte E J R Schyns  1 , Mark Podesta  1 , Ana Vaniqui  1 , Isabel P Almeida  1 , Guillaume Landry  2 , Frank Verhaegen  1
Affiliations

VOXSI: A voxelized single- and dual-energy CT scenario generator for quantitative imaging

Brent van der Heyden et al. Phys Imaging Radiat Oncol. .

Abstract

Background and purpose: Dedicated CT simulation models have the potential to investigate several acquisition, reconstruction, or post-processing parameters without giving any radiation dose to patients. A software program was developed for the simulation and the analysis of single-energy and dual-energy CT images. Simulation and analysis functionalities of the software are described.

Materials and methods: In the software, named VOXSI (VOXelized CT SImulator), the X-ray source, user specified simulation geometry, CT setup and the detector energy response can be varied. CT image reconstructions can be performed with an implementation of the ASTRA toolbox. In the DECT post processing toolkit, GUI tools are provided to calculate effective atomic number, relative electron density, pseudo-monoenergetic images, and material map images. Quantitative CT number validation, based on a RMI 467 tissue characterization phantom model, was performed between experimental and simulated CT scans at three different X-ray tube potentials (80, 120, and 140 kVp) with a third generation CT scanner.

Results: Overall, a good agreement was found for the mean CT numbers of the RMI 467 inserts. For all energies, the maximum difference in CT numbers between experimental and simulated data was below 17 HU for the soft tissues and below 48 HU for the osseous tissues.

Conclusion: The software's simulation algorithm showed a good agreement between the CT measurements and CT simulations of the RMI 467 phantom at different energies. The capabilities of the software are demonstrated by an elaborated dual-energy CT research example.

Keywords: Dual-energy CT; Single-energy CT; VOXSI; Voxelized CT scenario generator.

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Figures

Fig. 1
Fig. 1
The flowchart of VOXSI. The X-ray source, simulation geometry, CT setup, and the detector energy response (top row) must be defined before a simulation can be started. After the simulation, the projections are exportable, or can be reconstructed using the implemented ASTRA toolbox and MATLAB’s FBP algorithm. As an alternative, the open-source image reconstruction toolkit (RTK) can be used externally (not implemented in the GUI) to reconstruct the projections (dotted line). The SECT and DECT image analysis toolkit provides tools to analyze the reconstructed CT images. Snapshots of VOXSI’s interface are added in Supplementary material 1.
Fig. 2
Fig. 2
Comparison of the measured and simulated CT numbers averaged in a circular region of interest (±1 standard deviation (SD)), in Hounsfield Units, for polychromatic 80, 120, and 140 kVp CT X-ray spectra of the RMI 467 soft tissue mimicking inserts (left panel) and the osseous tissue mimicking inserts (middle panel). The right panel plots the absolute differences between the measured and simulated CT numbers for all RMI 467 phantom inserts.
Fig. 3
Fig. 3
The relative electron density (RED) and effective atomic number (Zeff) calibration curves fitted on the simulated image data of the RMI 467 phantom (left panels) (±1 SD). In the Zeff calibration curve, only 8 of the 11 data points are clearly visible because 3 points closely overlap with another data point. The RED and Zeff images of the simulated XCAT phantom are depicted in the middle panels. The relative differences between the calculated images and the ground truth are shown in the right panels.
See this image and copyright information in PMC

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