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Review
. 2017 Jan;90(1069):20160480.
doi: 10.1259/bjr.20160480. Epub 2016 Nov 2.

Optimizing dual energy cone beam CT protocols for preclinical imaging and radiation research

Lotte E J R Schyns  1 , Isabel P Almeida  1 , Stefan J van Hoof  1 , Benedicte Descamps  2 , Christian Vanhove  2 , Guillaume Landry  3 , Patrick V Granton  1 , Frank Verhaegen  1   4
Affiliations
Review

Optimizing dual energy cone beam CT protocols for preclinical imaging and radiation research

Lotte E J R Schyns et al. Br J Radiol. 2017 Jan.

Abstract

Objective: The aim of this work was to investigate whether quantitative dual-energy CT (DECT) imaging is feasible for small animal irradiators with an integrated cone-beam CT (CBCT) system.

Methods: The optimal imaging protocols were determined by analyzing different energy combinations and dose levels. The influence of beam hardening effects and the performance of a beam hardening correction (BHC) were investigated. In addition, two systems from different manufacturers were compared in terms of errors in the extracted effective atomic numbers (Zeff) and relative electron densities (ρe) for phantom inserts with known elemental compositions and relative electron densities.

Results: The optimal energy combination was determined to be 50 and 90 kVp. For this combination, Zeff and ρe can be extracted with a mean error of 0.11 and 0.010, respectively, at a dose level of 60 cGy.

Conclusion: Quantitative DECT imaging is feasible for small animal irradiators with an integrated CBCT system. To obtain the best results, optimizing the imaging protocols is required. Well-separated X-ray spectra and a sufficient dose level should be used to minimize the error and noise for Zeff and ρe. When no BHC is applied in the image reconstruction, the size of the calibration phantom should match the size of the imaged object to limit the influence of beam hardening effects. No significant differences in Zeff and ρe errors are observed between the two systems from different manufacturers. Advances in knowledge: This is the first study that investigates quantitative DECT imaging for small animal irradiators with an integrated CBCT system.

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Figures

Figure 1.
Figure 1.
Phantom layout. Numbers 1–12 relate to Table 1.
Figure 2.
Figure 2.
Simulated CT images (50 kVp) of the phantoms with different diameters: 3, 5 and 7 cm (top row: calibration phantom, bottom row: validation phantom).
Figure 3.
Figure 3.
Effective atomic number (Zeff) − μratio calibration curve [50- and 90-kVp combination; X-RAD 225Cx (Precision X-ray, North Branford, CT)]. The dashed line indicates the minimum μratio for which a Zeff value can be assigned.
Figure 4.
Figure 4.
Mean effective atomic number (Zeff) and relative electron density (ρe) error for different energy combinations [X-RAD 225Cx (Precision X-ray, North Branford, CT)].
Figure 5.
Figure 5.
Mean error and standard deviation for effective atomic number (Zeff) and relative electron density (ρe) for different dose levels [50- and 90-kVp combination; X-RAD 225Cx (Precision X-ray, North Branford, CT)].
Figure 6.
Figure 6.
Mean effective atomic number (Zeff) and relative electron density (ρe) error for the different phantom sizes [50- and 90- kVp combination, ImaSim simulations, no beam hardening correction (BHC) applied].
Figure 7.
Figure 7.
Simulated effective atomic number (Zeff) and relative electron density (ρe) with and without beam hardening correction (50- and 90-kVp combination; ImaSim simulations).
Figure 8.
Figure 8.
Measured vs reference effective atomic number (Zeff) and relative electron density (ρe) (50- and 90-kVp combination).
None
Figure A1. Simulated vs measured Zeff and ρe (50- and 90-kVp combination).
None
Figure A2. CT, Zeff and ρe images of the validation phantom (50- and 90-kVp combination) (top row: X-RAD 225Cx, bottom row: SARRP).
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