Beam hardening correction in polychromatic x-ray grating interferometry

Yan, Aimin; Wu, Xizeng; Liu, Hong

doi:10.1364/oe.25.024690

Cited by 11 publications

(6 citation statements)

References 32 publications

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“…Similar effects exist for differential phase and normalized visibility contrast mechanisms in polychromatic grating‐based experiments 8 . The degree of bias in phase measurements differs from that of absorption due to the different physical contrast mechanisms 9 and the different energy dependencies, which have been reported to be between

\frac{1}{E}

and

\frac{1}{E^{2}}

for phase 10,11 . In addition, while normalized visibility is sensitive to unresolvable microstructures, it is also influenced by beam hardening 12 .…”

Section: Introductionmentioning

confidence: 68%

“…Early corrections used specialized calibration phantoms to appropriately scale each contrast projection to match expected values for the given phantom geometry and composition 11 . Analytical methods overcome the need for phantom calibration scans but require detailed system knowledge of the source spectra and detector response, while making assumptions on spectral responses of the sample and gratings 10 . One solution developed to compensate for spectral artifacts from primary modulators lessens these assumptions by using iterative methods to estimate both the spectra and the effective modulator thickness at each detector pixel 15 .…”

Section: Introductionmentioning

confidence: 99%

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Empirical beam hardening and ring artifact correction for x‐ray grating interferometry (EBHC‐GI)

et al. 2021

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Purpose Talbot‐Lau grating interferometry enables the use of polychromatic x‐ray sources, extending the range of potential applications amenable to phase contrast imaging. However, these sources introduce beam hardening effects not only from the samples but also from the gratings. As a result, grating inhomogeneities due to manufacturing imperfections can cause spectral nonuniformity artifacts when used with polychromatic sources. Consequently, the different energy dependencies of absorption, phase, and visibility contrasts impose challenges that so far have limited the achievable image quality. The purpose of this work was to develop and validate a correction strategy for grating‐based x‐ray imaging that accounts for beam hardening generated from both the imaged object and the gratings. Methods The proposed two‐variable polynomial expansion strategy was inspired by work performed to address beam hardening from a primary modulator. To account for the multicontrast nature of grating interferometry, this approach was extended to each contrast to obtain three sets of correction coefficients, which were determined empirically from a calibration scan. The method’s feasibility was demonstrated using a tabletop Talbot‐Lau grating interferometer micro‐computed tomography (CT) system using CT acquisitions of a water sample and a silicon sample, representing low and high atomic number materials. Spectral artifacts such as cupping and ring artifacts were quantified using mean squared error (MSE) from the beam‐hardening‐free target image and standard deviation within a reconstructed image of the sample. Finally, the model developed using the water sample was applied to a fixated murine lung sample to demonstrate robustness for similar materials. Results The water sample’s absorption CT image was most impacted by spectral artifacts, but following correction to decrease ring artifacts, an 80% reduction in MSE and 57% reduction in standard deviation was observed. The silicon sample created severe artifacts in all contrasts, but following correction, MSE was reduced by 94% in absorption, 96% in phase, and 90% in visibility images. These improvements were due to the removal of ring artifacts for all contrasts and reduced cupping in absorption and phase images and reduced capping in visibility images. When the water calibration coefficients were applied to the lung sample, ring artifacts most prominent in the absorption contrast were eliminated. Conclusions The described method, which was developed to remove artifacts in absorption, phase, and normalized visibility micro‐CT images due to beam hardening in the system gratings and imaged object, reduced the MSE by up to 96%. The method depends on calibrations that can be performed on any system and does not require detailed knowledge of the x‐ray spectrum, detector energy response, grating attenuation properties and imperfections, or the geometry and composition of the imaged object.

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\frac{1}{E}

and

\frac{1}{E^{2}}

for phase 10,11 . In addition, while normalized visibility is sensitive to unresolvable microstructures, it is also influenced by beam hardening 12 .…”

Section: Introductionmentioning

confidence: 68%

Section: Introductionmentioning

confidence: 99%

Empirical beam hardening and ring artifact correction for x‐ray grating interferometry (EBHC‐GI)

et al. 2021

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“…Hence, different from the work [21], the derived fringe-visibility formulas Eqs. (20) and (23) derived in this work provide useful tools for design optimization of dual phase grating interferometry.…”

Section: Discussionmentioning

confidence: 99%

“…In recent years, X-ray grating interferometry has attracted a lot of efforts in research and development [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]. In this phase contrast imaging technique, one usually utilizes a phase grating as a beam splitter to divide the incident beam into different diffraction orders.…”

Section: Introductionmentioning

confidence: 99%

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Quantitative theory of X-ray interferometers based on dual phase grating: fringe period and visibility

Yan

Liu

2018

Opt. Express

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In most of grating x-ray interferometry one needs an absorbing grating as the analyzer to measure high-resolution interference fringes. Dual phase grating interferometry is a technique to get rid of the absorbing grating for radiation dose reduction. The authors present a quantitative theory of dual grating x-ray interferometry. The theory elucidates the fringe formation mechanism. The derived formulas of fringe period and fringe visibility provide useful tools for design optimization of dual phase grating interferometers.

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Metal Artifacts in Attenuation and Phase Contrast X-Ray Microcomputed Tomography: A Comparative Study

et al. 2022

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Background Metal artifacts arising around high-density components are a widely known problem in X-ray computed tomography (XCT) for both medical and industrial applications. Although phase contrast imaging XCT (PCI-XCT) is known to be less prone to metal artifacts caused by beam hardening, so far only little effort was made for its comparison to other, more established methods. Objective In the course of this work, this absence in literature is addressed by a quantitative comparison of PCI-XCT to attenuation contrast XCT (AC-XCT). Methods A polymer specimen including four Ti6Al4V inserts was investigated by PCI- and AC-XCT with different pre-filter settings and metal artifact reduction (MAR) algorithm. Artifacts and image quality were evaluated by a streak index which provides a quantitative metric for the assessment of streak artifacts and contrast-to-noise ratio (CNR). Results Results showed that streak artifacts are significantly reduced in PCI-XCT and only matched by AC-XCT in combination with hardware pre-filtering of the X-ray beam and post-processing by a MAR algorithm. However, hardware pre-filtering leads to worse CNR and artifacts close to the surface of metal inserts could not be removed sufficiently by the MAR algorithm. Conclusions This work demonstrates the potential of PCI-XCT for the reduction of metal artifacts and presents the first quantitative comparison to established AC-XCT methods.

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Beam hardening correction in polychromatic x-ray grating interferometry

Cited by 11 publications

References 32 publications

Empirical beam hardening and ring artifact correction for x‐ray grating interferometry (EBHC‐GI)

Empirical beam hardening and ring artifact correction for x‐ray grating interferometry (EBHC‐GI)

Quantitative theory of X-ray interferometers based on dual phase grating: fringe period and visibility

Metal Artifacts in Attenuation and Phase Contrast X-Ray Microcomputed Tomography: A Comparative Study

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