Metal Artifact Reduction for Polychromatic X-ray CT Based on a Beam-Hardening Corrector

Park, Hyoung Suk; Hwang, Dosik; Seo, Jin Keun

doi:10.1109/tmi.2015.2478905

Cited by 85 publications

(81 citation statements)

References 36 publications

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“…Here,

χ_{{normalΩ}_{j}}

denotes the characteristic function, which is 1 in region

Ω_{j}

and 0 otherwise. Considering a two‐dimensional parallel beam, we define the projection data (or sinogram)

P_{f} false(italicφ, s false)

along rotation direction (cos φ , sin φ ), φ ∈ [0,2 π ) by

P_{f} false(italicφ, s false) = - ln (\int italicη (E) e^{{- R f}^{E} (φ, s)} d E),

where η denotes the normalized X‐ray spectrum of the incident X‐ray beam (i.e., ∫ η ( E ) dE = 1) and

scriptR

the Radon transform . Upon treating pixel

Ω_{j}

as a point

{bold-italicx}_{j}

(being the center of

Ω_{j}

P_{f}

can be expressed as

P_{f} false(italicφ, s false) \approx - ln (\int italicη (E) e^{- \sum_{j = 1}^{N} μ_{{normalΩ}_{j}} (E) scriptR χ_{{normalΩ}_{j}} (φ, s)} d E) .

…”

Section: Methodsmentioning

confidence: 99%

“…According to a previous study, there exists, for each

false(italicφ, s false) \in [0, 2 π) \times R

h_{φ, s} \in R

that satisfies the following identity

\int false[italicη (E) - {\overset{false~}{italicη}}_{h_{φ, s}} (E) false] e^{- {italicα}_{φ, s} false(E - E^{*} false) R {italicχ}_{D} false(italicφ, s false)} d E = 0,

where

{\overset{false~}{italicη}}_{h_{φ, s}}

is given by

{\overset{η}{true}}_{h_{italicφ, s}} false(E false) = \{\begin{matrix} \frac{1}{2 h_{italicφ, s}} & if false| E - E^{*} false| < h_{φ, s} \\ 0 & otherwise \end{matrix}

…”

Section: Methodsmentioning

confidence: 99%

“… Purpose This study aims to propose a physics‐based method of reducing beam‐hardening artifacts induced by high‐attenuation materials such as metal stents or other metallic implants. Methods The proposed approach consists of deriving a sinogram inconsistency formula representing the energy dependence of the attenuation coefficient of high‐attenuation materials. This inconsistency formula more accurately represents the inconsistencies of the sinogram than that of a previously reported formula (called the MAC ‐ BC method). This is achieved by considering the properties of the high‐attenuation materials, which include the materials’ shapes and locations and their effects on the incident X‐ray spectrum, including their attenuation coefficients. Results Numerical simulation and phantom experiment demonstrate that the modeling error of MAC ‐ BC method are nearly completely removed by means of the proposed method. Conclusion The proposed method reduces beam‐hardening artifacts arising from high‐attenuation materials by relaxing the assumptions of the MAC ‐ BC method.…”

mentioning

confidence: 90%

“…The proposed approach consists of deriving a sinogram inconsistency formula representing the energy dependence of the attenuation coefficient of high‐attenuation materials. This inconsistency formula more accurately represents the inconsistencies of the sinogram than that of a previously reported formula (called the MAC ‐ BC method). This is achieved by considering the properties of the high‐attenuation materials, which include the materials’ shapes and locations and their effects on the incident X‐ray spectrum, including their attenuation coefficients.…”

mentioning

confidence: 99%

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Technical Note: A model‐based sinogram correction for beam hardening artifact reduction in CT

et al. 2017

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“…Here,

χ_{{normalΩ}_{j}}

denotes the characteristic function, which is 1 in region

Ω_{j}

and 0 otherwise. Considering a two‐dimensional parallel beam, we define the projection data (or sinogram)

P_{f} false(italicφ, s false)

along rotation direction (cos φ , sin φ ), φ ∈ [0,2 π ) by

P_{f} false(italicφ, s false) = - ln (\int italicη (E) e^{{- R f}^{E} (φ, s)} d E),

where η denotes the normalized X‐ray spectrum of the incident X‐ray beam (i.e., ∫ η ( E ) dE = 1) and

scriptR

the Radon transform . Upon treating pixel

Ω_{j}

as a point

{bold-italicx}_{j}

(being the center of

Ω_{j}

P_{f}

can be expressed as

P_{f} false(italicφ, s false) \approx - ln (\int italicη (E) e^{- \sum_{j = 1}^{N} μ_{{normalΩ}_{j}} (E) scriptR χ_{{normalΩ}_{j}} (φ, s)} d E) .

…”

Section: Methodsmentioning

confidence: 99%

“…According to a previous study, there exists, for each

false(italicφ, s false) \in [0, 2 π) \times R

h_{φ, s} \in R

that satisfies the following identity

\int false[italicη (E) - {\overset{false~}{italicη}}_{h_{φ, s}} (E) false] e^{- {italicα}_{φ, s} false(E - E^{*} false) R {italicχ}_{D} false(italicφ, s false)} d E = 0,

where

{\overset{false~}{italicη}}_{h_{φ, s}}

is given by

{\overset{η}{true}}_{h_{italicφ, s}} false(E false) = \{\begin{matrix} \frac{1}{2 h_{italicφ, s}} & if false| E - E^{*} false| < h_{φ, s} \\ 0 & otherwise \end{matrix}

…”

Section: Methodsmentioning

confidence: 99%

mentioning

confidence: 90%

mentioning

confidence: 99%

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Technical Note: A model‐based sinogram correction for beam hardening artifact reduction in CT

et al. 2017

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“…Some hybrid methods have been also introduced to balance the metal artifact reduction and the computational cost [22, 23]. Recently, a metal artifact reduction method has been introduced with consideration of the beam hardening effect of a polychromatic x-ray beam [24]. …”

Section: Introductionmentioning

confidence: 99%

A metal artifact reduction method for a dental CT based on adaptive local thresholding and prior image generation

2016

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BackgroundMetal artifacts appearing as streaks and shadows often compromise readability of computed tomography (CT) images. Particularly in a dental CT in which high resolution imaging is crucial for precise preparation of dental implants or orthodontic devices, reduction of metal artifacts is very important. However, metal artifact reduction algorithms developed for a general medical CT may not work well in a dental CT since teeth themselves also have high attenuation coefficients.MethodsTo reduce metal artifacts in dental CT images, we made prior images by weighted summation of two images: one, a streak-reduced image reconstructed from the metal-region-modified projection data, and the other a metal-free image reconstructed from the original projection data followed by metal region deletion. To make the streak-reduced image, we precisely segmented the metal region based on adaptive local thresholding, and then, we modified the metal region on the projection data using linear interpolation. We made forward projection of the prior image to make the prior projection data. We replaced the pixel values at the metal region in the original projection data with the ones taken from the prior projection data, and then, we finally reconstructed images from the replaced projection data. To validate the proposed method, we made computational simulations and also we made experiments on teeth phantoms using a micro-CT. We compared the results with the ones obtained by the fusion prior-based metal artifact reduction (FP-MAR) method.ResultsIn the simulation studies using a bilateral prostheses phantom and a dental phantom, the proposed method showed a performance similar to the FP-MAR method in terms of the edge profile and the structural similarity index when an optimal global threshold was chosen for the FP-MAR method. In the imaging studies of teeth phantoms, the proposed method showed a better performance than the FP-MAR method in reducing the streak artifacts without introducing any contrast anomaly.ConclusionsThe simulation and experimental imaging studies suggest that the proposed method can be used for reducing metal artifacts in dental CT images.

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Characterization of Metal Artifacts in X‐Ray Computed Tomography

Park

Choi

Seo

2017

Comm Pure Appl Math

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Metal streak artifacts in X‐ray computerized tomography (CT) are characterized here using the notion of the wavefront set from microlocal analysis. The metal artifacts are caused mainly from the mismatch of the forward model of the filtered back‐projection; the presence of metallic subjects in an imaging subject violates the model's assumption of the CT sinogram data being the Radon transform of an image. The increasing use of metallic implants has increased demand for the reduction of metal artifacts in the field of dental and medical radiography. However, it is a challenging issue due to the serious difficulties in analyzing the X‐ray data, which depends nonlinearly on the distribution of the metallic subject. In this paper, we, for the first time, provide a mathematical analysis to characterize the structure of metal streaking artifacts. The metal streaking artifacts are produced along the line tangent to boundaries of the metal region touching at least two different boundaries. We also found a sufficient condition for the nonexistence of the metal streaking artifacts. © 2017 Wiley Periodicals, Inc.

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Metal Artifact Reduction for Polychromatic X-ray CT Based on a Beam-Hardening Corrector

Cited by 85 publications

References 36 publications

Technical Note: A model‐based sinogram correction for beam hardening artifact reduction in CT

Technical Note: A model‐based sinogram correction for beam hardening artifact reduction in CT

A metal artifact reduction method for a dental CT based on adaptive local thresholding and prior image generation

Characterization of Metal Artifacts in X‐Ray Computed Tomography

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