Data consistency condition–based beam-hardening correction

Mou, Xuanqin

doi:10.1117/1.3599869

Cited by 11 publications

(3 citation statements)

References 47 publications

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“…Future work should incorporate those effects into the model. As we could only compare our algorithm to one other calibration-free method, another important future work is a comparison to other methods such as the ones by Krumm et al 7 , Van Gompel et al 8 , Abdurahman et al 20 or Tang et al 13…”

Section: Discussionmentioning

confidence: 99%

“…For parallel-beam acquisition, data consistency conditions like the Helgason-Ludwig consistency conditions 9,10 or the Fourier consistency condition 11,12 have been known for a long time. Tang et al 13 presented a beam hardening reduction method based on optimization of the Helgason-Ludwig consistency conditions. While only requiring a single reconstruction, this method is restricted to parallel-beam geometry.…”

Section: Introductionmentioning

confidence: 99%

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Calibration‐free beam hardening reduction in x‐ray CBCT using the epipolar consistency condition and physical constraints

et al. 2019

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Background The beam hardening effect is a typical source of artifacts in x‐ray cone beam computed tomography (CBCT). It causes streaks in reconstructions and corrupted Hounsfield units toward the center of objects, widely known as cupping artifacts. Purpose We present a novel efficient projection data‐based method for reduction of beam‐hardening artifacts and incorporate physical constraints on the shape of the compensation functions. The method is calibration‐free and requires no additional knowledge of the scanning setup. Method The mathematical model of the beam hardening effect caused by a single material is analyzed. We show that the effect of beam hardening on the resulting functions on the line integral measurements are monotonous and concave functions of the ideal data. This holds irrespective of any limiting assumptions on the energy dependency of the material, the detector response or properties of the x‐ray source. A regression model for the beam hardening effect respecting these theoretical restrictions is proposed. Subsequently, we present an efficient method to estimate the parameters of this model directly in projection domain using an epipolar consistency condition. Computational efficiency is achieved by exploiting the linearity of an intermediate function in the formulation of our optimization problem. Results Our evaluation shows that the proposed physically constrained ECC2 algorithm is effective even in challenging measured data scenarios with additional sources of inconsistency. Conclusions The combination of mathematical consistency condition and a compensation model that is based on the properties of x‐ray physics enables us to improve image quality of measured data retrospectively and to decrease the need for calibration in a data‐driven manner.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Calibration‐free beam hardening reduction in x‐ray CBCT using the epipolar consistency condition and physical constraints

et al. 2019

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“…In clinical CT, the polynomial coefficients are estimated using homogeneous water phantoms during the scanner's calibration [22] [23]. Instead of tedious and recurrent calibrations, the optimal polynomial coefficients can be estimated using DCCs as described in [24] [25] [26]. The key idea here is to optimize the polynomials by minimizing the inconsistencies due to the violation of the linear forward model of projection generation caused by polychromatic X-ray attenuation.…”

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confidence: 99%

Comparative Evaluation of Cone-Beam Consistency Conditions for Mono-Material Beam Hardening Correction in Flat Detector Computed Tomography

Abdurahman

Frysch

Pfeiffer

et al. 2023

IEEE Trans. Radiat. Plasma Med. Sci.

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Consistency conditions have been successfully utilized for data-driven artifact reductions in cone-beam computed tomography systems equipped with a large area flat-panel detector. Recently, many formulations and applications of pair-wise cone-beam consistency conditions have been published, including Grangeat, Smith, and fan-beam consistency conditions. Previous works demonstrated that the polynomial coefficients for beam hardening correction could be directly computed from cone-beam raw data by enforcing consistency conditions on projection pairs. This paper compares the effectiveness of pair-wise consistency conditions for mono-material beam hardening correction using a second-degree polynomial. The results from our studies show that similar corrections could be achieved for ideal polychromatic projections. We also investigated the effectiveness of corrections after perturbing the projections with an increasing degree of errors other than those caused by beam hardening. The studies indicate the superior robustness of fan-beam consistency conditions towards Poisson noise, axial truncation, detector shift, and scatter, while Grangeat consistency conditions were less vulnerable to projection intensity errors. The optimal choice of consistency conditions depends on the CBCT system geometry, physical phenomena other than beam hardening, and the availability and accuracy of pre-processing and artifact corrections algorithms before beam hardening correction.

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Calibration‐free beam hardening correction for myocardial perfusion imaging using CT

et al. 2019

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Purpose Computed tomography myocardial perfusion imaging (CT‐MPI) and coronary CTA have the potential to make CT an ideal noninvasive imaging gatekeeper exam for invasive coronary angiography. However, beam hardening (BH) artifacts prevent accurate blood flow calculation in CT‐MPI. BH correction methods require either energy‐sensitive CT, not widely available, or typically, a calibration‐based method in conventional CT. We propose a calibration‐free, automatic BH correction (ABHC) method suitable for CT‐MPI and evaluate its ability to reduce BH artifacts in single “static‐perfusion” images and to create accurate myocardial blood flow (MBF) in dynamic CT‐MPI. Methods In the algorithm, we used input CT DICOM images and iteratively optimized parameters in a polynomial BH correction until a BH‐sensitive cost function was minimized on output images. An input image was segmented into a soft tissue image and a highly attenuating material (HAM) image containing bones and regions of high iodine concentrations, using mean HU and temporal enhancement properties. We forward projected HAM, corrected projection values according to a polynomial correction, and reconstructed a correction image to obtain the current iteration's BH corrected image. The cost function was sensitive to BH streak artifacts and cupping. We evaluated the algorithm on simulated CT and physical phantom images, and on preclinical porcine with optional coronary obstruction and clinical CT‐MPI data. Assessments included measures of BH artifact in single images as well as MBF estimates. We obtained CT images on a prototype spectral detector CT (SDCT, Philips Healthcare) scanner that provided both conventional and virtual keV images, allowing us to quantitatively compare corrected CT images to virtual keV images. To stress test the method, we evaluated results on images from a different scanner (iCT, Philips Healthcare) and different kVp values. Results In a CT‐simulated digital phantom consisting of water with iodine cylinder insets, BH streak artifacts between simulated iodine inserts were reduced from 13 ± 2 to 0 ± 1 HU. In a similar physical phantom having higher iodine concentrations, BH streak artifacts were reduced from 48 ± 6 to 1 ± 5 HU and cupping was reduced by 86%, from 248 to 23 HU. In preclinical CT‐MPI images without coronary obstruction, BH artifact was reduced from 24 ± 6 HU to less than 5 ± 4 HU at peak enhancement. Standard deviation across different regions of interest (ROI) along the myocardium was reduced from 13.26 to 6.86 HU for ABHC, comparing favorably to measurements in the corresponding virtual keV image. Corrections greatly reduced variations in preclinical MBF maps as obtained in normal animals without obstruction (FFR = 1). Coefficients of variations were 22% (conventional CT), 9% (ABHC), and 5% (virtual keV). Moreover, variations in flow tended to be localized after ABHC, giving result which would not be confused with a flow deficit in a coronary vessel...

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Data consistency condition–based beam-hardening correction

Cited by 11 publications

References 47 publications

Calibration‐free beam hardening reduction in x‐ray CBCT using the epipolar consistency condition and physical constraints

Calibration‐free beam hardening reduction in x‐ray CBCT using the epipolar consistency condition and physical constraints

Comparative Evaluation of Cone-Beam Consistency Conditions for Mono-Material Beam Hardening Correction in Flat Detector Computed Tomography

Calibration‐free beam hardening correction for myocardial perfusion imaging using CT

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