Scatter correction method for x‐ray CT using primary modulation: Phantom studies

Gao, Hewei; Fahrig, Rebecca; Bennett, N. Robert; Sun, Mengtao; Star‐Lack, Josh; Zhu, Lei

doi:10.1118/1.3298014

Cited by 70 publications

(87 citation statements)

References 38 publications

(46 reference statements)

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“…However, even using the fast algorithm, the formidably heavy computation load associated with Monte Carlo scatter estimation hinders its real‐life applications. The third category of methods estimates the contribution of scatter in the measured projection data and then subtracts it from the measured projection data, such as the beam‐stop array method, (10) the moving blocker method, (11) primary modula‐tion, 12 , 13 , 14 artifact‐suppressed dictionary learning method, 15 , 16 and others 17 , 18 . However, these types of correction methods add extra hardware to the CBCT system, which can add difficulty and complexity.…”

Section: Introductionmentioning

confidence: 99%

An energy minimization method for the correction of cupping artifacts in cone‐beam CT

Xie

Zhuang

2016

J Applied Clin Med Phys

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The purpose of this study was to reduce cupping artifacts and improve quantitative accuracy of the images in cone‐beam CT (CBCT). An energy minimization method (EMM) is proposed to reduce cupping artifacts in reconstructed image of the CBCT. The cupping artifacts are iteratively optimized by using efficient matrix computations, which are verified to be numerically stable by matrix analysis. Moreover, the energy in our formulation is convex in each of its variables, which brings the robustness of the proposed energy minimization algorithm. The cupping artifacts are estimated as a result of minimizing this energy. The results indicate that proposed algorithm is effective for reducing the cupping artifacts and preserving the quality of the reconstructed image. The proposed method focuses on the reconstructed image without requiring any additional physical equipment; it is easily implemented and provides cupping correction using a single scan acquisition. The experimental results demonstrate that this method can successfully reduce the magnitude of cupping artifacts. The correction algorithm reported here may improve the uniformity of the reconstructed images, thus assisting the development of perfect volume visualization and threshold‐based visualization techniques for reconstructed images.PACS number(s): 87.57.cp

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Section: Introductionmentioning

confidence: 99%

An energy minimization method for the correction of cupping artifacts in cone‐beam CT

Xie

Zhuang

2016

J Applied Clin Med Phys

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“…ABOCS accurately estimates the data fidelity tolerance used in the algorithm from the raw data using Eq. (14). Equivalently, we use μ = 1 in Eq.…”

Section: Iiia Digital Phantom Studymentioning

confidence: 99%

“…To convert the measured flat field in detector unit on a clinical system to that in the number of photons, we calculate the I 0 image used in the total noise variance estimation [Eq. (14)] as…”

Section: Iif2 Head Phantom Studymentioning

confidence: 99%

“…After the effective data correction algorithms already implemented on a CBCT system, including scatter and beamhardening corrections, [11][12][13][14][15][16][17] the residual nonstatistical errors on the projections are expected to be small as compared to the Poisson noise. In this paper, we assume that this condition is true.…”

Section: Iic Estimation Of Data Fidelity Tolerancementioning

confidence: 99%

“…Note that, the user-defined parameter ε is interpreted as the variance of the difference between the predicted and the raw projections. After effective data correction for scatter and beam-hardening effects, [11][12][13][14][15][16][17][18] most of the projection errors in CT scans are from Poisson statistics of the incident photons, except for very lowdose imaging cases. [19][20][21] ε can therefore be readily estimated from the measured projections.…”

Section: Introductionmentioning

confidence: 99%

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Accelerated barrier optimization compressed sensing (ABOCS) reconstruction for cone-beam CT: Phantom studies

2012

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Purpose: Recent advances in compressed sensing (CS) enable accurate CT image reconstruction from highly undersampled and noisy projection measurements, due to the sparsifiable feature of most CT images using total variation (TV). These novel reconstruction methods have demonstrated advantages in clinical applications where radiation dose reduction is critical, such as onboard cone-beam CT (CBCT) imaging in radiation therapy. The image reconstruction using CS is formulated as either a constrained problem to minimize the TV objective within a small and fixed data fidelity error, or an unconstrained problem to minimize the data fidelity error with TV regularization. However, the conventional solutions to the above two formulations are either computationally inefficient or involved with inconsistent regularization parameter tuning, which significantly limit the clinical use of CS-based iterative reconstruction. In this paper, we propose an optimization algorithm for CS reconstruction which overcomes the above two drawbacks. Methods:The data fidelity tolerance of CS reconstruction can be well estimated based on the measured data, as most of the projection errors are from Poisson noise after effective data correction for scatter and beam-hardening effects. We therefore adopt the TV optimization framework with a data fidelity constraint. To accelerate the convergence, we first convert such a constrained optimization using a logarithmic barrier method into a form similar to that of the conventional TV regularization based reconstruction but with an automatically adjusted penalty weight. The problem is then solved efficiently by gradient projection with an adaptive Barzilai-Borwein step-size selection scheme. The proposed algorithm is referred to as accelerated barrier optimization for CS (ABOCS), and evaluated using both digital and physical phantom studies. Results: ABOCS directly estimates the data fidelity tolerance from the raw projection data. Therefore, as demonstrated in both digital Shepp-Logan and physical head phantom studies, consistent reconstruction performances are achieved using the same algorithm parameters on scans with different noise levels and/or on different objects. On the contrary, the penalty weight in a TV regularization based method needs to be fine-tuned in a large range (up to seven times) to maintain the reconstructed image quality. The improvement of ABOCS on computational efficiency is demonstrated in the comparisons with adaptive-steepest-descent-projection-onto-convex-sets (ASD-POCS), an existing CS reconstruction algorithm also using constrained optimization. ASD-POCS alternatively minimizes the TV objective using adaptive steepest descent (ASD) and the data fidelity error using projection onto convex sets (POCS). For similar image qualities of the Shepp-Logan phantom, ABOCS requires less computation time than ASD-POCS in MATLAB by more than one order of magnitude. Conclusions: We propose ABOCS for CBCT reconstruction. As compared to other published CSbased algorithms, our method has at...

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Impact of scatter radiation on spectral quantification performance of first‐ and second‐generation dual‐layer spectral computed tomography

Salazar,

Liu,

Perkins

et al. 2024

J Applied Clin Med Phys

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ObjectiveTo assess the impact of scatter radiation on quantitative performance of first and second‐generation dual‐layer spectral computed tomography (DLCT) systems.MethodA phantom with two iodine inserts (1 and 2 mg/mL) configured to intentionally introduce high scattering conditions was scanned with a first‐ and second‐generation DLCT. Collimation widths (maximum of 4 cm for first generation and 8 cm for second generation) and radiation dose levels were varied. To evaluate the performance of both systems, the mean CT numbers of virtual monoenergetic images (MonoEs) at different energies were calculated and compared to expected values. MonoEs at 50 versus 150 keV were plotted to assess material characterization of both DLCTs. Additionally, iodine concentrations were determined, plotted, and compared against expected values. For each experimental scenario, absolute errors were reported.ResultsAn experimental setup, including a phantom design, was successfully implemented to simulate high scatter radiation imaging conditions. Both CT scanners illustrated high spectral accuracy for small collimation widths (1 and 2 cm). With increased collimation (4 cm), the second‐generation DLCT outperformed the earlier DLCT system. Further, the spectral performance of the second‐generation DLCT at an 8 cm collimation width was comparable to a 4 cm collimation on the first‐generation DLCT. A comparison of the absolute errors between both systems at lower energy MonoEs illustrates that, for the same acquisition parameters, the second‐generation DLCT generated results with decreased errors. Similarly, the maximum error in iodine quantification was less with second‐generation DLCT (0.45 and 0.33 mg/mL for the first and second‐generation DLCT, respectively).ConclusionThe implementation of a two‐dimensional anti‐scatter grid in the second‐generation DLCT improves the spectral quantification performance. In the clinical routine, this improvement may enable additional clinical benefits, for example, in lung imaging.

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Scatter correction method for x‐ray CT using primary modulation: Phantom studies

Cited by 70 publications

References 38 publications

An energy minimization method for the correction of cupping artifacts in cone‐beam CT

An energy minimization method for the correction of cupping artifacts in cone‐beam CT

Accelerated barrier optimization compressed sensing (ABOCS) reconstruction for cone-beam CT: Phantom studies

Impact of scatter radiation on spectral quantification performance of first‐ and second‐generation dual‐layer spectral computed tomography

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