X‐ray scatter correction algorithm for cone beam CT imaging

Ning, Ruola; Tang, Xiangyang; Conover, David L.

doi:10.1118/1.1711475

Cited by 303 publications

(269 citation statements)

References 38 publications

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“…5 Previous studies proposed various methods to correct those artifacts using analytical methods, 6 Monte Carlo simulations, 7 and experimental techniques. 8 It has been reported that photon dose calculation discrepancy caused by CBCT HU error can reach up to 11% without any scatter correction and can be reduced to <1% with scatter correction. 9 As a similar concept to ART, adaptive proton therapy (APT) was introduced.…”

Section: Introductionmentioning

confidence: 99%

Proton dose calculation on scatter‐corrected CBCT image: Feasibility study for adaptive proton therapy

et al. 2015

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Purpose: To demonstrate the feasibility of proton dose calculation on scatter-corrected cone-beam computed tomographic (CBCT) images for the purpose of adaptive proton therapy. Methods: CBCT projection images were acquired from anthropomorphic phantoms and a prostate patient using an on-board imaging system of an Elekta infinity linear accelerator. Two previously introduced techniques were used to correct the scattered x-rays in the raw projection images: uniform scatter correction (CBCT us ) and a priori CT-based scatter correction (CBCT ap ). CBCT images were reconstructed using a standard FDK algorithm and GPU-based reconstruction toolkit. Soft tissue ROI-based HU shifting was used to improve HU accuracy of the uncorrected CBCT images and CBCT us , while no HU change was applied to the CBCT ap . The degree of equivalence of the corrected CBCT images with respect to the reference CT image (CT ref ) was evaluated by using angular profiles of water equivalent path length (WEPL) and passively scattered proton treatment plans. The CBCT ap was further evaluated in more realistic scenarios such as rectal filling and weight loss to assess the effect of mismatched prior information on the corrected images. Results: The uncorrected CBCT and CBCT us images demonstrated substantial WEPL discrepancies (7.3 ± 5.3 mm and 11.1 ± 6.6 mm, respectively) with respect to the CT ref , while the CBCT ap images showed substantially reduced WEPL errors (2.4 ± 2.0 mm). Similarly, the CBCT ap -based treatment plans demonstrated a high pass rate (96.0% ± 2.5% in 2 mm/2% criteria) in a 3D gamma analysis. Conclusions: A priori CT-based scatter correction technique was shown to be promising for adaptive proton therapy, as it achieved equivalent proton dose distributions and water equivalent path lengths compared to those of a reference CT in a selection of anthropomorphic phantoms. C 2015 American Association of Physicists in Medicine. [http://dx

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Section: Introductionmentioning

confidence: 99%

Proton dose calculation on scatter‐corrected CBCT image: Feasibility study for adaptive proton therapy

et al. 2015

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“…Scatter profiles can be measured by variety of techniques. 8,10,[13][14][15][16] Experimental techniques have the advantage that they give the scatter magnitude directly in detector signal units, but require the introduction of attenuators, two projections per view in some cases, or require reducing Z-axis coverage. Alternatively, computational methods for estimating scatter corrections can be used, including Monte Carlo ͑MC͒ simulation 5,17 and analytical calculations.…”

Section: Introductionmentioning

confidence: 99%

“…8,9 In addition, algorithmic methods for mathematically subtracting scatter from the sinogram data have been investigated. 10,11 ASGs are a well-known, effective means of scatter rejection in projection radiography. Grids always reduce the scatter-to-primary ratio ͑SPR͒, thereby improving contrast and image uniformity, but absorb useful primary photons, resulting in increased image noise.…”

Section: Introductionmentioning

confidence: 99%

Monte Carlo evaluation of scatter mitigation strategies in cone‐beam CT

Lazos

Williamson

2010

Medical Physics

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Purpose: To investigate the efficacy of two widely used scatter mitigation methods: antiscatter grids ͑ASGs͒ and beam modulating with bowtie filters ͑BTFs͒, in combination with subtractive scatter correction or zeroth order normalization phantom calibration, for improving image noise, contrast, contrast-to-noise ratio ͑CNR͒, and image uniformity for on-board cone-beam CT ͑CBCT͒ imaging systems used for image-guided radiation therapy. Methods: PTRAN Monte Carlo CBCT x-ray projections of head and pelvic phantoms were calculated for combinations of beam-modulation and scatter rejection methods and images were reconstructed by in-house developed software. In addition, a simple one-dimensional analytic model was developed to predict scatter-to-primary ratio ͑SPR͒ and CNR as a function of cylindrical phantom thickness, ASG transmission, and beam modulation with bow-tie filters. Results: ASGs were found to have slightly negative or no effect on head phantom image CNR and to modestly improve CNR ͑10%-20%͒ in pelvic phantom images. However, scatter subtraction and norm-phantom calibration perform better when applied on data acquired with ASGs. Scatter subtraction improves CT number accuracy, but increases noise, and in high SPR/low primary-photon transmission scenarios can dramatically reduce CNR and introduce streaking artifacts. The BTF is found to reduce SPR and image noise, resulting in a better trade-off between CNR and imaging dose, but introduces a circular band artifact. Conclusions: Our study shows that ASGs have a modest positive impact in pelvic scans and negative in head scans, scatter subtraction improves the HU accuracy but reduces CNR, while BTF has a clearly positive effect.

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“…Similar results have been demonstrated by others when a subtraction algorithm was applied to CBCT projection data prior to reconstruction. 12,13,[22][23][24] Scatter is considered to be one of the fundamental limitations of CBCT image quality. 12 Also, not only does scatter result in the cupping effect artefact, but scatter radiation can produce grey level non-uniformity throughout the FOV.…”

Section: Discussionmentioning

confidence: 99%

Characterization and correction of cupping effect artefacts in cone beam CT

Hunter¹,

McDavid

2012

Dentomaxillofacial Radiology

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Objective: The purpose of this study was to demonstrate and correct the cupping effect artefact that occurs owing to the presence of beam hardening and scatter radiation during image acquisition in cone beam CT (CBCT). Methods: A uniform aluminium cylinder (6061) was used to demonstrate the cupping effect artefact on the Planmeca Promax 3D CBCT unit (Planmeca OY, Helsinki, Finland). The cupping effect was studied using a line profile plot of the grey level values using ImageJ software (National Institutes of Health, Bethesda, MD). A hardware-based correction method using copper pre-filtration was used to address this artefact caused by beam hardening and a software-based subtraction algorithm was used to address scatter contamination. Results: The hardware-based correction used to address the effects of beam hardening suppressed the cupping effect artefact but did not eliminate it. The software-based correction used to address the effects of scatter resulted in elimination of the cupping effect artefact. Conclusion: Compensating for the presence of beam hardening and scatter radiation improves grey level uniformity in CBCT.

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X‐ray scatter correction algorithm for cone beam CT imaging

Cited by 303 publications

References 38 publications

Proton dose calculation on scatter‐corrected CBCT image: Feasibility study for adaptive proton therapy

Proton dose calculation on scatter‐corrected CBCT image: Feasibility study for adaptive proton therapy

Monte Carlo evaluation of scatter mitigation strategies in cone‐beam CT

Characterization and correction of cupping effect artefacts in cone beam CT

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