Virtual Monochromatic Spectral Imaging with Fast Kilovoltage Switching: Reduction of Metal Artifacts at CT

Pessis, É.; Campagna, R.; Sverzut, Jean-Michel; Bach, Fabienne; Rodallec, M.; Guérini, H.; Feydy, A.; Drapé, Jean‐Luc

doi:10.1148/rg.332125124

Cited by 193 publications

(142 citation statements)

References 14 publications

(25 reference statements)

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“…This application makes it possible to obtain images as though they had been acquired with a monoenergetic high-energy beam, which would lead to reduction of metal artefacts caused by beam hardening. [5][6][7][8][9] In addition to monoenergetic reconstructions in DECT, dedicated MAR algorithms have become available for clinical practice in the past couple of years. MAR algorithms in both single-energy CT imaging [10][11][12][13][14] and DECT imaging 8,9 have been shown to reduce metal artefacts.…”

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confidence: 99%

“…[5][6][7][8][9][10][11][12][13] Monoenergetic images, reconstructed from DECT data, have been shown to enhance the diagnostic value of CT images containing orthopaedic implants. [5][6][7][8][9][10] Li et al 12 studied the application of a commercially available MAR algorithm in radiotherapy treatment planning and concluded that it improved CT number accuracy and structure visualization in CT images of orthopaedic implants. However, the improvement in CT number accuracy was shown not to have any significant clinical impact on photon dose calculations.…”

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confidence: 99%

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Metal artefact reduction in CT imaging of hip prostheses—an evaluation of commercial techniques provided by four vendors

Andersson¹,

Nowik²,

Persliden³

et al. 2015

BJR

109

106

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Objective: The aim of this study was to evaluate commercial metal artefact reduction (MAR) techniques in X-ray CT imaging of hip prostheses. Methods: Monoenergetic reconstructions of dual-energy CT (DECT) data and several different MAR algorithms, combined with single-energy CT or DECT, were evaluated by imaging a bilateral hip prosthesis phantom. The MAR images were compared with uncorrected images based on CT number accuracy and noise in different regions of interest. Results: The three MAR algorithms studied implied a general noise reduction (up to 67%, 74% and 77%) and an improvement in CT number accuracy, both in regions close to the prostheses and between the two prostheses. The application of monoenergetic reconstruction, without any MAR algorithm, did not decrease the noise in the regions close to the prostheses to the same extent as did the MAR algorithms and even increased the noise in the region between the prostheses. Conclusion: The MAR algorithms evaluated generally improved CT number accuracy and substantially reduced the noise in the hip prostheses phantom images, both close to the prostheses and between the two prostheses. The study showed that the monoenergetic reconstructions evaluated did not sufficiently reduce the severe metal artefact caused by large orthopaedic implants. Advances in knowledge: This study evaluates several commercially available MAR techniques in CT imaging of large orthopaedic implants.Images degraded by metal artefacts are a common problem in X-ray CT imaging. Artefacts caused by the presence of metallic implants in the CT scanned volume, such as hip prostheses or dental fillings, appear as dark and bright streaks across the reconstructed image. Metal artefacts can severely degrade the image quality and hence limit the diagnostic value of a CT scan. 1 Hip prostheses cause severe artefacts when present in a CT scanned volume, and the resulting degradation of image quality leads to difficulties in diagnosing fractures, implant loosening or pathology in organs or soft tissue in the pelvic area. If CT images containing hip prostheses are used in radiotherapy treatment planning for tissue heterogeneity correction, the metal artefacts may introduce inaccuracies in dose calculations.Metal artefacts in CT imaging are mainly caused by beam hardening and photon starvation. Photon starvation artefacts are created when X-rays traverse materials with high attenuation coefficients, which leads to an insufficient amount of photons reaching the detectors and results in very noisy projections. The noise is magnified in the reconstruction process and the resulting streaks can be seen in the reconstructed image. Beam hardening refers to the fact that low-energy photons are attenuated to a greater degree than high-energy photons when passing through the scanned volume. This effect is more pronounced when the X-ray beam passes through high-density materials such as metals.

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confidence: 99%

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confidence: 99%

Metal artefact reduction in CT imaging of hip prostheses—an evaluation of commercial techniques provided by four vendors

Andersson¹,

Nowik²,

Persliden³

et al. 2015

BJR

109

106

View full text Add to dashboard Cite

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“…A monochromatic CT image can be useful in improving the visualization of a contrast agent and, as in this study, reducing metal-induced artefacts. 17 Filtered back projection (FBP) represents the current standard image reconstruction method, given its relative sensitivity to noise. Owing to Poisson statistics in X-ray imaging, lowering the dose by reducing the tube current may result in an unacceptable increase in image noise.…”

Section: Discussionmentioning

confidence: 99%

CT of facial fracture fixation: an experimental study of artefact reducing methods

Peltola¹,

Mäkelä²,

Haapamäki³

et al. 2017

Dentomaxillofacial Radiology

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Objectives: This study aimed to determine the optimal post-operative CT imaging method that enables best visualization of facial bony structures in the vicinity of osteosynthesis material. Methods: Conducted at Töölö Hospital (Helsinki, Finland), this study relied on scanning a phantom with CBCT, 64-slice CT and high-definition multislice CT with dual-energy scan (providing monochromatic images of 70-, 100-, 120-and 140-keV energy levels) and iterative reconstruction (IR) methods. Two radiologists assessed the image quality, and the assessments were analyzed. In addition, a physicist performed a semi-quantitative analysis of the metalinduced artefacts. Results: The three subjects most easily assessed were the loose screw and both the bone structure and the fracture further away from the screw and the plate. Soft tissues adjacent to the screw and the plate remained more difficult for assessment. Both image interpreters agreed that the artefacts disturbed their assessments under dual energy. Metal artefacts disturbed the least under multislice CT with IR [adaptive statistical iterative reconstruction (ASiR) and VEO]. Neither interpreter found metal suppression helpful in CBCT. Conclusions: CBCT with or without a metal artefact reduction algorithm was not optimal for post-operative facial imaging compared with multislice CT with IR. Multislice CT with ASiR filtering offered good image quality performance with fast image volume reconstruction, representing the current sweet spot in post-operative maxillofacial imaging.

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“…Beam hardening artifacts are minimized on high monoenergetic images (6). Beam hardening artifacts also arise from high attenuating implanted objects such as stents or pacing wires common in cardiovasSpectral detector CT for cardiovascular applications • 189 (6)(7)(8). Again, with SDCT, the spectral data necessary to create virtual high monoenergetic images is available by default if incidentally encountered artifacts interfere with image evaluation.…”

Section: Beam Hardening Artifactsmentioning

confidence: 99%

Spectral detector CT for cardiovascular applications

Rajiah¹,

Abbara²,

Halliburton³

2017

Diagn Interv Radiol

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In spectral computed tomography (CT), multiple spectrally distinct attenuation data sets are obtained from the same scan, which enables material composition analysis not possible with conventional CT. Dual-energy CT (DECT), where a low and high energy data set are obtained, is currently available in clinical practice using the following approaches: a) Dual source technology: two x-ray tube/detector systems separated by approximately 90 o and operated at different tube potentials (1) (Fig. 1a); b) Rapid tube potential switching technology: the potential applied across a single x-ray tube is switched rapidly between a high and low setting (1, 2) (Fig. 1b); c) Dual-spin technology: the same anatomical region is scanned twice during two consecutive rotations, once with a high potential applied across the x-ray tube and once with a low potential applied (1) (Fig. 1c); d) Split-beam technology: the spectrum emitted from a single tube is split into high and low energy spectra (3).Spectral detector CT (SDCT) (IQon, Philips Healthcare) is a novel technology introduced for clinical DECT data acquisition. A single potential is applied across a single x-ray tube and two layers of detectors separate low and high energy data: the top layer absorbs low energy photons and the bottom layer absorbs high energy photons (Fig. 1d). In addition to conventional (polyenergetic) images, projection data simultaneously obtained from both detector layers can also be utilized to generate spectral images. The spectral images useful for cardiovascular assessment include virtual monoenergetic images (Fig. 2a), iodine density maps (Fig. 2b), virtual unenhanced images (Fig. 2c), and effective atomic number (Z effective ) images (Fig. 2d). An important feature of SDCT technology is that spectral information is available in all patients without a priori selection of a special protocol or exposure to additional radiation. Images are available at full field-of-view and a minimum rotation time of 0.27 seconds (s) with complete temporal and spatial registration.In this paper, we present our initial clinical experience based on the acquisition of data from over 200 patients who underwent cardiovascular studies (i.e., cardiac, aorta, pulmonary veins, pulmonary arteries) using SDCT including the impact of this technology on radiation dose and contrast dose. The creation of spectral images from spectral data is discussed and the utility of these images is demonstrated for specific cardiovascular applications. 187From the Department of Radiology (P.R. ABSTRACTSpectral detector computed tomography (SDCT) is a novel technology that uses two layers of detectors to simultaneously collect low and high energy data. Spectral data is used to generate conventional polyenergetic images as well as dedicated spectral images including virtual monoenergetic and material composition (iodine-only, virtual unenhanced, effective atomic number) images. This paper provides an overview of SDCT technology and a description of some spectral image types. The potential utility o...

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Virtual Monochromatic Spectral Imaging with Fast Kilovoltage Switching: Reduction of Metal Artifacts at CT

Cited by 193 publications

References 14 publications

Metal artefact reduction in CT imaging of hip prostheses—an evaluation of commercial techniques provided by four vendors

Metal artefact reduction in CT imaging of hip prostheses—an evaluation of commercial techniques provided by four vendors

CT of facial fracture fixation: an experimental study of artefact reducing methods

Spectral detector CT for cardiovascular applications

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