PET/MR imaging of the pelvis in the presence of endoprostheses: reducing image artifacts and increasing accuracy through inpainting

Ladefoged, Claes Nøhr; Andersen, Flemming; Keller, Sune H.; Löfgren, Johan; Hansen, Adam E.; Holm, Søren; Højgaard, Liselotte; Beyer, Thomas

doi:10.1007/s00259-012-2316-4

Cited by 42 publications

(49 citation statements)

References 21 publications

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“…Besides the simple algorithm proposed here, complex algorithms for correction of MR-AC image artifacts have been proposed to correct for the MR-AC image artifacts. 34,35,37 A second limitation is that not all image artifacts were corrected in this study. For example, misalignment artifacts (PMA) caused by breathing during MR-AC acquisitions were not compensated for, due to the gradual change of the respiratory phase throughout acquisition.…”

Section: Discussionmentioning

confidence: 99%

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Assessment of attenuation correction for myocardial PET imaging using combined PET/MRI

Lassen

Rasul

Beitzke

et al. 2019

Journal of Nuclear Cardiology

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Objective. To evaluate the frequency of artifacts in MR-based attenuation correction (AC) maps and their impact on the quantitative accuracy of PET-based flow and metabolism measurements in a cohort of consecutive heart failure patients undergoing combined PET/MR imaging.Methods. Myocardial viability studies were performed in 20 patients following a dualtracer protocol involving the assessment of myocardial perfusion ( 13 N-NH 3 : 813 ± 86 MBq) and metabolism ( 18 F-FDG: 335 ± 38 MBq). All acquisitions were performed using a fully-integrated PET/MR system, with standard DIXON-attenuation correction (DIXON-AC) mapping for each PET scan. All AC maps were examined for spatial misalignment with the emission data, total lung volume, susceptibility artifacts, and tissue inversion (TI). Misalignment and susceptibility artifacts were corrected using rigid co-registration and retrospective filling of the susceptibility-induced gaps, respectively. The effects of the AC artifacts were evaluated by relative difference measures and perceived changes in clinical interpretations.Results. Average respiratory misalignment of (7 ± 4) mm of the PET-emission data and the AC maps was observed in 18 (90%) patients. Substantial changes in the lung volumes of the AC maps were observed in the test-retest analysis (ratio: 1.0 ± 0.2, range: 0.8-1.4). Susceptibility artifacts were observed in 10 (50%) patients, while six (30%) patients had TI artifacts. Average differences of 14 ± 10% were observed for PET images reconstructed with the artifactual AC maps. The combined artifact effects caused false-positive findings in three (15%) patients.Conclusion. Standard DIXON-AC maps must be examined carefully for artifacts and misalignment effects prior to AC correction of cardiac PET/MRI studies in order to avoid misinterpretation of biased perfusion and metabolism readings from the PET data. (J Nucl Cardiol 2017)

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Section: Discussionmentioning

confidence: 99%

“…[34][35][36][37] Misalignment artifacts, on another hand, can be corrected retrospectively using manual coregistrations of the AC maps and the emission data. 19,20 Tissue inversion, however, is more challenging to correct.…”

Section: Discussionmentioning

confidence: 99%

Assessment of attenuation correction for myocardial PET imaging using combined PET/MRI

Lassen

Rasul

Beitzke

et al. 2019

Journal of Nuclear Cardiology

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“…Ladefoged et al 105 proposed to semiautomatically segment the signal voids caused by endoprotheses and to fill them with soft-tissue attenuation coefficients. It was demonstrated that the resulting attenuation maps can substantially reduce the underestimation of the SUVs.…”

Section: B1 Void Regions Segmentationmentioning

confidence: 99%

“…It has been reported that the resulting erroneous attenuation map can lead to substantial SUV underestimation by about 50% in the case of hip prosthesis 36 and >100% in dental filling cases. 104 The correction of MR susceptibility artifacts has been explored using the following approaches.…”

Section: B Mr Susceptibility and Respiratory Artifact Reductionmentioning

confidence: 99%

Vision 20/20: Magnetic resonance imaging‐guided attenuation correction in PET/MRI: Challenges, solutions, and opportunities

2016

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Attenuation correction is an essential component of the long chain of data correction techniques required to achieve the full potential of quantitative positron emission tomography (PET) imaging. The development of combined PET/magnetic resonance imaging (MRI) systems mandated the widespread interest in developing novel strategies for deriving accurate attenuation maps with the aim to improve the quantitative accuracy of these emerging hybrid imaging systems. The attenuation map in PET/MRI should ideally be derived from anatomical MR images; however, MRI intensities reflect proton density and relaxation time properties of biological tissues rather than their electron density and photon attenuation properties. Therefore, in contrast to PET/computed tomography, there is a lack of standardized global mapping between the intensities of MRI signal and linear attenuation coefficients at 511 keV. Moreover, in standard MRI sequences, bones and lung tissues do not produce measurable signals owing to their low proton density and short transverse relaxation times. MR images are also inevitably subject to artifacts that degrade their quality, thus compromising their applicability for the task of attenuation correction in PET/MRI. MRI-guided attenuation correction strategies can be classified in three broad categories: (i) segmentation-based approaches, (ii) atlasregistration and machine learning methods, and (iii) emission/transmission-based approaches. This paper summarizes past and current state-of-the-art developments and latest advances in PET/MRI attenuation correction. The advantages and drawbacks of each approach for addressing the challenges of MR-based attenuation correction are comprehensively described. The opportunities brought by both MRI and PET imaging modalities for deriving accurate attenuation maps and improving PET quantification will be elaborated. Future prospects and potential clinical applications of these techniques and their integration in commercial systems will also be discussed. C 2016 American Association of Physicists in Medicine. [http://dx

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“…The accuracy of MR attenuation correction (AC) is challenged by susceptibility effects caused by dental fillings and metal braces. [4][5][6][7] The effect of a metal implant can be a signal void around the metal filling in the MR images [Figs. 1(a)-1(c)], resulting in the area incorrectly being set to air in the μ-map [ Fig.…”

Section: Introductionmentioning

confidence: 99%

Automatic correction of dental artifacts in PET/MRI

et al. 2015

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Abstract.A challenge when using current magnetic resonance (MR)-based attenuation correction in positron emission tomography/MR imaging (PET/MRI) is that the MRIs can have a signal void around the dental fillings that is segmented as artificial air-regions in the attenuation map. For artifacts connected to the background, we propose an extension to an existing active contour algorithm to delineate the outer contour using the nonattenuation corrected PET image and the original attenuation map. We propose a combination of two different methods for differentiating the artifacts within the body from the anatomical air-regions by first using a template of artifact regions, and second, representing the artifact regions with a combination of active shape models and knearest-neighbors. The accuracy of the combined method has been evaluated using 25 18 F-fluorodeoxyglucose PET/MR patients. Results showed that the approach was able to correct an average of 97 AE 3% of the artifact areas. © The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

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PET/MR imaging of the pelvis in the presence of endoprostheses: reducing image artifacts and increasing accuracy through inpainting

Abstract: Endoprostheses cause PET/MR artifacts that exceed the volume occupied by the implants, and bias PET quantification. Artifacts and bias can be corrected by semiautomated inpainting with soft tissue with a single composition prior to MR-AC, thus restoring quantitative activity distribution.

Cited by 42 publications

References 21 publications

Assessment of attenuation correction for myocardial PET imaging using combined PET/MRI

Assessment of attenuation correction for myocardial PET imaging using combined PET/MRI

Vision 20/20: Magnetic resonance imaging‐guided attenuation correction in PET/MRI: Challenges, solutions, and opportunities

Automatic correction of dental artifacts in PET/MRI

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