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  1. Article ; Online: Data Extrapolation From Learned Prior Images for Truncation Correction in Computed Tomography.

    Huang, Yixing / Preuhs, Alexander / Manhart, Michael / Lauritsch, Guenter / Maier, Andreas

    IEEE transactions on medical imaging

    2021  Volume 40, Issue 11, Page(s) 3042–3053

    Abstract: Data truncation is a common problem in computed tomography (CT). Truncation causes cupping artifacts inside the field-of-view (FOV) and anatomical structures missing outside the FOV. Deep learning has achieved impressive results in CT reconstruction from ...

    Abstract Data truncation is a common problem in computed tomography (CT). Truncation causes cupping artifacts inside the field-of-view (FOV) and anatomical structures missing outside the FOV. Deep learning has achieved impressive results in CT reconstruction from limited data. However, its robustness is still a concern for clinical applications. Although the image quality of learning-based compensation schemes may be inadequate for clinical diagnosis, they can provide prior information for more accurate extrapolation than conventional heuristic extrapolation methods. With extrapolated projection, a conventional image reconstruction algorithm can be applied to obtain a final reconstruction. In this work, a general plug-and-play (PnP) method for truncation correction is proposed based on this idea, where various deep learning methods and conventional reconstruction algorithms can be plugged in. Such a PnP method integrates data consistency for measured data and learned prior image information for truncated data. This shows to have better robustness and interpretability than deep learning only. To demonstrate the efficacy of the proposed PnP method, two state-of-the-art deep learning methods, FBPConvNet and Pix2pixGAN, are investigated for truncation correction in cone-beam CT in noise-free and noisy cases. Their robustness is evaluated by showing false negative and false positive lesion cases. With our proposed PnP method, false lesion structures are corrected for both deep learning methods. For FBPConvNet, the root-mean-square error (RMSE) inside the FOV can be improved from 92HU to around 30HU by PnP in the noisy case. Pix2pixGAN solely achieves better image quality than FBPConvNet solely for truncation correction in general. PnP further improves the RMSE inside the FOV from 42HU to around 27HU for Pix2pixGAN. The efficacy of PnP is also demonstrated on real clinical head data.
    MeSH term(s) Algorithms ; Artifacts ; Cone-Beam Computed Tomography ; Tomography, X-Ray Computed
    Language English
    Publishing date 2021-10-27
    Publishing country United States
    Document type Journal Article
    ZDB-ID 622531-7
    ISSN 1558-254X ; 0278-0062
    ISSN (online) 1558-254X
    ISSN 0278-0062
    DOI 10.1109/TMI.2021.3072568
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  2. Article ; Online: Nonradiology Health-Care Professionals Significantly Benefit From AI Assistance in Emergency-Related Chest Radiography Interpretation.

    Rudolph, Jan / Huemmer, Christian / Preuhs, Alexander / Buizza, Guiulia / Hoppe, Boj F / Dinkel, Julien / Koliogiannis, Vanessa / Fink, Nicola / Goller, Sophia S / Schwarze, Vincent / Mansour, Nabeel / Schmidt, Vanessa F / Fischer, Maximilian / Jörgens, Maximilian / Ben Khaled, Najib / Liebig, Thomas / Ricke, Jens / Rueckel, Johannes / Sabel, Bastian O

    Chest

    2024  

    Abstract: Background: Chest radiographs (CXRs) are still of crucial importance in primary diagnostics, but their interpretation poses difficulties at times.: Research question: Can a convolutional neural network-based artificial intelligence (AI) system that ... ...

    Abstract Background: Chest radiographs (CXRs) are still of crucial importance in primary diagnostics, but their interpretation poses difficulties at times.
    Research question: Can a convolutional neural network-based artificial intelligence (AI) system that interprets CXRs add value in an emergency unit setting?
    Study design and methods: A total of 563 CXRs acquired in the emergency unit of a major university hospital were retrospectively assessed twice by three board-certified radiologists, three radiology residents, and three emergency unit-experienced nonradiology residents (NRRs). They used a two-step reading process: (1) without AI support (woAI); and (2) with AI support (wAI) providing additional images with AI overlays. Suspicion of four suspected pathologies (pleural effusion, pneumothorax, consolidations suspicious for pneumonia, and nodules) was reported on a five-point confidence scale. Confidence scores of the board-certified radiologists were converted into four binary reference standards (RFS I-IV) of different sensitivities. Performance by radiology residents and NRRs woAI/wAI were statistically compared by using receiver-operating characteristics (ROCs), Youden statistics, and operating point metrics derived from fitted ROC curves.
    Results: NRRs could significantly improve performance, sensitivity, and accuracy wAI in all four pathologies tested. In the most sensitive RFS IV, NRR consensus improved the area under the ROC curve (mean, 95% CI) in the detection of the time-critical pathology pneumothorax from 0.846 (0.785-0.907) woAI to 0.974 (0.947-1.000) wAI (P < .001), which represented a gain of 30% in sensitivity and 2% in accuracy (while maintaining an optimized specificity). The most pronounced effect was observed in nodule detection, with NRR wAI improving sensitivity by 53% and accuracy by 7% (area under the ROC curve woAI, 0.723 [0.661-0.785]; wAI, 0.890 [0.848-0.931]; P < .001). The RR consensus wAI showed smaller, mostly nonsignificant gains in performance, sensitivity, and accuracy.
    Interpretation: In an emergency unit setting without 24/7 radiology coverage, the presented AI solution features an excellent clinical support tool to nonradiologists, similar to a second reader, and allows for a more accurate primary diagnosis and thus earlier therapy initiation.
    Language English
    Publishing date 2024-01-29
    Publishing country United States
    Document type Journal Article
    ZDB-ID 1032552-9
    ISSN 1931-3543 ; 0012-3692
    ISSN (online) 1931-3543
    ISSN 0012-3692
    DOI 10.1016/j.chest.2024.01.039
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  3. Book ; Online: Field of View Extension in Computed Tomography Using Deep Learning Prior

    Huang, Yixing / Gao, Lei / Preuhs, Alexander / Maier, Andreas

    2019  

    Abstract: In computed tomography (CT), data truncation is a common problem. Images reconstructed by the standard filtered back-projection algorithm from truncated data suffer from cupping artifacts inside the field-of-view (FOV), while anatomical structures are ... ...

    Abstract In computed tomography (CT), data truncation is a common problem. Images reconstructed by the standard filtered back-projection algorithm from truncated data suffer from cupping artifacts inside the field-of-view (FOV), while anatomical structures are severely distorted or missing outside the FOV. Deep learning, particularly the U-Net, has been applied to extend the FOV as a post-processing method. Since image-to-image prediction neglects the data fidelity to measured projection data, incorrect structures, even inside the FOV, might be reconstructed by such an approach. Therefore, generating reconstructed images directly from a post-processing neural network is inadequate. In this work, we propose a data consistent reconstruction method, which utilizes deep learning reconstruction as prior for extrapolating truncated projections and a conventional iterative reconstruction to constrain the reconstruction consistent to measured raw data. Its efficacy is demonstrated in our study, achieving small average root-mean-square error of 24 HU inside the FOV and a high structure similarity index of 0.993 for the whole body area on a test patient's CT data.

    Comment: Submitted to Bildverarbeitung fuer die Medizin 2020
    Keywords Electrical Engineering and Systems Science - Image and Video Processing ; Computer Science - Computer Vision and Pattern Recognition ; Physics - Medical Physics
    Subject code 006 ; 004
    Publishing date 2019-11-04
    Publishing country us
    Document type Book ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  4. Book ; Online: Data Consistent CT Reconstruction from Insufficient Data with Learned Prior Images

    Huang, Yixing / Preuhs, Alexander / Manhart, Michael / Lauritsch, Guenter / Maier, Andreas

    2020  

    Abstract: Image reconstruction from insufficient data is common in computed tomography (CT), e.g., image reconstruction from truncated data, limited-angle data and sparse-view data. Deep learning has achieved impressive results in this field. However, the ... ...

    Abstract Image reconstruction from insufficient data is common in computed tomography (CT), e.g., image reconstruction from truncated data, limited-angle data and sparse-view data. Deep learning has achieved impressive results in this field. However, the robustness of deep learning methods is still a concern for clinical applications due to the following two challenges: a) With limited access to sufficient training data, a learned deep learning model may not generalize well to unseen data; b) Deep learning models are sensitive to noise. Therefore, the quality of images processed by neural networks only may be inadequate. In this work, we investigate the robustness of deep learning in CT image reconstruction by showing false negative and false positive lesion cases. Since learning-based images with incorrect structures are likely not consistent with measured projection data, we propose a data consistent reconstruction (DCR) method to improve their image quality, which combines the advantages of compressed sensing and deep learning: First, a prior image is generated by deep learning. Afterwards, unmeasured projection data are inpainted by forward projection of the prior image. Finally, iterative reconstruction with reweighted total variation regularization is applied, integrating data consistency for measured data and learned prior information for missing data. The efficacy of the proposed method is demonstrated in cone-beam CT with truncated data, limited-angle data and sparse-view data, respectively. For example, for truncated data, DCR achieves a mean root-mean-square error of 24 HU and a mean structure similarity index of 0.999 inside the field-of-view for different patients in the noisy case, while the state-of-the-art U-Net method achieves 55 HU and 0.995 respectively for these two metrics.

    Comment: 10 pages, 9 figures
    Keywords Electrical Engineering and Systems Science - Image and Video Processing ; Computer Science - Computer Vision and Pattern Recognition ; Computer Science - Machine Learning
    Subject code 006
    Publishing date 2020-05-20
    Publishing country us
    Document type Book ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  5. Article ; Online: Deep Learning-Based ECG-Free Cardiac Navigation for Multi-Dimensional and Motion-Resolved Continuous Magnetic Resonance Imaging.

    Hoppe, Elisabeth / Wetzl, Jens / Yoon, Seung Su / Bacher, Mario / Roser, Philipp / Stimpel, Bernhard / Preuhs, Alexander / Maier, Andreas

    IEEE transactions on medical imaging

    2021  Volume 40, Issue 8, Page(s) 2105–2117

    Abstract: For the clinical assessment of cardiac vitality, time-continuous tomographic imaging of the heart is used. To further detect e.g., pathological tissue, multiple imaging contrasts enable a thorough diagnosis using magnetic resonance imaging (MRI). For ... ...

    Abstract For the clinical assessment of cardiac vitality, time-continuous tomographic imaging of the heart is used. To further detect e.g., pathological tissue, multiple imaging contrasts enable a thorough diagnosis using magnetic resonance imaging (MRI). For this purpose, time-continous and multi-contrast imaging protocols were proposed. The acquired signals are binned using navigation approaches for a motion-resolved reconstruction. Mostly, external sensors such as electrocardiograms (ECG) are used for navigation, leading to additional workflow efforts. Recent sensor-free approaches are based on pipelines requiring prior knowledge, e.g., typical heart rates. We present a sensor-free, deep learning-based navigation that diminishes the need for manual feature engineering or the necessity of prior knowledge compared to previous works. A classifier is trained to estimate the R-wave timepoints in the scan directly from the imaging data. Our approach is evaluated on 3-D protocols for continuous cardiac MRI, acquired in-vivo and free-breathing with single or multiple imaging contrasts. We achieve an accuracy of > 98% on previously unseen subjects, and a well comparable image quality with the state-of-the-art ECG-based reconstruction. Our method enables an ECG-free workflow for continuous cardiac scans with simultaneous anatomic and functional imaging with multiple contrasts. It can be potentially integrated without adapting the sampling scheme to other continuous sequences by using the imaging data for navigation and reconstruction.
    MeSH term(s) Deep Learning ; Electrocardiography ; Heart/diagnostic imaging ; Humans ; Imaging, Three-Dimensional ; Magnetic Resonance Imaging ; Motion
    Language English
    Publishing date 2021-07-30
    Publishing country United States
    Document type Journal Article
    ZDB-ID 622531-7
    ISSN 1558-254X ; 0278-0062
    ISSN (online) 1558-254X
    ISSN 0278-0062
    DOI 10.1109/TMI.2021.3073091
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  6. Article ; Online: X-Ray Scatter Estimation Using Deep Splines.

    Roser, Philipp / Birkhold, Annette / Preuhs, Alexander / Syben, Christopher / Felsner, Lina / Hoppe, Elisabeth / Strobel, Norbert / Kowarschik, Markus / Fahrig, Rebecca / Maier, Andreas

    IEEE transactions on medical imaging

    2021  Volume 40, Issue 9, Page(s) 2272–2283

    Abstract: X-ray scatter compensation is a very desirable technique in flat-panel X-ray imaging and cone-beam computed tomography. State-of-the-art U-net based scatter removal approaches yielded promising results. However, as there are no physics' constraints ... ...

    Abstract X-ray scatter compensation is a very desirable technique in flat-panel X-ray imaging and cone-beam computed tomography. State-of-the-art U-net based scatter removal approaches yielded promising results. However, as there are no physics' constraints applied to the output of the U-Net, it cannot be ruled out that it yields spurious results. Unfortunately, in the context of medical imaging, those may be misleading and could lead to wrong conclusions. To overcome this problem, we propose to embed B-splines as a known operator into neural networks. This inherently constrains their predictions to well-behaved and smooth functions. In a study using synthetic head and thorax data as well as real thorax phantom data, we found that our approach performed on par with U-net when comparing both algorithms based on quantitative performance metrics. However, our approach not only reduces runtime and parameter complexity, but we also found it much more robust to unseen noise levels. While the U-net responded with visible artifacts, the proposed approach preserved the X-ray signal's frequency characteristics.
    MeSH term(s) Algorithms ; Artifacts ; Cone-Beam Computed Tomography ; Image Processing, Computer-Assisted ; Phantoms, Imaging ; Scattering, Radiation ; X-Rays
    Language English
    Publishing date 2021-08-31
    Publishing country United States
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 622531-7
    ISSN 1558-254X ; 0278-0062
    ISSN (online) 1558-254X
    ISSN 0278-0062
    DOI 10.1109/TMI.2021.3074712
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  7. Article ; Online: Appearance Learning for Image-Based Motion Estimation in Tomography.

    Preuhs, Alexander / Manhart, Michael / Roser, Philipp / Hoppe, Elisabeth / Huang, Yixing / Psychogios, Marios / Kowarschik, Markus / Maier, Andreas

    IEEE transactions on medical imaging

    2020  Volume 39, Issue 11, Page(s) 3667–3678

    Abstract: In tomographic imaging, anatomical structures are reconstructed by applying a pseudo-inverse forward model to acquired signals. Geometric information within this process is usually depending on the system setting only, i.e., the scanner position or ... ...

    Abstract In tomographic imaging, anatomical structures are reconstructed by applying a pseudo-inverse forward model to acquired signals. Geometric information within this process is usually depending on the system setting only, i.e., the scanner position or readout direction. Patient motion therefore corrupts the geometry alignment in the reconstruction process resulting in motion artifacts. We propose an appearance learning approach recognizing the structures of rigid motion independently from the scanned object. To this end, we train a siamese triplet network to predict the reprojection error (RPE) for the complete acquisition as well as an approximate distribution of the RPE along the single views from the reconstructed volume in a multi-task learning approach. The RPE measures the motion-induced geometric deviations independent of the object based on virtual marker positions, which are available during training. We train our network using 27 patients and deploy a 21-4-2 split for training, validation and testing. In average, we achieve a residual mean RPE of 0.013mm with an inter-patient standard deviation of 0.022mm. This is twice the accuracy compared to previously published results. In a motion estimation benchmark the proposed approach achieves superior results in comparison with two state-of-the-art measures in nine out of twelve experiments. The clinical applicability of the proposed method is demonstrated on a motion-affected clinical dataset.
    MeSH term(s) Artifacts ; Humans ; Image Processing, Computer-Assisted ; Motion ; Tomography ; Tomography, X-Ray Computed
    Language English
    Publishing date 2020-10-28
    Publishing country United States
    Document type Journal Article
    ZDB-ID 622531-7
    ISSN 1558-254X ; 0278-0062
    ISSN (online) 1558-254X
    ISSN 0278-0062
    DOI 10.1109/TMI.2020.3002695
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  8. Article ; Online: XDose: toward online cross-validation of experimental and computational X-ray dose estimation.

    Roser, Philipp / Birkhold, Annette / Preuhs, Alexander / Ochs, Philipp / Stepina, Elizaveta / Strobel, Norbert / Kowarschik, Markus / Fahrig, Rebecca / Maier, Andreas

    International journal of computer assisted radiology and surgery

    2020  Volume 16, Issue 1, Page(s) 1–10

    Abstract: Purpose: As the spectrum of X-ray procedures has increased both for diagnostic and for interventional cases, more attention is paid to X-ray dose management. While the medical benefit to the patient outweighs the risk of radiation injuries in almost all ...

    Abstract Purpose: As the spectrum of X-ray procedures has increased both for diagnostic and for interventional cases, more attention is paid to X-ray dose management. While the medical benefit to the patient outweighs the risk of radiation injuries in almost all cases, reproducible studies on organ dose values help to plan preventive measures helping both patient as well as staff. Dose studies are either carried out retrospectively, experimentally using anthropomorphic phantoms, or computationally. When performed experimentally, it is helpful to combine them with simulations validating the measurements. In this paper, we show how such a dose simulation method, carried out together with actual X-ray experiments, can be realized to obtain reliable organ dose values efficiently.
    Methods: A Monte Carlo simulation technique was developed combining down-sampling and super-resolution techniques for accelerated processing accompanying X-ray dose measurements. The target volume is down-sampled using the statistical mode first. The estimated dose distribution is then up-sampled using guided filtering and the high-resolution target volume as guidance image. Second, we present a comparison of dose estimates calculated with our Monte Carlo code experimentally obtained values for an anthropomorphic phantom using metal oxide semiconductor field effect transistor dosimeters.
    Results: We reconstructed high-resolution dose distributions from coarse ones (down-sampling factor 2 to 16) with error rates ranging from 1.62 % to 4.91 %. Using down-sampled target volumes further reduced the computation time by 30 % to 60 %. Comparison of measured results to simulated dose values demonstrated high agreement with an average percentage error of under [Formula: see text] for all measurement points.
    Conclusions: Our results indicate that Monte Carlo methods can be accelerated hardware-independently and still yield reliable results. This facilitates empirical dose studies that make use of online Monte Carlo simulations to easily cross-validate dose estimates on-site.
    MeSH term(s) Computer Simulation ; Humans ; Monte Carlo Method ; Phantoms, Imaging ; Radiation Dosage ; Radiometry/methods ; Retrospective Studies ; X-Rays
    Language English
    Publishing date 2020-12-04
    Publishing country Germany
    Document type Journal Article
    ZDB-ID 2365628-1
    ISSN 1861-6429 ; 1861-6410
    ISSN (online) 1861-6429
    ISSN 1861-6410
    DOI 10.1007/s11548-020-02298-6
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  9. Book ; Online: Reconstruction of Voxels with Position- and Angle-Dependent Weightings

    Felsner, Lina / Würfl, Tobias / Syben, Christopher / Roser, Philipp / Preuhs, Alexander / Maier, Andreas / Riess, Christian

    2020  

    Abstract: The reconstruction problem of voxels with individual weightings can be modeled a position- and angle- dependent function in the forward-projection. This changes the system matrix and prohibits to use standard filtered backprojection. In this work we ... ...

    Abstract The reconstruction problem of voxels with individual weightings can be modeled a position- and angle- dependent function in the forward-projection. This changes the system matrix and prohibits to use standard filtered backprojection. In this work we first formulate this reconstruction problem in terms of a system matrix and weighting part. We compute the pseudoinverse and show that the solution is rank-deficient and hence very ill posed. This is a fundamental limitation for reconstruction. We then derive an iterative solution and experimentally show its uperiority to any closed-form solution.

    Comment: This paper was originally published at the 6th International Conference on Image Formation in X-Ray Computed Tomography (CTmeeting 2020)
    Keywords Computer Science - Computer Vision and Pattern Recognition
    Publishing date 2020-10-27
    Publishing country us
    Document type Book ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  10. Book ; Online: 2-D Respiration Navigation Framework for 3-D Continuous Cardiac Magnetic Resonance Imaging

    Hoppe, Elisabeth / Wetzl, Jens / Roser, Philipp / Felsner, Lina / Preuhs, Alexander / Maier, Andreas

    2020  

    Abstract: Continuous protocols for cardiac magnetic resonance imaging enable sampling of the cardiac anatomy simultaneously resolved into cardiac phases. To avoid respiration artifacts, associated motion during the scan has to be compensated for during ... ...

    Abstract Continuous protocols for cardiac magnetic resonance imaging enable sampling of the cardiac anatomy simultaneously resolved into cardiac phases. To avoid respiration artifacts, associated motion during the scan has to be compensated for during reconstruction. In this paper, we propose a sampling adaption to acquire 2-D respiration information during a continuous scan. Further, we develop a pipeline to extract the different respiration states from the acquired signals, which are used to reconstruct data from one respiration phase. Our results show the benefit of the proposed workflow on the image quality compared to no respiration compensation, as well as a previous 1-D respiration navigation approach.

    Comment: Accepted for Bildverarbeitung f\"ur die Medizin, 07.-09.03.2021
    Keywords Computer Science - Computer Vision and Pattern Recognition
    Publishing date 2020-12-26
    Publishing country us
    Document type Book ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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