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  1. Article: Clone temporal centrality measures for incomplete sequences of graph snapshots

    Foraita, Ronja / Hanke, Moritz

    BMC bioinformatics, 18: 261

    2017  

    Abstract: BACKGROUND: Different phenomena like the spread of a disease, social interactions or the biological relation between genes can be thought of as dynamic networks. These can be represented as a sequence of static graphs (so called graph snapshots). Based ... ...

    Institution Leibniz-Institut für Präventionsforschung und Epidemiologie
    Abstract BACKGROUND: Different phenomena like the spread of a disease, social interactions or the biological relation between genes can be thought of as dynamic networks. These can be represented as a sequence of static graphs (so called graph snapshots). Based on this graph sequences, classical vertex centrality measures like closeness and betweenness centrality have been extended to quantify the importance of single vertices within a dynamic network. An implicit assumption for the calculation of temporal centrality measures is that the graph sequence contains all information about the network dynamics over time. This assumption is unlikely to be justified in many real world applications due to limited access to fully observed network data. Incompletely observed graph sequences lack important information about duration or existence of edges and may result in biased temporal centrality values. RESULTS: To account for this incompleteness, we introduce the idea of extending original temporal centrality metrics by cloning graphs of an incomplete graph sequence. Focusing on temporal betweenness centrality as an example, we show for different simulated scenarios of incomplete graph sequences that our approach improves the accuracy of detecting important vertices in dynamic networks compared to the original methods. An age-related gene expression data set from the human brain illustrates the new measures. Additional results for the temporal closeness centrality based on cloned snapshots support our findings. We further introduce a new algorithm called REN to calculate temporal centrality measures. Its computational effort is linear in the number of snapshots and benefits from sparse or very dense dynamic networks. CONCLUSIONS: We suggest to use clone temporal centrality measures in incomplete graph sequences settings. Compared to approaches that do not compensate for incompleteness our approach will improve the detection rate of important vertices. The proposed REN algorithm allows to calculate (clone) temporal centrality measures even for long snapshot sequences.
    Keywords Centrality measures ; Closeness ; Betweenness ; Dynamic graphs ; Dynamic networks ; Shortest temporal path ; Time varying networks
    Language English
    Document type Article
    Database Repository for Life Sciences

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  2. Article ; Online: Variable selection in linear regression models: Choosing the best subset is not always the best choice.

    Hanke, Moritz / Dijkstra, Louis / Foraita, Ronja / Didelez, Vanessa

    Biometrical journal. Biometrische Zeitschrift

    2023  Volume 66, Issue 1, Page(s) e2200209

    Abstract: We consider the question of variable selection in linear regressions, in the sense of identifying the correct direct predictors (those variables that have nonzero coefficients given all candidate predictors). Best subset selection (BSS) is often ... ...

    Abstract We consider the question of variable selection in linear regressions, in the sense of identifying the correct direct predictors (those variables that have nonzero coefficients given all candidate predictors). Best subset selection (BSS) is often considered the "gold standard," with its use being restricted only by its NP-hard nature. Alternatives such as the least absolute shrinkage and selection operator (Lasso) or the Elastic net (Enet) have become methods of choice in high-dimensional settings. A recent proposal represents BSS as a mixed-integer optimization problem so that large problems have become computationally feasible. We present an extensive neutral comparison assessing the ability to select the correct direct predictors of BSS compared to forward stepwise selection (FSS), Lasso, and Enet. The simulation considers a range of settings that are challenging regarding dimensionality (number of observations and variables), signal-to-noise ratios, and correlations between predictors. As fair measure of performance, we primarily used the best possible F1-score for each method, and results were confirmed by alternative performance measures and practical criteria for choosing the tuning parameters and subset sizes. Surprisingly, it was only in settings where the signal-to-noise ratio was high and the variables were uncorrelated that BSS reliably outperformed the other methods, even in low-dimensional settings. Furthermore, FSS performed almost identically to BSS. Our results shed new light on the usual presumption of BSS being, in principle, the best choice for selecting the correct direct predictors. Especially for correlated variables, alternatives like Enet are faster and appear to perform better in practical settings.
    MeSH term(s) Linear Models ; Computer Simulation
    Language English
    Publishing date 2023-08-29
    Publishing country Germany
    Document type Journal Article
    ZDB-ID 131640-0
    ISSN 1521-4036 ; 0323-3847 ; 0006-3452
    ISSN (online) 1521-4036
    ISSN 0323-3847 ; 0006-3452
    DOI 10.1002/bimj.202200209
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  3. Conference proceedings: Joint damage detected by preoperative MR arthrography under leg traction improves prediction of failure at 2–5 years following arthroscopic FAI surgery

    Hanke, Markus / Nanavati, Andreas / Wagner, Moritz / Brunner, Alexander / Vavron, Peter / Lerch, Till / Steppacher, Simon / Tannast, Moritz / Schmaranzer, Ehrenfried / Schmaranzer, Florian

    2023  , Page(s) IN37–2311

    Event/congress Deutscher Kongress für Orthopädie und Unfallchirurgie (DKOU 2023); Berlin; ; Berufsverband für Orthopädie und Unfallchirurgie; 2023
    Keywords Medizin, Gesundheit ; hip ; FAI ; joint preserving surgery
    Publishing date 2023-10-23
    Publisher German Medical Science GMS Publishing House; Düsseldorf
    Document type Conference proceedings
    DOI 10.3205/23dkou699
    Database German Medical Science

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  4. Article ; Online: No robust online effects of transcranial direct current stimulation on corticospinal excitability.

    Pillen, Steven / Knodel, Nicole / Hermle, Dominik / Hanke, Moritz / Ziemann, Ulf / Bergmann, Til Ole

    Brain stimulation

    2022  Volume 15, Issue 5, Page(s) 1254–1268

    Abstract: Transcranial direct current stimulation (tDCS) has been used for over twenty years to modulate cortical (particularly motor corticospinal) excitability both during (online) and outlasting (offline) the stimulation, with the former effects associated to ... ...

    Abstract Transcranial direct current stimulation (tDCS) has been used for over twenty years to modulate cortical (particularly motor corticospinal) excitability both during (online) and outlasting (offline) the stimulation, with the former effects associated to the latter. However, tDCS effects are highly variable, partially because stimulation intensity is commonly not adjusted individually (in contrast to transcranial magnetic stimulation, TMS). In Experiment 1, we therefore explored an empirical approach of personalizing tDCS intensity for the primary motor cortex (M1) based on dose-response curves (DRCs), individually relating tDCS Intensity (in steps from 0.3 to 2.0 mA) and Polarity (anodal, cathodal) to the online modulation of concurrent TMS motor evoked potentials (MEP), assessing DRC reliability across two separate days. No robust DRCs could be observed, neither at the individual nor at the group level, with the only robust effect being a (paradoxical) MEP facilitation during cathodal tDCS at 2.0 mA, but no modulation at traditional intensities of or near 1 mA. In Experiment 2, we therefore attempted to replicate the classical bidirectional online MEP modulation during 1 mA tDCS that had been reported by several of the early seminal tDCS papers. We either closely recreated stimulation parameters and temporal protocol of these original studies (Experiment 2A) or slightly modernized them according to current standards (Experiment 2B). In neither experiment did we observed any significant online MEP modulation. We conclude that an empirical titration of individually effective tDCS intensities may not be feasible as online tDCS effects do not appear to be sufficiently robust.
    MeSH term(s) Evoked Potentials, Motor/physiology ; Motor Cortex/physiology ; Reproducibility of Results ; Transcranial Direct Current Stimulation/methods ; Transcranial Magnetic Stimulation/methods
    Language English
    Publishing date 2022-09-07
    Publishing country United States
    Document type Journal Article
    ZDB-ID 2394410-9
    ISSN 1876-4754 ; 1935-861X
    ISSN (online) 1876-4754
    ISSN 1935-861X
    DOI 10.1016/j.brs.2022.08.024
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  5. Article ; Online: Clone temporal centrality measures for incomplete sequences of graph snapshots.

    Hanke, Moritz / Foraita, Ronja

    BMC bioinformatics

    2017  Volume 18, Issue 1, Page(s) 261

    Abstract: Background: Different phenomena like the spread of a disease, social interactions or the biological relation between genes can be thought of as dynamic networks. These can be represented as a sequence of static graphs (so called graph snapshots). Based ... ...

    Abstract Background: Different phenomena like the spread of a disease, social interactions or the biological relation between genes can be thought of as dynamic networks. These can be represented as a sequence of static graphs (so called graph snapshots). Based on this graph sequences, classical vertex centrality measures like closeness and betweenness centrality have been extended to quantify the importance of single vertices within a dynamic network. An implicit assumption for the calculation of temporal centrality measures is that the graph sequence contains all information about the network dynamics over time. This assumption is unlikely to be justified in many real world applications due to limited access to fully observed network data. Incompletely observed graph sequences lack important information about duration or existence of edges and may result in biased temporal centrality values.
    Results: To account for this incompleteness, we introduce the idea of extending original temporal centrality metrics by cloning graphs of an incomplete graph sequence. Focusing on temporal betweenness centrality as an example, we show for different simulated scenarios of incomplete graph sequences that our approach improves the accuracy of detecting important vertices in dynamic networks compared to the original methods. An age-related gene expression data set from the human brain illustrates the new measures. Additional results for the temporal closeness centrality based on cloned snapshots support our findings. We further introduce a new algorithm called REN to calculate temporal centrality measures. Its computational effort is linear in the number of snapshots and benefits from sparse or very dense dynamic networks.
    Conclusions: We suggest to use clone temporal centrality measures in incomplete graph sequences settings. Compared to approaches that do not compensate for incompleteness our approach will improve the detection rate of important vertices. The proposed REN algorithm allows to calculate (clone) temporal centrality measures even for long snapshot sequences.
    MeSH term(s) Algorithms ; Brain/metabolism ; Humans ; Metabolic Networks and Pathways ; Protein Interaction Maps
    Language English
    Publishing date 2017-05-16
    Publishing country England
    Document type Journal Article
    ZDB-ID 2041484-5
    ISSN 1471-2105 ; 1471-2105
    ISSN (online) 1471-2105
    ISSN 1471-2105
    DOI 10.1186/s12859-017-1677-x
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  6. Article ; Online: Non-contrast-enhanced MR-angiography (MRA) of lower extremity peripheral arterial disease at 3 tesla: Examination time and diagnostic performance of 2D quiescent-interval single-shot MRA vs. 3D fast spin-Echo MRA.

    Knobloch, Gesine / Lauff, Marie-Teres / Hanke, Moritz / Schwenke, Carsten / Hamm, Bernd / Wagner, Moritz

    Magnetic resonance imaging

    2020  Volume 76, Page(s) 17–25

    Abstract: Purpose: Non-contrast enhanced MRA is a promising diagnostic alternative to contrast-enhanced (CE-) MRA or CT in patients with lower extremity peripheral arterial disease (PAD) but potentially associated with prolonged examination times and inferior ... ...

    Abstract Purpose: Non-contrast enhanced MRA is a promising diagnostic alternative to contrast-enhanced (CE-) MRA or CT in patients with lower extremity peripheral arterial disease (PAD) but potentially associated with prolonged examination times and inferior diagnostic performance. We aimed to compare examination times and diagnostic performance of non-contrast enhanced quiescent-interval slice-selective (QISS)-MRA and fast-spin-echo (FSE)-MRA at 3.0 T.
    Materials and methods: Forty-five patients with PAD were recruited for this IRB approved prospective study. Subjects underwent lower extremity MRA with 1) QISS-MRA, 2) FSE-MRA, and 3) CE-MRA (continuous table movement MRA and time-resolved MRA of the calf), which served as the standard of reference. Scan times for each examination step and total examination times for each of the three techniques was determined. Image quality and degree of stenosis were rated by two readers on a 5-point Likert scale. Sensitivity, specificity and diagnostic accuracy for relevant (>50%) stenosis were calculated.
    Results: Median total examination time was 27:02 min for QISS-MRA (IQR, 25:13-31:01 min), 28:37 min for FSE-MRA (IQR, 25:51-33:12 min), and 31:22 min for CE-MRA (IQR, 26:41-33:23 min). Acquisition time for QISS-MRA was significantly longer compared to FSE-MRA and CE-MRA (p ≤ 0.0001), while time for localizers, scouts and planning of the MRA sequence was significantly shorter for QISS-MRA compared to FSE-MRA and CE-MRA (p ≤ 0.0001). QISS-MRA had significantly better image quality compared to FSE-MRA with less segments classified as non-diagnostic (Reader 1: 3% vs. 35%; Reader 2: 3% vs. 50%, p ≤ 0.0001). Overall, QISS-MRA showed significantly better diagnostic performance than FSE-MRA (sensitivity, 85% vs. 54%; specificity, 90% vs. 47%, diagnostic accuracy, 89% vs. 48%; p ≤ 0.0001).
    Conclusion: Total examination time of QISS-MRA and FSE-MRA was comparable with a conventional CE-MRA protocol. QISS-MRA showed significantly higher diagnostic performance than FSE-MRA.
    MeSH term(s) Adult ; Aged ; Constriction, Pathologic/diagnostic imaging ; Female ; Humans ; Lower Extremity/blood supply ; Lower Extremity/diagnostic imaging ; Magnetic Resonance Angiography ; Male ; Middle Aged ; Peripheral Arterial Disease/diagnostic imaging ; Prospective Studies ; Reproducibility of Results ; Sensitivity and Specificity
    Language English
    Publishing date 2020-11-04
    Publishing country Netherlands
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 604885-7
    ISSN 1873-5894 ; 0730-725X
    ISSN (online) 1873-5894
    ISSN 0730-725X
    DOI 10.1016/j.mri.2020.10.016
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  7. Article ; Online: Clone temporal centrality measures for incomplete sequences of graph snapshots

    Moritz Hanke / Ronja Foraita

    BMC Bioinformatics, Vol 18, Iss 1, Pp 1-

    2017  Volume 18

    Abstract: Abstract Background Different phenomena like the spread of a disease, social interactions or the biological relation between genes can be thought of as dynamic networks. These can be represented as a sequence of static graphs (so called graph snapshots). ...

    Abstract Abstract Background Different phenomena like the spread of a disease, social interactions or the biological relation between genes can be thought of as dynamic networks. These can be represented as a sequence of static graphs (so called graph snapshots). Based on this graph sequences, classical vertex centrality measures like closeness and betweenness centrality have been extended to quantify the importance of single vertices within a dynamic network. An implicit assumption for the calculation of temporal centrality measures is that the graph sequence contains all information about the network dynamics over time. This assumption is unlikely to be justified in many real world applications due to limited access to fully observed network data. Incompletely observed graph sequences lack important information about duration or existence of edges and may result in biased temporal centrality values. Results To account for this incompleteness, we introduce the idea of extending original temporal centrality metrics by cloning graphs of an incomplete graph sequence. Focusing on temporal betweenness centrality as an example, we show for different simulated scenarios of incomplete graph sequences that our approach improves the accuracy of detecting important vertices in dynamic networks compared to the original methods. An age-related gene expression data set from the human brain illustrates the new measures. Additional results for the temporal closeness centrality based on cloned snapshots support our findings. We further introduce a new algorithm called REN to calculate temporal centrality measures. Its computational effort is linear in the number of snapshots and benefits from sparse or very dense dynamic networks. Conclusions We suggest to use clone temporal centrality measures in incomplete graph sequences settings. Compared to approaches that do not compensate for incompleteness our approach will improve the detection rate of important vertices. The proposed REN algorithm allows to calculate (clone) temporal ...
    Keywords Dynamic networks ; Dynamic graphs ; Betweenness ; Closeness ; Centrality measures ; Time varying networks ; Computer applications to medicine. Medical informatics ; R858-859.7 ; Biology (General) ; QH301-705.5
    Subject code 006
    Language English
    Publishing date 2017-05-01T00:00:00Z
    Publisher BMC
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  8. Article ; Online: Does the dGEMRIC Index Recover 3 Years After Surgical FAI Correction and an Initial dGEMRIC Decrease at 1-Year Follow-up? A Controlled Prospective Study.

    Meier, Malin Kristin / Scheuber, Samira / Hanke, Markus Simon / Haefeli, Pascal Cyrill / Ruckli, Adrian Cyrill / Liechti, Emanuel Francis / Gerber, Nicolas / Lerch, Till Dominic / Tannast, Moritz / Siebenrock, Klaus Arno / Steppacher, Simon Damian / Schmaranzer, Florian

    The American journal of sports medicine

    2023  Volume 51, Issue 7, Page(s) 1808–1817

    Abstract: Background: Delayed gadolinium-enhanced magnetic resonance imaging of cartilage (dGEMRIC) allows objective and noninvasive assessment of cartilage quality. An interim analysis 1 year after correction of femoroacetabular impingement (FAI) previously ... ...

    Abstract Background: Delayed gadolinium-enhanced magnetic resonance imaging of cartilage (dGEMRIC) allows objective and noninvasive assessment of cartilage quality. An interim analysis 1 year after correction of femoroacetabular impingement (FAI) previously showed that the dGEMRIC index decreased despite good clinical outcome.
    Purpose: To evaluate dGEMRIC indices longitudinally in patients who underwent FAI correction and in a control group undergoing nonoperative treatment for FAI.
    Study design: Cohort study; Level of evidence, 3.
    Methods: This prospective, comparative longitudinal study included 39 patients (40 hips) who received either operative (n = 20 hips) or nonoperative (n = 20 hips) treatment. Baseline demographic characteristics and presence of osseous deformities did not differ between groups. All patients received indirect magnetic resonance arthrography at 3 time points (baseline, 1 and 3 years of follow-up). The 3-dimensional cartilage models were created using a custom-developed deep learning-based software. The dGEMRIC indices were determined separately for acetabular and femoral cartilage. A mixed-effects model was used for statistical analysis in repeated measures.
    Results: The operative group showed an initial (preoperative to 1-year follow-up) decrease of dGEMRIC indices: acetabular from 512 ± 174 to 392 ± 123 ms and femoral from 530 ± 173 to 411 ± 117 ms (both
    Conclusion: This study showed that 3 years after FAI correction, the dGEMRIC indices improved compared with short-term 1-year follow-up. This may be due to normalized joint biomechanics or regressive postoperative activation of the inflammatory cascade after intra-articular surgery.
    MeSH term(s) Humans ; Femoracetabular Impingement/diagnostic imaging ; Femoracetabular Impingement/surgery ; Femoracetabular Impingement/pathology ; Prospective Studies ; Hip Joint/surgery ; Gadolinium ; Cohort Studies ; Longitudinal Studies ; Follow-Up Studies ; Contrast Media ; Cartilage, Articular/diagnostic imaging ; Cartilage, Articular/surgery ; Cartilage, Articular/pathology ; Magnetic Resonance Imaging/methods
    Chemical Substances Gadolinium (AU0V1LM3JT) ; Contrast Media
    Language English
    Publishing date 2023-05-15
    Publishing country United States
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 197482-8
    ISSN 1552-3365 ; 0363-5465
    ISSN (online) 1552-3365
    ISSN 0363-5465
    DOI 10.1177/03635465231167854
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  9. Article ; Online: Improved Cartilage Quality on Delayed Gadolinium-Enhanced MRI of Hip Cartilage after Subchondral Drilling of Acetabular Cartilage Flaps in Femoroacetabular Impingement Surgery at Minimum 5-Year Follow-Up.

    Schmaranzer, Florian / Haefeli, Pascal C / Liechti, Emanuel F / Hanke, Markus S / Tannast, Moritz / Büchler, Lorenz

    Cartilage

    2020  Volume 13, Issue 1_suppl, Page(s) 617S–629S

    Abstract: Objective: To assess whether subchondral drilling of acetabular cartilage flaps during femoroacetabular impingement (FAI) surgery improves (1) acetabular dGEMRIC indices and (2) morphologic magnetic resonance imaging (MRI) scores, compared with hips in ... ...

    Abstract Objective: To assess whether subchondral drilling of acetabular cartilage flaps during femoroacetabular impingement (FAI) surgery improves (1) acetabular dGEMRIC indices and (2) morphologic magnetic resonance imaging (MRI) scores, compared with hips in which no additional treatment of cartilage lesions had been performed; and (3) whether global dGEMRIC indices and MRI scores correlate.
    Design: Prospective cohort study of consecutive patients with symptomatic FAI treated with open surgery between 2000 and 2007. Patients with subchondral drilling of acetabular cartilage flaps were allocated to the study group, those without drilling to the control group. All patients underwent indirect 3-T MR arthrography to assess cartilage quality by dGEMRIC indices and a semiquantitative morphologic MRI score at minimum 5 years after surgery. dGEMRIC indices and morphologic MRI scores were compared between and among groups using analysis of covariance/paired
    Results: No significant difference was found between the global dGEMRIC indices of the study group (449 ± 147 ms, 95% CI 432-466 ms) and the control group (428 ± 143 ms, 95% CI 416-442 ms;
    Conclusions: Treatment of acetabular cartilage flaps with subchondral drilling leads to better cartilage quality in regions with cartilage flaps at minimum 5 years of follow-up.
    MeSH term(s) Arthroplasty, Subchondral ; Cartilage, Articular/diagnostic imaging ; Cartilage, Articular/pathology ; Cartilage, Articular/surgery ; Femoracetabular Impingement/diagnostic imaging ; Femoracetabular Impingement/pathology ; Femoracetabular Impingement/surgery ; Follow-Up Studies ; Gadolinium ; Hip Joint/diagnostic imaging ; Hip Joint/pathology ; Hip Joint/surgery ; Humans ; Magnetic Resonance Imaging/methods ; Prospective Studies
    Chemical Substances Gadolinium (AU0V1LM3JT)
    Language English
    Publishing date 2020-07-19
    Publishing country United States
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 2515870-3
    ISSN 1947-6043 ; 1947-6035
    ISSN (online) 1947-6043
    ISSN 1947-6035
    DOI 10.1177/1947603520941241
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  10. Conference proceedings: Proximal Femoral Osteotomy to increase Femoral Version for patients with Femoral Retrotorsion and FAI are safe and show good short term results

    Lerch, Till / Hanke, Markus / Boschung, Adam / Steppacher, Simon / Siebenrock, Klaus / Tannast, Moritz

    2021  , Page(s) AB69–39

    Event/congress Deutscher Kongress für Orthopädie und Unfallchirurgie (DKOU 2021); Berlin; ; Berufsverband für Orthopädie und Unfallchirurgie; 2021
    Keywords Medizin, Gesundheit ; Rotational femoral osteotomies ; FAI ; Femoroacetabular Impingement ; Femoral version ; femoral torsion ; femoral torsional deformities
    Publishing date 2021-10-26
    Publisher German Medical Science GMS Publishing House; Düsseldorf
    Document type Conference proceedings
    DOI 10.3205/21dkou425
    Database German Medical Science

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