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Artikel ; Online: Reference-free Bayesian model for pointing errors of typein neurosurgical planning.

Baxter, John S H / Croci, Stéphane / Delmas, Antoine / Bredoux, Luc / Lefaucheur, Jean-Pascal / Jannin, Pierre

International journal of computer assisted radiology and surgery

2023 Band 18, Heft 7, Seite(n) 1269–1277

Abstract: Purpose: Many neurosurgical planning tasks rely on identifying points of interest in volumetric images. Often, these points require significant expertise to identify correctly as, in some cases, they are not visible but instead inferred by the clinician. ...

Abstract	Purpose: Many neurosurgical planning tasks rely on identifying points of interest in volumetric images. Often, these points require significant expertise to identify correctly as, in some cases, they are not visible but instead inferred by the clinician. This leads to a high degree of variability between annotators selecting these points. In particular, errors of type are when the experts fundamentally select different points rather than the same point with some inaccuracy. This complicates research as their mean may not reflect any of the experts' intentions nor the ground truth. Methods: We present a regularised Bayesian model for measuring errors of type in pointing tasks. This model is reference-free; in that it does not require a priori knowledge of the ground truth point but instead works on the basis of the level of consensus between multiple annotators. We apply this model to simulated data and clinical data from transcranial magnetic stimulation for chronic pain. Results: Our model estimates the probabilities of selecting the correct point in the range of 82.6[Formula: see text]88.6% with uncertainties in the range of 2.8[Formula: see text]4.0%. This agrees with the literature where ground truth points are known. The uncertainty has not previously been explored in the literature and gives an indication of the dataset's strength. Conclusions: Our reference-free Bayesian framework easily models errors of type in pointing tasks. It allows for clinical studies to be performed with a limited number of annotators where the ground truth is not immediately known, which can be applied widely for better understanding human errors in neurosurgical planning.
Mesh-Begriff(e)	Humans ; Bayes Theorem ; Probability ; Uncertainty
Sprache	Englisch
Erscheinungsdatum	2023-05-30
Erscheinungsland	Germany
Dokumenttyp	Journal Article
ZDB-ID	2365628-1
ISSN	1861-6429 ; 1861-6410
ISSN (online)	1861-6429
ISSN	1861-6410
DOI	10.1007/s11548-023-02943-w
Datenquelle	MEDical Literature Analysis and Retrieval System OnLINE

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Artikel ; Online: Targeting Lower Limb, Upper Limb, and Face Representation in the Primary Motor Cortex for the Practice of Neuronavigated Transcranial Magnetic Stimulation.

Lefaucheur, Jean-Pascal / Nguyen, Jean-Paul / Delmas, Antoine / Croci, Stéphane / Bredoux, Luc / Hodaj, Hasan

Neuromodulation : journal of the International Neuromodulation Society

2023 Band 27, Heft 3, Seite(n) 572–583

Abstract: Objective: The primary motor cortex (M1) is a usual target for therapeutic application of repetitive transcranial magnetic stimulation (rTMS), especially the region of hand motor representation. However, other M1 regions can be considered as potential ... ...

Abstract	Objective: The primary motor cortex (M1) is a usual target for therapeutic application of repetitive transcranial magnetic stimulation (rTMS), especially the region of hand motor representation. However, other M1 regions can be considered as potential rTMS targets, such as the region of lower limb or face representation. In this study, we assessed the localization of all these regions on magnetic resonance imaging (MRI) with the aim of defining three standardized M1 targets for the practice of neuronavigated rTMS. Materials and methods: A pointing task of these targets was performed by three rTMS experts on 44 healthy brain MRI data to assess interrater reliability (including the calculation of intraclass correlation coefficients [ICCs] and coefficients of variation [CoVs] and the construction of Bland-Altman plots). In addition, two "standard" brain MRI data were randomly interspersed with the other MRI data to assess intrarater reliability. A barycenter was calculated for each target (with x-y-z coordinates provided in normalized brain coordinate systems), in addition to the geodesic distance between the scalp projection of the barycenters of these different targets. Results: Intrarater and interrater agreement was good, according to ICCs, CoVs, or Bland-Altman plots, although interrater variability was greater for anteroposterior (y) and craniocaudal (z) coordinates, especially for the face target. The scalp projection of the barycenters between the different cortical targets ranged from 32.4 to 35.5 mm for either the lower-limb-to-upper-limb target distance or the upper-limb-to-face target distance. Conclusions: This work clearly delineates three different targets for the application of motor cortex rTMS that correspond to lower limb, upper limb, and face motor representations. These three targets are sufficiently spaced to consider that their stimulation can act on distinct neural networks.
Mesh-Begriff(e)	Humans ; Motor Cortex/diagnostic imaging ; Transcranial Magnetic Stimulation/methods ; Reproducibility of Results ; Hand ; Lower Extremity/diagnostic imaging
Sprache	Englisch
Erscheinungsdatum	2023-05-22
Erscheinungsland	United States
Dokumenttyp	Journal Article
ZDB-ID	1500372-3
ISSN	1525-1403 ; 1094-7159
ISSN (online)	1525-1403
ISSN	1094-7159
DOI	10.1016/j.neurom.2023.04.470
Datenquelle	MEDical Literature Analysis and Retrieval System OnLINE

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Artikel ; Online: Automatic cortical target point localisation in MRI for transcranial magnetic stimulation via a multi-resolution convolutional neural network.

Baxter, John S H / Bui, Quoc Anh / Maguet, Ehouarn / Croci, Stéphane / Delmas, Antoine / Lefaucheur, Jean-Pascal / Bredoux, Luc / Jannin, Pierre

International journal of computer assisted radiology and surgery

2021 Band 16, Heft 7, Seite(n) 1077–1087

Abstract: Purpose: Transcranial magnetic stimulation (TMS) is a growing therapy for a variety of psychiatric and neurological disorders that arise from or are modulated by cortical regions of the brain represented by singular 3D target points. These target points ...

Abstract	Purpose: Transcranial magnetic stimulation (TMS) is a growing therapy for a variety of psychiatric and neurological disorders that arise from or are modulated by cortical regions of the brain represented by singular 3D target points. These target points are often determined manually with assistance from a pre-operative T1-weighted MRI, although there is growing interest in automatic target point localisation using an atlas. However, both approaches can be time-consuming which has an effect on the clinical workflow, and the latter does not take into account patient variability such as the varying number of cortical gyri where these targets are located. Methods: This paper proposes a multi-resolution convolutional neural network for point localisation in MR images for a priori defined points in increasingly finely resolved versions of the input image. This approach is both fast and highly memory efficient, allowing it to run in high-throughput centres, and has the capability of distinguishing between patients with high levels of anatomical variability. Results: Preliminary experiments have found the accuracy of this network to be [Formula: see text] mm, compared to [Formula: see text] mm for deformable registration and [Formula: see text] mm for a human expert. For most treatment points, the human expert and proposed CNN statistically significantly outperform registration, but neither statistically significantly outperforms the other, suggesting that the proposed network has human-level performance. Conclusions: The human-level performance of this network indicates that it can improve TMS planning by automatically localising target points in seconds, avoiding more time-consuming registration or manual point localisation processes. This is particularly beneficial for out-of-hospital centres with limited computational resources where TMS is increasingly being administered.
Mesh-Begriff(e)	Brain/diagnostic imaging ; Humans ; Image Processing, Computer-Assisted/methods ; Magnetic Resonance Imaging/methods ; Nervous System Diseases/diagnosis ; Nervous System Diseases/therapy ; Neural Networks, Computer ; Reproducibility of Results ; Transcranial Magnetic Stimulation/methods
Sprache	Englisch
Erscheinungsdatum	2021-06-05
Erscheinungsland	Germany
Dokumenttyp	Comparative Study ; Journal Article
ZDB-ID	2365628-1
ISSN	1861-6429 ; 1861-6410
ISSN (online)	1861-6429
ISSN	1861-6410
DOI	10.1007/s11548-021-02386-1
Datenquelle	MEDical Literature Analysis and Retrieval System OnLINE

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Artikel ; Online: MRI 'EXPOSIMETRY': HOW TO ANALYZE, COMPARE AND REPRESENT WORKER EXPOSURE TO STATIC MAGNETIC FIELD?

Delmas, Antoine / Weber, Nicolas / Piffre, Joris / Pasquier, Cédric / Felblinger, Jacques / Vuissoz, Pierre-André

Radiation protection dosimetry

2017 Band 177, Heft 4, Seite(n) 415–423

Abstract: Worker exposure to electromagnetic fields (EMF) is a growing concern of international commissions. A European directive from 2013 (2013/35/EU) recommend to estimate or measure EMF exposure of all exposed workers. Magnetic resonance imaging (MRI) workers ... ...

Abstract	Worker exposure to electromagnetic fields (EMF) is a growing concern of international commissions. A European directive from 2013 (2013/35/EU) recommend to estimate or measure EMF exposure of all exposed workers. Magnetic resonance imaging (MRI) workers are specially concerned by this point because they work all day long in the vicinity of a very strong magnet (generally 1.5 or 3 T), which cannot be turned off. Setting up a magnetic field monitoring device on these workers would therefore be a good way to ensure their security. European directive threshold adequacy could then be verified. But this verification does not ensure a complete analysis of the worker exposure. Such an analysis based on quality control charts and exposure time's metrics has been described in this paper. The proposed magnetic field exposure analysis has additionally been tested on a long-term exposure follow-up of 18 MRI workers during 2 months.
Mesh-Begriff(e)	Electromagnetic Fields ; Europe ; Humans ; Magnetic Resonance Imaging/instrumentation ; Occupational Exposure/analysis ; Radiation Monitoring/methods ; Radiation Protection/methods
Sprache	Englisch
Erscheinungsdatum	2017-12-01
Erscheinungsland	England
Dokumenttyp	Journal Article
ZDB-ID	225912-6
ISSN	1742-3406 ; 0144-8420
ISSN (online)	1742-3406
ISSN	0144-8420
DOI	10.1093/rpd/ncx060
Datenquelle	MEDical Literature Analysis and Retrieval System OnLINE

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Artikel ; Online: Evaluation of occupational exposure to static magnetic field in MRI sites based on body pose estimation and SMF analytical computation.

Belguerras, Lamia / Kadkhodamohammadi, A Rahim / Delmas, Antoine / Miralipoor, Meysam / Weber, Nicolas / Gangi, Afshin / Felblinger, Jacques / Padoy, Nicolas / Pasquier, Cédric

Bioelectromagnetics

2018 Band 39, Heft 7, Seite(n) 503–515

Abstract: This paper tackles the problem of estimating exposure to static magnetic field (SMF) in magnetic resonance imaging (MRI) sites using a non-invasive approach. The proposed approach relies on a vision-based system to detect people's body parts and on a ... ...

Abstract	This paper tackles the problem of estimating exposure to static magnetic field (SMF) in magnetic resonance imaging (MRI) sites using a non-invasive approach. The proposed approach relies on a vision-based system to detect people's body parts and on a mathematical model to compute SMF exposure. A multi-view camera system was used to capture the MRI room, and a vision-based system was applied to detect body parts. The detected localization was then fed into a mathematical model to compute SMF exposure. In this study, we focused on exposure at the neck due to two main reasons. First, according to regulations, the limit of exposure at head and trunk for MR workers is higher than that for the general public. Second, it was easier to attach a dosimeter at the neck to perform measurements, which allowed a quantitative evaluation of our approach. This approach was applied to two scenarios simulating the daily movements of medical workers for which dosimeter measurements were also recorded. The results indicated that the proposed approach predicted occupational SMF exposure with reasonable accuracy compared with the dosimeter measurements. The proposed approach is a simple safe working procedure to estimate the exposure of MR workers at different parts of the body without wearing any marker detection. It can be applied to reduce occupational SMF exposure, without changes in workers' performances. For that reason, our non-invasive proposed method can be used as a simple safety tool to estimate occupational SMF exposure in MR sites. Bioelectromagnetics. 39:503-515, 2018.© 2018 Wiley Periodicals, Inc.
Mesh-Begriff(e)	Algorithms ; Humans ; Magnetic Fields ; Magnetic Resonance Imaging/instrumentation ; Movement ; Occupational Exposure/analysis ; Posture
Sprache	Englisch
Erscheinungsdatum	2018-10-11
Erscheinungsland	United States
Dokumenttyp	Journal Article
ZDB-ID	760683-7
ISSN	1521-186X ; 0197-8462
ISSN (online)	1521-186X
ISSN	0197-8462
DOI	10.1002/bem.22145
Datenquelle	MEDical Literature Analysis and Retrieval System OnLINE

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Artikel ; Online: Calibration and non-orthogonality correction of three-axis Hall sensors for the monitoring of MRI workers' exposure to static magnetic fields.

Delmas, Antoine / Belguerras, Lamia / Weber, Nicolas / Odille, Freddy / Pasquier, Cédric / Felblinger, Jacques / Vuissoz, Pierre-André

Bioelectromagnetics

2018 Band 39, Heft 2, Seite(n) 108–119

Abstract: A Magnetic Resonance Imaging (MRI) scanner uses three different electromagnetic fields (EMF) to produce body images: a static permanent magnetic field (MF), several pulsed magnetic gradients, and a radiofrequency pulse. As a result, any occupation that ... ...

Abstract	A Magnetic Resonance Imaging (MRI) scanner uses three different electromagnetic fields (EMF) to produce body images: a static permanent magnetic field (MF), several pulsed magnetic gradients, and a radiofrequency pulse. As a result, any occupation that includes an MRI exposes workers to a strong MF. The World Health Organization has now given the monitoring of occupational EMF exposure a high priority. One design for a low-cost, compact MF exposure monitor (« MR exposimeter ») uses a set of three orthogonally assembled Hall sensors. However, at such a strong EMF exposure intensity, the non-linearity and non-orthogonality (misalignment between the three Hall sensors) have an impact on the accuracy of EMF measurement. Therefore, a sensor characterization was performed in order to link Hall-effect output voltage to MF intensity. The sensor was then calibrated using an orthogonalization matrix and an offset vector. For each sensor configuration, the matrix and vector parameters were optimized with a calibration set generated by the movement of a three-axis sensor inside homogeneous MF areas. Once calibrated, the sensor was tested at different MF intensities and returned accuracy improvements. This calibration procedure was tested on synthetic data and performed on experimental data. The calibration parameters can be easily reused by the user, and their stability could be used as a quality control sensor. Finally, real-time monitoring test for static MF exposure was completed and validated on an MRI worker during a typical working day. Bioelectromagnetics. 39:108-119, 2018. © 2018 Wiley Periodicals, Inc.
Mesh-Begriff(e)	Calibration ; Humans ; Magnetic Fields/adverse effects ; Magnetic Resonance Imaging/adverse effects ; Occupational Exposure/analysis
Sprache	Englisch
Erscheinungsdatum	2018-02
Erscheinungsland	United States
Dokumenttyp	Journal Article
ZDB-ID	760683-7
ISSN	1521-186X ; 0197-8462
ISSN (online)	1521-186X
ISSN	0197-8462
DOI	10.1002/bem.22102
Datenquelle	MEDical Literature Analysis and Retrieval System OnLINE

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Artikel ; Online: Design and Validation of a Novel MR-Compatible Sensor for Respiratory Motion Modeling and Correction.

Chen, Bailiang / Weber, Nicolas / Odille, Freddy / Large-Dessale, Claire / Delmas, Antoine / Bonnemains, Laurent / Felblinger, Jacques

IEEE transactions on bio-medical engineering

2017 Band 64, Heft 1, Seite(n) 123–133

Abstract: Goal: A novel magnetic resonance (MR) compatible accelerometer for respiratory motion sensing (MARMOT) is developed as a surrogate of the vendors' pneumatic belts. We aim to model and correct respiratory motion for free-breathing thoracic-abdominal MR ... ...

Abstract	Goal: A novel magnetic resonance (MR) compatible accelerometer for respiratory motion sensing (MARMOT) is developed as a surrogate of the vendors' pneumatic belts. We aim to model and correct respiratory motion for free-breathing thoracic-abdominal MR imaging and to simplify patient installation. Methods: MR compatibility of MARMOT sensors was assessed in phantoms and its motion modeling/correction efficacy was demonstrated on 21 subjects at 3 T. Respiration was modeled and predicted from MARMOT sensors and pneumatic belts, based on real-time images and a regression method. The sensor accuracy was validated by comparing motion errors in the liver/kidney. Sensor data were also exploited as inputs for motion-compensated reconstruction of free-breathing cardiac cine MR images. Multiple and single sensor placement strategies were compared. Results: The new sensor is compatible with the MR environment. The average motion modeling and prediction errors with MARMOT sensors and with pneumatic belts were comparable (liver and kidney) and were below 2 mm with all tested configurations (belts, multiple/single MARMOT sensor). Motion corrected cardiac cine images were of improved image quality, as assessed by an entropy metric (p < 10 Conclusion: The proposed sensor can model and predict respiratory motion with sufficient accuracy to allow free-breathing MR imaging strategy. Significance: It provides an alternative sensor solution for the respiratory motion problem during MR imaging and may improve the convenience of patient setup.
Mesh-Begriff(e)	Accelerometry/instrumentation ; Artifacts ; Computer Simulation ; Computer-Aided Design ; Equipment Design ; Equipment Failure Analysis ; Humans ; Image Enhancement/instrumentation ; Magnetic Resonance Imaging/instrumentation ; Models, Biological ; Reproducibility of Results ; Respiratory Mechanics/physiology ; Respiratory-Gated Imaging Techniques/instrumentation ; Respiratory-Gated Imaging Techniques/methods ; Sensitivity and Specificity ; Transducers
Sprache	Englisch
Erscheinungsdatum	2017-01
Erscheinungsland	United States
Dokumenttyp	Evaluation Studies ; Journal Article ; Validation Studies
ZDB-ID	160429-6
ISSN	1558-2531 ; 0018-9294
ISSN (online)	1558-2531
ISSN	0018-9294
DOI	10.1109/TBME.2016.2549272
Datenquelle	MEDical Literature Analysis and Retrieval System OnLINE

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