References of "Pierard, Sébastien"
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See detailDefining a score based on gait analysis for the longitudinal follow-up of MS patients
Azrour, Samir ULg; Pierard, Sébastien ULg; Van Droogenbroeck, Marc ULg

in Multiple Sclerosis Journal (2015, October 09), 23(S11), 408-409

BACKGROUND. The project GAIMS [ECTRIMS 2013 P800] aims at developing a gait measuring system particularily suited for the clinical routine, and providing a reference database with the gait characteristics ... [more ▼]

BACKGROUND. The project GAIMS [ECTRIMS 2013 P800] aims at developing a gait measuring system particularily suited for the clinical routine, and providing a reference database with the gait characteristics of many MS patients (MSP) and healthy people (HP). As the gait impairments are related to the disease progression, defining an objective and quantitative score based on the gait characteristics would be useful for the longitudinal follow-up. Based on the dataset of GAIMS and machine learning techniques (MLT), a score, well correlated with the EDSS, can be defined [Azrour et al. ESANN 2014]. OBJECTIVE. Burggraaff et al. [ECTRIMS 2014 P033] showed that paired comparisons can help human raters to better judge the state of the patients. In the same spirit, we aim at predicting the difference of EDSS between two persons or between two visits of a same person, based on clinical gait measures. We show that the pairwise comparison strategy leads to a score (Gait-Score) well correlated with the EDSS and sensitive to small modifications of the gait. METHODS. The gait of 162 HP and 72 MSP (44 with EDSS>3) has been recorded and analyzed with GAIMS. The Gait-Score is defined using the MLT of [Geurts et al. 2006]. We can compute the Gait-Score of a person by comparing him to others with known EDSS, and compute the difference of Gait-Score of a same person at two different moments. We measure the merits of the Gait-Score by the correlation between the predicted Gait-Score and the EDSS, as well as the ability to detect subtle gait deteriorations among people with ataxia induced by a low dose of alcohol (data of [Piérard et al. ESANN 2014]). RESULTS. The Gait-Score is well correlated with the EDSS (Pearson’s correlation=0.8743). Moreover, it manages to detect a gait deterioration after a small alcohol intake for 19 persons out of 24 (79% correct) which is much better than what was obtained by visual inspection of neurologists (62% according to [Piérard et al. ESANN 2014]). CONCLUSIONS. Based on the accurate gait measures provided by GAIMS, we are able to derive a Gait-Score, automatically, that is well correlated with the EDSS. Moreover, this score is able to detect subtle deteriorations of the gait caused by a low dose of alcohol. These results reinforce our conviction that the use of an automatic method based on gait analysis is very promising for the longitudinal follow-up of MS patients and the assessment of the impact of new drugs and rehabilitation programs. [less ▲]

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See detailUnderstanding how people with MS get tired while walking
Pierard, Sébastien ULg; Phan-Ba, Rémy; Van Droogenbroeck, Marc ULg

in Multiple Sclerosis Journal (2015, October 09), 23(S11), 406

BACKGROUND. Walking impairment is frequent, appears early in the disease course of MS patients (MSP), and is perceived as the most disabling symptom. When walking, patients get tired more and differently ... [more ▼]

BACKGROUND. Walking impairment is frequent, appears early in the disease course of MS patients (MSP), and is perceived as the most disabling symptom. When walking, patients get tired more and differently than healthy people (HP) [Phan-Ba et al PLOS 2012]. This limits their walking perimeter. Understanding this phenomenon is thus important to suggest adequate therapies at the right time. OBJECTIVE. Our aim is to understand how MSP get tired while walking compared to HP. Two groups of MSP are considered: those with a low disability level (MSPL) and those with a high one (MSPH). We consider two criteria to measure the disability: the EDSS and the deceleration index (DI) [Phan-Ba et al PLOS 2012]. The limit between the groups is set at DI=0.8 and EDSS=3 (inclusive for MSPL). METHODS. Many gait characteristics (GC) have been measured with the system GAIMS along a 500m path walked as fast as possible. The dataset gathers 464 visits of HP and 70 of MSP. Some people have been assessed several times. There are 33 visits in the group MSPL with the EDSS criterion, and 25 with the DI criterion. Statistical tests (Welch) were performed on the differences and relative differences of the GC measured during the first and last 100m of the test to detect differences between HP and MSPL, and between MSPL and MSPH, as in [ECTRIMS 2012 P755]. RESULTS. Both criteria for defining the groups lead to similar conclusions. For many GC, the distributions of the variations are significantly different between MSPL and MSPH. The largest difference is for the relative difference of speed (p=0.000119 for EDSS and p=0.000021 for DI). In contrast, only the variation of the average lateral distance between the feet, which is related to the size of the base of support (and thus to the balance) shows a very significant difference between HP and MSPL (p=0.000116 for EDSS and p=0.000120 for DI). The balance does not seem to change much from MSPL to MSPH. Besides, we note that the variance decreases slightly from HP to MSPL and increases a lot from MSPL to MSPH. CONCLUSIONS. Statistically, from the motor fatigue point of view, it seems that the course of the MS disease is divided in two different stages. In the first one, MSP get more tired than HP because of a deterioration of the balance. Then, in the second one, their fatigue becomes related to a faster decrease of the walking speed. This suggests that physical therapy exercises focused on the balance could be given to MSP in the early stage of the disease. [less ▲]

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See detailA perfect estimation of a background image does not lead to a perfect background subtraction: analysis of the upper bound on the performance
Pierard, Sébastien ULg; Van Droogenbroeck, Marc ULg

in International Conference on Image Analysis and Processing (ICIAP) (2015, September)

The quest for the “best” background subtraction technique is ongoing. Despite that a considerable effort has been undertaken to develop flexible and efficient methods, some elementary questions are still ... [more ▼]

The quest for the “best” background subtraction technique is ongoing. Despite that a considerable effort has been undertaken to develop flexible and efficient methods, some elementary questions are still unanswered. One of them is the existence of an intrinsic upper bound to the performance. In fact, data are affected by noise, and therefore it is illusory to believe that it is possible to achieve a perfect segmentation. This paper aims at exploring some intrinsic limitations of the principle of background subtraction. The purpose consists in studying the impact of several limiting factors separately. One of our conclusions is that even if an algorithm would be able to calculate a perfect background image, it is not sufficient to achieve a perfect segmentation with background subtraction, due to other intrinsic limitations. [less ▲]

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See detailNonlinear Background Filter to Improve Pedestrian Detection
Wang, Yi; Pierard, Sébastien ULg; Su, Song-Zhi et al

in New Trends in Image Analysis and Processing - ICIAP 2015 Workshops (2015, September)

In this paper, we propose a simple nonlinear filter which improves the detection of pedestrians walking in a video. We do so by first cumulating temporal gradient of moving objects into a motion history ... [more ▼]

In this paper, we propose a simple nonlinear filter which improves the detection of pedestrians walking in a video. We do so by first cumulating temporal gradient of moving objects into a motion history image (MHI). Then we apply to each frame of the video a motion-guided nonlinear filter whose goal is to smudge out background details while leaving untouched foreground moving objects. The resulting blurry-background image is then fed to a pedestrian detector. Experiments reveal that for a given miss rate, our motion-guided nonlinear filter can decrease the number of false positives per image (FPPI) by a factor of up to 26. Our method is simple, computationally light, and can be applied on a variety of videos to improve the performances of almost any kind of pedestrian detectors. [less ▲]

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See detailSimple Median-Based Method for Stationary Background Generation Using Background Subtraction Algorithms
Laugraud, Benjamin ULg; Pierard, Sébastien ULg; Braham, Marc ULg et al

in New Trends in Image Analysis and Processing - ICIAP 2015 Workshops (2015, September)

The estimation of the background image from a video sequence is necessary in some applications. Computing the median for each pixel over time is effective, but it fails when the background is visible for ... [more ▼]

The estimation of the background image from a video sequence is necessary in some applications. Computing the median for each pixel over time is effective, but it fails when the background is visible for less than half of the time. In this paper, we propose a new method leveraging the segmentation performed by a background subtraction algorithm, which reduces the set of color candidates, for each pixel, before the median is applied. Our method is simple and fully generic as any background subtraction algorithm can be used. While recent background subtraction algorithms are excellent in detecting moving objects, our experiments show that the frame difference algorithm is a technique that compare advantageously to more advanced ones. Finally, we present the background images obtained on the SBI dataset, which appear to be almost perfect. The source code of our method can be downloaded at http://www.ulg.ac.be/telecom/research/sbg . [less ▲]

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See detailGAIMS: a tool specifically developed for the clinical gait analysis of patients with multiple sclerosis
Pierard, Sébastien ULg; Phan-Ba, Rémy; Giet, Amaury et al

in Multiple Sclerosis Journal (2015, April), 21(4), 498-499

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See detailIndividual variation of gait characteristics along a 500 meter walk in people with multiple sclerosis and healthy volunteers
Phan-Ba, Rémy; Pierard, Sébastien ULg; Giet, Amaury et al

in Multiple Sclerosis Journal (2015, April), 21(4), 532-533

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See detail3D human motion analysis based on ultra-low resolution sensors
Pierard, Sébastien ULg

Scientific conference (2015, February 27)

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See detailRegarder dans une boule de cristal et dépister des sujets à risque pour le mélanome cutané
Pierard, Gérald ULg; Franchimont, Claudine ULg; Hermanns-Lê, Trinh ULg et al

in Revue Médicale de Liège (2015), 70

Cutaneous melanoma is the deadliest skin cancer showing an increasingly growing incidence in white populations of Europe and United States. Intensive research in recent years has begun to unlock its ... [more ▼]

Cutaneous melanoma is the deadliest skin cancer showing an increasingly growing incidence in white populations of Europe and United States. Intensive research in recent years has begun to unlock its molecular pathogenesis. Screening the neoplasm at an early stage remains primordial. Hence, targeting populations at risk is likely efficient. In such an attempt, the regular clinical examination benefits from a series of non invasive procedures such as skin surface biopsies, in vivo confocal microscopy, dermoscopy and specular fluorescent light reflectance. [less ▲]

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See detailComment j'explore ... le "cheetah-look". Regard sur la peau sous des longueurs d'ondes particulieres de la lumiere.
Pierard-Franchimont, Claudine ULg; Hermanns-Lê, Trinh ULg; Pierard, Gérald ULg et al

in Revue medicale de Liege (2015), 70(4), 204-6

The melanotic facial pigmentation of each individual is frequently heterogeneous, even when this condition remains imperceptible under natural ambient light. However, with aging, this aspect may appear to ... [more ▼]

The melanotic facial pigmentation of each individual is frequently heterogeneous, even when this condition remains imperceptible under natural ambient light. However, with aging, this aspect may appear to everybody. The melanin heterochromia has various origins including ethnicity, the hormonal impact, the influence of various inflammatory, toxic and drug-induced disorders, as well as the impact of photoaging. The cheetah-look aspect is thus established and well identified under ultraviolet light or using an ingenious trick selecting some wavelengths of visible light. [less ▲]

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See detailThe marauder's map or the use of non-intrusive range laser scanners in the context of smart rooms
Pierard, Sébastien ULg

Scientific conference (2014, October 24)

Dans cette présentation, je vais expliquer comment des capteurs laser peuvent être utilisés pour réaliser différentes fonctionnalités importantes pour les environnements intelligents. Je montrerai comment ... [more ▼]

Dans cette présentation, je vais expliquer comment des capteurs laser peuvent être utilisés pour réaliser différentes fonctionnalités importantes pour les environnements intelligents. Je montrerai comment créer une carte précise et y représenter le mouvement de toutes les personnes, en particulier les trajectoires de leurs pieds. Celles-ci peuvent servir à identifier la personne observée, car chacune a sa propre démarche. Ceci ouvre des voies dans les domaines de la domotique, des environnements intelligents et de la sécurité. Les trajectoires de pieds ont également de nombreuses applications dans le domaine médical, en particulier pour la gériatrie, la kinésithérapie et la neurologie, ce que je détaillerai. Je démontrerai également que cette technologie permet de détecter les situations de piggybacking et de tailgating. Tout ceci étant rendu possible par une chaîne de traitement de signal minutieusement étudiée et par des techniques d'apprentissage automatique. [less ▲]

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See detailDiagnosing multiple sclerosis with a gait measuring system, an analysis of the motor fatigue, and machine learning
Pierard, Sébastien ULg; Azrour, Samir ULg; Phan-Ba, Rémy et al

in Multiple Sclerosis Journal (2014, September 11), 20(S1), 171

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See detailIn vivo skin fluorescence imaging in young Caucasian adults with early malignant melanomas
PIERARD, Gérald ULg; Hermanns-Lê, Trinh ULg; Pierard, Sébastien ULg et al

in Clinical, Cosmetic and Investigational Dermatology (2014), 7

Background: Human cutaneous malignant melanoma (CMM) is an aggressive cancer showing a dramatic worldwide increase in incidence over the past few decades. The most prominent relative epidemiological ... [more ▼]

Background: Human cutaneous malignant melanoma (CMM) is an aggressive cancer showing a dramatic worldwide increase in incidence over the past few decades. The most prominent relative epidemiological increase has been disclosed in young women. The aim of the study was to assess the effects of chronic sun exposures in order to rate the extend of melanocytic stimulations in the vicinity of CMM. Methods: The study was designed to evaluate the melanin distribution and density using ultraviolet light illumination. The present study was performed on surgical excision specimens of thin CMM lesion removed from the upper limbs of 55 Caucasian adults (37 women and 18 men). Two control groups comprised 23 men and 21 women of similar ages who had medium-size congenital melanocytic nevi, also present on the upper limbs. The peritumoral skin was scrutinized using a Visioscan® VC98 device, revealing the faint mosaic melanoderma (FMM) pattern that grossly indicates early signs of chronic photodamage in epidermal melanin units. Results: The median extent of relative FMM was significantly higher in the CMM male group. By contrast, the CMM female group showed a reverse bimodal distribution in FMM size. Only 12/37 (32.5%) of the CMM female group had an increased FMM size, whereas 25/37 (67.5%) of females with CMM had a global FMM extent in the normal range, relative to the controls. Conclusion: Thin CMM supervening in young women appear unrelated to repeat photoexposure. Other mechanisms are possibly involved. [less ▲]

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See detailOverview and Benchmarking of Motion Detection Methods
Jodoin, Pierre-Marc; Pierard, Sébastien ULg; Wang, Yi et al

in Bouwmans; Porikli; Hoferlin (Eds.) et al Background Modeling and Foreground Detection for Video Surveillance (2014)

In this chapter, we provide an overview of the most highly cited motion detection meth- ods. We identify the most commonly used background models together with their features, the kind of updating scheme ... [more ▼]

In this chapter, we provide an overview of the most highly cited motion detection meth- ods. We identify the most commonly used background models together with their features, the kind of updating scheme they use, some spatial aggregation models as well as the most widely used post-processing operations. We also provide an overview of datasets used to validate motion detection methods. Please note that this literature review is by no means exhaustive and thus we provide a list of surveys that the reader can rely on for further details. [less ▲]

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See detailIntroduction to Bayes' classifier and to the on-the-fly bayesian domain adaptation
Pierard, Sébastien ULg

Scientific conference (2014, June 19)

Detailed reference viewed: 30 (12 ULg)