Label Fusion Strategy Selection

Label fusion is used in medical image segmentation to combine several different labels of the same entity into a single discrete label, potentially more accurate, with respect to the exact, sought segmentation, than the best input element. Using simulated data, we compared three existing label fusion techniques—STAPLE, Voting, and Shape-Based Averaging (SBA)—and observed that none could be considered superior depending on the dissimilarity between the input elements. We thus developed an empirical, hybrid technique called SVS, which selects the most appropriate technique to apply based on this dissimilarity. We evaluated the label fusion strategies on two- and three-dimensional simulated data and showed that SVS is superior to any of the three existing methods examined. On real data, we used SVS to perform fusions of 10 segmentations of the hippocampus and amygdala in 78 subjects from the ICBM dataset. SVS selected SBA in almost all cases, which was the most appropriate method overall

Optimisation de l'instrumentation pour le monitoring respiratoire par tomographie d'impédance électrique

Principes de la tomographie d'imédance électrique (TIE) -- Imagerie pulmonaire -- Comparaison de systèmes récemment développés -- Méthodes et instrumentation -- Description du système TIE-4 -- Unité de contrôle du système TIE-4 -- Nouvelle carte d'électrodes actives -- Interface de communication pour le système TIE-5 -- Améliorations apportées et anticipées -- Résultats des essais effectués sur la ceinture et la carte d'électrodes actives -- Discussion et travaux futurs -- Atteinte des objectifs du projet de maîtrise -- Développement du nouveau système TIE-5

High-dimensional medial lobe morphometry : an automated MRI biomarker for the new AD diagnostic criteria

Introduction. Medial temporal lobe atrophy assessment via magnetic resonance imaging (MRI) has been proposed in recent criteria as an in vivo diagnostic biomarker of Alzheimer’s disease (AD). However, practical application of these criteria in a clinical setting will require automated MRI analysis techniques. To this end, we wished to validate our automated, high-dimensional morphometry technique to the hypothetical prediction of future clinical status from baseline data in a cohort of subjects in a large, multicentric setting, compared to currently known clinical status for these subjects. Materials and Methods. The study group consisted of 214 controls, 371 mild cognitive impairment (147 having progressed to probable AD and 224 stable), and 181 probable AD from the Alzheimer’s Disease Neuroimaging Initiative, with data acquired on 58 different 1.5 T scanners. We measured the sensitivity and specificity of our technique in a hierarchical fashion, first testing the effect of intensity standardization, then between different volumes of interest, and finally its generalizability for a large, multicentric cohort. Results. We obtained 73.2% prediction accuracy with 79.5% sensitivity for the prediction of MCI progression to clinically probable AD. The positive predictive value was 81.6% for MCI progressing on average within 1.5 (0.3 s.d.) year. Conclusion. With high accuracy, the technique’s ability to identify discriminant medial temporal lobe atrophy has been demonstrated in a large, multicentric environment. It is suitable as an aid for clinical diagnostic of AD

Toward dynamic pain expressions in avatars : perceived realism and pain level of diffrent action unit orders

The facial expression of pain can be decomposed in three sets of Action Units (AUs), the smallest discriminating facial movements: Brow lowering (B), Nose wrinkling + Upper lip raising (N), and Orbit tightening + Eyelid closure (O). This study compared the perception of realism and pain level from different onset orders of AUs in avatars. Seven videos of facial expressions of pain were created with four different avatars (2 women): six sequential onsets combining the three sets of AUs and one synchronized onset. 45 healthy adults (22 women; aged 23.6 ± 5.2 years) rated the realism of facial movements, and the level of intensity and unpleasantness of perceived pain. A more realistic expression was associated with the onset of O before or at the same time as N, a more intense expression was associated when B occurred last, and a higher level of unpleasantness was associated with the onset of N before B. Therefore, the sequence ONB yielded the highest ratings on both measures of realism and pain levels. These findings describe the perceived content of different orders of facial movements that could contribute to the creation of realistic pain-expressing virtual agents designed to study human-computer interactions

Tissue-Based MRI Intensity Standardization: Application to Multicentric Datasets

Intensity standardization in MRI aims at correcting scanner-dependent intensity variations. Existing simple and robust techniques aim at matching the input image histogram onto a standard, while we think that standardization should aim at matching spatially corresponding tissue intensities. In this study, we present a novel automatic technique, called STI for STandardization of Intensities, which not only shares the simplicity and robustness of histogram-matching techniques, but also incorporates tissue spatial intensity information. STI uses joint intensity histograms to determine intensity correspondence in each tissue between the input and standard images. We compared STI to an existing histogram-matching technique on two multicentric datasets, Pilot E-ADNI and ADNI, by measuring the intensity error with respect to the standard image after performing nonlinear registration. The Pilot E-ADNI dataset consisted in 3 subjects each scanned in 7 different sites. The ADNI dataset consisted in 795 subjects scanned in more than 50 different sites. STI was superior to the histogram-matching technique, showing significantly better intensity matching for the brain white matter with respect to the standard image

Assessments of the Extent to which Health‐Care Providers Involve Patients in Decision Making: A Systematic Review of Studies Using the OPTION Instrument

Background: We have no clear overview of the extent to which health-care providers involve patients in the decision-making process during consultations. The Observing Patient Involvement in Decision Making instrument (OPTION) was designed to assess this. Objective: To systematically review studies that used the OPTION instrument to observe the extent to which health-care providers involve patients in decision making across a range of clinical contexts, including different health professions and lengths of consultation. We conducted online literature searches in multiple databases (2001-12) and gathered further data through networking

On the control of visual spatial attention: evidence from human electrophysiology

Abstract We used electrophysiological methods to track the deployment of visual spatial attention while observers were engaged in concurrent central attentional processing, using a variant of the attentional blink paradigm. Two visual targets (T 1 , T 2 ) were presented at a stimulus onset asynchrony of either 200 ms or 800 ms. T 1 was a white digit among white letters presented on a dark background using rapid serial visual presentation at fixation. T 2 was another digit that was presented to the left or right of fixation simultaneously with a distractor digit in the opposite visual field, each followed by a pattern mask. In each T 2 display, one digit was red and one was green. Half of the subjects reported the red digit and ignored the green one, whereas the other half reported the green digit and ignored the red one. T 1 and T 2 were reported in one block of trials, and only T 2 in another block (order counterbalanced across subjects). Accuracy of report of T 2 was lower at short SOA than at long SOA when both T 1 and T 2 were reported, but was similar across SOA when only T 2 was reported. The electrophysiological results focused on the N2pc component, which was used as an index of the locus of spatial attention. N2pc was reduced in amplitude when subjects reported T 1 , and particularly so at the short SOA. The results suggest that attention to T 1 interfered with the deployment of visual spatial attention to T 2

Real-time modulation of visual feedback on human full-body movements in a virtual mirror: development and proof-of-concept

BACKGROUND: Virtual reality (VR) provides interactive multimodal sensory stimuli and biofeedback, and can be a powerful tool for physical and cognitive rehabilitation. However, existing systems have generally not implemented realistic full-body avatars and/or a scaling of visual movement feedback. We developed a "virtual mirror" that displays a realistic full-body avatar that responds to full-body movements in all movement planes in real-time, and that allows for the scaling of visual feedback on movements in real-time. The primary objective of this proof-of-concept study was to assess the ability of healthy subjects to detect scaled feedback on trunk flexion movements. METHODS: The "virtual mirror" was developed by integrating motion capture, virtual reality and projection systems. A protocol was developed to provide both augmented and reduced feedback on trunk flexion movements while sitting and standing. The task required reliance on both visual and proprioceptive feedback. The ability to detect scaled feedback was assessed in healthy subjects (n = 10) using a two-alternative forced choice paradigm. Additionally, immersion in the VR environment and task adherence (flexion angles, velocity, and fluency) were assessed. RESULTS: The ability to detect scaled feedback could be modelled using a sigmoid curve with a high goodness of fit (R2 range 89-98%). The point of subjective equivalence was not significantly different from 0 (i.e. not shifted), indicating an unbiased perception. The just noticeable difference was 0.035 +/- 0.007, indicating that subjects were able to discriminate different scaling levels consistently. VR immersion was reported to be good, despite some perceived delays between movements and VR projections. Movement kinematic analysis confirmed task adherence. CONCLUSIONS: The new "virtual mirror" extends existing VR systems for motor and pain rehabilitation by enabling the use of realistic full-body avatars and scaled feedback. Proof-of-concept was demonstrated for the assessment of body perception during active movement in healthy controls. The next step will be to apply this system to assessment of body perception disturbances in patients with chronic pain