SEEG dipole source localization based on an empirical Bayesian approach taking into account forward model uncertainties.

Electromagnetic brain source localization consists in the inversion of a forward model based on a limited number of potential measurements. A wide range of methods has been developed to regularize this severely ill-posed problem and to reduce the solution space, imposing spatial smoothness, anatomical constraint or sparsity of the activated source map. This last criteria, based on physiological assumptions stating that in some particular events (e.g., epileptic spikes, evoked potential) few focal area of the brain are simultaneously actives, has gained more and more interest. Bayesian approaches have the ability to provide sparse solutions under adequate parametrization, and bring a convenient framework for the introduction of priors in the form of probabilistic density functions. However the quality of the forward model is rarely questioned while this parameter has undoubtedly a great influence on the solution. Its construction suffers from numerous approximation and uncertainties, even when using realistic numerical models. In addition, it often encodes a coarse sampling of the continuous solution space due to the computational burden its inversion implies. In this work we propose an empirical Bayesian approach to take into account the uncertainties of the forward model by allowing constrained variations around a prior physical model, in the particular context of SEEG measurements. We demonstrate on simulations that the method enhance the accuracy of the source time-course estimation as well as the sparsity of the resulting source map. Results on real signals prove the applicability of the method in real contexts.

Evaluating dipolar source localization feasibility from intracerebral SEEG recordings.

Stereo-electroencephalography (SEEG) is considered as the golden standard for exploring targeted structures during pre-surgical evaluation in drug-resistant partial epilepsy. The depth electrodes, inserted in the brain, consist of several collinear measuring contacts (sensors). Clinical routine analysis of SEEG signals is performed on bipolar montage, providing a focal view of the explored structures, thus eliminating activities of distant sources that propagate through the brain volume. We propose in this paper to exploit the common reference SEEG signals. In this case, the volume propagation information is preserved and electrical source localization (ESL) approaches can be proposed. Current ESL approaches used to localize and estimate the activity of the neural generators are mainly based on surface EEG/MEG signals, but very few studies exist on real SEEG recordings, and the case of equivalent current dipole source localization has not been explored yet in this context. In this study, we investigate the influence of volume conduction model, spatial configuration of SEEG sensors and level of noise on the ESL accuracy, using a realistic simulation setup. Localizations on real SEEG signals recorded during intracerebral electrical stimulations (ICS, known sources) as well as on epileptic interictal spikes are carried out. Our results show that, under certain conditions, a straightforward approach based on an equivalent current dipole model for the source and on simple analytical volume conduction models yields sufficiently precise solutions (below 10mm) of the localization problem. Thus, electrical source imaging using SEEG signals is a promising tool for distant brain source investigation and might be used as a complement to routine visual interpretations.

Instantaneous Position and Orientation of the Body Segments as an Arbitrary Object in 3D Space by Merging Gyroscope and Accelerometer Information / Posición y orientación instantánea de los segmentos corporales como un objeto arbitrario en el espacio 3D a través de la fusión de la información de acelerómetros y giroscopios

This work presents an algorithm to determine instantaneous orientation of an object in 3D space. The orientation was determined by using a Direction Cosine Matrix (DCM), performed by the combination of three consecutive rotations, around each to the main axes of the evaluated system, using quaternions. An inertial measurement unit (IMU), consisting of 3 axes gyroscope and 3 axes accelerometer was used in order to establish 2 coordinate systems; The first one describes object movement, by using gyroscope as a main source of information, relating the angular rate of change along time. The second defines a coordinate reference system, relating the acceleration of gravity to an inertial direction vector. A proportional integral (PI) feedback controller was used, which includes sensors information, eliminating offset, cancelling drift and improving the accuracy of the orientation. The proposed algorithm can be used for assessing both the position and orientation of the body segments which is very important in orthopedic, traumatology and rheumatology important for diagnosis, prognostic, therapeutic, research and as well as the design and fabrication of measuring devices used in surgical instrumentation, prostheses and ortheses. It is important to note that the developed system opens the opportunities to be implemented on ambulatory joint evaluation through a wearable system, due to the dimensions and requirements of the sensors.

El presente trabajo presenta un algoritmo para determinar la orientación instantánea de un objeto en el espacio 3D. La orientación fue determinada utilizando una matriz de cosenos directores (DCM) conformada por la combinación de 3 rotaciones consecutivas alrededor de cada uno de los ejes del sistema evaluado, utilizando cuaterniones. Una unidad inercial de medida (IMU) compuesta por un giroscopio de 3 ejes y un acelerómetro de 3 ejes fue utilizada con el objetivo de establecer 2 sistemas coordenados; Un sistema coordenado describiendo el movimiento del objeto, utilizando al giroscopio como fuente principal de información, estableciendo la relación de cambio con respecto al tiempo. Un sistema coordenado de referencia, relacionando la aceleración gravitacional a un vector inercial. Un control por retroalimentación proporcional integral (PI) fue utilizado con el objetivo de combinar la información de los sensores, eliminando las desviaciones por offset y deriva, mejorando la precisión en la orientación. Dadas sus características, el algoritmo propuesto permite su utilización en la evaluación de la posición y la orientación de los segmentos corporales, siendo de suma importancia en ortopedia, traumatología y reumatología para la determinación de diagnósticos, pronósticos terapéuticos e investigación así como el diseño y fabricación de dispositivos de medición, instrumentación quirúrgica, prótesis y ortesis. Cabe destacar que el sistema desarrollado abre oportunidades de ser implementado en el diseño de sistemas ambulatorios de evaluación de las articulaciones, mediante el uso de elementos transportables dadas las reducidas dimensiones y limitaciones de los sensores empleados.

EEG preprocessing for synchronization estimation and epilepsy lateralization.

The global framework of this paper is the synchronization analysis in EEG recordings. Two main objectives are pursued: the evaluation of the synchronization estimation for lateralization purposes in epileptic EEGs and the evaluation of the effect of the preprocessing (artifact and noise cancelling by blind source separation, wavelet denoising and classification) on the synchronization analysis. We propose a new global synchronization index, based on the classical cross power spectrum, estimated for each cerebral hemisphere. After preprocessing, the proposed index is able to correctly lateralize the epileptic zone in over 90% of the cases.

Reference estimation in EEG recordings.

This work aims to analyze the reference (montage) problem in electroencephalographic (EEG) recordings. It is well accepted that EEG signals are a mixture of cerebral and extracerebral sources, and the solution to the reference problem depends on the hypothesized mixing model. We focus here on an acquisition model using a distant reference electrode and propose a method for determining and eliminating the reference signal which develops and improves Hu et al. work from [1]. The obtained solution, based on a constrained blind source separation (BSS) algorithm, outperforms the cited method on simulated noisy EEG signals for all noise levels.

Influence of source separation and montage on ictal source localization.

The aim of this paper is to evaluate the influence of the reference electrode (introduced to form an augmented average montage) and of the artifact elimination by blind source separation on the ictal electrical source imaging. We present here a preliminary study on one patient only. The results seem to indicate that the montage (and thus the reference handling method) has a limited but existent influence on the quality of the source localization. Artifact elimination highly improves this quality as well.

Seizure lateralization in scalp EEG using Hjorth parameters.

OBJECTIVE: This paper describes and assesses a new semi-automatic method for temporal lobe seizures lateralization using raw scalp EEG signals. METHODS: We used the first two Hjorth parameters to estimate quadratic mean and dominant frequency of signals. Their mean values were computed on each side of the brain and segmented taking into account the seizure onset time identified by the electroencephalographist, to keep only the initial part of the seizure, before a possible spreading to the contralateral side. The means of segmented variables were used to characterize the seizure by a point in a (frequency, amplitude) plane. Six criteria were proposed for the partitioning of this plane for lateralization. RESULTS: The procedure was applied to 45 patients (85 seizures). The two best criteria yielded, for the first one, a correct lateralization for 96% of seizures and, for the other, a lateralization rate of 87% without incorrect lateralization. CONCLUSIONS: The method produced satisfactory results, easy to interpret. The setting of procedure parameters was simple and the approach was robust to artifacts. It could constitute a help for neurophysiologists during visual inspection. SIGNIFICANCE: The difference of quadratic mean and dominant frequency on each side of the brain allows lateralizing the seizure onset.

EEG ocular artefacts and noise removal.

The general framework of this research is the pre-processing of the electroencephalographic (EEG) signals. The goal of this paper is to compare several combinations of wavelet denoising (WD) and independent component analysis (ICA) algorithms for noise and artefacts removal. These methods are tested on simulated EEG, using different evaluation criteria. According to our results, the most effective method consists in source separation by SOBI-RO [1], followed by wavelet denoising by SURE thresholding [2].

Principal component analysis and interpretation of bowel sounds.

This paper presents a method for abdominal sounds analysis based on principal component analysis (PCA). The first steps (wavelet denoising and segmentation, followed by spatial localization) were presented in previous works. After extracting physical features (activity indices) from long time six channel recordings, we propose a reduced representation space obtained by PCA and we present our results in phonoenterogram analysis.

Skeletal stability of Le Fort I osteotomy in patients with isolated cleft palate and bilateral cleft lip and palate.

The skeletal stability of Le Fort I osteotomy was evaluated retrospectively in 14 patients with isolated cleft palate (CP, mean age 27.2 years) and 11 patients with bilateral cleft lip and palate (BCLP, mean age 23.7 years). The osteotomy was fixed with titanium plates and the osteotomy gap was grafted with autologous bone. Neither intermaxillary fixation nor occlusal splints were used postoperatively. Skeletal stability was analysed both horizontally and vertically by cephalograms taken shortly before operation, immediately afterwards, and at six months and at one year postoperatively. In the CP group the mean maxillary horizontal advancement (point A) was 4.7 mm (range 0.3-7.8) and the mean vertical lengthening 3.6 mm (range 0.7-6.1). One year postoperatively the mean relapse was 8.5% (0.4 mm) horizontally and 16.7% (0.6 mm) vertically. In the BCLP group the mean horizontal advancement was 5.3 mm (range 0.2-10.7) and the mean vertical lengthening 7.3 mm (range 0.6-11.8). The mean postoperative relapse was 9.4% (0.5 mm) horizontally and 17.8% (1.3 mm) vertically. The skeletal stability and relapse were similar in both cleft types although BCLP patients had more residual cleft problems and their mean surgical advancement was greater. There was great individual variation.

Associations between lateral cephalometric dimensions and misarticulations of Finnish dental consonants in cleft lip/palate children.

The purpose of this study was to examine the associations between lateral cephalometric variables and the misarticulation of /r/, /s/ and /l/ sound in cleft lip/palate children. The subjects were 134 Finnish-speaking 6-year-old boys with isolated cleft palate (CP, n = 33), unilateral (n = 44), bilateral (BCLP, n = 19) cleft lip and cleft lip/alveolus (n = 38); /r/, /s/ and /l/ distortions were obtained from original hospital records which were based on perceptual speech follow-ups performed by experienced speech pathologists. Cephalometric measurement points were determined from standardized lateral roentgen cephalograms and traced twice by a computer-connected digitizer. The data were entered into a microcomputer and analysed by NCSS 6.0 for Windows using appropriate tests. The results revealed new significant associations between cephalometric measurements and misarticulations, especially that of the /r/ sound in CP and BCLP groups. Children with /r/ distortion had upward rotation of the mandible, maxillary protrusion and a higher position of the hyoid bone in the CP group. In the BLCP group, on the contrary, the mandible had downward rotation, mandibular retrusion and narrower nasopharyngeal port. The /s/ and /l/ sounds were less clearly associated with craniofacial morphology. The anteroposterior relationship of the maxilla and the mandible did not have any association with dentoalveolar misarticulations, instead, the systematic vertical, particularly posterior relationship of the jaws seems to be associated with /r/ sound production in CP and BCLP boys.

The effect of an irregular shift system on sleepiness at work in train drivers and railway traffic controllers.

Sleepiness and fatigue are frequent problems in railway transportation with occasional monotony and irregular shift schedules. This study aimed at (1) studying the prevalence of severe sleepiness in shifts and (2) examining which shift and sleep-related factors were associated with the occurrence of severe sleepiness in an irregular shift system. A total of 126 randomly selected male train drivers (Tdrs) and 104 railway traffic controllers (Tcos) were investigated using questionnaires and sleep-wake diaries. A sleep diary was used to collect information on sleepiness at work and sleeping times during the 21 consecutive days of the study. The prevalence of severe sleepiness at work (i.e. Karolinska Sleepiness Scale 7 or higher) was modelled by a logistic regression analysis for repeated measurements (GEE) using different shift schedule related factors and sleep length as explanatory variables. Severe sleepiness was reported in 49% (Tdrs) and 50% (Tcos) of the night shifts and in 20% (Tdrs) and 15% (Tcos) of the morning shifts. The odds ratios showed that the risk for severe sleepiness was 6-14 times higher in the night shift and about twice as high in the morning shift compared with the day shift. Age affected the two occupational samples differently: with Tdrs increased age was associated with an additional 8% reduction of risk for severe sleepiness for each year of age, while the Tcos did not show any age dependency. Shift length increased the risk by 15% for each hour of the shift and main sleep period decreased the risk by 15% for each hour of the main sleep. The risk of severe sleepiness was not consistently related to the time-off period before the shifts. The results indicate that adjustments for shift timing, length and off-duty time, in addition to actions aiming at extending the main sleep period, would probably decrease severe sleepiness in railway transportation.

Effects of worksite physical exercise intervention on physical fitness, perceived health status, and work ability among home care workers: five-year follow-up.

OBJECTIVE: The effects and constancy of a worksite physical exercise intervention were examined in relation to the physical fitness, perceived health status, and work ability of female service workers during periods of 1 and 5 years. METHODS: The subjects comprised female home care workers divided into an intervention group (n = 50, mean age 41.8 (SD 10.4) years) and a control group (n = 37, mean age 43.3 (SD 8.8) years). The intervention group participated in 9 months of supervised exercise intervention twice a week during the workday. Functional capacity, perceived health, and work ability were assessed at the beginning of the study and after a 1- and a 5-year period of follow-up. RESULTS: In the 1-year follow-up measurements, body fat had decreased (4%) and dynamic muscle performance and maximal oxygen consumption in relation to body mass (30-38 and 7%, respectively) had increased in the intervention group. The differences in outcome variables between the intervention and the control groups were significant (from P = 0.014 to P < 0.001). These positive effects of worksite exercise were observed despite the age of the subjects, and the changes were consistent during a 5-year period. In the control group the decline of the work ability index (L smean) was about three times faster than in the intervention group during the 5-year period. CONCLUSIONS: Physical exercise executed in work units can be used to improve the physical capacity of female home care aides and prevent the early decline of their work ability. In jobs that are physically demanding, such as home care work, early prevention must start before the age-related deterioration of health and physical capacity.

Association between velopharyngeal function and dental-consonant misarticulations in children with cleft lip/palate.

We studied the association between velopharyngeal function and misarticulation of the dental consonants /r/, /s/ and /l/ in children with cleft lip/palate. We assessed 278 6-year-old Finnish-speaking non-syndromic children (115 girls, 163 boys) with isolated cleft palate (n= 81), cleft lip/alveolus (n= 82) or unilateral (n= 84) or bilateral (n= 31) cleft lip and palate. Auditory analysis of speech and velopharyngeal function, the presence of fistulae, previous velopharyngoplasty and speech therapy, as well as surgical technique and timing of primary palatal surgery were obtained from the hospital records. The misarticulations of the sounds /r/, /s/ and /l/ were evaluated in spontaneous speech by two experienced speech pathologists from the cleft team. Velopharyngeal function was categorised, on the basis of the effect on speech, into competent, marginal incompetent and obvious incompetent. Nasal grimace and distortions due to palatal fistulae were registered. The results indicated that velopharyngeal function was not significantly associated with misarticulation of any of the sounds /r/, /s/ and /l/ or their combinations in any cleft groups. The technique and timing of primary palatal surgery, the presence of fistulae and previous pharyngoplasty were not associated with misarticulations. On the basis of these results we conclude that dental-consonant misarticulations occur independently of velopharyngeal function, primary palatal surgical technique and timing of palatoplasty.

Skeletal stability of Le Fort I osteotomy in patients with unilateral cleft lip and palate.

The skeletal stability of Le Fort I osteotomy was evaluated cephalometrically in 40 consecutive patients with unilateral cleft lip and palate (UCLP) (27 male and 13 female) who were operated on between 1987-1995. Their mean age at the time of operation was 23.7 years (range 16.3-40.4). The one-piece Le Fort I osteotomy was fixed with titanium plates and the osteotomy line was bone-grafted. Neither intermaxillary fixation nor occlusal splints were used postoperatively. Skeletal stability was analysed both horizontally and vertically on cephalograms taken shortly before operation, immediately afterwards, and at six months and at one year postoperatively. The mean maxillary advancement (point A) during the Le Fort I was 3.9 mm (range 0-8.9) and mean vertical lengthening 4.5 mm (range -0.6-10.5). One year postoperatively the mean maxillary horizontal relapse was 20.5% (0.8 mm, range 0-3.7) whereas the mean vertical relapse was 22.2% (1 mm, range 0-5.7). The vertical relapse reduced from 38% to 8.3% between 1987 and 1995, and there was a positive correlation between the amount of maxillary advancement and relapse both horizontally and vertically.

Comparisons of speech aerodynamics and lateral craniofacial cephalometrics in cleft lip and palate patients with and without Finnish /r/-sound distortion.

To study the associations between the articulation of the Finnish /r/ sound and dentofacial and pharyngeal lateral cephalometric morphology and speech physiology, 18 (12 females, 6 males) young adult cleft patients' /r/ sound was analysed auditorily by 3 speech experts. Laryngeal resistance (LARE), the smallest nasal cross-sectional area (NASA), nasal resistance (NASAR) and velopharyngeal orifice area (VEPA) were measured with pressure flow technique, and 31 points were identified from the lateral cephalograms to landmark the skeletal structure, pharyngeal airway diameters, and position of the hyoid bone. The present results showed no significant differences in lateral cephalometric skeletal, nasopharyngeal, oropharyngeal or hypopharyngeal morphology between subjects with and without /r/-sound distortion. There were no significant correlations either between /r/ distortions and NASA, NASAR or VEPA. An anteriorly positioned hyoid bone was significantly associated with decreased LARE and /r/ distortion. LARE was significantly lower in subjects with /r/ distortion.

Velopharyngeal function from the age of three to eight years in cleft palate patients.

The purpose of this investigation was to study changes of velopharyngeal function between the ages of 3 and 8 years. The subjects were 65 (30 girls and 35 boys) Finnish-speaking non-syndromic children with isolated cleft palate (CP, n = 35) and with unilateral cleft lip and palate (UCLP, n = 30) operated primarily at the age of 1.0-2.0 years. Before the age of 8 years, 16 children required velopharyngoplasty (VPP, ad modum Hoenig). The children were followed up for speech at the age of 3, 6 and 8 years. The perceptual speech characteristics nasal air emission, hypernasality, weakness of pressure consonants and compensatory articulations were registered. Indications for a velopharyngeal flap (by VPP) were identified on the basis of perceptual speech characteristics and confirmed by instrumental examinations. The results indicated that the method and timing of primary palatoplasty and sex did not correlate with the quality of velopharyngeal function. It was good both in children treated conservatively or with VPP at the age of 8 years. The children with a flap required speech therapy significantly more often than other children. No child with VPP and only 12% of the children without VPP had simultaneous nasal air emissions and hypernasality. Compensatory articulation was completely eliminated and weakness of pressure consonants was diagnosed only in 1 child without VPP. The CP children required significantly more often a velopharyngeal flap than the UCLP children. In conclusion, the CP and UCLP children develop a similar velopharyngeal function but in a different way.

Changes in soft tissue thickness after Le Fort I osteotomy in different cleft types.

The soft tissue thickness before and after Le Fort I osteotomy was evaluated in 46 cleft patients. The sample consisted of 10 patients with isolated cleft palate (CP, mean age 25.5 years); 10 patients with bilateral cleft lip and palate (BCLP, mean age 21.7 years); and 26 patients with unilateral cleft lip and palate (UCLP, mean age 22.9 years). Patients with bimaxillary surgery, simultaneous rhinoplasty, or V-Y plasty of the upper lip were excluded. Soft tissue changes were analyzed by cephalograms taken shortly before surgery and at 6 months postoperatively. Horizontal advancement varied from 4.1 mm in the UCLP group to 5 mm in the BCLP group. The vertical lengthening varied from 3.7 mm in the CP group to 7.2 mm in the BCLP group. In all cleft types, thinning of the subnasal area, superior labial sulcus, and upper lip (anterior nasal spine-subnasale, point A-soft tissue point A, and prosthion-labrale superius) took place. Significant thinning of the upper lip occurred in the UCLP and BCLP patients. Surgical changes of the lower lip and mandibular area were small and insignificant. There were significant differences in soft tissue thicknesses between different types of clefts. The subnasal area and superior labial sulcus were significantly thicker in the CP group than in the BCLP or UCLP groups, both pre- and postoperatively. The upper lip was thickest in the BCLP group preoperatively but thickest in the CP group postoperatively. The upper lip was thinnest in the UCLP group both before and after the operation.