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A device with four parallel channels was designed and manufactured by 3D printing in titanium. A simple experimental setup allowed splitting of the mobile phase in four parallel streams, such that a single sample could be analysed four times simultaneously. The four capillary channels were filled with a monolithic stationary phase, prepared using a zwitterionic functional monomer in combination with various dimethacrylate cross-linkers. The resulting stationary phases were applicable in both reversed-phase and hydrophilic-interaction retention mechanisms. The mobile-phase composition was optimized by means of a window diagram so as to obtain the highest possible resolution of dopamine precursors and metabolites on all columns. Miniaturized electrochemical detectors with carbon fibres as working electrodes and silver micro-wires as reference electrodes were integrated in the device at the end of each column. Experimental separations were successfully compared with those predicted by a three-parameter retention model. Finally, dopamine was determined in human urine to further confirm applicability of the developed device.
In surgical practice, small metallic instruments are frequently used to perform various tasks inside the human body. We address the problem of their accurate localization in the tissue. Recent experiments using medical ultrasound have shown that this modality is suitable for real-time visualization of anatomical structures as well as the position of surgical instruments. We propose an image-processing algorithm that permits automatic estimation of the position of a line-segment-shaped object. This method was applied to the localization of a thin metallic electrode in biological tissue. We show that the electrode axis can be found through maximizing the parallel integral projection transform that is a form of the Radon transform. To accelerate this step, hierarchical mesh-grid algorithm is implemented. Once the axis position is known, localization of the electrode tip is performed. The method was tested on simulated images, on ultrasound images of a tissue mimicking phantom containing a metallic electrode, and on real ultrasound images from breast biopsy. The results indicate that the algorithm is robust with respect to variations in electrode position and speckle noise. Localization accuracy is of the order of hundreds of micrometers and is comparable to the ultrasound system axial resolution.
- MeSH
- fantomy radiodiagnostické MeSH
- implantace protézy metody MeSH
- implantované elektrody MeSH
- interpretace obrazu počítačem metody MeSH
- intervenční ultrasonografie metody přístrojové vybavení MeSH
- lidé MeSH
- reprodukovatelnost výsledků MeSH
- senzitivita a specificita MeSH
- vylepšení obrazu metody MeSH
- zobrazování trojrozměrné metody MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- práce podpořená grantem MeSH
The paper describes a novel control strategy for simultaneous manipulation of several microscale particles over a planar microelectrode array using dielectrophoresis. The approach is based on a combination of numerical nonlinear optimization, which gives a systematic computational procedure for finding the voltages applied to the individual electrodes, and exploitation of the intrinsic noise, which compensates for the loss of controllability when two identical particles are exposed to identical forces. Although interesting on its own, the proposed functionality can also be seen as a preliminary achievement in a quest for a technique for separation of two particles. The approach is tested experimentally with polystyrene beads (50 microns in diameter) immersed in deionized water on a flat microelectrode array with parallel electrodes. A digital camera and computer vision algorithm are used to measure the positions. Two distinguishing features of the proposed control strategy are that the range of motion is not limited to interelectrode gaps and that independent manipulation of several particles simultaneously is feasible even on a simple microelectrode array.
- MeSH
- algoritmy MeSH
- design vybavení MeSH
- elektrody MeSH
- elektroforéza metody MeSH
- hluk MeSH
- mikromanipulace přístrojové vybavení metody MeSH
- mikrosféry MeSH
- počítačové zpracování signálu přístrojové vybavení MeSH
- teoretické modely MeSH
- zpětná vazba * MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Klíčová slova
- optické podněty v optickém analyzátoru a v proprioceptivním integrátoru,
- MeSH
- experimenty na zvířatech MeSH
- implantované elektrody využití MeSH
- kočky MeSH
- mozková kůra anatomie a histologie fyziologie MeSH
- nervové analyzátory anatomie a histologie fyziologie MeSH
- statistika jako téma MeSH
- světelná stimulace * metody MeSH
- zrakové evokované potenciály * fyziologie MeSH
- zvířata MeSH
- Check Tag
- kočky MeSH
- zvířata MeSH
- Klíčová slova
- akustický analyzátor a proprioceptivní integrátor,
- MeSH
- akustická stimulace * metody využití MeSH
- experimenty na zvířatech MeSH
- implantované elektrody využití MeSH
- kočky MeSH
- mozková kůra anatomie a histologie fyziologie MeSH
- nervové analyzátory * anatomie a histologie fyziologie MeSH
- nervový systém anatomie a histologie MeSH
- sluchové evokované potenciály fyziologie MeSH
- statistika jako téma MeSH
- zvířata MeSH
- Check Tag
- kočky MeSH
- zvířata MeSH
INTRODUCTION: Although microrecording is common in subthalamic stimulation, microelectrode monitoring prolongs surgical time and may increase the risk of haemorrhagic complications. The main reason for electrophysiological mapping is the discrepancy between the calculated anatomical and final electrophysiological targets. The aim of this paper is to describe the relationship between anatomical and electrophysiological targets defined as the best electrophysiological recordings from multiple parallel electrode tracts, explaining the target discrepancy with attention paid to the role of brain shift and patient- and disease-related factors. MATERIALS AND METHODS: Subthalamic electrodes were stereotactically implanted in 58 patients using microrecording by means of parallel electrodes at defined distances. The relationship between the final electrode placement to its anatomical trajectory and the relationship between the definitive electrodes implanted on the right and left sides were analysed, as was the influence of patient age, Parkinson's disease duration, and late motor complications duration. RESULTS: Final electrode placement matched the anatomical trajectory in 53.4% of patients on the right side and 43.1% of patients on the left side. Electrode positions were symmetrical in 38.3% of patients. The analysis of left and right electrode positions does not prove a statistically significant prevalence of lateral and posterior final electrode trajectories as could be expected from lateral and posterior movements of the brain caused by brain shift, although there was some tendency for a larger percentage of lateral electrodes on the left side. Age, Parkinson's disease duration, and L-DOPA effect duration were not confirmed as responsible factors. CONCLUSIONS: The difference between anatomical trajectory and final electrode placement supports the use of functional microelectrode monitoring in subthalamic deep brain stimulation. Brain shift is not the only causative factor of the difference. The possible roles of age, Parkinson's disease duration, and late motor complications duration were also not confirmed by study results.
- MeSH
- hluboká mozková stimulace metody MeSH
- implantované elektrody MeSH
- levodopa fyziologie MeSH
- lidé středního věku MeSH
- lidé MeSH
- mozek fyziologie MeSH
- nucleus subthalamicus patologie patofyziologie MeSH
- Parkinsonova nemoc patologie patofyziologie terapie MeSH
- pohyb fyziologie MeSH
- věkové faktory MeSH
- Check Tag
- lidé středního věku MeSH
- lidé MeSH
- mužské pohlaví MeSH
- ženské pohlaví MeSH
- Publikační typ
- časopisecké články MeSH
The automated detection of arrhythmia in a Holter ECG signal is a challenging task due to its complex clinical content and data quantity. It is also challenging due to the fact that Holter ECG is usually affected by noise. Such noise may be the result of the regular activity of patients using the Holter ECG-partially unplugged electrodes, short-time disconnections due to movement, or disturbances caused by electric devices or infrastructure. Furthermore, regular patient activities such as movement also affect the ECG signals and, in connection with artificial noise, may render the ECG non-readable or may lead to misinterpretation of the ECG. OBJECTIVE: In accordance with the PhysioNet/CinC Challenge 2017, we propose a method for automated classification of 1-lead Holter ECG recordings. APPROACH: The proposed method classifies a tested record into one of four classes-'normal', 'atrial fibrillation', 'other arrhythmia' or 'too noisy to classify'. It uses two machine learning methods in parallel. The first-a bagged tree ensemble (BTE)-processes a set of 43 features based on QRS detection and PQRS morphology. The second-a convolutional neural network connected to a shallow neural network (CNN/NN)-uses ECG filtered by nine different filters (8× envelograms, 1× band-pass). If the output of CNN/NN reaches a specific level of certainty, its output is used. Otherwise, the BTE output is preferred. MAIN RESULTS: The proposed method was trained using a reduced version of the public PhysioNet/CinC Challenge 2017 dataset (8183 records) and remotely tested on the hidden dataset on PhysioNet servers (3658 records). The method achieved F1 test scores of 0.92, 0.82 and 0.74 for normal recordings, atrial fibrillation and recordings containing other arrhythmias, respectively. The overall F1 score measured on the hidden test-set was 0.83. SIGNIFICANCE: This F1 score led to shared rank #2 in the follow-up PhysioNet/CinC Challenge 2017 ranking.
Mathematical models of dielectrophoresis play an important role in the design of experiments, analysis of results, and even operation of some devices. In this paper, we test the accuracy of existing models in both simulations and laboratory experiments. We test the accuracy of the most common model that involves a point-dipole approximation of the induced field, when the small-particle assumption is broken. In simulations, comparisons against a model based on the Maxwell stress tensor show that even the point-dipole approximation provides good results for a large particle close to the electrodes. In addition, we study a refinement of the model offered by multipole approximations (quadrupole, and octupole). We also show that the voltages on the electrodes influence the error of the model because they affect the positions of the field nulls and the nulls of the higher-order derivatives. Experiments with a parallel electrode array and a polystyrene microbead reveal that the models predict the force with an error that cannot be eliminated even with the most accurate model. Nonetheless, it is acceptable for some purposes such as a model-based control system design.
OBJECTIVE: The aim of the paper was to describe the relationship of the anatomical and electrophysiological target for the subthalamic electrode implantation in Parkinson's disease patients defined as the best electrophysiological recordings from multiple paralel electrodes tracts with a target discrepancy explanation. BACKGROUND: Although microrecording is the standard in subthalamic stimulation, microelectrode monitoring prolongs surgical time and may increase the risk of haemorrhagic complications. The main purpose for the electrophysiological mapping is to overcome the discrepancy between the anatomical and electrophysiological targets. METHODS: Subthalamic electrodes were stereotactically implanted in 58 patients using microrecording by means of parallel electrodes at defined distances. The relationship of the final electrode to the anatomical trajectory, the subthalamic nucleus electrical activity length, and the relationship of right and left electrodes were analysed. RESULTS: The final electrode placement matched the anatomical trajectory in 53.4 % of patients on the right side, and 43.1 % of patients on the left side. The electrode position was symmetrical in 38.3 % of patients. The analysis of left and right electrode positions did not prove brain shift as the sole factor responsible for anatomy-functional discrepancy. Further, neither age, Parkinson's disease duration, or L-DOPA adverse effects were confirmed as responsible factors. CONCLUSIONS: The difference between the anatomical trajectory and the final electrode placement underlined the need for functional microelectrode monitoring. Brain shift is not the only causative factor for the difference (Tab. 7, Ref. 27).
- MeSH
- design vybavení MeSH
- dospělí MeSH
- hluboká mozková stimulace přístrojové vybavení MeSH
- lidé středního věku MeSH
- lidé MeSH
- monitorování fyziologických funkcí MeSH
- Parkinsonova nemoc terapie MeSH
- senioři MeSH
- thalamus MeSH
- Check Tag
- dospělí MeSH
- lidé středního věku MeSH
- lidé MeSH
- mužské pohlaví MeSH
- senioři MeSH
- ženské pohlaví MeSH
- Publikační typ
- časopisecké články MeSH
