Аналіз роботоздатності редуктора копачів коренезбиральної машини

Models and simulations are commonly used to study deep brain stimulation (DBS). Simulated stimulation fields are often defined and visualized by electric field isolevels or volumes of tissue activated (VTA). The aim of the present study was to evaluate the relationship between stimulation field strength as defined by the electric potential V, the electric field E, and the divergence of the electric field ∇(2) V, and neural activation. Axon cable models were developed and coupled to finite-element DBS models in three-dimensional (3-D). Field thresholds ( VT , ET, and ∇(2) VT ) were derived at the location of activation for various stimulation amplitudes (1 to 5 V), pulse widths (30 to 120 μs), and axon diameters (2.0 to 7.5 μm). Results showed that thresholds for VT and ∇(2) VT were highly dependent on the stimulation amplitude while ET were approximately independent of the amplitude for large axons. The activation field strength thresholds presented in this study may be used in future studies to approximate the VTA during model-based investigations of DBS without the need of computational axon models.This work was supported by the European Union's Seventh Framework Programme IMPACT (Grant 305814) and by the Swedish Research Council (Grant 621-2013-6078). Asterisk indicates corresponding author.</p

Modeling and Simulation of Microdialysis in the Deep Brain Structures

Microdialysis is a method for monitoring of the local biochemical environment in a region of interest. The method uses a catheter, mimicking the function of a blood capillary, to sample substances from the surrounding medium through diffusion. A recent application for microdialysis is the sampling of neuroactive substances in the deep brain, or basal ganglia, during deep brain stimulation (DBS) for patients with Parkinson’s disease. The basal ganglia consist of nuclei interconnected by chemical synapses, and it is hypothesized that the levels of neurotransmitter substances around the synapses are affected by DBS treatment. In order to relate the microdialysis data to their anatomical origin and to the effects of DBS, it is suitable to estimate the tissue volume which is sampled during a microdialysis experiment. In this thesis, the maximum tissue volume of influence (TVImax) for a microdialysis catheter was simulated and evaluated using the finite element method (FEM), to allow interpretation of biochemical data in relation to anatomical structures. A FEM model for simulation of the TVImax for a microdialysis catheter placed in grey brain matter was set up, using Fick’s law of diffusion. The model was used to investigate the impact of the analyte diffusion coefficient (D), the tissue tortuosity (λ) and the loss rate constant (k) on the size of the TVImax by regression analysis. Using relevant parameter intervals, the radius of the TVImax of a neurotransmitter was estimated to 0.85 ± 0.25 mm. A microdialysis experiment on calf brain tissue showed agreement with the regression model. A heterogeneous anisotropic FEM model based on diffusion tensor imaging (DTI) showed that the radius of the TVImax may vary by up to 0.5 mm as a consequence of local tissue properties, which was reasonable in relation to the 95% confidence interval from the regression estimation. The TVImax was simulated and patient-specifically visualized in relation to MRI images for four patients undergoing microdialysis in parallel to DBS. The size of the TVImax showed to be relevant in relation to the basal ganglia nuclei, and the obtained microdialysis data indicated that the biochemical response to DBS depends on the catheter position. The simulations of the TVImax were combined with patient-specific DBS electric field simulations, for further interpretation of the results in relation to the effects of DBS. In conclusion, simulations and visualizations of the TVImax allowed relating microdialysis data to its anatomical origin. Detailed knowledge about the parameters affecting the microdialysis sampling volume is valuable for the current application as well as other applications related to the migration of analytes in tissue.Mikrodialys är en metod som används för studera lokala nivåer av biokemiska substanser i ett specifict organ eller struktur. Metoden använder sig av en kateter med ett semipermeabelt membran, över vilket utbyte av substanser sker genom diffusion. Mikrodialys har nyligen använts för att studera nivåer av neurotransmittorer i de djupa hjärnstrukturerna, ävan kallade basala ganglierna, under djup hjärnstimulering (DBS) för patienter med Parkinsons sjukdom. De basala ganglierna består av ett antal millimeterstora hjärnstrukturer, sammankopplade via biokemiska synapser, och nivåerna av signalsubstanser runt dessa synapser tros påverkas av DBS. För att relatera mikrodialysmätningarna till dess anatomiska ursprung, och till effekterna av DBS, är det önskvärt att få en uppskattning av den vävnadsvolym som påverkar mätningen från en mikrodialyskateter. Målet med denna licentiatavhandling har varit att simulera och utvärdera den maximala påverkansvolymen (TVImax) för en mikrodialyskateter med hjälp av finita element-metoden (FEM), för att underlätta tolkningen av de biokemiska data som samlats in. En FEM-modell sattes upp för att simulera TVImax för en kateter placerad i grå hjärnvävnad, baserat på Ficks diffusionslag och lämpliga rand- och initialvillkor. Modellen användes för att göra en regressionsanalys av hur TVImax påverkades av analytens diffusionskoefficient (D), hjärnvävnadens tortuositet (λ) och analytens nedbrytningshastighet (k), och radien för TVImax för en neurotransmitter uppskattades till 0.85 ± 0.25 mm då fysiologiskt relevanta parameterintervall användes. En experimentell studie av mikrodialys på hjärnvävnad från kalv gav god överensstämmelse med simuleringsresultaten. En heterogen och anisotrop FEM-modell sattes upp med hjälp av diffusionstensordata (DTI), vilket visade att lokala vävnadsegenskaper påverkar diffusionen av analyter i de basala ganglierna med upp till 0.5 mm i enighet med den regressionsmodell som tagits fram. TVImax simulerades och visualiserades sedan i relation till MRI-bilder för fyra patienter som genomgått mikrodialys parallellt med DBS. Målområdena för mikrodialysmätningarna visade sig skilja mellan patienterna, och den insamlade mikrodialysdatan indikerade att den biokemiska responsen på DBS berodde på kateterns position. För att ytterligare underlätta tolkningen av resultatet i relation till effekterna av DBS, kombinerades TVImax-simuleringarna med simuleringar av det elektriska fältet runt DBS-elektroderna. Sammanfattningsvis kan simuleringar av TVImax vara en hjälp vid den fysiologiska tolkningen av insamlad mikrodialysdata, vilket underlättar jämförelser mellan patienter. Detaljerad kunskap om de parametrar som påverkar samplingsvolymen för en mikrodialyskateter är värdefulla både för den aktuella applikationen, och övriga applikationer relaterade till diffusion av substanser i vävnad

Modeling and Simulation of Microdialysis in the Deep Brain Structures

Microdialysis is a method for monitoring of the local biochemical environment in a region of interest. The method uses a catheter, mimicking the function of a blood capillary, to sample substances from the surrounding medium through diffusion. A recent application for microdialysis is the sampling of neuroactive substances in the deep brain, or basal ganglia, during deep brain stimulation (DBS) for patients with Parkinson’s disease. The basal ganglia consist of nuclei interconnected by chemical synapses, and it is hypothesized that the levels of neurotransmitter substances around the synapses are affected by DBS treatment. In order to relate the microdialysis data to their anatomical origin and to the effects of DBS, it is suitable to estimate the tissue volume which is sampled during a microdialysis experiment. In this thesis, the maximum tissue volume of influence (TVImax) for a microdialysis catheter was simulated and evaluated using the finite element method (FEM), to allow interpretation of biochemical data in relation to anatomical structures. A FEM model for simulation of the TVImax for a microdialysis catheter placed in grey brain matter was set up, using Fick’s law of diffusion. The model was used to investigate the impact of the analyte diffusion coefficient (D), the tissue tortuosity (λ) and the loss rate constant (k) on the size of the TVImax by regression analysis. Using relevant parameter intervals, the radius of the TVImax of a neurotransmitter was estimated to 0.85 ± 0.25 mm. A microdialysis experiment on calf brain tissue showed agreement with the regression model. A heterogeneous anisotropic FEM model based on diffusion tensor imaging (DTI) showed that the radius of the TVImax may vary by up to 0.5 mm as a consequence of local tissue properties, which was reasonable in relation to the 95% confidence interval from the regression estimation. The TVImax was simulated and patient-specifically visualized in relation to MRI images for four patients undergoing microdialysis in parallel to DBS. The size of the TVImax showed to be relevant in relation to the basal ganglia nuclei, and the obtained microdialysis data indicated that the biochemical response to DBS depends on the catheter position. The simulations of the TVImax were combined with patient-specific DBS electric field simulations, for further interpretation of the results in relation to the effects of DBS. In conclusion, simulations and visualizations of the TVImax allowed relating microdialysis data to its anatomical origin. Detailed knowledge about the parameters affecting the microdialysis sampling volume is valuable for the current application as well as other applications related to the migration of analytes in tissue.Mikrodialys är en metod som används för studera lokala nivåer av biokemiska substanser i ett specifict organ eller struktur. Metoden använder sig av en kateter med ett semipermeabelt membran, över vilket utbyte av substanser sker genom diffusion. Mikrodialys har nyligen använts för att studera nivåer av neurotransmittorer i de djupa hjärnstrukturerna, ävan kallade basala ganglierna, under djup hjärnstimulering (DBS) för patienter med Parkinsons sjukdom. De basala ganglierna består av ett antal millimeterstora hjärnstrukturer, sammankopplade via biokemiska synapser, och nivåerna av signalsubstanser runt dessa synapser tros påverkas av DBS. För att relatera mikrodialysmätningarna till dess anatomiska ursprung, och till effekterna av DBS, är det önskvärt att få en uppskattning av den vävnadsvolym som påverkar mätningen från en mikrodialyskateter. Målet med denna licentiatavhandling har varit att simulera och utvärdera den maximala påverkansvolymen (TVImax) för en mikrodialyskateter med hjälp av finita element-metoden (FEM), för att underlätta tolkningen av de biokemiska data som samlats in. En FEM-modell sattes upp för att simulera TVImax för en kateter placerad i grå hjärnvävnad, baserat på Ficks diffusionslag och lämpliga rand- och initialvillkor. Modellen användes för att göra en regressionsanalys av hur TVImax påverkades av analytens diffusionskoefficient (D), hjärnvävnadens tortuositet (λ) och analytens nedbrytningshastighet (k), och radien för TVImax för en neurotransmitter uppskattades till 0.85 ± 0.25 mm då fysiologiskt relevanta parameterintervall användes. En experimentell studie av mikrodialys på hjärnvävnad från kalv gav god överensstämmelse med simuleringsresultaten. En heterogen och anisotrop FEM-modell sattes upp med hjälp av diffusionstensordata (DTI), vilket visade att lokala vävnadsegenskaper påverkar diffusionen av analyter i de basala ganglierna med upp till 0.5 mm i enighet med den regressionsmodell som tagits fram. TVImax simulerades och visualiserades sedan i relation till MRI-bilder för fyra patienter som genomgått mikrodialys parallellt med DBS. Målområdena för mikrodialysmätningarna visade sig skilja mellan patienterna, och den insamlade mikrodialysdatan indikerade att den biokemiska responsen på DBS berodde på kateterns position. För att ytterligare underlätta tolkningen av resultatet i relation till effekterna av DBS, kombinerades TVImax-simuleringarna med simuleringar av det elektriska fältet runt DBS-elektroderna. Sammanfattningsvis kan simuleringar av TVImax vara en hjälp vid den fysiologiska tolkningen av insamlad mikrodialysdata, vilket underlättar jämförelser mellan patienter. Detaljerad kunskap om de parametrar som påverkar samplingsvolymen för en mikrodialyskateter är värdefulla både för den aktuella applikationen, och övriga applikationer relaterade till diffusion av substanser i vävnad

Modeling and Simulation of Microdialysis in the Deep Brain

Microdialysis is a method for monitoring of the local biochemical environment in a region of interest. The method uses a catheter, mimicking the function of a blood capillary, to sample substances from the surrounding medium through diffusion. A recent application for microdialysis is the sampling of neuroactive substances in the deep brain, or basal ganglia, during deep brain stimulation (DBS) for patients with Parkinson’s disease. The basal ganglia consist of nuclei interconnected by chemical synapses, and it is hypothesized that the levels of neurotransmitter substances around the synapses are affected by DBS treatment. In order to relate the microdialysis data to their anatomical origin and to the effects of DBS, it is suitable to estimate the tissue volume which is sampled during a microdialysis experiment. In this thesis, the maximum tissue volume of influence (TVImax) for a microdialysis catheter was simulated and evaluated using the finite element method (FEM), to allow interpretation of biochemical data in relation to anatomical structures. A FEM model for simulation of the TVImax for a microdialysis catheter placed in grey brain matter was set up, using Fick’s law of diffusion. The model was used to investigate the impact of the analyte diffusion coefficient (D), the tissue tortuosity (λ) and the loss rate constant (k) on the size of the TVImax by regression analysis. Using relevant parameter intervals, the radius of the TVImax of

Non-Invasive Methods for Detecting Drug and Alcohol Impaired Drivers : - a Study of Alcohol and Drug Biomarkers and Optical Detection Techniques

In recent years, the use of alcohol and psychoactive drugs in combination withdriving has recieved increased attention. The lack of in-vehicle devices capable ofdetecting recent drug consumption and the difficulties associated with the breathbasedalcolocks in use today makes it interesting to investigate methods that areable to non-invasivelly measure analytes directly in the blood. The assignment of this project, commissioned by Volvo Technology Corporationand Volvo Car Corporation, is to map substances that constitute a possible threatto traffic safety, identify suitable detection markers as a proof of administrationof these substances, and study possible non-invasive techniques to detect thesemarkers. The objective is to present for Volvo if and how to continue evaluatingand developing a non-invasive detection device. The project has been carried out by performing an extensive literature study and averification experiment. From the literature review, a number of substances affectingdriving performance could be identified, and a metabolic study was performedfor each drug to map suitable biomarkers. Furthermore, two potential techniquesfor non-invasive detection, near-infrared Raman spectroscopy and near-infraredspectroscopy, were found and evaluated. The experiment was conducted usingnear-infrared Raman spectroscopy, with the aim of investigating the sensitivityand linearity of the method for ethanol detection. Based on the theoretical evaluation, both near-infrared Raman spectroscopy andnear-infrared spectroscopy are expected to have potential for non-invasive detectionof ethanol. The experiment further proved the theoretical conclusionsmade for near-infrared Raman spectroscopy. However, neither of the techniquesis thought to have potential for drug detection.Altogether, we believe that non-invasive ethanol detection is possible, but suggestfurther experiments in order to determine which technique to be preferred

http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-72087 Patient-Specific Modeling and Simulation of Deep Brain Stimulation

Abstract. Deep brain stimulation (DBS) is widely used for reduction of symptoms caused by movement disorders. In this chapter a patient-specific finite element method for modeling and simulation of DBS electric parameters is presented. The individual’s stereotactic preoperative MR-batch of images is used as input to the model in order to classify tissue type and allotte electrical conductivity for cerebrospinal fluid, blood and grey as well as white matter. With patient-specific positioning of the DBS electrodes the method allows for investigation of the relative electric field changes in relation to anatomy and DBS-settings. Examples of visualization of the patient-specific electric entities together with the surrounding anatomy are given. The use of the method is exemplified on patients with Parkinson’s disease. Future applications including multiphysics simulations and applicability for new DBS targets and symptoms are discussed. Deep brain stimulation has become one of the most important brain stimulation techniques for clinical use (Benabid, 2003). The application of DBS for movemen

Corresponding author:

A model for simulation and patient-specific visualization of the tissue volume of influenc

Relationship between Neural Activation and Electric Field Distribution during Deep Brain Stimulation

Models and simulations are commonly used to study deep brain stimulation (DBS). Simulated stimulation fields are often defined and visualized by electric field isolevels or volumes of tissue activated (VTA). The aim of the present study was to evaluate the relationship between stimulation field strength as defined by the electric potential V, the electric field E, and the divergence of the electric field ∇(2) V, and neural activation. Axon cable models were developed and coupled to finite-element DBS models in three-dimensional (3-D). Field thresholds ( VT , ET, and ∇(2) VT ) were derived at the location of activation for various stimulation amplitudes (1 to 5 V), pulse widths (30 to 120 μs), and axon diameters (2.0 to 7.5 μm). Results showed that thresholds for VT and ∇(2) VT were highly dependent on the stimulation amplitude while ET were approximately independent of the amplitude for large axons. The activation field strength thresholds presented in this study may be used in future studies to approximate the VTA during model-based investigations of DBS without the need of computational axon models.This work was supported by the European Union's Seventh Framework Programme IMPACT (Grant 305814) and by the Swedish Research Council (Grant 621-2013-6078). Asterisk indicates corresponding author.</p