We used a mathematical model describing traveling-wave electroosmotic micropumps to explain their rather poor ability to work against pressure loads. The mathematical model is based upon the Poisson-Nernst-Planck-Navier-Stokes approach, that is, a direct numerical simulation, which allows a detail study of the energy transformations and the charging dynamics of the electric double layers. Using Matlab and COMSOL Multiphysics, we performed a set of extensive parametric studies to determine the dependence of generated electroosmotic flow on the geometric arrangement of the pump. The results suggest that the performance of AC electroosmotic pumps should improve with miniaturization. The AC electroosmosis is likely to be suitable only at submicrometer scale, as the pump's ability to work against pressure load diminishes rapidly when increasing the channel diameter.
The goal of the study was to simulate electrical activation of the heart ventricles and corresponding body surface potentials (BSPs) during premature ventricular contractions (PVC) using the patient specific realistic homogeneous model of cardiac ventricles and the torso. Real position of the initial ectopic activation during PVC was determined by intracardial measurement in the upper part of the right ventricle near the His bundle and confirmed by successful catheter ablation of the PVC origin. Simulated electrical activation in the ventricular model was started at the position of the initial ectopic activation as well as at several other sites at various distances from this position. The propagation of electrical activation in the ventricular model was modeled using bidomain reaction-diffusion (RD) equations with the ionic transmembrane current density defined by the modified FitzHugh-Nagumo (FHN) equations. The torso was modeled as a homogeneous passive volume conductor. The RD equations were numerically solved in the Comsol Multiphysics environment. Simulated ECG signals and BSPs were compared with those measured during PVC in a real patient. The polarity and shape of simulated and measured ECG leads as well as the BSP distribution during the PVC were in best agreement when the stimulated region was less than 10 mm from the position of the initial ectopic activation.
BACKGROUND: This study is focused on the opening technique of the cervical vertebrae during laminoplasty which serves to substantially reduce the most severe adverse effects of the simple resection of posterior vertebral elements. This computational study aims to clarify by an optimisation approach what shape and position upon the lamina the groove should have. METHODS: The computational model was developed in the computational software COMSOL Multiphysics 5.6a based on a computer tomography data obtained from the C4 vertebra. For finding the optimal minimum or maximum of a function (surface), optimisation algorithms are developed following the Nelder-Mead algorithm. RESULTS: The reaction-opening force increases with a decreasing groove radius and an increasing position from the vertebra body. The created area increases with a decreasing groove radius and a decreasing position. As the opening happens mostly only above the groove, the opening area increases only in this location. Moreover, the von Mises stress peak value is almost twice as large as in the case of maximization of the opening area, which might result in breaking of the lamina as the thickness of the lamina would be reduced to its minimum. CONCLUSION: The groove radius and position can affect the opening force and the opening area in case of double door laminoplasty. The opening force is highly influenced by the groove position and radius. The best position for placing the groove is in the middle of the lamina and the radius of the groove should be as large as possible.
- MeSH
- Algorithms MeSH
- Biomechanical Phenomena MeSH
- Cervical Vertebrae diagnostic imaging surgery MeSH
- Laminoplasty * adverse effects MeSH
- Humans MeSH
- Tomography, X-Ray Computed MeSH
- Check Tag
- Humans MeSH
- Publication type
- Journal Article MeSH
Introduction: Conventional biopsy, based on extraction from a tumor of a solid tissue specimen requiring needles, endoscopic devices, excision or surgery, is at risk of infection, internal bleeding or prolonged recovery. A non-invasive liquid biopsy is one of the greatest axiomatic consequences of the identification of circulating tumor DNA (ctDNA) as a replaceable surgical tumor bioQpsy technique. Most of the literature studies thus far presented ctDNA detection at almost final stage III or IV of cancer, where the treatment option or cancer management is nearly impossible for diagnosis. Objective: Hence, this paper aims to present a simulation study of extraction and separation of ctDNA from the blood plasma of cancer patients of stage I and II by superparamagnetic (SPM) bead particles in a microfluidic platform for early and effective cancer detection. Method: The extraction of ctDNA is based on microfiltration of particle size to filter some impurities and thrombocytes plasma, while the separation of ctDNA is based on magnetic manipulation to high yield that can be used for the upstream process. Result: Based on the simulation results, an average of 5.7 ng of ctDNA was separated efficiently for every 10 μL blood plasma input and this can be used for early analysis of cancer management. The particle tracing module from COMSOL Multiphysics traced ctDNA with 65.57% of sensitivity and 95.38% of specificity. Conclusion: The findings demonstrate the ease of use and versatility of a microfluidics platform and SPM bead particles in clinical research related to the preparation of biological samples. As a sample preparation stage for early analysis and cancer diagnosis, the extraction and separation of ctDNA is most important, so precision medicine can be administered.
- MeSH
- Circulating Tumor DNA * MeSH
- Humans MeSH
- Magnetic Iron Oxide Nanoparticles MeSH
- Microfluidics MeSH
- Neoplasms * diagnosis MeSH
- Liquid Biopsy MeSH
- Check Tag
- Humans MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
INTRODUCTION AND HYPOTHESIS: Quantitative characterization of the birth canal and critical structures before delivery may provide risk assessment for maternal birth injury. The objective of this study was to explore imaging capability of an antepartum tactile imaging (ATI) probe. METHODS: Twenty randomly selected women older than 21 years with completed 35th week of pregnancy and a premise of vaginal delivery were enrolled in the feasibility study. The biomechanical data were acquired using the ATI probe with a double-curved surface, shaped according to the fetal skull and equipped with 168 tactile sensors and an electromagnetic motion tracking sensor. Software package COMSOL Multiphysics was used for finite element modeling. Subjects were asked for assessment of pain and comfort levels experienced during the ATI examination. RESULTS: All 20 nulliparous women were successfully examined with the ATI. Mean age was 27.8 ± 4.1 years, BMI 30.7 ± 5.8, and week of pregnancy 38.8 ± 1.4. Biomechanical mapping with the ATI allowed real-time observation of the probe location, applied load to the vaginal walls, and a 3D tactile image composition. The nonlinear finite element model describing the stress-strain relationship of the pelvic tissue was developed and used for calculation of Young's modulus (E). Average perineal elastic modulus was 11.1 ± 4.3 kPa, levator ani 4.8 ± 2.4 kPa, and symphysis-perineum distance was 30.1 ± 6.9 mm. The pain assessment level for the ATI examination was 2.1 ± 0.8 (scale 1-4); the comfort level was 2.05 ± 0.69 (scale 1-3). CONCLUSIONS: The antepartum examination with the ATI probe allowed measurement of the tissue elasticity and anatomical distances. The pain level was low and the comfort level was comparable with manual palpation.
- MeSH
- Adult MeSH
- Elasticity Imaging Techniques * MeSH
- Humans MeSH
- Young Adult MeSH
- Pelvic Floor * diagnostic imaging MeSH
- Perineum diagnostic imaging MeSH
- Parturition MeSH
- Feasibility Studies MeSH
- Pregnancy MeSH
- Imaging, Three-Dimensional MeSH
- Check Tag
- Adult MeSH
- Humans MeSH
- Young Adult MeSH
- Pregnancy MeSH
- Female MeSH
- Publication type
- Journal Article MeSH
The goal of the study was to design a model of cardiac ventricles with realistic geometry that enables simulation of the ventricular activation with normal conduction system functions, as well as with bundle branch blocks. In ventricles, electrical activation propagates from the His bundle to the left and right bundle branches and continues to the fascicles and branching fibers of the Purkinje system. The role of these parts of the conduction system is to lead the activation rapidly and synchronously to the left and right ventricle. The velocity of propagation in the conduction system is several times higher than in the surrounding ventricular myocardium. If the conduction system works normally, QRS duration representing the total activation time of the ventricles lies in the physiological range of about 80 to 120 ms but it is more than 120 ms in the case of bundle branch blocks. In our study, the realistic geometry of the ventricles was constructed on the base of a patient CT scan, defining epicardial and endocardial surfaces. The first part of the conduction system (fast-conducting bundle branches, fascicles in the left ventricle and initial parts of the Purkinje fibers) was modeled as polyline pathways isolated from the surrounding ventricular tissue. The remaining part of the Purkinje system was modeled as an endocardial layer with higher conduction velocity. The propagation of the electrical activation in the ventricular model was modeled using reaction-diffusion (RD) equations, except for the first part of the conduction system, where the activation times were evaluated algebraically with respect to predefined velocity of propagation and estimated distance between the His bundle and particular entry point to the layer with higher conduction velocity. Propagation of activation in cardiac ventricles was numerically solved in Comsol Multiphysics environment. Several configurations of the first part of the conduction system with different number of polyline pathways and entry points were proposed and tested to achieve realistic activation propagation. For the model with 9 starting points, realistic total activation time (TAT) of the whole ventricles of about 108 ms was obtained for the model with normal conduction system, and realistic TAT of 126 ms and 149 ms were obtained for the right and left bundle branch block (RBBB, LBBB), respectively. Very similar TAT was found also for the model with 7 starting points, but unrealistically long TAT was obtained in LBBB simulation for the model with only 5 starting points.
- MeSH
- Models, Anatomic MeSH
- Biomedical Technology methods MeSH
- Biomedical Research instrumentation trends MeSH
- Bundle-Branch Block * diagnostic imaging physiopathology MeSH
- Humans MeSH
- Models, Cardiovascular MeSH
- Computer Simulation classification MeSH
- Heart Ventricles anatomy & histology MeSH
- Check Tag
- Humans MeSH
- Publication type
- Research Support, Non-U.S. Gov't MeSH
- Review MeSH
