Current Issue : October - December Volume : 2016 Issue Number : 4 Articles : 5 Articles
Background: Blood oxygen saturation of vein (SvO2) is an important clinical parameter\nfor patient monitoring. However, the existing clinical methods are invasive, expensive,\nwhich are also painful for patients.\nMethods: Based on light-absorption, this study describes a new noninvasive SvO2\nmeasurement method by using external stimulation signal to generate cyclical fluctuation\nsignal in the vein, which overcomes the low signal-to-noise ratio problem in the\nmeasurement process. In this way, the value of SvO2 can be obtained continuously in\nreal time.\nResults: The experimental results demonstrate that the method can successfully\nmeasure venous oxygen saturation by artificial addition of stimulation. Under hypoxic\nconditions, the system can reflect the overall decline of venous oxygen saturation\nbetter. When the results measured by the new method are compared with those\nmeasured by the invasive method, the root mean square error of the difference is 5.31\nand the correlation coefficient of the difference is 0.72. The new method can be used\nto measure SvO2 and evaluate body oxygen consumption, and its accuracy needs\nimprovement.\nConclusions: Real-time and continuous monitoring can be achieved by replacing\ninvasive method with noninvasive method, which provides more comprehensive\nclinical information in a timely manner and better meet the needs of clinical treatment.\nHowever, the accuracy of the new noninvasive SvO2 measurement based on lightabsorption\nhas to be further improved....
Abstract\nBackground: Preservation of the hepatic vessels while dividing the parenchyma is\nkey to achieving safe liver resection in a timely manner. In this study, we assessed the\nfeasibility of a newly developed, piezo actuator-driven pulsed water jet (ADPJ) for liver\nresection in a surviving swine model.\nMethods: Ten domestic pigs underwent liver resection. Parenchymal transection and\nvessel skeletonization were performed using the ADPJ (group A, n = 5) or an ultrasonic\naspirator (group U, n = 5). The water jet was applied at a frequency of 400 Hz and a\ndriving voltage of 80 V. Physiological saline was supplied at a flow rate of 7 ml/min.\nAfter 7 days, the animals were killed and their short-term complications were examined\nand compared between the two groups.\nResults: No significant complications, such as massive bleeding, occurred in either\ngroup during the surgical procedures. The transection time per transection area\nwas significantly shorter in group A than in group U (1.5 �± 0.3 vs. 2.3 �± 0.5 min/cm2,\nrespectively, P = 0.03). Blood loss per transection area was not significantly different\nbetween groups A and U (9.3 �± 4.2 vs. 11.7 �± 2.3 ml/cm2, P = 0.6). All pigs in group\nA survived for 7 days. No postoperative bleeding or bile leakage was observed in any\nanimal at necropsy.\nConclusion: The present results suggested that the ADPJ reduces transection time\nwithout increasing blood loss. ADPJ is a safe and feasible device for liver parenchymal\ntransection....
Background: Hydrocephalus is a medical condition consisting of an abnormal\naccumulation of cerebrospinal fluid within the brain. A catheter is inserted in one of\nthe brain ventricles and then connected to an external valve to drain the excess of\ncerebrospinal fluid. The main drawback of this technique is that, over time, the ventricular\ncatheter ends up getting blocked by the cells and macromolecules present in\nthe cerebrospinal fluid. A crucial factor influencing this obstruction is a non-uniform\nflow pattern through the catheter, since it facilitates adhesion of suspended particles to\nthe walls. In this paper we focus on the effects that tilted holes as well as conical holes\nhave on the flow distribution and shear stress.\nMethods: We have carried out 3D computational simulations to study the effect of the\nhole geometry on the cerebrospinal fluid flow through ventricular catheters. All the simulations\nwere done with the OpenFOAM�® toolbox. In particular, three different groups of\nmodels were investigated by varying (i) the tilt angles of the holes, (ii) the inner and outer\ndiameters of the holes, and (iii) the distances between the so-called hole segments.\nResults: The replacement of cylindrical holes by conical holes was found to have a\nstrong influence on the flow distribution and to lower slightly the shear stress. Tilted\nholes did not involve flow distribution changes when the hole segments are sufficiently\nseparated, but the mean shear stress was certainly reduced.\nConclusions: The authors present new results about the behavior of the fluid flow\nthrough ventricular catheters. These results complete earlier work on this topic by adding\nthe influence of the hole geometry. The overall objective pursued by this research is to\nprovide guidelines to improve existing commercially available ventricular catheters....
Backround: Currently, the effect of vascular dynamic bending (VDB) has not been\nfully considered when studying cardiovascular stents� long-term mechanical properties,\nas the previous studies about stent�s mechanical properties mostly focus on the effect\nof vascular pulsation (VP). More and more clinical reports suggested that the effect of\nVDB have a significant impact on stent.\nMethods: In this paper, an explicit-implicit coupling simulation method was applied\nto analyze the mechanical responses of cardiovascular stents considering the effect of\nVDB. The effect of VP on stent mechanical properties was also studied and compared\nto the effect of VDB.\nResults: The results showed that the dynamic bending deformation occurred in stents\ndue to the effect of VDB. The effects of VDB and VP resulted in alternating stress states\nof the stent, while the VDB alternate stresses effective on the stent were almost three\ntimes larger than that of the VP. The stress concentration under VDB mainly occurred\nin bridge struts and the maximal stress was located in the middle loops of the stent.\nHowever, the stress distributed uniformly in the stents under the effect of VP. Stent\nfracture occurred more frequently as a result of VDB with the predicted fracture position\nlocated in the bridging struts of the stent. These results are consistent with the\nreported data in clinical literatures. The stress of the vessel under VDB was higher, than\nthat caused by VP.\nConclusions: The results showed that the effect of VDB has a significant impact on the\nstent�s stress distribution, fatigue performance and overall stress on the vessel, thus it is\nnecessary to be considered when analyzing stent�s long-term mechanical properties.\nMeanwhile, the results showed that the explicit-implicit coupling simulation can be\napplied to analyze stent mechanical properties....
A novel imaging approach utilizing microwave scattering was proposed in order to analyze various\nproperties of bone. Microwave frequencies of 900 MHz, 1 GHz, and 2.4 GHz were used during this\nstudy. This investigation�s objectives were to emphasize characteristics of abnormalities in human\nbones and to detect fine fractures through contrasts in bone density. The finite element method\n(FEM) presented here is generated from COMSOL software at different frequencies. The study identified\nthe optimum transmission directed at the interface layers from an external microwave source.\nIt was found that approximately 900 MHz microwave power was ideal for this application. This can\nbe attributed to the penetration depth where the power dissipation is analyzed based on bone condition.\nThe microwave energy was generated from an exterior antenna that was interfaced, via catheter,\nto skeletal bone. The power transmitted to bone was converted into thermal energy, and has\nled to a visible temperature distribution pattern, which reflects the bone density level, and accordingly,\nthe type of bone under investigation. The electrical and thermal properties, including the dielectric\npermittivity, thermal conductivity, and heat flux absorption through the bone substance,\nhave great implications on the FEM distribution. The boundary conditions using tangential matching\nof field components at the tissue-bone interface were incorporated into the finite element method.\nThe average power from the electromagnetic fields (estimated from the Poynting�s vector, P = E*H),\nwas assumed to be fully absorbed as heat due to the conductivity of the bone material. Furthermore,\nmicrowave energy was applied as a delta function and the thermal distributions have been analyzed\nin order to distinguish between normal healthy bone and bones with structural or metabolic abnormalities.\nThe latter was emulated by different bone density to contrast normal bone anatomy.\nThe FEM simulation suggests that thermography microwave imaging could be a good tool for bone\ncharacterization in order to detect skeletal abnormalities. This approach could be advantageous\nover other existing methods such as X-ray imaging....
Loading....