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1.
By means of FEM, the physiological blood flow in coronary bypass graft is simulated. The stenosis in coronary artery is involved in the graft model,and the deformation of graft end to allow the surgical suture with a smaller diameter coronary is taken into consideration. The flow pattern, secondary flow and wall shear stress in the vicinity of anastomosis are analyzed. It is shown that a zone of low wall stress and high wall stress gradient exists downstream the toe. The floor opposed to the anastomosis is an area of high wall stress and high wall stress gradient. Both the toe downstream and the anastomosis bottom floor are prone to intimal hyperplasia.  相似文献   

2.
Coronary Artery Bypass Graft (CABG) is an important surgical treatment for critically stenosed arteries. Unfortunately restenosis always occurs after CABG surgery, which bring about surgery failure, lntimal thickening in the CABG distal anastomosis has been implicated as the major cause of restenosis and long-term graft failure. The nonuniform hemodynamics including disturbed flows, recirculation zones, oscillating wall shear stress, and long particle residence time were thought to be the possible etiologies. Numerical simulation was proved to be of great help and guidance meaning for the biofluid mechanics research and the CABG surgical plan. The present study was based on the hypothesis that the geometry configuration of CABG could greatly influence the hemodynamics in the vicinity of anastomosis. The hemodynamic features of two geometry models of end-to-side CABG were studied and compared. One simulated a conventional CABG with 1-way bypass graft, and the other simulated a modified CABG with symmetric 2-way bypass graft. The numerical investigations of hemodynamics in these two models with fully stenosed coronary arteries were accomplished using finite element method. The temporal and spatial distributions of hemodynamics were analyzed and compared. Results showed that the presence of symmetric 2-way bypass graft was of reasonable and favorable hemodynamics than 1-way bypass graft. The modified CABG model created a more hemodynamically efficient streamlined environment with higher mean and maximum axial velocities and lower radial velocities than the conventional 1-way model. Meanwhile, the symmetric 2-way bypass graft was featured with low pressure near the wall, high and uniform WSS in the host artery. All of these were favorable for inhibiting the development of intimal thickening, restenosis, and ultimate failure of the CABG, and it could considerably improve the flow conditions and decrease the probability of intimal hyperplasia and restenosis of CABG.  相似文献   

3.
We report a rare case of internal carotid artery agenesis with stenosed intercavernous anastomosis.A 59-yearold male patient presented with a new infarction in the left basal ganglia.Magnetic resonance angiography and cerebral angiography showed that the right internal carotid artery disappeared from the origin to the foramen lacerum segment,and there was an anastomotic artery with severe stenosis passed through the floor of the sella and in front of the cavernous sinus.The right A1 segment of the anterior cerebral artery was absent and A2 segment was supplied by the normal contralateral internal carotid artery via the anterior communicating artery.  相似文献   

4.
Heart disease is the leading cause of death. Each year in the United States, more than 500,000 men and women die from coronary artery disease (CAD). CAD results from the narrowing of blood vessels that sup- ply the heart. The blood vessels become narrow when fatty deposits build up inside the arterial wall. When the arteries become clogged, the blood flow to the myocardium is impaired and a heart attack can occur. Nuclear cardiology studies use noninvasive imaging techniques to assess myocardial blood flow.  相似文献   

5.
In a new step forward in artificial heart technology, French medical company has developed a new artificial heart that is part bovine and part machine. The idea behind this design was to use actual bovine tissue for parts of the artificial heart that would come in contact with a wearer's blood, thus leading to greater biocompatibility. Their design consists of two chambers separated by a membrane taken from a cow's heart. One chamber houses the wearer's actual blood and the other chamber houses hydraulic fluid that is driven by a motor to exert force on the membrane, thereby causing flow in the chamber housing blood, leading to circulation. In addition to the dividing membrane being made of bovine tissue, the heart valves are also made of components taken from cows. The bovine components used to make the valve not only serves the purpose of greater biocompatibility, but is also equipped with embedded sensors to measure the pressure on them. Such measurements could be used to monitor exertion and adiust "hear rate" as needed.  相似文献   

6.
BACKGROUND: Drug eluting stents and endothelium stents for clinical treatment of vascular stenosis can lead to delayed endothelialization and restenosis. The authors’ previous in vitro studies have shown a rapamycin eluting stent combined with CD133 antibody can play a synergistic role to offset delayed endothelialization and intimal hyperplasia due to antiproliferative drugs. OBJECTIVE: To observe the efficacy of anti-CD133 antibody applied on a rapamycin eluting stent in the minipig coronary artery injury model. METHODS: Rapamycin-eluting stents, anti-CD133 antibody stents, and anti-CD133 antibody applied on rapamycin-eluting stents were implanted in minipig coronary arteries in the rapamycin group, CD133 antibody group, and rapamycin/CD133 antibody group, respectively. Animal experiments were approved by the Laboratory Animal Ethics Committee of Central Hospital Affiliated to Shenyang Medical College (approval No. 20190017) on March 15, 2019. RESULTS AND CONCLUSION: (1) There were differences in the endothelialization extent in the three groups at 14 days and 1 month after implantation. The stent endothelial coverage of the rapamycin group was lower than that of the CD133 antibody group and the rapamycin/CD133 antibody group. (2) At 3 and 6 months after implantation, the luminal stenosis rate of the rapamycin group and the rapamycin/CD133 antibody group was lower, but there was obvious inflammation in the surrounding tissues of the rapamycin stent, and the CD133 antibody stent could cause obvious intimal hyperplasia and lumen stenosis. (3) It is suggested that rapamycin combined with CD133 antibody stent can achieve early endothelialization in vivo, promote endothelial cell repair, and reduce the inflammation of surrounding tissues after implantation, and its anti-proliferative effect is similar to that of rapamycin stent within 6 months. © 2022, Publishing House of Chinese Journal of Tissue Engineering Research. All rights reserved.  相似文献   

7.
Coronary stents are metal coils or mesh tubes delivered to blocked vessels through catheters, whic Recently, special drugs h are expanded by balloons to reopen and scaffold target vessels. are carried by stents (drug-eluting stents) to further reduce instent restenosis rate after stenting procedure. However, continual study on biomechanical characteristics of stents is necessary provide a more suitable drug loading for better interactions between stents and tissue, or to platform for drug-eluting stents. The purpose of this paper is to show how finite element methods can be used to study cell area and strut distribution changes of bent coronary stents. A same bending deformation was applied to two commercial coronary stent models by a rigid curved vessel. Results show that the stent design influenced the changes of cell area and strut distribution under bending situation. The stent with links had more cell area changes at outer curvature, and the stent with peak-peak ( 〉 〈 ) strut design could have strut contact and overlapping at inner curvature. In conclusion, this finite element method can be used to study and compare cell area and strut distribution changes of bent stents, and to provide a convenient tool for designers in testing and improving biomechanical characteristics of new stents.  相似文献   

8.
Glioma has the highestincidence in the brain tumors.Though treated with sur-gical resection,external beam radiation therapy,and systemic chemotherapy,pa-tients with glioma have poor prognosis because of glioma recurrence.Because of theBlood Brain Barrier,chemotherapeutic drugs can tpenetrate into brain freely,theirconcentrations can t reach a effective level.Interstitial chemotherapy is a new kindof chemotherapy protocols.Itcan deliverchemotherapeutic agents directly to the tu-mor bed bypass…  相似文献   

9.
Developing a shear thinning non-Newtonian fluid to substitute blood is desirable in studies of biomedicine engineering since blood is a shear thinning nonNewtonian fluid that exhibits both viscous and elastic properties, and generally not available in large volume. The rheological properties of aqueous Xanthan gum with different concentrations and temperatures were studied in present paper. The resuits show that aqueous Xanthan gum is a non-Newtonian fluid which displays remarkable shear thinning behaviour and is a suitable blood analog fluid. There is a power law distribution relationship between shear stress and shear rate, and the higher the solution concentration is, the more strongly it displays shear thinning behaviours. Viscosity values of aqueous Xanthan gum increase with the solution temperature decrease or with the solution concentration increase in linearity. Moreover at the temperature of 37℃, aqueous Xanthan gum with concentration of 0.4%e and 0.6%0 matches human blood best in rheological properties. According to the resuits, the viscosity expression varied with temperature and concentrition is obtained, and the stability of Xanthan gum solution is discussed.  相似文献   

10.
A novel biological small-diameter vascular graft was evaluated in a canine model. 3 cm long segments with 4 mm I. D. were implanted end-to-end in the carotid position of 12 dogs for 6 months. Color Doppler sonography was performed at the first week post-operation, and angiography was then administered to 9 grafts at 4th week, 12th week and 24th week respectively to monitor the graft pantency and blood flow characteristics. Vascular samples containing the grafts were collected at 1st week, 8th week, 12th week and 24th week after implantation. Morphological changes of the grafts were observed by optical and scanning electron microscopic (SEM) studies and compared with that of the original prosthesis and the normal host vessel. All grafts were patent throughout the experiment except one graft. Histopathology and SEM demonstrated both a nearly complete inner capsule of varied thickness lining the graft luminal surface and connective tissue adventitia formation at one-week post-operation. The neointima became confluent at 8 weeks and then compact but had no signs of hyperplasia up to 12 weeks; meanwhile on the neointimal surface newly grown endothelial-like cells were migrating from the stoma to the middle portion. The grafts also illustrated endothelialization in many "islands" in the mid-segment luminal surface of the grafts. In addition, the closer distance the cells towards the stoma were, the more morphological similarity the cells with the normal endothelial were. Taken together, the biological vascular graft remained patent for 24 weeks as a carotid prosthesis, characterized by the early and complete neointima formation plus endothelialization starting before 12 weeks post grafting. Therefore, the graft seems suitable for reconstruction of vascular lesions in dogs. Further studies may be carried out to extend the graft application for the clinical use.  相似文献   

11.
To examine the effect of sleep deprivation (SD) on eye movement be- havior in flight task, four subjects who were skilled in flight simulator participated in the experiment, which were asked to perform a level flight task in a flight simulator. Eye movement data and flight performance data were measured at the following hours: 11:00, 15:00, 04:00, 11:00, 15:00. The subjects workload and fatigue were assessed with the method of national aeronautics and space administration-task load index (NASA-TLX) and rating of perceived exertion (RPE). Eye movement indices of average pupil area, av- erage saceade amplitude and average saccade velocity decreased during the 32 h of SD and they all showed significantly change in the final SD while the index of average fixa- tion time increased in the final SD. Flight performance deteriorated during the 32 h of SD, but not significantly. The feeling of fatigue and workload reported by subjects both increased during the 32 h of SD. Daily rhythm effects on the measured indices were also found, there were a obviously change at the hour of 04:00. 32 h of SD has obvious effect on eye movement behaviors which have close relation to fatigue because of SD. The eye movement measurement can be served as a tool to continually monitor fatigue online.  相似文献   

12.
In this paper, we applied RobustICA to speech separation and made a comprehensive comparison to FastICA according to the separation results. Through a series of speech signal separation test, RobustICA reduced the separation time consumed by FastICA with higher stability, and speeches separated by RobustICA were proved to having lower separation errors. In the 14 groups of speech separation tests, separation time consumed by RobustICA was 3.185 s less than FastICA by nearly 68%. Separation errors of FastICA had a float between 0.004 and 0.02, while the errors of RobustlCA remained around 0.003. Furthermore, compared to FastICA, RobustlCA showed better separation robustness. Experimental results showed that RohustICA was successful to apply to the speech signal separation, and showed superiority to FastlCA in speech separation.  相似文献   

13.
Hydrogel materials were prepared by thermopolymerization with different content of glyceryl methacrylate and hydroxyethyl methacrylate. The different states of water in swelling hydrogels were described and studied by differential scanning calorimetry (DSC). It was found that the hydrophilicity of GMA was stronger than HEMA, the water content and bound water of GMA hydrogel are higher than HEMA hydrogel. With the increase of GMA content, the content of free water in hydrogel increased. When GMA content was lower than 50%, the increase of GMA content also increased the content of bound water; but when GMA content was higher than 50%, the increase of GMA content decreased the content of bound water, which was caused by the chain hydrogen bond formed on the GMA chain with hydroxyl group each other.  相似文献   

14.
Attenuated Listeria monocytogenes (LM) is a promising candidate vector for the delivery of cancer vaccines. After phagocytosis by antigen-presenting cells, this bacterium stimulates the major histocompatibility complex (MHC)-I and MHC-II pathways and induces the proliferation of antigen-specific T lymphocytes. A new strategy involving genetic modification of the replication-deficient LM strain AdalAdat (Lmdd) to express and secrete human CD24 protein has been developed. CD24 is a hepatic cancer stem cell biomarker that is closely associated with apoptosis, metastasis and recurrence of hepatocellular carcinoma (HCC). After intravenous administration in mice, Lmdd-CD24 was distributed primarily in the spleen and liver and did not cause severe organ injury. Lmdd-CD24 effectively increased the number of interferon (IFN)-7-producing CD8+ T cells and IFN-7 secretion. Lmdd-CD24 also enhanced the number of IL-4- and IL-lO-producing T helper 2 cells. The efficacy of the Lmdd-CD24 vaccine was further investigated against Hepa1- 6-CD24 tumors, which were inguinally inoculated into mice. Lmdd-CD24 significantly reduced the tumor size in mice and increased their survival. Notably, a reduction of T regulatory cell (Treg) numbers and an enhancement of specific CD8+ T-cell activity were observed in the tumor-infiltrating lymphocytes (TILs). These results suggest a potential application of the Lmdd-CD24 vaccine against HCC.  相似文献   

15.
Objective: To achieve an optimized method for soluble expression of human carboxylesterase 1 (hCE-1) in escherichia coil and purification by Ni2+-NTA agarose affinity chromatography, to get improved protein yield and purity for further development of hepatocellular carcinoma (HCC) diagnosis ELISA kits. Methods: The best antigen epitopes of hCE1 were predicted by comparing secondary structure, flexible regions, hydrophilicity, antigenic index surface probability of residues. Afterwards, pET-42a (+) with a His-tag and a GST-tag was applied to form recombinant plasmid pET-42a (+)/hCE1, which facilitated purification when using Ni2+-NTA agarose affinity chromatography. Protein quality was measured by SDS-PAGE and BCA protein assay. Western-blot identification was also performed to ensure the correct expression of hCE1 protein. Results: The residues from 500 to 567 near C-terminal of hCE1 protein were considered the best epitopes which exhibited high hydrophilicity and high surface probability and relatively flexible secondary structure and low homology compared with hCE2 and hCE3. His-hCE1 500-567 fusion protein was achieved by IPTG-inducted expression with an expected mass of 42 kDa. After purification, the final product was specially identified, which reached over 95%purity and more than 10 mg/L of microbial culture. In Western blot, the purified fusion protein was recognized by anti-hCE1 monoclonal antibody, along with previous sequencing validation, which demonstrated the correct preparation of soluble hCE1 protein. Conclusion: This is an efficacious and affordable strategy to generate fusion hCE1 of high quality in E coli, which facilitates preparation of hCE1 monoclonal antibody and further HCC diagnosis research.  相似文献   

16.
This paper proposes an image segmentation method based on the combination of the wavelet multi-scale edge detection and the entropy iterative threshold selection. Image for segmentation is divided into two parts by high- and low-frequency. In the high-frequency part the wavelet multiscale was used for the edge detection, and the low-frequency part conducted on segmentation using the entropy iterative threshold selection method. Through the consideration of the image edge and region, a CT image of the thorax was chosen to test the proposed method for the segmentation of the lungs. Experimental results show that the method is efficient to segment the interesting region of an image compared with conventional methods.  相似文献   

17.
Saturation of peripheral oxygen (SpO2) is one of the most important parameters of vital signs. Pulse oximeter based on near-infrared spectroscopy is commonly used as a non-invasive method to measure SpO2 yl. Currently, medical device manufacturers as well as metrology measurement agencies in China usually use pulse oximeter simulator as the commonly accepted functional calibration equipment for pulse oximeters. So far, no experimental protocol or devices can be used to test the accuracy and reliability of a pulse oximeter simulator. Therefore, a set of new metrology apparatus with the name of calibration device for pulse oximeter simulator have been designed in order to make a traceable system for the calibration or verification of pulse oximeter simulators. The principles and some research methods of this calibration device for pulse oximeter simulator will be discussed in this paper. Besides that, many experiments have been applied in order to guarantee the accuracy as well as traceability of this set of device.  相似文献   

18.
In order to explore the correlation between the adjacent segments of a long term EEG, an improved principal component analysis(PCA) method based on mutual information algorithm is proposed. A one-dimension EEG time series is divided equally into many segments, so that each segment can be regarded as an independent variables and multi-segmented EEG can be expressed as a data matrix. Then, we substitute mutual information matrix for covariance matrix in PCA and conduct the relevance analysis of segmented EEG. The experimental results show that the contribution rate of first principal component(FPC) of segmented EEG is more larger than others, which can effectively reflect the difference of epileptic EEG and normal EEG with the change of segment number. In addition, the evolution of FPC conduce to identify the time-segment locations of abnormal dynamic processes of brain activities,these conclusions are helpful for the clinical analysis of EEG.  相似文献   

19.
A key step of constructing active appearance model is requiring a set of appropriate training shapes with well-defined correspondences. In this paper, we introduce a novel point correspondence method (FB-CPD), which can improve the accuracy of coherent point drift (CPD) by using the information of image feature. The objective function of the proposed method is defined by both of geometric spatial information and image feature information, and the origin Gaussian mixture model in CPD is modified according to the image feature of points. FB-CPD is tested on the 3D prostate and liver point sets through the simulation experiments. The registration error can be reduced efficiently by FB-CPD. Moreover, the active appearance model constructed by FB-CPD can obtain fine segmentation in 3D CT prostate image. Compared with the original CPD, the overlap ratio of voxels was improved from 88.7% to 90.2% by FB-CPD.  相似文献   

20.
To effectively suppress white noise and preserve more useful components of electrocardiogram (ECG) signal, a novel de-noising method based on morphological component analysis (MCA) is proposed. MCA is a method which allows us to separate features contained in an original signal when these features present different morphological aspects. According to the features of ECG, we used the UWT dictionary to sparsely represent mutated component, and used the DCT dictionary to sparsely represent smooth component. The experimental results of the samples choosing from MIT-BIH databases show that the MCA-based method is effective for white noise removal.  相似文献   

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