A calibration scheme under spherical coordinates is described for a magnetic tracker used in VR (virtual reality) system. A look up table containing data of tracked values for certain positions in the working space, ...A calibration scheme under spherical coordinates is described for a magnetic tracker used in VR (virtual reality) system. A look up table containing data of tracked values for certain positions in the working space, spe cified in spherical coordinates, is generated first, which is then used to calibrate the tracking results by a two dimensional interpolation. The scheme can effectively correct the static errors in the magnetic tracking system. The employment of spherical coordinates significantly reduces the calculation complexity in calibration.展开更多
In the last decade,significant progress has been made in applying passive capsule endoscopes(CE)to medical diagnostics.However,disadvantages still need to be overcome for better utilization.A major challenge is to act...In the last decade,significant progress has been made in applying passive capsule endoscopes(CE)to medical diagnostics.However,disadvantages still need to be overcome for better utilization.A major challenge is to actively control the movement of the CE and provide real-time location information.This paper proposes a magnetic tracking method for CE driven by an external magnetic field that is generated by four sets of electromagnetic coils around the CE.The tracking method is based on a magnetic sensor array.The magnetic actuation constitutes three steps.First,the driving current from each coil is obtained according to the control requirement for a certain position and orientation.Second,the magnetic field that is generated by the driving current in the tracking space is estimated according to the magnetic field model.It can also be measured by Hall-effect sensors embedded in the position system.Third,the magnetic field generated by the CE is subtracted from the total magnetic field measured by the sensors,and then the magnetic position algorithm is applied.In the experiments,the positioning error is found to be within5.6 mm and the orientation error is under 8.5°.The proposed localization method would be used for closed-loop control of CE to achieve better and safer performance.展开更多
In vitro experiments have demonstrated that neuronal-like cells derived from bone marrow mesen- chymal stem cells can survive, migrate, integrate and help to restore the function and behaviors of spinal cord injury mo...In vitro experiments have demonstrated that neuronal-like cells derived from bone marrow mesen- chymal stem cells can survive, migrate, integrate and help to restore the function and behaviors of spinal cord injury models, and that they may serve as a suitable approach to treating spinal cord injury. However, it is very difficult to track transplanted cells in vivo. In this study, we injected su- perparamagnetic iron oxide-labeled neuronal-like cells into the subarachnoid space in a rabbit model of spinal cord injury. At 7 days after cell transplantation, a small number of dot-shaped low signal intensity shadows were observed in the spinal cord injury region, and at 14 days, the number of these shadows increased on T2-weighted imaging. Perl＇s Prussian blue staining detected dot-shaped low signal intensity shadows in the spinal cord injury region, indicative of superpara- magnetic iron oxide nanoparticle-labeled cells. These findings suggest that transplanted neu- ronal-like cells derived from bone marrow mesenchymal stem cells can migrate to the spinal cord injury region and can be tracked by magnetic resonance in vivo. Magnetic resonance imaging represents an efficient noninvasive technique for visually tracking transplanted cells in vivo.展开更多
The present study was carried out in order to track the maximum power point in a variable speed turbine by minimizing electromechanical torque changes using a sliding mode control strategy. In this strategy, first, th...The present study was carried out in order to track the maximum power point in a variable speed turbine by minimizing electromechanical torque changes using a sliding mode control strategy. In this strategy, first, the rotor speed is set at an optimal point for different wind speeds. As a result of which, the tip speed ratio reaches an optimal point, mechanical power coefficient is maximized, and wind turbine produces its maximum power and mechanical torque. Then, the maximum mechanical torque is tracked using electromechanical torque. In this technique, tracking error integral of maximum mechanical torque, the error, and the derivative of error are used as state variables. During changes in wind speed, sliding mode control is designed to absorb the maximum energy from the wind and minimize the response time of maximum power point tracking(MPPT). In this method, the actual control input signal is formed from a second order integral operation of the original sliding mode control input signal. The result of the second order integral in this model includes control signal integrity, full chattering attenuation, and prevention from large fluctuations in the power generator output. The simulation results, calculated by using MATLAB/m-file software, have shown the effectiveness of the proposed control strategy for wind energy systems based on the permanent magnet synchronous generator(PMSG).展开更多
BACKGROUND： Resovist, a superparamagnetic iron oxide, can be used to label neural stem cells （NSCs）. Magnetic resonance tracking of superparamagnetic iron oxide-labeled NSCs is a non-invasive technique to track tra...BACKGROUND： Resovist, a superparamagnetic iron oxide, can be used to label neural stem cells （NSCs）. Magnetic resonance tracking of superparamagnetic iron oxide-labeled NSCs is a non-invasive technique to track transplanted NSCs following focal cerebral ischemia. OBJECTIVE： To observe survival and migration of transplanted NSCs in a rat model of focal ischemia/repeffusion using magnetic resonance imaging （MRI）. DESIGN, TIME AND SETTING： An in vitro, in vivo, tracking study was performed at the Basic Laboratory of Harbin Medical University and the Room of MRI, Second Affiliated Hospital of Harbin Medical University, China from December 2006 to December 2009. MATERIALS： Resovist （Schering, Germany） and Achieva 1.5TMR imaging system （Philips, Amsterdam, the Netherlands） were utilized in the present study. METHODS： NSCs were harvested from brain tissues of neonatal Sprague Dawley rats and were labeled with Resovist （11.2μg/mL and 5 ×10^5 cells/mL）. A total of 15 adult, Sprague Dawley rats were randomly assigned to model （n = 9） and control （n = 6） groups. All rats were utilized to establish models of middle cerebral artery occlusion. Rats in the model group were subjected to Resovist-labeled NSCs transplantation by injection of cell suspension into both ventricles （5μL/ ventricle）. Rats in the control group were treated with an equal volume of physiological saline. MAIN OUTCOME MEASURES： Immunocytochemistry, transmission electron microscopy, and Prussian blue staining were employed to observe whether cells phagocytized iron particles. In addition, 3-（4, 5-dimethylthiazol-2-yl）-2, 5-diphenyltetrazolium bromide assay was used to measure viability and differentiation of NSCs labeled by various concentrations of Resovist. MRI was used to trace survival and migration of Resovist-labeled NSCs. RESULTS： Following Resovist and NSCs co-incubation, Prussian blue staining revealed iron particles in cells. In addition, staining was observed in daughter cells following cell division under transmission electron microscopy. A significant difference in viability and differentiation of NSCs in vitro labeled by various Resovist concentrations （2.8-11.2 μg/mL） was not detected （P 〉 0.05）. Resovist （〉 22.4 μg/mL） decreased cell viability and differentiation （P 〈 0.05）./n vivo MRI of Resovist-labeled NSCs （11.2 μg/mL） revealed low signals. However, cells migrated towards the ischemic focus over time. CONCLUSION： Resovist, a magnetic probe, successfully labeled NSCs. MRI was successfully used to trace magnetic-labeled NSCs in vivo and allowed observation of cell survival and migration following transplantation.展开更多
Some specially imaging of magnetic resonance imaging,the diffusion-weighted imaging(DWI),the diffusion tensor imaging and fractional anisotropy(FA),are useful to described,detect,and map the extent of spinal cord lesi...Some specially imaging of magnetic resonance imaging,the diffusion-weighted imaging(DWI),the diffusion tensor imaging and fractional anisotropy(FA),are useful to described,detect,and map the extent of spinal cord lesions.FA measurements may are used to predicting the outcome of patients who have spinal cord lesions.Fiber tracking enable to visualizing the integrity of white matter tracts surrounding some lesions,and this information could be used to formulating a differential diagnosis and planning biopsies or resection.In this article,we will describe the current uses for DWI and fiber tracking and speculate on others in which we believe these techniques will be useful in the future.展开更多
Cu-Ni core-shell nanowires, with an inner Cu core diameter of about 60 nm and varying Ni shell thicknesses （10, 30, 50, 60, and 80 nm）, were successfully fabricated in porous polycarbonate （PC） ion- track template...Cu-Ni core-shell nanowires, with an inner Cu core diameter of about 60 nm and varying Ni shell thicknesses （10, 30, 50, 60, and 80 nm）, were successfully fabricated in porous polycarbonate （PC） ion- track templates by a two-step etching and electrodeposition method. In our experiment, the thickness of Ni shell can be effectively tuned through the etching time of templates. The core-shell structure was confirmed by scanning electron microscopy （SEM） and transmission electron microscopy （TEM）. The X-ray diffraction （XRD） pattern elucidates the co-existence of characteristic peaks for both Cu and Ni, indicating no other phases were formed during preparation. Magnetic hysteresis loops measured via vibrating sample magnetometry （VSM） revealed that Cu-Ni core-shell nanowires with thinner Ni shell exhibited obviously diamagnetic character and together with a weak ferromagnetic activity, whereas ferromagnetic behavior was primarily measured for the wires with thicker Ni shell. With increasing Ni shell thickness, the squareness and coercivity value became smaller due to the shape anisotropy and the formation of multi-domain structure.展开更多
Objective To investigate the impact of microvascular obstruction(MVO)on the global and regional myocardial function by cardiac magnetic resonance feature-tracking(CMR-FT)in ST-segment-elevation myocardial infarction(S...Objective To investigate the impact of microvascular obstruction(MVO)on the global and regional myocardial function by cardiac magnetic resonance feature-tracking(CMR-FT)in ST-segment-elevation myocardial infarction(STEMI)patients after percutaneous coronary intervention.Methods Consecutive acute STEMI patients who underwent cardiac magnetic resonance imaging 1-7 days after successful reperfusion by percutaneous coronary intervention treatment were included in this retrospective study.Based on the presence or absence of MVO on late gadolinium enhancement images,patients were divided into groups with MVO and without MVO.The infarct zone,adjacent zone,and remote zone were determined based on a myocardial 16-segment model.The radial strain(RS),circumferential strain(CS),and longitudinal strain(LS)of the global left ventricle(LV)and the infarct,adjacent,and remote zones were measured by CMRFT from cine images and compared between patients with and without MVO using independent-samples t-test.Logistic regression analysis was used to assess the association of MVO with the impaired LV function.Results A total of 157 STEMI patients(mean age 56.66±11.38 years)were enrolled.MVO was detected in 37.58%(59/157)of STEMI patients,and the mean size of MVO was 3.00±3.76 mL.Compared with patients without MVO(n=98),the MVO group had significantly reduced LV global RS(t=-4.30,P<0.001),global CS(t=4.99,P<0.001),and global LS(t=3.51,P=0.001).The RS and CS of the infarct zone in patients with MVO were significantly reduced(t=-3.38,P=0.001;t=2.64,P=0.01;respectively)and the infarct size was significantly larger(t=8.37,P<0.001)than that of patients without MVO.The presence of LV MVO[OR=4.10,95%CI:2.05-8.19,P<0.001]and its size[OR=1.38,95%CI:1.10-1.72,P=0.01],along with the heart rate and LV infarct size were significantly associated with impaired LV global CS in univariable Logistic regression analysis,while only heart rate(OR=1.08,95%CI:1.03-1.13,P=0.001)and LV infarct size(OR=1.10,95%CI:1.03-1.16,P=0.003)were independent influencing factors for the impaired LV global CS in multivariable Logistic regression analysis.Conclusion The infarct size was larger in STEMI patients with MVO,and MVO deteriorates the global and regional LV myocardial function.展开更多
Low back pain is a common clinical problem, which leads to significant social, economic and public health costs. Intervertebral disc(IVD) degeneration is accepted as a common cause of low back pain. Initially, this is...Low back pain is a common clinical problem, which leads to significant social, economic and public health costs. Intervertebral disc(IVD) degeneration is accepted as a common cause of low back pain. Initially, this is characterized by a loss of proteoglycans from the nucleus pulposus resulting in loss of tissue hydration and hydrostatic pressure. Conservative management,including analgesia and physiotherapy often fails and surgical treatment, such as spinal fusion, is required. Stem cells offer an exciting possible regenerative approach to IVD disease. Preclinical research has demonstrated promising biochemical, histological and radiological results in restoring degenerate IVDs. Cell tracking provides an opportunity to develop an in-depth understanding of stem cell survival, differentiation and migration, enabling optimization of stem cell treatment. Magnetic Resonance Imaging(MRI) is a non-invasive, non-ionizing imaging modality with high spatial resolution, ideally suited for stem cell tracking. Furthermore, novel MRI sequences have the potential to quantitatively assess IVD disease, providing an improved method to review response to biological treatment. Superparamagnetic iron oxide nanoparticles have been extensively researched for the purpose of cell tracking. These particles are biocompatible, non-toxic and act as excellent MRI contrast agents. This review will explore recent advances and issues in stem cell tracking and molecular imaging in relation to the IVD.展开更多
The targeted drug delivery and targeted drug therapy transport a drug directly to the center of the disease under various conditions and thereby treat it deliber- ately without effects on the body. This paper studies ...The targeted drug delivery and targeted drug therapy transport a drug directly to the center of the disease under various conditions and thereby treat it deliber- ately without effects on the body. This paper studies the magnetic drug targeting （MDT） technique by particle tracking in the presence of magnetic field in bifurcation vessels of a healthy person and a diabetes patient. The Lagrangian particle tracking is performed to estimate particle behavior under effects of imposed magnetic field gradients along the bifurcation. The results show that the magnetic field increases the volume fraction of particle in the target region, and the efficiency of MDT on a patient with the diabetes disease is better than a healthy person. Also, for the higher magnetic numbers, the flow in the upper branch is strongly affected by the magnetic field.展开更多
在当今数字化时代,海量数据的生成和积累呈现出爆炸式增长的趋势,因此对存储容量的需求急速上升.传统磁记录磁盘CMR因其高容量和低成本而被视为解决海量数据存储的首选.然而,由于超顺磁效应的制约,CMR(Conventional Magnetic Recording...在当今数字化时代,海量数据的生成和积累呈现出爆炸式增长的趋势,因此对存储容量的需求急速上升.传统磁记录磁盘CMR因其高容量和低成本而被视为解决海量数据存储的首选.然而,由于超顺磁效应的制约,CMR(Conventional Magnetic Recording)磁盘面密度的提升已触及极限.为了突破这一限制,叠瓦式磁记录技术SMR(Shingled Magnetic Recording)应运而生.基于传统硬盘架构,该技术以重叠磁道的方式,显著提升了磁盘面密度.但SMR磁盘在处理随机写时,会产生不可预测的写放大效应,从而严重影响I/O性能.为解决这一问题,业界随即提出了交错式磁记录技术IMR(Interlaced Magnetic Recording),利用优化的磁道布局和热辅助磁记录技术,有效实现了存储容量与性能的平衡.本文首先详细介绍了SMR和IMR的技术原理和磁盘类型,并量化分析了影响设备I/O性能的关键问题.然后,重点介绍了设备级优化方案,分析并总结了不同策略的优缺点与优化目标.接着,概述了面向设备的系统级和应用级设计方案,如文件系统、独立磁盘阵列技术和数据库等.最后讨论了在未来优化SMR磁盘和IMR磁盘性能可能的研究方向.展开更多
Therapies based on stem cell transplants offer significant potential in the field of regenerative medicine. Monitoring the fate of the transplanted stem cells in a timely manner is considered one of the main limitatio...Therapies based on stem cell transplants offer significant potential in the field of regenerative medicine. Monitoring the fate of the transplanted stem cells in a timely manner is considered one of the main limitations for long-standing success of stem cell transplants. Imaging methods that visualize and track stem cells<i> in vivo</i> non-invasively in real time are helpful towards the development of successful cell transplantation techniques. Novel molecular imaging methods which are non-invasive particularly such as MRI have been of great recent interest. Hence, mouse models which are of clinical relevance have been studied by injecting contrast agents used for labelling cells such as super-paramagnetic iron-oxide (SPIO) nanoparticles for cellular imaging. The MR techniques which can be used to generate positive contrast images have been of much relevance recently for tracking of the labelled cells. Particularly when the off-resonance region in the vicinity of the labeled cells is selectively excited while suppressing the signals from the non-labeled regions by the method of spectral dephasing. Thus, tracking of magnetically labelled cells employing positive contrast<i> in vivo</i> MR imaging methods in a burn mouse model in a non-invasive way has been the scope of this study. The consequences have direct implications for monitoring labeled stem cells at some stage in wound healing. We suggest that our approach can be used in clinical trials in molecular and regenerative medicine.展开更多
文摘A calibration scheme under spherical coordinates is described for a magnetic tracker used in VR (virtual reality) system. A look up table containing data of tracked values for certain positions in the working space, spe cified in spherical coordinates, is generated first, which is then used to calibrate the tracking results by a two dimensional interpolation. The scheme can effectively correct the static errors in the magnetic tracking system. The employment of spherical coordinates significantly reduces the calculation complexity in calibration.
基金supported in part by National Natural Science Foundation of China under Grant 61803123in part by the Science and Technology Innovation Committee of Shenzhen under Grant JCYJ20170413110250667 and JCYJ20170307151715204in part by Shenzhen Key Lab Fund of Mechanisms and Control in Aerospace under Grant No.ZDSYS201703031002066.
文摘In the last decade,significant progress has been made in applying passive capsule endoscopes(CE)to medical diagnostics.However,disadvantages still need to be overcome for better utilization.A major challenge is to actively control the movement of the CE and provide real-time location information.This paper proposes a magnetic tracking method for CE driven by an external magnetic field that is generated by four sets of electromagnetic coils around the CE.The tracking method is based on a magnetic sensor array.The magnetic actuation constitutes three steps.First,the driving current from each coil is obtained according to the control requirement for a certain position and orientation.Second,the magnetic field that is generated by the driving current in the tracking space is estimated according to the magnetic field model.It can also be measured by Hall-effect sensors embedded in the position system.Third,the magnetic field generated by the CE is subtracted from the total magnetic field measured by the sensors,and then the magnetic position algorithm is applied.In the experiments,the positioning error is found to be within5.6 mm and the orientation error is under 8.5°.The proposed localization method would be used for closed-loop control of CE to achieve better and safer performance.
基金supported by a grant from Science and Technology Research Projects of Shanxi Province,No.20120321028-02a grant from the Scientific and Technical Foundation of Shanxi Provincial Health Department,No.201201067+1 种基金a grant from University Research and Development Projects of Shanxi Province,No.20131101grant from the National Natural Science Foundation of China,No.81371628
文摘In vitro experiments have demonstrated that neuronal-like cells derived from bone marrow mesen- chymal stem cells can survive, migrate, integrate and help to restore the function and behaviors of spinal cord injury models, and that they may serve as a suitable approach to treating spinal cord injury. However, it is very difficult to track transplanted cells in vivo. In this study, we injected su- perparamagnetic iron oxide-labeled neuronal-like cells into the subarachnoid space in a rabbit model of spinal cord injury. At 7 days after cell transplantation, a small number of dot-shaped low signal intensity shadows were observed in the spinal cord injury region, and at 14 days, the number of these shadows increased on T2-weighted imaging. Perl＇s Prussian blue staining detected dot-shaped low signal intensity shadows in the spinal cord injury region, indicative of superpara- magnetic iron oxide nanoparticle-labeled cells. These findings suggest that transplanted neu- ronal-like cells derived from bone marrow mesenchymal stem cells can migrate to the spinal cord injury region and can be tracked by magnetic resonance in vivo. Magnetic resonance imaging represents an efficient noninvasive technique for visually tracking transplanted cells in vivo.
文摘The present study was carried out in order to track the maximum power point in a variable speed turbine by minimizing electromechanical torque changes using a sliding mode control strategy. In this strategy, first, the rotor speed is set at an optimal point for different wind speeds. As a result of which, the tip speed ratio reaches an optimal point, mechanical power coefficient is maximized, and wind turbine produces its maximum power and mechanical torque. Then, the maximum mechanical torque is tracked using electromechanical torque. In this technique, tracking error integral of maximum mechanical torque, the error, and the derivative of error are used as state variables. During changes in wind speed, sliding mode control is designed to absorb the maximum energy from the wind and minimize the response time of maximum power point tracking(MPPT). In this method, the actual control input signal is formed from a second order integral operation of the original sliding mode control input signal. The result of the second order integral in this model includes control signal integrity, full chattering attenuation, and prevention from large fluctuations in the power generator output. The simulation results, calculated by using MATLAB/m-file software, have shown the effectiveness of the proposed control strategy for wind energy systems based on the permanent magnet synchronous generator(PMSG).
基金the Scientific Research Program of Health Department in Heilongjiang Province,No.2007-331the Doctoral Foundation of the Second Affiliated Hospital of Harbin Medical University,No.BS2006-29
文摘BACKGROUND： Resovist, a superparamagnetic iron oxide, can be used to label neural stem cells （NSCs）. Magnetic resonance tracking of superparamagnetic iron oxide-labeled NSCs is a non-invasive technique to track transplanted NSCs following focal cerebral ischemia. OBJECTIVE： To observe survival and migration of transplanted NSCs in a rat model of focal ischemia/repeffusion using magnetic resonance imaging （MRI）. DESIGN, TIME AND SETTING： An in vitro, in vivo, tracking study was performed at the Basic Laboratory of Harbin Medical University and the Room of MRI, Second Affiliated Hospital of Harbin Medical University, China from December 2006 to December 2009. MATERIALS： Resovist （Schering, Germany） and Achieva 1.5TMR imaging system （Philips, Amsterdam, the Netherlands） were utilized in the present study. METHODS： NSCs were harvested from brain tissues of neonatal Sprague Dawley rats and were labeled with Resovist （11.2μg/mL and 5 ×10^5 cells/mL）. A total of 15 adult, Sprague Dawley rats were randomly assigned to model （n = 9） and control （n = 6） groups. All rats were utilized to establish models of middle cerebral artery occlusion. Rats in the model group were subjected to Resovist-labeled NSCs transplantation by injection of cell suspension into both ventricles （5μL/ ventricle）. Rats in the control group were treated with an equal volume of physiological saline. MAIN OUTCOME MEASURES： Immunocytochemistry, transmission electron microscopy, and Prussian blue staining were employed to observe whether cells phagocytized iron particles. In addition, 3-（4, 5-dimethylthiazol-2-yl）-2, 5-diphenyltetrazolium bromide assay was used to measure viability and differentiation of NSCs labeled by various concentrations of Resovist. MRI was used to trace survival and migration of Resovist-labeled NSCs. RESULTS： Following Resovist and NSCs co-incubation, Prussian blue staining revealed iron particles in cells. In addition, staining was observed in daughter cells following cell division under transmission electron microscopy. A significant difference in viability and differentiation of NSCs in vitro labeled by various Resovist concentrations （2.8-11.2 μg/mL） was not detected （P 〉 0.05）. Resovist （〉 22.4 μg/mL） decreased cell viability and differentiation （P 〈 0.05）./n vivo MRI of Resovist-labeled NSCs （11.2 μg/mL） revealed low signals. However, cells migrated towards the ischemic focus over time. CONCLUSION： Resovist, a magnetic probe, successfully labeled NSCs. MRI was successfully used to trace magnetic-labeled NSCs in vivo and allowed observation of cell survival and migration following transplantation.
文摘Some specially imaging of magnetic resonance imaging,the diffusion-weighted imaging(DWI),the diffusion tensor imaging and fractional anisotropy(FA),are useful to described,detect,and map the extent of spinal cord lesions.FA measurements may are used to predicting the outcome of patients who have spinal cord lesions.Fiber tracking enable to visualizing the integrity of white matter tracts surrounding some lesions,and this information could be used to formulating a differential diagnosis and planning biopsies or resection.In this article,we will describe the current uses for DWI and fiber tracking and speculate on others in which we believe these techniques will be useful in the future.
基金Funded by the National Natural Science Foundation of China(Nos.11175221,11179003,11005134,11375241,and 11275237)the West Light Foundation of Chinese Academy of Sciences(CAS)
文摘Cu-Ni core-shell nanowires, with an inner Cu core diameter of about 60 nm and varying Ni shell thicknesses （10, 30, 50, 60, and 80 nm）, were successfully fabricated in porous polycarbonate （PC） ion- track templates by a two-step etching and electrodeposition method. In our experiment, the thickness of Ni shell can be effectively tuned through the etching time of templates. The core-shell structure was confirmed by scanning electron microscopy （SEM） and transmission electron microscopy （TEM）. The X-ray diffraction （XRD） pattern elucidates the co-existence of characteristic peaks for both Cu and Ni, indicating no other phases were formed during preparation. Magnetic hysteresis loops measured via vibrating sample magnetometry （VSM） revealed that Cu-Ni core-shell nanowires with thinner Ni shell exhibited obviously diamagnetic character and together with a weak ferromagnetic activity, whereas ferromagnetic behavior was primarily measured for the wires with thicker Ni shell. With increasing Ni shell thickness, the squareness and coercivity value became smaller due to the shape anisotropy and the formation of multi-domain structure.
文摘Objective To investigate the impact of microvascular obstruction(MVO)on the global and regional myocardial function by cardiac magnetic resonance feature-tracking(CMR-FT)in ST-segment-elevation myocardial infarction(STEMI)patients after percutaneous coronary intervention.Methods Consecutive acute STEMI patients who underwent cardiac magnetic resonance imaging 1-7 days after successful reperfusion by percutaneous coronary intervention treatment were included in this retrospective study.Based on the presence or absence of MVO on late gadolinium enhancement images,patients were divided into groups with MVO and without MVO.The infarct zone,adjacent zone,and remote zone were determined based on a myocardial 16-segment model.The radial strain(RS),circumferential strain(CS),and longitudinal strain(LS)of the global left ventricle(LV)and the infarct,adjacent,and remote zones were measured by CMRFT from cine images and compared between patients with and without MVO using independent-samples t-test.Logistic regression analysis was used to assess the association of MVO with the impaired LV function.Results A total of 157 STEMI patients(mean age 56.66±11.38 years)were enrolled.MVO was detected in 37.58%(59/157)of STEMI patients,and the mean size of MVO was 3.00±3.76 mL.Compared with patients without MVO(n=98),the MVO group had significantly reduced LV global RS(t=-4.30,P<0.001),global CS(t=4.99,P<0.001),and global LS(t=3.51,P=0.001).The RS and CS of the infarct zone in patients with MVO were significantly reduced(t=-3.38,P=0.001;t=2.64,P=0.01;respectively)and the infarct size was significantly larger(t=8.37,P<0.001)than that of patients without MVO.The presence of LV MVO[OR=4.10,95%CI:2.05-8.19,P<0.001]and its size[OR=1.38,95%CI:1.10-1.72,P=0.01],along with the heart rate and LV infarct size were significantly associated with impaired LV global CS in univariable Logistic regression analysis,while only heart rate(OR=1.08,95%CI:1.03-1.13,P=0.001)and LV infarct size(OR=1.10,95%CI:1.03-1.16,P=0.003)were independent influencing factors for the impaired LV global CS in multivariable Logistic regression analysis.Conclusion The infarct size was larger in STEMI patients with MVO,and MVO deteriorates the global and regional LV myocardial function.
文摘Low back pain is a common clinical problem, which leads to significant social, economic and public health costs. Intervertebral disc(IVD) degeneration is accepted as a common cause of low back pain. Initially, this is characterized by a loss of proteoglycans from the nucleus pulposus resulting in loss of tissue hydration and hydrostatic pressure. Conservative management,including analgesia and physiotherapy often fails and surgical treatment, such as spinal fusion, is required. Stem cells offer an exciting possible regenerative approach to IVD disease. Preclinical research has demonstrated promising biochemical, histological and radiological results in restoring degenerate IVDs. Cell tracking provides an opportunity to develop an in-depth understanding of stem cell survival, differentiation and migration, enabling optimization of stem cell treatment. Magnetic Resonance Imaging(MRI) is a non-invasive, non-ionizing imaging modality with high spatial resolution, ideally suited for stem cell tracking. Furthermore, novel MRI sequences have the potential to quantitatively assess IVD disease, providing an improved method to review response to biological treatment. Superparamagnetic iron oxide nanoparticles have been extensively researched for the purpose of cell tracking. These particles are biocompatible, non-toxic and act as excellent MRI contrast agents. This review will explore recent advances and issues in stem cell tracking and molecular imaging in relation to the IVD.
文摘The targeted drug delivery and targeted drug therapy transport a drug directly to the center of the disease under various conditions and thereby treat it deliber- ately without effects on the body. This paper studies the magnetic drug targeting （MDT） technique by particle tracking in the presence of magnetic field in bifurcation vessels of a healthy person and a diabetes patient. The Lagrangian particle tracking is performed to estimate particle behavior under effects of imposed magnetic field gradients along the bifurcation. The results show that the magnetic field increases the volume fraction of particle in the target region, and the efficiency of MDT on a patient with the diabetes disease is better than a healthy person. Also, for the higher magnetic numbers, the flow in the upper branch is strongly affected by the magnetic field.
文摘在当今数字化时代,海量数据的生成和积累呈现出爆炸式增长的趋势,因此对存储容量的需求急速上升.传统磁记录磁盘CMR因其高容量和低成本而被视为解决海量数据存储的首选.然而,由于超顺磁效应的制约,CMR(Conventional Magnetic Recording)磁盘面密度的提升已触及极限.为了突破这一限制,叠瓦式磁记录技术SMR(Shingled Magnetic Recording)应运而生.基于传统硬盘架构,该技术以重叠磁道的方式,显著提升了磁盘面密度.但SMR磁盘在处理随机写时,会产生不可预测的写放大效应,从而严重影响I/O性能.为解决这一问题,业界随即提出了交错式磁记录技术IMR(Interlaced Magnetic Recording),利用优化的磁道布局和热辅助磁记录技术,有效实现了存储容量与性能的平衡.本文首先详细介绍了SMR和IMR的技术原理和磁盘类型,并量化分析了影响设备I/O性能的关键问题.然后,重点介绍了设备级优化方案,分析并总结了不同策略的优缺点与优化目标.接着,概述了面向设备的系统级和应用级设计方案,如文件系统、独立磁盘阵列技术和数据库等.最后讨论了在未来优化SMR磁盘和IMR磁盘性能可能的研究方向.
文摘Therapies based on stem cell transplants offer significant potential in the field of regenerative medicine. Monitoring the fate of the transplanted stem cells in a timely manner is considered one of the main limitations for long-standing success of stem cell transplants. Imaging methods that visualize and track stem cells<i> in vivo</i> non-invasively in real time are helpful towards the development of successful cell transplantation techniques. Novel molecular imaging methods which are non-invasive particularly such as MRI have been of great recent interest. Hence, mouse models which are of clinical relevance have been studied by injecting contrast agents used for labelling cells such as super-paramagnetic iron-oxide (SPIO) nanoparticles for cellular imaging. The MR techniques which can be used to generate positive contrast images have been of much relevance recently for tracking of the labelled cells. Particularly when the off-resonance region in the vicinity of the labeled cells is selectively excited while suppressing the signals from the non-labeled regions by the method of spectral dephasing. Thus, tracking of magnetically labelled cells employing positive contrast<i> in vivo</i> MR imaging methods in a burn mouse model in a non-invasive way has been the scope of this study. The consequences have direct implications for monitoring labeled stem cells at some stage in wound healing. We suggest that our approach can be used in clinical trials in molecular and regenerative medicine.
