Pub Date : 1993-10-28DOI: 10.1109/IEMBS.1993.978687
G. Ye, M. W. Moore, D. Buerk, D. Jaron
m. In this paper we describe a time-varying modei for oxygen-carbon dioxide coupled transport in the human cerebral microcirculation-tissue system. ”tis model is based on our previous derivation using space-averaging of the corresponding distributed model. Our results show that this time-varying model is consistent with results of our previous steady-state models. It is also supported by a reported experiment
{"title":"Extension of a multielement compartmental model for O/sub 2/-CO/sub 2/ transport to time-varying applications","authors":"G. Ye, M. W. Moore, D. Buerk, D. Jaron","doi":"10.1109/IEMBS.1993.978687","DOIUrl":"https://doi.org/10.1109/IEMBS.1993.978687","url":null,"abstract":"m. In this paper we describe a time-varying modei for oxygen-carbon dioxide coupled transport in the human cerebral microcirculation-tissue system. ”tis model is based on our previous derivation using space-averaging of the corresponding distributed model. Our results show that this time-varying model is consistent with results of our previous steady-state models. It is also supported by a reported experiment","PeriodicalId":408657,"journal":{"name":"Proceedings of the 15th Annual International Conference of the IEEE Engineering in Medicine and Biology Societ","volume":"36 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1993-10-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117344169","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1993-10-28DOI: 10.1109/IEMBS.1993.978897
M. Moulton, L. Creswell, S. Wyers, R.L. Actist, B. Szabó, M.W. Vannie, M. Pasque
A material identification algorithm is described for determining the iri vivo material properties of the diastolic myocardium. A nonlinear optimization algorithm is used to solve a least squares objective function. The objective function relates the least squares difference of model-predicted displacements obtained from a finite element (FE) solution to measured displacements. obtained in the irt vivo case from magnetic resonance imaging (MRI) radiofrequency (RF) tissue-tagging. The algorithm is validated using a simple analytic test case by examining the effects of noise in the measured data and numerical error in the FE solution. Nonhomogeneous, linearly elastic and isotropic material parameters are determined for a normal adult mongrel dog. INTRODUCTION Continuum mechanical models of the heart provide important insight into the relationship between the microscopic structure and function of ventricular muscle and global ventricular function. The solution of boundary value problems encountered in deformation and stress analysis of the heart requires the application of physical laws as goveming differential equations when the geomey, boundary conditions and material properties are known. The material properties are the least well characterized input to the forward boundary value problem. Previous investigators have examined isolated samples of myocardium in the laboratory using loaddeformation testing. These analyses have been successful in delineating the anisotropic, nonlinear and non-homogeneous nature of passive myocardial material behavior. While the iri virro approach to material characterization has been successful in delineating the general form of the constitutive law, technical difficulties and natural objections to extrapolating iri vriru tests on small samples to the irr vivo beating heart, limit its applicability. An alternative approach, taken in this paper, dctermines unknown material parameters in the irt vivo heart for a proposed constitutive law. The material identification algorithm uses a customized nonlinear optimization algorithm to solve an inverse boundary value problem. The inverse problem is posed as a least squares minimization problem. The difference between model-predicted and mcasured displacements are minimized with respect to unknown malerial parameters. METHODS Statement of the problem. Unknown material parameters for a proposed constitutive law are determined by minimizing the least squares difference between modelpredicted and measured displacements with respect to material parameters: where it,, are model displacements. i,, are measured dispacements and & is the vector of unknown material parameters. The model displacements are determined from the finite element matrix equations. K(&)u = f , using the p version FE method [ l l where f is the load vector and the parameters are contained in the finite element stiffness matrix. K. The objective function. S, is minimized by solving the JS equations = 0. JP, Solutio
{"title":"An inverse material identification algorithm for determining in vivo myocardial material properties","authors":"M. Moulton, L. Creswell, S. Wyers, R.L. Actist, B. Szabó, M.W. Vannie, M. Pasque","doi":"10.1109/IEMBS.1993.978897","DOIUrl":"https://doi.org/10.1109/IEMBS.1993.978897","url":null,"abstract":"A material identification algorithm is described for determining the iri vivo material properties of the diastolic myocardium. A nonlinear optimization algorithm is used to solve a least squares objective function. The objective function relates the least squares difference of model-predicted displacements obtained from a finite element (FE) solution to measured displacements. obtained in the irt vivo case from magnetic resonance imaging (MRI) radiofrequency (RF) tissue-tagging. The algorithm is validated using a simple analytic test case by examining the effects of noise in the measured data and numerical error in the FE solution. Nonhomogeneous, linearly elastic and isotropic material parameters are determined for a normal adult mongrel dog. INTRODUCTION Continuum mechanical models of the heart provide important insight into the relationship between the microscopic structure and function of ventricular muscle and global ventricular function. The solution of boundary value problems encountered in deformation and stress analysis of the heart requires the application of physical laws as goveming differential equations when the geomey, boundary conditions and material properties are known. The material properties are the least well characterized input to the forward boundary value problem. Previous investigators have examined isolated samples of myocardium in the laboratory using loaddeformation testing. These analyses have been successful in delineating the anisotropic, nonlinear and non-homogeneous nature of passive myocardial material behavior. While the iri virro approach to material characterization has been successful in delineating the general form of the constitutive law, technical difficulties and natural objections to extrapolating iri vriru tests on small samples to the irr vivo beating heart, limit its applicability. An alternative approach, taken in this paper, dctermines unknown material parameters in the irt vivo heart for a proposed constitutive law. The material identification algorithm uses a customized nonlinear optimization algorithm to solve an inverse boundary value problem. The inverse problem is posed as a least squares minimization problem. The difference between model-predicted and mcasured displacements are minimized with respect to unknown malerial parameters. METHODS Statement of the problem. Unknown material parameters for a proposed constitutive law are determined by minimizing the least squares difference between modelpredicted and measured displacements with respect to material parameters: where it,, are model displacements. i,, are measured dispacements and & is the vector of unknown material parameters. The model displacements are determined from the finite element matrix equations. K(&)u = f , using the p version FE method [ l l where f is the load vector and the parameters are contained in the finite element stiffness matrix. K. The objective function. S, is minimized by solving the JS equations = 0. JP, Solutio","PeriodicalId":408657,"journal":{"name":"Proceedings of the 15th Annual International Conference of the IEEE Engineering in Medicine and Biology Societ","volume":"7 2","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1993-10-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"120913359","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1993-10-28DOI: 10.1109/IEMBS.1993.978658
H. Hong, M. Fox
The assessment of the vascular lumen is of intense interest to clinicians because of the importance of early detection and quantification of atherosclerosis. We have developed a new technique (to our knowledge) for the assessment of anomalies in electrically conductive tubular smctures like blood vessels. We inject current (minimally invasive and potentially noninvasive) into the vessel, detect the resulting magnetic flux and then backproject to show any deviations from the linear flow of blood. which can indicate the narrowing of the vascular lumen by atheromatous plaque. Preliminary results on a phantom show that attainable resolution is within 1.02 mm. Introduction The measurement of the magnetic field from the human body (biomagnetism) has been used to detect the natural current flow especially around the brain and spinal cord. The magnetic energy is not significantly distorted or attenuated by human tissues, according to both electromagnetic field theory and experiment [11. The detection of natural biomagnetism requires ultrasensitive SQUID (Superconducting Quantum Interference Devices) magnetic sensors. However the SQUID needs cryogenic conditions, which leads to a high cost of manufacturing and maintenance. The system we developed also measures the magnetic field outside of the body, as in biomagnetism, but utilizes a Hall effect sensor which is small, cost effective and easy to maintain at m m temperature. The system we are developing uses injected c m n t which is high enough to generate a magnetic field detectable by a Hall sensor, but safe enough (less than 100 mA of IO kI-k ac current) for diagnostic screening use (21. The BiotSavart law and the preliminary results of our biomagnetism studies suggest that the direction and location of current generating a magnetic field can be determined from the magnetic flux pauem. Our hypothesis is that because of plasma electrolytes, the resistivity of blood (1.75 ohm m) is much lower than that of the wall layers, i.e., tunica intima, media and adventitia (200 ohm m), of the blood vessel [31. Therefore, injected current would flow along the blood stream. The blood vessel wall works as an insuIator like in electric cable. Therefore, the backprojection lines of magnetic flux would meet at one single point which is on the center line of current carrying conductor (blood). Any abnormality in the blood vessel corresponds to a deviation from the major center line of the blood stream, which is detectable by backprojection of magnetic flux. Our model studies were directed at confming this hypothesis in vitro. Method When the current injected into the blood, i, generates a magnetic field (Ampere’s law) like that shown in Fig.1, the magneric flux density, B. is given by the vectorial form of the Biot-Savart law: where B, I, and a, are vectors and X denotes vector cross product. Therefore, the direction of B is determined by the angIe formed between dl (direction of the blood vessel) and ar (unit vector) alo
由于动脉粥样硬化的早期检测和量化的重要性，对血管腔的评估是临床医生非常感兴趣的。我们已经开发了一种新技术(据我们所知)来评估导电管状结构(如血管)的异常。我们将电流(微创和潜在的非侵入性)注入血管，检测产生的磁通量，然后反向投影以显示血液线性流动的任何偏差。这表明血管腔因动脉粥样硬化斑块而变窄。在一个模型上的初步结果表明，可达到的分辨率在1.02毫米以内。人体磁场的测量(生物磁学)已被用于检测自然电流，特别是在大脑和脊髓周围。根据电磁场理论和实验，磁场能量不会被人体组织明显扭曲或衰减[11]。天然生物磁学的检测需要超灵敏的超导量子干涉装置磁传感器。然而，SQUID需要低温条件，这导致制造和维护成本高。我们开发的系统也可以测量身体外的磁场，就像生物磁学一样，但使用的是霍尔效应传感器，它体积小，成本效益高，易于在m - m温度下保持。我们正在开发的系统使用注入c m nt的高磁场，足以产生霍尔传感器检测到的磁场，但足够安全(小于100 mA的IO kI-k交流电流)，用于诊断筛查(21)。BiotSavart定律和我们的生物磁学研究的初步结果表明，产生磁场的电流的方向和位置可以由磁通量来确定。我们的假设是，由于血浆电解质的存在，血液的电阻率(1.75欧姆)远低于血管壁层，即内膜、中膜和外膜的电阻率(200欧姆)[31]。因此，注入的电流将沿着血流流动。血管壁像电缆一样起着绝缘体的作用。因此，磁通量的反投影线会在载流导体(血)的中心线上的一个单点相交。血管中的任何异常都与血液主要中心线的偏离相对应，这是通过磁通的反向投影检测到的。我们的模型研究旨在在体外证实这一假设。方法当注入血液的电流i产生如图1所示的磁场(安培定律)时，磁通密度B用比奥-萨瓦定律的矢量形式给出，其中B、i、a为矢量，X为矢量外积。因此，B的方向由dl(血管方向)和ar(单位矢量)沿从血管中心到测量点距离r的方向€形成的夹角决定。电流垂直于磁场平面，磁场方向(磁通密度)B与半径r圆相切，垂直于a。因此，反投影弦L B P ~和L B P ~(如图1所示)相交于一个单点，即电流载波的中心(图1中位置0)。霍尔效应传感器对磁通密度很敏感。B，产生输出电压VH，其中k、d、i、q分别为霍尔传感器增益、霍尔元件深度、霍尔元件长度和电子电荷。根据偏置电流I和磁通密度B之间的几何形状，VH仅表示B的水平(Va)或垂直(V H ~)分量，即B, By。根据反投影线应与磁通量垂直，确定载流血流的相应中心位置(xc, yc)为。
{"title":"Magnetic backprojection imaging","authors":"H. Hong, M. Fox","doi":"10.1109/IEMBS.1993.978658","DOIUrl":"https://doi.org/10.1109/IEMBS.1993.978658","url":null,"abstract":"The assessment of the vascular lumen is of intense interest to clinicians because of the importance of early detection and quantification of atherosclerosis. We have developed a new technique (to our knowledge) for the assessment of anomalies in electrically conductive tubular smctures like blood vessels. We inject current (minimally invasive and potentially noninvasive) into the vessel, detect the resulting magnetic flux and then backproject to show any deviations from the linear flow of blood. which can indicate the narrowing of the vascular lumen by atheromatous plaque. Preliminary results on a phantom show that attainable resolution is within 1.02 mm. Introduction The measurement of the magnetic field from the human body (biomagnetism) has been used to detect the natural current flow especially around the brain and spinal cord. The magnetic energy is not significantly distorted or attenuated by human tissues, according to both electromagnetic field theory and experiment [11. The detection of natural biomagnetism requires ultrasensitive SQUID (Superconducting Quantum Interference Devices) magnetic sensors. However the SQUID needs cryogenic conditions, which leads to a high cost of manufacturing and maintenance. The system we developed also measures the magnetic field outside of the body, as in biomagnetism, but utilizes a Hall effect sensor which is small, cost effective and easy to maintain at m m temperature. The system we are developing uses injected c m n t which is high enough to generate a magnetic field detectable by a Hall sensor, but safe enough (less than 100 mA of IO kI-k ac current) for diagnostic screening use (21. The BiotSavart law and the preliminary results of our biomagnetism studies suggest that the direction and location of current generating a magnetic field can be determined from the magnetic flux pauem. Our hypothesis is that because of plasma electrolytes, the resistivity of blood (1.75 ohm m) is much lower than that of the wall layers, i.e., tunica intima, media and adventitia (200 ohm m), of the blood vessel [31. Therefore, injected current would flow along the blood stream. The blood vessel wall works as an insuIator like in electric cable. Therefore, the backprojection lines of magnetic flux would meet at one single point which is on the center line of current carrying conductor (blood). Any abnormality in the blood vessel corresponds to a deviation from the major center line of the blood stream, which is detectable by backprojection of magnetic flux. Our model studies were directed at confming this hypothesis in vitro. Method When the current injected into the blood, i, generates a magnetic field (Ampere’s law) like that shown in Fig.1, the magneric flux density, B. is given by the vectorial form of the Biot-Savart law: where B, I, and a, are vectors and X denotes vector cross product. Therefore, the direction of B is determined by the angIe formed between dl (direction of the blood vessel) and ar (unit vector) alo","PeriodicalId":408657,"journal":{"name":"Proceedings of the 15th Annual International Conference of the IEEE Engineering in Medicine and Biology Societ","volume":"78 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1993-10-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"120992135","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1993-10-28DOI: 10.1109/IEMBS.1993.978816
G. Huiskamp
Simulations of paced ventricular excitation using a model based on Beeler/Reuter ion dynamics have been performed. The resulting activation sequence is compared to one computed from ECG's measured on a patient undergoing cardiac pacing at the same stimulus location. Results show that in spite of the isotropic, homogeneous structure of the model major characteristics of the activation sequences are similar. In addition, ECG waveforms in the extremity leads computed from the simulated seqlience are similar to the ones measured on the patient.
{"title":"Simulation of paced excitation in a large scale realistic ventricular model","authors":"G. Huiskamp","doi":"10.1109/IEMBS.1993.978816","DOIUrl":"https://doi.org/10.1109/IEMBS.1993.978816","url":null,"abstract":"Simulations of paced ventricular excitation using a model based on Beeler/Reuter ion dynamics have been performed. The resulting activation sequence is compared to one computed from ECG's measured on a patient undergoing cardiac pacing at the same stimulus location. Results show that in spite of the isotropic, homogeneous structure of the model major characteristics of the activation sequences are similar. In addition, ECG waveforms in the extremity leads computed from the simulated seqlience are similar to the ones measured on the patient.","PeriodicalId":408657,"journal":{"name":"Proceedings of the 15th Annual International Conference of the IEEE Engineering in Medicine and Biology Societ","volume":"1997 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1993-10-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121073831","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1993-10-28DOI: 10.1109/IEMBS.1993.978431
M. Kejariwal, K. Kaster, J. Jurist, J. Pakanati
A WO dimensional. 16-electrode Electrical Impedance Tomography (EIT) system has been simulated using PSPICE to determine whether EIT can be used as a screening technique for early breast cancer detection. Simulation results show that a tumor of area of 1% of the cross-sectional breast model area produces more than 4% variation in the voltage magnitude at the surface electrodes when compared to the voltages for a normal breast. This variation is observed for the optimum current injecting and reference electrode positions.
{"title":"Breast cancer detection using electrical impedance tomography: spice simulation","authors":"M. Kejariwal, K. Kaster, J. Jurist, J. Pakanati","doi":"10.1109/IEMBS.1993.978431","DOIUrl":"https://doi.org/10.1109/IEMBS.1993.978431","url":null,"abstract":"A WO dimensional. 16-electrode Electrical Impedance Tomography (EIT) system has been simulated using PSPICE to determine whether EIT can be used as a screening technique for early breast cancer detection. Simulation results show that a tumor of area of 1% of the cross-sectional breast model area produces more than 4% variation in the voltage magnitude at the surface electrodes when compared to the voltages for a normal breast. This variation is observed for the optimum current injecting and reference electrode positions.","PeriodicalId":408657,"journal":{"name":"Proceedings of the 15th Annual International Conference of the IEEE Engineering in Medicine and Biology Societ","volume":"89 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1993-10-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127189758","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1993-10-28DOI: 10.1109/IEMBS.1993.979153
P.A. Williams, S. Saha
This paper discusses the design and application of a capacitive proximity device for use as an input-interface by children wi th disabilities. Such a device could be used to augmentiassist a handicapped child's abil ity so that he/she can function more independently. This type of device would be an addition to the other interface devices available and would allow a special education professional a wider choice of assist ive too ls in providing the best system for the child.
{"title":"Design of a capacitive proximity device for children mtn disabilities","authors":"P.A. Williams, S. Saha","doi":"10.1109/IEMBS.1993.979153","DOIUrl":"https://doi.org/10.1109/IEMBS.1993.979153","url":null,"abstract":"This paper discusses the design and application of a capacitive proximity device for use as an input-interface by children wi th disabilities. Such a device could be used to augmentiassist a handicapped child's abil ity so that he/she can function more independently. This type of device would be an addition to the other interface devices available and would allow a special education professional a wider choice of assist ive too ls in providing the best system for the child.","PeriodicalId":408657,"journal":{"name":"Proceedings of the 15th Annual International Conference of the IEEE Engineering in Medicine and Biology Societ","volume":"49 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1993-10-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127231873","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1993-10-28DOI: 10.1109/IEMBS.1993.978500
T. Ryan, A. Hartov, T. Colacchio
A novel. movable beam therapeutic ultrasound applicator was fabricated and tested. Each element was individually powered and directed under computer control. Beam steering experiments were done in a water tank with a needle hydrophone. The elements moved under steppermotor control. Acoustic pressure measurements were compared to computed results for the cases of 0". 15" in and 15" out, at fixed angles. Power could be modulated during the excursion for each element. Measured results matched well with computed results and suggest that beam steering allows power control throughout the heated region. Water tank tests and perfused phantom experiments verified that the collimated acoustic beams were independently steenble and that shaping of power deposition is possible with this system. Although the planar elements were 3.0 x 3.0 cm. rectangular and smaller elements, or non-planar could be ulilized. Also. lower frequencies (such as 0.5 MHz) or higher frequencies (3.0 to 4.0 MHz) could also be used in the same applicator to provide control over depth of penetration.
{"title":"Steerable-beam therapeutic ultrasound for superficial heat treatments","authors":"T. Ryan, A. Hartov, T. Colacchio","doi":"10.1109/IEMBS.1993.978500","DOIUrl":"https://doi.org/10.1109/IEMBS.1993.978500","url":null,"abstract":"A novel. movable beam therapeutic ultrasound applicator was fabricated and tested. Each element was individually powered and directed under computer control. Beam steering experiments were done in a water tank with a needle hydrophone. The elements moved under steppermotor control. Acoustic pressure measurements were compared to computed results for the cases of 0\". 15\" in and 15\" out, at fixed angles. Power could be modulated during the excursion for each element. Measured results matched well with computed results and suggest that beam steering allows power control throughout the heated region. Water tank tests and perfused phantom experiments verified that the collimated acoustic beams were independently steenble and that shaping of power deposition is possible with this system. Although the planar elements were 3.0 x 3.0 cm. rectangular and smaller elements, or non-planar could be ulilized. Also. lower frequencies (such as 0.5 MHz) or higher frequencies (3.0 to 4.0 MHz) could also be used in the same applicator to provide control over depth of penetration.","PeriodicalId":408657,"journal":{"name":"Proceedings of the 15th Annual International Conference of the IEEE Engineering in Medicine and Biology Societ","volume":"32 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1993-10-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126088232","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1993-10-28DOI: 10.1109/IEMBS.1993.978449
M.B. Gokgoz, M. Demirtork, A. Ercil, Y. Ulgen
{"title":"Enhancement of tissue contrast in multifrequency ELT","authors":"M.B. Gokgoz, M. Demirtork, A. Ercil, Y. Ulgen","doi":"10.1109/IEMBS.1993.978449","DOIUrl":"https://doi.org/10.1109/IEMBS.1993.978449","url":null,"abstract":"","PeriodicalId":408657,"journal":{"name":"Proceedings of the 15th Annual International Conference of the IEEE Engineering in Medicine and Biology Societ","volume":"21 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1993-10-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126100405","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1993-10-28DOI: 10.1109/IEMBS.1993.978811
J. Eason, N. Trayanova
A two-dimensional bidomain model is used to investigate the effects of fiber curvature in the presence of irregular boundaries in cardiac tissue subjected to a uniform field. The coupled differential equations are solved using the finite element method. Fiber curvature is found to produce regions of alternating polarity in the transmembrane potential throughout the bulk of the tissue. Also, the magnitude of the transmembrane potential increases with a decrease in the radius of curvature.
{"title":"The effects of fiber curvature in a bidomain tissue with irregular boundaries","authors":"J. Eason, N. Trayanova","doi":"10.1109/IEMBS.1993.978811","DOIUrl":"https://doi.org/10.1109/IEMBS.1993.978811","url":null,"abstract":"A two-dimensional bidomain model is used to investigate the effects of fiber curvature in the presence of irregular boundaries in cardiac tissue subjected to a uniform field. The coupled differential equations are solved using the finite element method. Fiber curvature is found to produce regions of alternating polarity in the transmembrane potential throughout the bulk of the tissue. Also, the magnitude of the transmembrane potential increases with a decrease in the radius of curvature.","PeriodicalId":408657,"journal":{"name":"Proceedings of the 15th Annual International Conference of the IEEE Engineering in Medicine and Biology Societ","volume":"32 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1993-10-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123436692","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1993-10-28DOI: 10.1109/IEMBS.1993.978486
J. Alakuijala, J. Oikarinen, Y. Louhisalmi, S. Sallinen, H. Helminen, J. Koivukangas
A data driven method for correcting low The basic assumption for this work was that the correcfrequency inhomogeneity in magnetic resonance images tion function can be found from small variations within is presented. Small variations within a tissue type are these homogeneous areas by extensive averaging. The efmodeled and a correction function is generated. The spefect of image of the magnetic properties on the correction ciality of this method i s that it is based on image feafunction must be minimized. lures and does not need a phantom nor user interaction We decided to approximate the correction function by to generate the correction function. The image correction separating its spatial variables (3). This works well for simplifies digital image analysis and can enhance clinical head coils, but can fail for surface coils. However, we sugevaluation. A s a result, the correction technique reduces gest that this approximation is good enough when only ihe inhomogeneity and improves the contrast of magnetic one surface coil is used. resonance images. M(p3 = ~ O ~ Z ( P . ) ~ , b J p , ) ~ ( 3 ) The images are first averaged spatially by using 3 x 3 block neighborhood. This removes some of the noise and Although magnetic resonance imaging (MRT) can provide a more Of and is generated. When accurate infomation from the human the correction function is calculated it is applied to the ous diagnostic PUrPoses, the analysis of the quantitative Original image and thus no blurr or lack of detail is visible infomation of Mm is still in its early stage 111. Image in the corrected images. The filtered images IF are j u s t inhomogeneity is the greatest single bad characteristic of used to calculate the correction function. MR images to i n d i t d e Some easy methods of image The average absolute difference between 4-connected segmentation such as tresholding 121. pixels is calculated. A small “variation” is defined to a The messured image I can be thought of being corndifference smaller than the average. A homogeneous area posed from three elements: ideal magnetic image M, is defined to an area in which d l the pixels have small N and radio frequency (m) disto&ion F. Letting difference with their connected pixels in the area. Let ~7 5 be a location in the image space, 8 following estimative and ?be 4-connected pixels and can be calculated from: equation can be written:
本研究的基本假设是磁共振图像函数的正频不均匀性可以从内部的微小变化中发现。一种组织类型内的微小变异是通过广泛平均得到的这些均匀区域。对模型进行建模并生成一个校正函数。该方法以图像为基础，必须尽量减少图像的磁性对校正性的影响。我们决定将修正函数近似为生成修正函数。图像校正分离其空间变量(3)。这可以很好地简化数字图像分析，并可以增强临床头部线圈，但对于表面线圈可能会失败。然而，我们建议评估。结果表明，校正技术降低了仅考虑非均匀性时的近似效果，提高了磁性单面线圈的对比度。磁共振图像。M(p3 = ~ O ~ Z (P .))~， b J p，) ~(3)首先利用3 × 3块邻域对图像进行空间平均。这消除了一些噪声，虽然磁共振成像(MRT)可以提供更多的和产生。当准确的信息从人类的校正函数计算出来，它被应用于我们的诊断目的，定量的原始图像的分析，从而没有模糊或缺乏细节可见的信息Mm仍处于其早期阶段111。图像中的校正图像。滤波后的图像IF为j，其中非均匀性是计算校正函数的最大单一缺点。一些简单的方法对图像进行4连通的平均绝对差分割，如阈值分割121。计算像素。一个小的“变化”被定义为A，测量的图像可以被认为是比平均值小的差。由三个元素构成的均匀区域:理想磁像M，定义为一个区域，其中d1像素具有较小的N和射频(M)分布f，使其与该区域内连接的像素存在差异。设~7 5为图像空间中的一个位置，下面8为估计像素，1为4连通像素，可由式计算:
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