Proceedings of the 15th Annual International Conference of the IEEE Engineering in Medicine and Biology Societ最新文献

{"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}

{"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}

{"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}

{"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}

{"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}

{"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}

{"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}

{"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}

{"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}

{"title":"Data driven MRI inhomogeneity correction","authors":"J. Alakuijala, J. Oikarinen, Y. Louhisalmi, S. Sallinen, H. Helminen, J. Koivukangas","doi":"10.1109/IEMBS.1993.978486","DOIUrl":"https://doi.org/10.1109/IEMBS.1993.978486","url":null,"abstract":"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:","PeriodicalId":408657,"journal":{"name":"Proceedings of the 15th Annual International Conference of the IEEE Engineering in Medicine and Biology Societ","volume":"38 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":"123530939","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}