Lu Weixue

Computer simulation of epicardial potentials using a heart-torso model with realistic geometry

Previous cardiac simulation studies have focused on simulating the activation isochrones and subsequently the body surface potentials. Epicardial potentials, which are important for clinical application as well as for electrocardiographic inverse problems studies, however, have usually been neglected. This paper describes a procedure of simulating epicardial potentials using a microcomputer-based heart-torso model with realistic geometry. Our heart model developed earlier is composed of approximately 65,000 cell units which are arranged in a cubic close-packed structure. An action potential waveform with variable in duration is assigned to each unit. The heart model, together with the epicardial surface model constructed recently, are mounted in an inhomogeneous human torso model. Electric dipoles, which are proportional to the spatial gradient of the action potential, are generated in all the cell units. These dipoles give rise to a potential distribution on the epicardial surface, which is calculated by means of the boundary element method. The simulated epicardial potential maps during a normal heart beat and in a preexcited beat to mimic Wolff-Parkinson-White (WPW) syndrome are in close agreement with those reported in the literature.

Microcomputer-based cardiac field simulation model.

Cardiac field simulation is one of the frontier subjects in electrocardiogram theory study. The paper describes a complete cardiac simulation model implemented on an IBM-PC/AT microcomputer. This model uses a new algorithm for excitation propagation simulation. In comparison with the previous rule-based algorithms, the new algorithm shows better in simulation speed and simulation accuracy.

Three-dimensional simulation of epicardial potentials using a microcomputer-based heart- torso model

Previous cardiac simulation studies have focused on simulating the activation isochrones and subsequently the body surface potentials. Epicardial potentials, which are important for clinical applications as well as for electrocardiography inverse problem studies, however, have usually been neglected. This paper presents a procedure of simulating epicardial potentials using a microcomputer-based heart-torso model with real geometry. The heart model developed earlier which was composed of more than 60,000 cell units was used in this study. To simulate the epicardial potentials, an epicardial surface model which enclosed the whole heart was constructed. The heart model, together with the epicardial surface model, are mounted in an inhomogeneous human torso model. Electric dipoles, which are proportional to the spatial gradient of the action potential, are generated in all cell units. These dipoles give rise to a potential distribution on the epicardial surface, which is calculated by means of the boundary element method. The simulated epicardial potential maps during a normal heart beat and in patients with left bundle branch block (LBBB) are in close agreement with those reported in the literature.

Automatic segmentation and classification of human brain images based on TT atlas

It is difficult to automatically segment and classify tomographic images of an actual patients brain. Therefore, many interactive operations are performed. It is very time consuming and its precision is user-dependent. Here, the authors combined a brain atlas and 3D fuzzy image segmentation into the image matching. It can not only find out the precise boundary of an anatomic structure, but also save time in the interactive operation. At first, the anatomic information of the atlas is mapped onto tomograph images of an actual brain with an image matching method. Then, based on the mapping result, a 3D fuzzy structure mask is calculated. With the fuzzy information of anatomic structure, a new method of fuzzy clustering is used to segment and classify the real brain image. There is only a minimum requirement of interaction in the whole process, including removing the skull and selecting some intrinsic point pairs.

Multicriteria Regularizing Neural Network Approach to Implicit Image Information Extraction from two Projections

This paper describes attempts to model the implicit image information extraction from two projections in terms of minimizing energy function of multicriteria regularizing neural network. It examines the success of using multicriteria-style analog network for solving such problem. Finally it discusses the computer simulation results of the energy function approach.

A Dexterous Anthropomorphic Finger for Measuring Human Pulse

We have developed a dexterous electric motor drive anthropomorphic finger. The artificial finger has four degrees of rotating freedom and is drived by three micro-electric motors with speed reducers and a sound-coil electric motor. A PVF2 tactile sensor array is mounted at the finger-tip. This finger may be used for active touch research in unstructured environment, especially for studying pulse diagnosis in traditional Chinese medicine.

Multimodality brain atlas based on the visible human project dataset

A multimodality brain atlas is implemented based on the visible human dataset. Firstly, the VHDs images of different modalities are interpolated and registered into a common cubic space. A global rotation and translation is then used to transform the registered dataset into the standard Talairach coordinate. The Talairach atlas is mapped onto the VHDs images with a piecewise linear scaling. A texture segmentation method is developed to label the different tissue types according to the knowledge provided by the Talairach atlas. Finally, the 3D rendering results are provided.

The Development Of A New Mininature Thin Film Dissolved Oxygen And Ionic Conductivity Sensor And Measurement System

The electrochemical dissolved oxygen sensor has been a powerful tool in medical, biological, environmental and clinic settings [1][2]. Obviously, only the sensor is properly designed can it be expected to have a good performance. In addition, the solution of oxygen in water decreases with increasing salt concentration at a constant temperature at the salting-out effect [3]. For accurate dissolved oxygen measurement, the ionic conductivity of aqueous medium must be considered concurrently. The present work attempts to provided a realistic simulation of the recessed array geometry. A finiteelement analysis on steady state recessed dissolved cathode array was made. Some design criteria to optimized the cathode array were provided. A new auto-calibrated microhole cathode array three electrode oxygen and ionic conductivity sensor has been developed.

Simulation Studies Of Various Degrees Of Bundle Branch Block With A New Computer Model

A computer model with a new excitation propagation algorithm is discussed. Thensimulations of complete and incomplete bundle branch block are studied. Some useful physiological results are obtained.

A auto-calibrated microhole cathode array dissolved oxygen and ionic conductivity sensor

A novel miniature auto-calibrated dissolved oxygen and ionic conductivity sensor has been developed. This sensor consists of two gold working electrodes, a Ag/AgCl reference electrode, a gold counter-electrode, and a Pt thermal resistant. It operates in a three-electrode potentiostatic mode. The two working electrodes have a multiple-cathode array separately. One is used for the measurement of oxygen and the other is used for calibration. The two working electrodes can also be used to measure the conductance of a solution by switching the sensor to the conductance measurement circuit. Evaluation of the sensor characteristics was undertaken and the results are promising. Calibration of the sensor was performed over the oxygen concentration range of 3-16 p.p.m. in a 0.1 N-1 N KCl solution in the 12-25 degrees C temperature range and at 760 torr pressure. A linear relationship is observed.<<ETX>>