Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Models, Anatomic”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 595 records · Page 33Linked to original sources
PubMed1992

Simulation of ozone uptake distribution in the human airways by orthogonal collocation on finite elements.

Ozone transport in a rigid single-pathway anatomic model of the lung was analyzed by a stable convergent numerical algorithm, the method of orthogonal collocation on finite elements. The simulations predicted the dynamic behavior of gas phase concentration profiles for both ozone and an insoluble inert gas. An internal quasi-stationary diffusion front was observed during early inspiration for both gases. In addition, the absorptive distribution of ozone in lung airways was computed as a total dose as well as a tissue dose. The total dose of ozone decreased along the airway path from the mouth. However, the tissue dose of ozone increased along the conducting airways, reached a maximal dose in the terminal bronchioles, and decreased sharply in the respiratory airways.

Algorithms↗
PubMed1987

Computer simulation of human mitral valve mechanics and motion.

The human mitral valve is the left atrio-ventricular valve which is composed of several components including leaflets, chordae tendineae, papillary muscles, and the valve annulus. Any or all of these components may fail and contribute to various valvular diseases including mitral regurgitation and mitral valve prolapse. A computer simulation of mitral valve mechanics and motion was written in BASIC for micro-computers. This program allows valvular geometry and biomechanical parameters to be varied and records time varying motion of the valve and all components during systole including a graphic display of the valve leaflets.

Chordae Tendineae↗
PubMed1995

Endoscopic surgery simulation in a virtual environment.

The minimally invasive nature of endoscopic surgery allows operations to be performed on patients through small incisions, often under local anaesthesia. Patient recovery times and cosmetic detriment are thus greatly reduced, while overall quality of care is improved. Presently, surgeons are trained to perform endosurgical procedures in a number of ways: practising with surgical training devices, using animal models and assisting experienced surgeons. In this paper, the focus is on answering the key question: "Can virtual environment technology assist surgeons in training and maintaining endoscopic surgery skills?" Initial developments towards surgical simulators have clearly demonstrated the great potential of virtual environment technology for surgical training purposes. Breakthroughs towards surgery are expected within the next 5 to 10 years.

Clinical Competence↗
PubMed1986

Magnetic localisation of intracranial dipoles: simulation with a physical model.

Current dipoles energized by isolated sources were located in known positions inside a human skull filled with an electrically conductive medium. Maps of the measured electrical and magnetic fields confirmed the predicted relationships between those fields for both single and multiple dipoles. Two methods of dipole localisation were compared: the peak-location method which used only the locations of the maximum and minimum recorded values, and a least-squares iterative method which found the parameters for a dipole such that the sum of squared differences between the recorded and predicted data was minimized. Also, in an attempt to account for some of the error due to the non-sphericity of the head, the measured distance from the centre of the skull to each recording position was used in the dipole calculations. This last technique resulted in the smallest 3-dimensional location error (averaging 3.5 mm) for the least-squares method, even when no recording positions were near the actual field extrema and the peak-location method therefore produced much greater error. Also investigated were combinations of two dipoles for which the magnetic field maps appeared similar to those for a single dipole and comparisons were made to determine how well single and double dipole models could account for the recorded data.

Brain↗
PubMed1994

High resolution EEG: 124-channel recording, spatial deblurring and MRI integration methods.

This paper describes a method for increasing the spatial detail of the EEG and for integrating physiological data with anatomical models based on magnetic resonance images (MRIs). This method includes techniques to efficiently record EEG data from up to 124 channels, to measure 3-D electrode positions for alignment with MRI-derived head models, and to estimate potentials near the outer convexity of the cortex using a spatial deblurring technique which uses a realistic model of the structure of the head and which makes no assumptions about the number or type of generator sources. The validity of this approach has been initially tested by comparing estimated cortical potentials with those measured with subdural grid recordings from two neurosurgical patients. The method is illustrated with somatosensory steady-state evoked potential data recorded from 5 healthy subjects. Results suggest that deblurred 124-channel topographic maps, registered with a subject's MRI and rendered in 3 dimensions, provide better spatial detail than has heretofore been obtained with scalp EEG recordings. The results also suggest that the potential for EEG as a functional neuroimaging modality has yet to be fully realized.

Adult↗
PubMed1989

Effects of cavities on EEG dipole localization and their relations with surface electrode positions.

Effects of cavities in the human head on EEG dipole localization have been investigated by computer simulation. The human head is represented by a homogeneous spherical conductor including an eccentric spherical cavity which approximates effects of actual cavities inside the head. The homogeneous sphere model is used for assessing the effects caused by neglecting the cavity in the volume conductor model in the inverse dipole fitting procedure. Four electrode configurations have been examined to investigate their relation to the EEG inverse dipole solution. After examination of 2520 dipoles in the brain, the effects of cavities in the human head are found to be negligible when the dipole is located in the cortex or in the subcortex. When the dipole is located in the brain stem, the EEG inverse dipole solution is strongly affected by the cavity and is sensitive to the electrode configuration on the scalp. The EEG inverse dipole solution in the deep brain is sensitive to inhomogeneity in the lower part of the head when a single positive or negative potential pole is observed by the electrodes on the scalp, and at the same time is sensitive to the extent of the scalp covered by the electrodes. In conclusion, the electrodes should cover as much of the upper scalp as possible for deep source localization.

Algorithms↗
PubMed1995

Particle-fluid suspension model of blood flow through stenotic vessels with applications.

The present study deals with the problem of blood flow through stenotic vessels when blood is represented by a particle-fluid suspension model, i.e. a suspension of red blood cells in plasma. The expression for the dimensionless resistance to flow, the wall shear stress, and the shearing stress on the wall at the maximum height of the stenosis are derived. The results obtained in the analysis are discussed in brief, both qualitatively and quantitatively by comparison with other theories. It is observed that the magnitudes of the blood flow characteristics significantly increase with an increase in the red cell concentration. The importance of the decreasing vessel diameter is also pointed out. Finally, to observe the biological relevance of the analysis, the results obtained are used to compute the blood flow characteristics for normal and diseased blood using the experimental data from published literature and results are compared with those computed using the present theoretical approach.

Algorithms↗