The Contribution of Vessel Volume Change and Blood Resistivity Change to the Electrical Impedance Pulse

1985 ◽  
Vol BME-32 (3) ◽  
pp. 192-198 ◽  
Author(s):  
T. M. Ravi Shankar ◽  
John G. Webster ◽  
Shu-Yong Shao
Keyword(s):  
Volume Change ◽  
Electrical Impedance ◽  
Resistivity Change ◽  
Blood Resistivity ◽  
Vessel Volume

scholarly journals Human CT Measurements of Structure/Electrode Position Changes During Respiration with Electrical Impedance Tomography

2013 ◽  
Vol 7 (1) ◽  
pp. 109-115 ◽  
Author(s):  
Jie Zhang ◽  
Lihong Qin ◽  
Tadashi Allen ◽  
Robert P Patterson
Keyword(s):  
Electrical Impedance Tomography ◽  
Electrical Impedance ◽  
Structural Changes ◽  
Electrode Placement ◽  
Accurate Information ◽  
Electrode Position ◽  
Resistivity Change ◽  
Ct Scanner ◽  
Impedance Tomography ◽  
Measured Resistivity

For pulmonary applications of Electrical Impedance Tomography (EIT) systems, the electrodes are placed around the chest in a 2D ring, and the images are reconstructed based on the assumptions that the object is rigid and the measured resistivity change in EIT images is only caused by the actual resistivity change of tissue. Structural changes are rarely considered. Previous studies have shown that structural changes which result in tissue/organ and electrode position changes tend to introduce artefacts to EIT images of the thorax. Since EIT reconstruction is an ill-posed inverse problem, any small inaccurate assumptions of object may cause large artefacts in reconstructed images. Accurate information on structure/electrode position changes is a need to understand factors contributing to the measured resistivity changes and to improve EIT reconstruction algorithm. Our previous study using MRI technique showed that chest expansion leads to electrode and tissue/organ movements but not significant as proposed. The accuracy of the measurements by MRI may be limited by its relatively low temporal and spatial resolution. In this study, structure/electrode position changes during respiration cycle in patients who underwent chest CT scans are further investigated. For each patient, sixteen fiduciary markers are equally spaced around the surface, the same as the electrode placement for EIT measurements. A CT scanner with respiration-gated ability is used to acquire images of the thorax. CT thoracic images are retrospectively reconstructed corresponding temporally to specific time periods within respiration cycle (from 0% to 90%, every 10%). The average chest expansions are 2 mm in anterior-posterior and -1.6 mm in lateral directions. Inside tissue/organ move down 9.0±2.5 mm with inspiration of tidal volume (0.54±0.14 liters), ranging from 6 mm to 12 mm. During normal quiet respiration, electrode position changes are smaller than expected. No general patterns of electrode position changes are observed. The results in this study provide guidelines for accommodating the motion that may introduce artefacts to EIT images.

Calibrated impedance plethysmograph

1980 ◽  
Vol 239 (2) ◽  
pp. H283-H288
Author(s):  
M. R. Yablonski ◽  
J. M. Van De Water ◽  
B. E. Mount ◽  
E. D. Laska ◽  
R. B. Indech
Keyword(s):  
Electrical Impedance ◽  
Correlation Coefficients ◽  
Pulse Frequency ◽  
Volume Measurement ◽  
Frequency Variation ◽  
Blood Resistivity ◽  
Impedance Model ◽  
Electrode Distance ◽  
Pulse Volume ◽  
Impedance Plethysmograph

The accuracy of quantitative pulse-volume measurement with a calibrated electrical impedance plethysmograph was determined on a laboratory limb-segment model. Changes in electrical impedance detected via a tetraprolar electode configuration were related to pulse-volume changes by the parallel-impedance model described by Nyboer et al. (The Impedance Plethysmograph: An Electrical Volume Recorder. Natl. Res. Council, Comm. Aviation Med. 149, 1943). The instrument employed in this study calculated pulse volume assuming two standard conditions: distance between voltage electrodes, l, is 15 cm, and resistivitiy of blood, rho b, is 150 omega x cm. The effects of varying tissue and blood resistivity, pulse frequency, and electrode distance were investigated. Measurements under three ionically distinct conditions gave an overall accuracy of 96.6% with correlation coefficients of 0.99 for each condition. Measurement accuracy was maintained with a pulse-frequency variation in the range of 15-150 pulses/min and with application of correction factors for electrode distance and blood resistivity other than the standard values.

Studies on the effect of controlled volume change on the thoracic electrical impedance

1978 ◽  
Vol 16 (5) ◽  
pp. 531-536 ◽  
Author(s):  
R. P. Patterson ◽  
W. G. Kubicek ◽  
D. A. Witsoe ◽  
A. H. L. From
Keyword(s):  
Volume Change ◽  
Electrical Impedance ◽  
Thoracic Electrical Impedance

Artifacts caused by dehydration and epoxy embedding in TEM

1991 ◽  
Vol 49 ◽  
pp. 338-339
Author(s):  
Hilton H. Mollenhauer
Keyword(s):  
Electron Microscopy ◽  
Electron Beam ◽  
Volume Change ◽  
Tissue Damage ◽  
Beam Specimen ◽  
Chemical Fixation ◽  
Resin Impregnation ◽  
Storage Vesicles ◽  
A Cell ◽  
Tissue Shrinkage

Various means have been devised to preserve biological specimens for electron microscopy, the most common being chemical fixation followed by dehydration and resin impregnation. It is intuitive, and has been amply demonstrated, that these manipulations lead to aberrations of many tissue elements. This report deals with three parts of this problem: specimen dehydration, epoxy embedding resins, and electron beam-specimen interactions. However, because of limited space, only a few points can be summarized.Dehydration: Tissue damage, or at least some molecular transitions within the tissue, must occur during passage of a cell or tissue to a nonaqueous state. Most obvious, perhaps, is a loss of lipid, both that which is in the form of storage vesicles and that associated with tissue elements, particularly membranes. Loss of water during dehydration may also lead to tissue shrinkage of 5-70% (volume change) depending on the tissue and dehydrating agent.

Short-term volume and turgor regulation in yeast

2008 ◽  
Vol 45 ◽  
pp. 147-160 ◽  
Author(s):  
Jörg Schaber ◽  
Edda Klipp
Keyword(s):  
Dynamic Model ◽  
Volume Change ◽  
Volume Regulation ◽  
Time Course ◽  
Osmotic Shock ◽  
Intracellular Concentration ◽  
Short Term ◽  
Hydrodynamic Property ◽  
Turgor Regulation ◽  
Thermodynamic Framework

Volume is a highly regulated property of cells, because it critically affects intracellular concentration. In the present chapter, we focus on the short-term volume regulation in yeast as a consequence of a shift in extracellular osmotic conditions. We review a basic thermodynamic framework to model volume and solute flows. In addition, we try to select a model for turgor, which is an important hydrodynamic property, especially in walled cells. Finally, we demonstrate the validity of the presented approach by fitting the dynamic model to a time course of volume change upon osmotic shock in yeast.

FREE VOLUME CHANGE OF METALLIC GLASSES STUDIED BY THERMAL EXPANSION MEASUREMENTS

1980 ◽  
Vol 41 (C8) ◽  
pp. C8-875-C8-877
Author(s):  
E. Girt ◽  
P. Tomić ◽  
A. Kuršumović ◽  
T. Mihać-Kosanović
Keyword(s):  
Thermal Expansion ◽  
Free Volume ◽  
Volume Change ◽  
Metallic Glasses

Volume-change response of precast concrete buildings

PCI Journal ◽  
2009 ◽  
Vol 54 (4) ◽  
pp. 112-131 ◽  
Author(s):  
Gary J. Klein ◽  
Richard E. Lindenberg
Keyword(s):  
Volume Change ◽  
Precast Concrete ◽  
Concrete Buildings ◽  
Change Response
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