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Contour Method (contour + method)

Distribution by Scientific Domains

Medical Sciences	75%

Selected Abstracts

Simultaneous quantification of cell motility and protein-membrane-association using active contours

CYTOSKELETON, Issue 4 2002
Dirk Dormann
Abstract We present a new method for the quantification of dynamic changes in fluorescence intensities at the cell membrane of moving cells. It is based on an active contour method for cell-edge detection, which allows tracking of changes in cell shape and position. Fluorescence intensities at specific cortical subregions can be followed in space and time and correlated with cell motility. The translocation of two GFP tagged proteins (CRAC and GRP1) from the cytosol to the membrane in response to stimulation with the chemoattractant cAMP during chemotaxis of Dictyostelium cells and studies of the spatio-temporal dynamics of this process exemplify the method: We show that the translocation can be correlated with motility parameters and that quantitative differences in the rate of association and dissociation from the membrane can be observed for the two PH domain containing proteins. The analysis of periodic CRAC translocation to the leading edge of a cell responding to natural cAMP waves in a mound demonstrates the power of this approach. It is not only capable of tracking the outline of cells within aggregates in front of a noisy background, but furthermore allows the construction of spatio-temporal polar plots, capturing the dynamics of the protein distribution at the cell membrane within the cells' moving co-ordinate system. Compilation of data by means of normalised polar plots is suggested as a future tool, which promises the so-far impossible practicability of extensive statistical studies and automated comparison of complex spatio-temporal protein distribution patterns. Cell Motil. Cytoskeleton 52:221,230, 2002. © 2002 Wiley-Liss, Inc. [source]

Bench to Bedside: Electrophysiologic and Clinical Principles of Noninvasive Hemodynamic Monitoring Using Impedance Cardiography

ACADEMIC EMERGENCY MEDICINE, Issue 6 2003
Richard L. Summers MD
Abstract The evaluation of the hemodynamic state of the severely ill patient is a common problem in emergency medicine. While conventional vital signs offer some insight into delineating the circulatory pathophysiology, it is often impossible to determine the true clinical state from an analysis of blood pressure and heart rate alone. Cardiac output measurements by thermodilution have been the criterion standard for the evaluation of hemodynamics. However, this technology is invasive, expensive, time-consuming, and impractical for most emergency department environments. Impedance cardiography (ICG) is a noninvasive method of obtaining continuous measurements of hemodynamic data such as cardiac output that requires little technical expertise. ICG technology was first developed by NASA in the 1960s and is based on the idea that the human thorax is electrically a nonhomogeneous, bulk conductor. Variation in the impedance to flow of a high-frequency, low-magnitude alternating current across the thorax results in the generation of a measured waveform from which stroke volume can be calculated by a modification of the pulse contour method. To adequately judge the possible role of this technology in the practice of emergency medicine, it is important to have a sufficient understanding of the basic scientific principles involved as well as the clinical validity and limitations of the technique. [source]

Performance of three minimally invasive cardiac output monitoring systems

ANAESTHESIA, Issue 7 2009
R. B. P. De Wilde
Summary We evaluated cardiac output (CO) using three new methods , the auto-calibrated FloTrac,Vigileo (COed), the non-calibrated Modelflow (COmf,) pulse contour method and the ultra-sound HemoSonic system (COhs) , with thermodilution (COtd) as the reference. In 13 postoperative cardiac surgical patients, 104 paired CO values were assessed before, during and after four interventions: (i) an increase of tidal volume by 50%; (ii) a 10 cm H2O increase in positive end-expiratory pressure; (iii) passive leg raising and (iv) head up position. With the pooled data the difference (bias (2SD)) between COed and COtd, COmf and COtd and COhs and COtd was 0.33 (0.90), 0.30 (0.69) and ,0.41 (1.11) l.min,1, respectively. Thus, Modelflow had the lowest mean squared error, suggesting that it had the best performance. COed significantly overestimates changes in cardiac output while COmf and COhs values are not significantly different from those of COtd. Directional changes in cardiac output by thermodilution were detected with a high score by all three methods. [source]

Circadian systemic haemodynamics in borderline and mild hypertension

CLINICAL PHYSIOLOGY AND FUNCTIONAL IMAGING, Issue 6 2000
R. Takalo
Circadian variations in blood pressure (BP), stroke volume (SV), heart rate (HR), cardiac output (CO) and total peripheral resistance (TPR) were determined by a pulse contour method from the intra-arterial pulse wave in 32 normotensive (NT), 32 borderline hypertensive (BHT) and 31 hypertensive (HT) middle-aged men. Daytime averages were used as the reference levels. The nocturnal decrease in BP and HR were similar in the three groups. In the night, SV did not change in the NT group, but was increased in the BHT and HT groups. The nocturnal increase in SV may reflect reduced venous capacity causing increased cardiac filling. As a consequence of the difference in SV, the nocturnal CO fall was diminished in the HT group as compared with the NT group. Moreover, TPR had a tendency to decrease in the HT group, which may be considered as a baroreflex response to buffer the expected rise in BP. Five years later, 25 NT, 24 BHT and 19 HT subjects were reassessed using casual BP measurements. In the NT and BHT groups, six and 17 subjects, respectively, had progressed to hypertension. In a logistic regression model for those who became HT, the nocturnal increase in SV was a significant predictor for future hypertension. In conclusion, the results suggest that circadian systemic haemodynamics may be altered before BP is markedly elevated, and that haemodynamic studies might be useful in predicting the development of sustained hypertension. [source]