1.1 COMPARISON OF VARIOUS METHODS FOR THE ESTIMATION FOR AORTIC CHARACTERISTIC IMPEDANCE IN TIME DOMAIN FROM VELOCITY-ENCODED MAGNETIC RESONANCE AND APPLANATION TONOMETRY DATA

2013 ◽  
Vol 7 (3-4) ◽  
pp. 161
Author(s):  
E. Bollache ◽  
N. Kachenoura ◽  
I. Bargiotas ◽  
A. de Cesare ◽  
M. Bensalah ◽  
...  
2015 ◽  
Vol 33 (3) ◽  
pp. 575-583 ◽  
Author(s):  
Emilie Bollache ◽  
Nadjia Kachenoura ◽  
Ioannis Bargiotas ◽  
Alain Giron ◽  
Alain De Cesare ◽  
...  

2021 ◽  
Vol 12 ◽  
Author(s):  
Tingting Dong ◽  
Qiuping Huang ◽  
Shucai Huang ◽  
Jiang Xin ◽  
Qiaolan Jia ◽  
...  

Methamphetamine (MA) can cause brain structural and functional impairment, but there are few studies on whether this difference will sustain on MA abstainers. The purpose of this study is to investigate the correlation of brain networks in MA abstainers. In this study, 47 people detoxified for at least 14 months and 44 normal people took a resting-state functional magnetic resonance imaging (RS-fMRI) scan. A dynamic (i.e., time-varying) functional connectivity (FC) is obtained by applying sliding windows in the time courses on the independent components (ICs). The windowed correlation data for each IC were then clustered by k-means. The number of subjects in each cluster was used as a new feature for individual identification. The results show that the classifier achieved satisfactory performance (82.3% accuracy, 77.7% specificity, and 85.7% sensitivity). We find that there are significant differences in the brain networks of MA abstainers and normal people in the time domain, but the spatial differences are not obvious. Most of the altered functional connections (time-varying) are identified to be located at dorsal default mode network. These results have shown that changes in the correlation of the time domain may play an important role in identifying MA abstainers. Therefore, our findings provide valuable insights in the identification of MA and elucidate the pathological mechanism of MA from a resting-state functional integration point of view.


2015 ◽  
Vol 121 ◽  
pp. 14-17 ◽  
Author(s):  
Paulo Falco Cobra ◽  
Bruna Ferreira Gomes ◽  
Cirlei Igreja Nascimento Mitre ◽  
Lucio Leonel Barbosa ◽  
Lucinéia Vizzotto Marconcini ◽  
...  

1982 ◽  
Vol 242 (2) ◽  
pp. H197-H202 ◽  
Author(s):  
J. P. Dujardin ◽  
D. N. Stone ◽  
C. D. Forcino ◽  
L. T. Paul ◽  
H. P. Pieper

Experiments were performed on eight anesthetized dogs to study the response of the characteristic impedance (Zc) of the main pulmonary artery to changes in circulating blood volume. Pressure and flow were measured in the proximal main pulmonary artery under control conditions, after hemorrhage (-15% of the estimated blood volume), again under control conditions, and finally after volume expansion (+30% of the estimated blood volume). Two different methods were used to determine Zc from these recordings. With the frequency-domain method values for Zc were obtained by averaging the input impedance moduli between 2 and 15 Hz. With the time-domain method Zc was derived as the slope of the early ejection pressure-flow relationship. The values for Zc obtained with the two methods were not statistically different. In the time-domain method the average increase in Zc with hemorrhage was 30.7 +/- 7.4 (SE) %, and the average decrease with volume expansion was -21.1 +/- 5.0 (SE) %. Because the time-domain method allowed the values of Zc during control conditions and after hemorrhage to be obtained in the same pressure range, it was concluded that the observed changes were caused by a change in the activity of the smooth muscle in the pulmonary arterial wall. Similarly, it was concluded that the decrease in Zc after volume expansion was active in nature.


2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Pauliina Kangas ◽  
Antti Tikkakoski ◽  
Jarkko Kettunen ◽  
Arttu Eräranta ◽  
Heini Huhtala ◽  
...  

AbstractThe increase in cardiovascular risk associated with metabolic syndrome (MS) seems higher in women than in men. We examined hemodynamics during head-up tilt in 252 men and 250 women without atherosclerosis, diabetes, or antihypertensive medication, mean age 48 years, using whole-body impedance cardiography and radial pulse wave analysis. MS was defined according to Alberti et al. 2009. Men and women with MS presented with corresponding elevations of systolic and diastolic blood pressure (10-14%, p ≤ 0.001) versus controls. Supine pulse wave velocity (16–17%, p < 0.001) and systemic vascular resistance (7–9%, p ≤ 0.026), and upright cardiac output (6–11%, p ≤ 0.008) were higher in both MS groups than controls. Elevation of supine aortic characteristic impedance was higher in women than in men with MS (16% vs. 8%, p = 0.026), and in contrast to men, no upright impedance reduction was observed in women. When upright, women but not men with MS showed faster return of reflected pressure wave (p = 0.036), and smaller decrease in left cardiac work (p = 0.035) versus controls. The faster upright return of reflected pressure, lower upright decrease in left cardiac work, and higher elevation of aortic characteristic impedance may contribute to the greater increase in MS-related cardiovascular risk in women than in men.


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