A Study of the Influence Scan Timing and Depiction of Blood Vessel Diameter in CE-3DMRA : Simulation by Pulsatile Flow

AbstractIt has been proposed that astrocytes should no longer be viewed purely as support cells for neurons, such as providing a constant environment and metabolic substrates, but that they should also be viewed as being involved in affecting synaptic activity in an active way and, therefore, an integral part of the information-processing properties of the brain. This essay discusses the possible differences between a support and an instructive role, and concludes that any distinction has to be blurred. In view of this, and a brief overview of the nature of the data, the new evidence seems insufficient to conclude that the physiological roles of mature astrocytes go beyond a general support role. I propose a model of mature protoplasmic astrocyte function that is drawn from the most recent data on their structure, the domain concept and their syncytial characteristics, of an independent rather than integrative functioning of the ends of each process where the activities that affect synaptic activity and blood vessel diameter will be concentrated.

Download Full-text

A realistic flow phantom model of the carotid artery in preterm infants for training and research

Ultrasound ◽

10.1177/1742271x20902189 ◽

2020 ◽

Vol 28 (3) ◽

pp. 145-154

Author(s):

Sujith Pereira ◽

Jonathan Reeves ◽

Malcolm Birch ◽

Sakthi Finton-James ◽

Komal Verma ◽

...

Keyword(s):

Blood Flow ◽

Cerebral Blood Flow ◽

Carotid Artery ◽

Preterm Infants ◽

Pulsatile Flow ◽

Vessel Diameter ◽

Flow Measurements ◽

Phantom Model ◽

Flow Phantom ◽

Volume Measurements

Introduction Cerebral blood flow is increasingly monitored in preterm infants. Doppler ultrasound of the carotid artery is a widely available method but is operator dependent. Our aim was to design and produce a realistic flow phantom model of the carotid artery of preterm infants. Methods Data from cerebral blood flow measurements using Doppler ultrasound of the right common carotid artery from 21 premature newborn infants were used to produce a Doppler flow phantom model with three different vessel diameters. Vessel diameter, continuous and pulsatile flow volume measurements were performed by two blinded observers (with more than eight and 20 years of experience). Results Vessel diameter measurements using the phantom were underestimated by 7%. Continuous flow volume measurements were overestimated by 7% by both observers (observer 1 mean difference 1.5 ± 1.96 SD −3.3 to 6.3 ml/min versus observer 2, 1.9 ± 1.96 SD −3.6 to 7.4 ml/min). Pulsatile flow measurements were overestimated by 12.6% by observer 1 (2.7 ± 1.96 SD −0.6 to 5.9 ml/min) and by 7.8% by observer 2 (1.7 ± 1.96 SD −1.6 to 4.9 ml/min). There was good interobserver and intraobserver reliability for the majority of measurements using continuous and pulsatile flow. Conclusion It is feasible to produce a realistic flow phantom model of the neonatal carotid artery of preterm infants. Diameter measurements were underestimated and flow measurements were overestimated. These errors fell within acceptable limits for in vivo measurements. If these limitations were related to materials, this could be explored using a wall-less model. The flow phantom could be utilised for research and training clinicians in measuring cerebral blood flow using the carotid artery in this vulnerable group of infants.

Download Full-text

Adaptive ultrasonic measurement of blood vessel diameter and wall thickness: theory and experimental results

IEEE Transactions on Ultrasonics Ferroelectrics and Frequency Control ◽

10.1109/58.677604 ◽

1998 ◽

Vol 45 (3) ◽

pp. 593-603 ◽

Cited By ~ 1

Author(s):

K. Rafii ◽

J.S. Jaffe

Keyword(s):

Blood Vessel ◽

Wall Thickness ◽

Vessel Diameter ◽

Ultrasonic Measurement ◽

Experimental Results

Download Full-text

Numerical simulation of physiologically relevant pulsatile flow of blood with shear-rate-dependent viscosity in a stenosed blood vessel

International Journal of Biomathematics ◽

10.1142/s1793524518500821 ◽

2018 ◽

Vol 11 (06) ◽

pp. 1850082

Author(s):

Subrata Mukhopadhyay ◽

Mani Shankar Mandal ◽

Swati Mukhopadhyay

Keyword(s):

Numerical Simulation ◽

Blood Flow ◽

Blood Vessel ◽

Pulsatile Flow ◽

Time Dependent ◽

Governing Equations ◽

Rate Dependent ◽

Realistic Situation ◽

Newtonian Case ◽

Dependent Viscosity

Pulsatile flow of blood in a blood vessel having time-dependent shape (diameter) is investigated numerically in order to understand some important physiological phenomena in arteries. A smooth axi-symmetric cosine shaped constriction is considered. To mimic the realistic situation as far as possible, viscosity of blood is taken to be non-uniform, a shear-thinning viscosity model is considered and a physiologically relevant pulsatile flow is introduced. Taking advantage of axi-symmetry in the proposed problem, the stream function–vorticity formulation is used to solve the governing equations for blood flow. Effect of different parameters associated with the problem on the flow pattern has been investigated and disparities from the Newtonian case are discussed in detail.

Download Full-text