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Blood flow
Published in Peter R Hoskins, Kevin Martin, Abigail Thrush, Diagnostic Ultrasound, 2019
The presence of arterial disease can significantly alter the resistance to flow, with the reduction in vessel diameter having a major effect on the change in resistance. The Doppler waveform shape will be affected by an increase in the resistance distal to the site from which the waveform was obtained. This observed change in waveform shape may help indicate the presence of an occlusion distal to the vessel being observed. For example, the waveform in Figure 8.17 shows a Doppler spectrum obtained from a common carotid artery proximal to an internal carotid artery occlusion. This waveform demonstrates a short acceleration time (from the beginning of systole to peak systole) but with an absence of any diastolic flow which is normally seen in the cerebral circulation (Figure 8.15).
Selected Case Studies
Published in Clement Kleinstreuer, Theory and Applications, 2017
Quite frequently the external carotid artery is highly diseased, i.e., severe stenoses with localized myointimal deterioration. Computational hemodynamics simulations and analyses of feasible design options are most valuable for practitioners before surgical intervention. In general, two of the characteristics that make the carotid bifurcation somewhat unique are the different blood flow requirements and waveforms of the internal carotid artery (ICA) and the external carotid artery (ECA). Cerebral blood flow is normally closely autoregulated to provide a flow rate of 50 to 55 ml/min to the brain (Boysen et al., 1972). The ICA has a relatively constant blood flow with a pulsatile waveform characterized by high diastolic flow, similar to the one found in solid organs like the kidney. In contrast, ECA flow can be highly variable and generally has a biphasic waveform with little diastolic flow, similar to resting upper and lower extremity arterial flows. Both the variability in ICA and ECA flow ratios and the quite different pulsatile flow waveforms are important components of adverse wall shear stresses, their directional changes, and their spatial gradients in the carotid bifurcation. A second closely related problem is the possible adverse effect of ECA flow and waveform on recurrent stenosis after carotid endarterectomy or perhaps even after angioplasty and stenting.
Central nervous system
Published in David A Lisle, Imaging for Students, 2012
US examination of the carotid arteries is a useful screening test able to diagnose atheromatous disease causing stenosis and occlusion. Carotid US combines direct visualization of the arterial wall, colour Doppler examination of the arterial lumen, and measurement of blood flow velocity in the common carotid artery (CCA) and internal carotid artery (ICA). Blood flow velocity measurements include measurements of peak systolic velocity (PSV) and end diastolic velocity (EDV) given in cm/sec. Comparison of PSV for the CCA and ICA gives the ICA/CCA ratio. Stenosis is indicated by direct visualization of arterial narrowing plus increased measured flow velocity in the internal carotid artery (Fig. 10.14).
Automated technique for carotid plaque characterisation and classification using RDWT in ultrasound images
Published in Computer Methods in Biomechanics and Biomedical Engineering: Imaging & Visualization, 2022
Arun Mailerum Perumal, G.N. Balaji, J. Dhiviya Rose, Asha Kulkarni, Francis H Shajin
The input images are taken from the B-mode datasets (Qian and Yang 2018) are related to the plaque classification project at Saint Mary’s Hospital, Imperial College of Medicine, Science and Technology, U.K. The database has 80 B-mode longitudinal ultrasound images and CCA blood flow. Here, the ultra sound images are taken from the group of 346 patients (mean age = 69.9 + 7.8, 39% females). Duplex ultrasound is utilised for obtaining imageries from patients through internal carotid artery diameter stenosis of 50–99%. The dataset has 196 patients with symptomatic plaque, 150 with asymptomatic plaque. The neurological abnormalities are expressed by none of the asymptomatic patients.