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Cerebral Circulation and Gravitational Stress
Published in Anthony N. Nicholson, The Neurosciences and the Practice of Aviation Medicine, 2017
Various techniques have been used to study cerebral blood flow. Since the 1980s changes have been estimated from velocity measurements in the middle cerebral artery using the transcranial Doppler technique (Aaslid et al., 1989). Flow within the artery is proportional to its cross-sectional area as well as to the velocity, but, as changes in the diameter of the middle cerebral artery are minimal in healthy conscious humans, flow is considered to be directly proportional to velocity (Schondorf et al., 1997; Serrador et al., 2000). It is also considered that flow in the middle cerebral artery is an indication of blood flow through all regions of the brain (Levine et al., 1994). Simultaneous measurements of total cerebral blood flow, intracranial compliance and intracranial pressure have been provided by imaging techniques (Alperin et al., 2005, 2006), while the venous drainage system has also been studied by angiography (Epstein et al., 1970, Dilemge and Perry, 1973) and by sonography (Valdueza et al., 2000; Suarez et al., 2002; Cirovic et al., 2003; Gisolf et al., 2004; Doepp et al., 2004).
Central nervous system
Published in David A Lisle, Imaging for Students, 2012
Most cerebral artery aneurysms are congenital ‘berry’ aneurysms. Berry aneurysms occur in 2 per cent of the population and are multiple in 10 per cent of cases. Increased incidence of berry aneurysms occurs in association with coarctation of the aorta and autosomal dominant polycystic kidney disease. Most berry aneurysms occur around the circle of Willis, the most common sites being:Anterior communicating arteryPosterior communicating arteryMiddle cerebral arteryBifurcation of internal carotid arteryTip of basilar artery.
Reproductive system
Published in A Stewart Whitley, Jan Dodgeon, Angela Meadows, Jane Cullingworth, Ken Holmes, Marcus Jackson, Graham Hoadley, Randeep Kumar Kulshrestha, Clark’s Procedures in Diagnostic Imaging: A System-Based Approach, 2020
A Stewart Whitley, Jan Dodgeon, Angela Meadows, Jane Cullingworth, Ken Holmes, Marcus Jackson, Graham Hoadley, Randeep Kumar Kulshrestha
The blood flow in the umbilical artery can be examined using Doppler ultrasound (Fig. 8.26c). The normal waveform shows pulsatile and unidirectional flow throughout the fetal cardiac cycle, indicative of good fetal cardiac output. If there is compromised cardiac output or increased placental resistance, the end-diastolic flow becomes reduced, absent and ultimately reversed. Other vessels can be assessed, such as the middle cerebral artery, to determine the severity of FGR and redistribution of blood flow. This information is used to manage the timing of delivery [83].
Review on the current treatment status of vein of Galen malformations and future directions in research and treatment
Published in Expert Review of Medical Devices, 2021
Panagiotis Primikiris, Georgios Hadjigeorgiou, Maria Tsamopoulou, Alessandra Biondi, Christina Iosif
Different studies have investigated predicting factors of outcome for the VOGMs [4,48,50,98,99]. Geibprasert et al. [48] reported factors associated with poor outcome (p< 0.05). These included neurological symptoms at presentation, a neonatal score <12/21, a very poor score (<2/5) in one (or more) of the categories: calcifications [more commonly periventricular, related to long standing venous congestion [43]], parenchymal changes (predominantly focal which are related with arterial steal), arterial steal (defined by the presence of leptomeningeal collaterals from the cortical branches of the middle cerebral artery or the anterior cerebral artery to the posterior cerebral artery territories). Finally, the authors also associated with poor outcome the presence of more than two groups of multiple arterial feeders (of a total of five groups: posterior choroidal, anterior choroidal, anterior cerebral, subependymal, or transdural arteries) [48].
Spectral decomposition and illustration-inspired visualisation of highly disturbed cerebrovascular blood flow dynamics
Published in Computer Methods in Biomechanics and Biomedical Engineering: Imaging & Visualization, 2020
Thangam Natarajan, Daniel E. MacDonald, Mehdi Najafi, Peter W. Coppin, David A. Steinman
A simpler approach suggested by Khan et al. (2017) used heuristic filters to isolate the high-frequency flow fluctuations from their pulsatile ‘carrier’ to develop a frequency-based descriptor called Spectral Power Index (SPI) as a marker for unstable flow phenotype. The present work builds on this concept where we present a frequency-based temporal filtering method to effectively decompose the pulsatile instantaneous velocity field based on the judicious choice of filter bandwidths. The resulting filtered components are then visualised by mapping them back spatially within the domain. This approach is shown to be useful in characterising the coherent structures that arise due to the different range of frequency fluctuations rather than to separate the contributions based on the energy content alone. Owing to the complexity of the data, as discussed later, we employ illustration-inspired approaches to visualise the filtered flow structures. The application of the present approach is demonstrated for three middle cerebral artery (MCA) aneurysms and three internal carotid artery (ICA) siphons.
Neurovascular devices for the treatment of intracranial aneurysms: emerging and future technologies
Published in Expert Review of Medical Devices, 2020
A retrospective, single-center study has been published in 2017 in 17 patients [37]. Aneurysms were located in the internal carotid artery (n = 3), the middle cerebral artery (n = 9), the anterior communicating artery (n = 3), and the basilar artery (n = 2). In the immediate post-treatment angiography, adequate occlusion (neck remnant or total occlusion) was observed in 16/17 (94.1%) of aneurysms. One patient experienced a transient ischemic attack. No permanent neurologic deficits were observed. 13/17 (76.5%) patients underwent short-term follow-up angiography after 3 months, all of which showed adequate occlusion of the aneurysm. The authors concluded that their limited data show nevertheless that stent-assisted coiling with the Barrel stent is a safe and effective option for the endovascular treatment of intracranial wide-necked bifurcation aneurysms.