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Central nervous 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 brain is supplied with blood from two sources. The bilateral internal carotid arteries arise from the bifurcation of the common carotid arteries in the neck and branch off to form the left and right anterior and middle cerebral arteries, which supply the forebrain. The vertebral arteries arise from the subclavian arteries and come together at the level of the pons to form the midline basilar artery. The posterior cerebral, basilar and vertebral arteries supply the posterior circulation of the brain, comprising posterior cortex, the midbrain and the brainstem. Cerebellum is also supplied by dorsolateral arteries such as the posterior inferior cerebellar artery (PICA) and the anterior inferior cerebellar artery (AICA) and superior cerebellar artery. An arterial ring called the circle of Willis connects the anterior and posterior cerebral circulation; thus, in the event of loss of blood supply to one area of the brain, it may be possible for blood to be supplied via a different arterial route.
Introduction to medical imaging
Published in David A Lisle, Imaging for Students, 2012
Widely accepted applications of MRI include: Imaging modality of choice for most brain and spine disordersMusculoskeletal disorders, including internal derangements of joints and staging of musculoskeletal tumoursCardiac MR is an established technique in specific applications including assessment of congenital heart disease and aortic disordersMR of the abdomen is used in adults for visualization of the biliary system, and for characterization of hepatic, renal, adrenal and pancreatic tumoursIn children, MR of the abdomen is increasingly replacing CT for the diagnosis and staging of abdominal tumoursMRA is widely used in the imaging of the cerebral circulation and in some centres is the initial angiographic method of choice for other areas including the renal and peripheral circulations.
Cardiac dysrhythmia management in the radiology department
Published in William H. Bush, Karl N. Krecke, Bernard F. King, Michael A. Bettmann, Radiology Life Support (Rad-LS), 2017
Actions/Indications Epinephrine is a potent, endogenously occurring catecholamine with both alpha- and beta-adrenergic effects.10–13 At low concentrations, as may be seen with subcutaneous or slow IV infusion (1–2 μg/min), beta-adrenergic effects predominate, while at higher rates (2–10 μg/min) and bolus doses used in cardiac resuscitation, alpha-adrenergic effects predominate.24 The alpha-adrenergic effects are highly desirable in the treatment of the arrested heart, because peripheral vasoconstriction raises blood pressure and favors blood supply to the coronary and cerebral circulations.15,23 Coronary blood flow is facilitated by the rise in aortic diastolic pressure which occurs with peripheral vasoconstriction. Cerebral circulation is favored because the external carotid (a peripheral branch) is selectively vasoconstricted, forcing more blood into the internal carotid artery. The beta-adrenergic component results in a dramatic positive inotropic and chronotropic cardiac response. Because of shortened repolarization time and increased conduction velocities, epinephrine may theoretically facilitate defibrillation of VF. This may be evident as conversion of low-amplitude ‘fine’ VF to higher-amplitude ‘coarse’ VF, which appears to be more susceptible to defibrillation.10,11 It is used in EMD in an attempt to increase myocardial contractility and blood pressure.25–27 In asystole, epinephrine may be able to generate some electrical and mechanical activity.10,11 Epinephrine is of great value in CPR due to preferential internal carotid perfusion.
Cognition impairment of rat in undersea environment
Published in International Journal of Environmental Health Research, 2022
Yingxin Zou, Ying Tang, Wei Fan, Lina Liu, Yong Jiao
The cognitive changes might have primarily occurred due to two reasons, either there was a direct stimulus from the undersea environment or there was an activation of the brain plasticity as an adaptative mechanism to deal with the extreme environment. The regulation of CBF is an important, established way of controlling brain plasticity. It undergoes autoregulation, which is a dynamic response to protect the cerebral circulation from matching the need for constant blood supply and water homeostasis. CBF comprises of key physiologic processes that maintain optimum functioning of the neural activity. Cerebral hypoperfusion may attenuate the brain function, including the autonomic nervous system. The regulation of CBF also plays an efficient role in the preservation of cognitive function (Ogoh 2017), though an increase in CBF does not necessarily lead to cognitive benefits (Haskell-Ramsay et al. 2018). During diving, cetaceans cognitively control bradycardia and vasoconstriction to decrease cardiac output and organ perfusion, maintain blood pressure, and redistribute the flow of blood to the hypoxia-sensitive brain and heart (Elmegaard et al. 2016). A lower CBF was associated with poor cognition (Purkayastha et al. 2019), though its autoregulation was observed to be preserved in sympathetically and parasympathetically denervated animals indicating that it was not a major contributing factor in the extrinsic neurogenic regulation. There is an increase in CBF in case of improvement in neuronal activity when there is an increased cognitive demand for the metabolic substrate glucose and oxygen (Haskell-Ramsay et al. 2018).
Numerical analysis of hemodynamic effect under different enhanced external counterpulsation (EECP) frequency for cerebrovascular disease: a simulation study
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2021
Siwei Ye, Ming Yang, Yuanfei Zhu, Xiaochen Gao, Fan Meng, Ruiliang Wu, Bo Yu
The human blood circulation is a highly complex multi-unit impedance network system, which can be analyzed based on an LPM (Mihalef et al. 2017). For ischemic stroke patients, CA ability is critical in maintaining brain health (Moerman and De Hert 2019). In previous studies (Li et al. 2019), researchers simulated the increase in CBF for ischemic stroke patients after EECP. The absolute increasing rate was approximately 35%, and much higher than corresponding data in this study. The potential cause may be the introducing of personal CA ability model. The ability of CA reflects the ability of cerebral circulation to maintain stable blood flow when the external cerebral perfusion pressure changes. Ischemic stroke patients generally have a certain degree of damage compared to healthy people. In this study, the damage degree to CA of patient A was less severe, which is also reflected in the increased CBF caused by EECP.
Diagnosing death 50 years after the Harvard brain death report
Published in The New Bioethics, 2021
Francis J. O’Keeffe, George L. Mendz
The Report recommends that ‘brain death’ be understood as ‘the complete and permanent loss of brain function as defined by an unresponsive coma with loss of capacity for consciousness, brainstem reflexes, and the ability to breathe independently’ (Greer et al.2020, p. E4). The document suggests that the terms whole brain death and brainstem death be abandoned and replaced with ‘brain death’ or ‘death by neurological criteria’ (BD/DNC). The rationale is that the clinical diagnosis of whole-brain death or brainstem death typically leads to the same conclusion, ‘differing only in the rare case of isolated primary brainstem or posterior cerebral circulation pathology’ (Greet et al.2020, p. E4). The Report acknowledges that brain-stem death and whole-brain death are distinct concepts, and that in some instances a proper diagnosis of whole-brain death requires more stringent measures. The BD/DNC criteria have limitations because ‘there remains a possibility that a person whose brain stem is destroyed but who nonetheless retains some higher-brain functions could be declared dead in the United Kingdom but not in the United States’ (Hanley 2020, p. 35). Countries such as France, Italy, Spain and Singapore have legislated a ‘four vessel test’ that measures blood flow in the right and left carotid and vertebral arteries, the test requires that there be zero blood flow ascertained by angiography after contrast dye has been injected into the blood vessels supplying the brain (Tonti-Filippini 2012).