Ultrasonography, Doppler, Transcranial: A non-invasive technique using ultrasound for the measurement of cerebrovascular hemodynamics, particularly cerebral blood flow velocity and cerebral collateral flow. With a high-intensity, low-frequency pulse probe, the intracranial arteries may be studied transtemporally, transorbitally, or from below the foramen magnum.Ultrasonography, Doppler: Ultrasonography applying the Doppler effect, with frequency-shifted ultrasound reflections produced by moving targets (usually red blood cells) in the bloodstream along the ultrasound axis in direct proportion to the velocity of movement of the targets, to determine both direction and velocity of blood flow. (Stedman, 25th ed)Cerebrovascular Circulation: The circulation of blood through the BLOOD VESSELS of the BRAIN.Blood Flow Velocity: A value equal to the total volume flow divided by the cross-sectional area of the vascular bed.Cerebral Arteries: The arterial blood vessels supplying the CEREBRUM.Ultrasonography, Doppler, Color: Ultrasonography applying the Doppler effect, with the superposition of flow information as colors on a gray scale in a real-time image. This type of ultrasonography is well-suited to identifying the location of high-velocity flow (such as in a stenosis) or of mapping the extent of flow in a certain region.Transcranial Magnetic Stimulation: A technique that involves the use of electrical coils on the head to generate a brief magnetic field which reaches the CEREBRAL CORTEX. It is coupled with ELECTROMYOGRAPHY response detection to assess cortical excitability by the threshold required to induce MOTOR EVOKED POTENTIALS. This method is also used for BRAIN MAPPING, to study NEUROPHYSIOLOGY, and as a substitute for ELECTROCONVULSIVE THERAPY for treating DEPRESSION. Induction of SEIZURES limits its clinical usage.Echoencephalography: Use of reflected ultrasound in the diagnosis of intracranial pathologic processes.Middle Cerebral Artery: The largest of the cerebral arteries. It trifurcates into temporal, frontal, and parietal branches supplying blood to most of the parenchyma of these lobes in the CEREBRAL CORTEX. These are the areas involved in motor, sensory, and speech activities.Ultrasonography: The visualization of deep structures of the body by recording the reflections or echoes of ultrasonic pulses directed into the tissues. Use of ultrasound for imaging or diagnostic purposes employs frequencies ranging from 1.6 to 10 megahertz.Intracranial Embolism and Thrombosis: Embolism or thrombosis involving blood vessels which supply intracranial structures. Emboli may originate from extracranial or intracranial sources. Thrombosis may occur in arterial or venous structures.Intracranial Pressure: Pressure within the cranial cavity. It is influenced by brain mass, the circulatory system, CSF dynamics, and skull rigidity.Valsalva Maneuver: Forced expiratory effort against a closed GLOTTIS.Ultrasonography, Doppler, Pulsed: Ultrasonography applying the Doppler effect, with velocity detection combined with range discrimination. Short bursts of ultrasound are transmitted at regular intervals and the echoes are demodulated as they return.Brain Hemorrhage, Traumatic: Bleeding within the brain as a result of penetrating and nonpenetrating CRANIOCEREBRAL TRAUMA. Traumatically induced hemorrhages may occur in any area of the brain, including the CEREBRUM; BRAIN STEM (see BRAIN STEM HEMORRHAGE, TRAUMATIC); and CEREBELLUM.Cerebrovascular Disorders: A spectrum of pathological conditions of impaired blood flow in the brain. They can involve vessels (ARTERIES or VEINS) in the CEREBRUM, the CEREBELLUM, and the BRAIN STEM. Major categories include INTRACRANIAL ARTERIOVENOUS MALFORMATIONS; BRAIN ISCHEMIA; CEREBRAL HEMORRHAGE; and others.Anemia, Sickle Cell: A disease characterized by chronic hemolytic anemia, episodic painful crises, and pathologic involvement of many organs. It is the clinical expression of homozygosity for hemoglobin S.Cerebral Angiography: Radiography of the vascular system of the brain after injection of a contrast medium.Heart Septal Defects, Atrial: Developmental abnormalities in any portion of the ATRIAL SEPTUM resulting in abnormal communications between the two upper chambers of the heart. Classification of atrial septal defects is based on location of the communication and types of incomplete fusion of atrial septa with the ENDOCARDIAL CUSHIONS in the fetal heart. They include ostium primum, ostium secundum, sinus venosus, and coronary sinus defects.Arterial Occlusive Diseases: Pathological processes which result in the partial or complete obstruction of ARTERIES. They are characterized by greatly reduced or absence of blood flow through these vessels. They are also known as arterial insufficiency.Ischemic Attack, Transient: Brief reversible episodes of focal, nonconvulsive ischemic dysfunction of the brain having a duration of less than 24 hours, and usually less than one hour, caused by transient thrombotic or embolic blood vessel occlusion or stenosis. Events may be classified by arterial distribution, temporal pattern, or etiology (e.g., embolic vs. thrombotic). (From Adams et al., Principles of Neurology, 6th ed, pp814-6)Intracranial Embolism: Blocking of a blood vessel in the SKULL by an EMBOLUS which can be a blood clot (THROMBUS) or other undissolved material in the blood stream. Most emboli are of cardiac origin and are associated with HEART DISEASES. Other non-cardiac sources of emboli are usually associated with VASCULAR DISEASES.Evoked Potentials, Motor: The electrical response evoked in a muscle or motor nerve by electrical or magnetic stimulation. Common methods of stimulation are by transcranial electrical and TRANSCRANIAL MAGNETIC STIMULATION. It is often used for monitoring during neurosurgery.Doppler Effect: Changes in the observed frequency of waves (as sound, light, or radio waves) due to the relative motion of source and observer. The effect was named for the 19th century Austrian physicist Johann Christian Doppler.Brain Ischemia: Localized reduction of blood flow to brain tissue due to arterial obstruction or systemic hypoperfusion. This frequently occurs in conjunction with brain hypoxia (HYPOXIA, BRAIN). Prolonged ischemia is associated with BRAIN INFARCTION.Prospective Studies: Observation of a population for a sufficient number of persons over a sufficient number of years to generate incidence or mortality rates subsequent to the selection of the study group.Carbon Dioxide: A colorless, odorless gas that can be formed by the body and is necessary for the respiration cycle of plants and animals.Stroke: A group of pathological conditions characterized by sudden, non-convulsive loss of neurological function due to BRAIN ISCHEMIA or INTRACRANIAL HEMORRHAGES. Stroke is classified by the type of tissue NECROSIS, such as the anatomic location, vasculature involved, etiology, age of the affected individual, and hemorrhagic vs. non-hemorrhagic nature. (From Adams et al., Principles of Neurology, 6th ed, pp777-810)Pulsatile Flow: Rhythmic, intermittent propagation of a fluid through a BLOOD VESSEL or piping system, in contrast to constant, smooth propagation, which produces laminar flow.Brain: The part of CENTRAL NERVOUS SYSTEM that is contained within the skull (CRANIUM). Arising from the NEURAL TUBE, the embryonic brain is comprised of three major parts including PROSENCEPHALON (the forebrain); MESENCEPHALON (the midbrain); and RHOMBENCEPHALON (the hindbrain). The developed brain consists of CEREBRUM; CEREBELLUM; and other structures in the BRAIN STEM.Ultrasonography, Prenatal: The visualization of tissues during pregnancy through recording of the echoes of ultrasonic waves directed into the body. The procedure may be applied with reference to the mother or the fetus and with reference to organs or the detection of maternal or fetal disease.Blood Pressure: PRESSURE of the BLOOD on the ARTERIES and other BLOOD VESSELS.Motor Cortex: Area of the FRONTAL LOBE concerned with primary motor control located in the dorsal PRECENTRAL GYRUS immediately anterior to the central sulcus. It is comprised of three areas: the primary motor cortex located on the anterior paracentral lobule on the medial surface of the brain; the premotor cortex located anterior to the primary motor cortex; and the supplementary motor area located on the midline surface of the hemisphere anterior to the primary motor cortex.Sensitivity and Specificity: Binary classification measures to assess test results. Sensitivity or recall rate is the proportion of true positives. Specificity is the probability of correctly determining the absence of a condition. (From Last, Dictionary of Epidemiology, 2d ed)Regional Blood Flow: The flow of BLOOD through or around an organ or region of the body.Echocardiography, Doppler, Pulsed: Echocardiography applying the Doppler effect, with velocity detection combined with range discrimination. Short bursts of ultrasound are transmitted at regular intervals and the echoes are demodulated as they return.Carotid Stenosis: Narrowing or stricture of any part of the CAROTID ARTERIES, most often due to atherosclerotic plaque formation. Ulcerations may form in atherosclerotic plaques and induce THROMBUS formation. Platelet or cholesterol emboli may arise from stenotic carotid lesions and induce a TRANSIENT ISCHEMIC ATTACK; CEREBROVASCULAR ACCIDENT; or temporary blindness (AMAUROSIS FUGAX). (From Adams et al., Principles of Neurology, 6th ed, pp 822-3)Basilar Artery: The artery formed by the union of the right and left vertebral arteries; it runs from the lower to the upper border of the pons, where it bifurcates into the two posterior cerebral arteries.Echocardiography, Doppler, Color: Echocardiography applying the Doppler effect, with the superposition of flow information as colors on a gray scale in a real-time image.Ultrasonography, Doppler, Duplex: Ultrasonography applying the Doppler effect combined with real-time imaging. The real-time image is created by rapid movement of the ultrasound beam. A powerful advantage of this technique is the ability to estimate the velocity of flow from the Doppler shift frequency.Circle of Willis: A polygonal anastomosis at the base of the brain formed by the internal carotid (CAROTID ARTERY, INTERNAL), proximal parts of the anterior, middle, and posterior cerebral arteries (ANTERIOR CEREBRAL ARTERY; MIDDLE CEREBRAL ARTERY; POSTERIOR CEREBRAL ARTERY), the anterior communicating artery and the posterior communicating arteries.Cerebral Infarction: The formation of an area of NECROSIS in the CEREBRUM caused by an insufficiency of arterial or venous blood flow. Infarcts of the cerebrum are generally classified by hemisphere (i.e., left vs. right), lobe (e.g., frontal lobe infarction), arterial distribution (e.g., INFARCTION, ANTERIOR CEREBRAL ARTERY), and etiology (e.g., embolic infarction).Carotid Artery, Internal: Branch of the common carotid artery which supplies the anterior part of the brain, the eye and its appendages, the forehead and nose.Embolism, Air: Blocking of a blood vessel by air bubbles that enter the circulatory system, usually after TRAUMA; surgical procedures, or changes in atmospheric pressure.Monitoring, Intraoperative: The constant checking on the state or condition of a patient during the course of a surgical operation (e.g., checking of vital signs).Reproducibility of Results: The statistical reproducibility of measurements (often in a clinical context), including the testing of instrumentation or techniques to obtain reproducible results. The concept includes reproducibility of physiological measurements, which may be used to develop rules to assess probability or prognosis, or response to a stimulus; reproducibility of occurrence of a condition; and reproducibility of experimental results.Umbilical Arteries: Specialized arterial vessels in the umbilical cord. They carry waste and deoxygenated blood from the FETUS to the mother via the PLACENTA. In humans, there are usually two umbilical arteries but sometimes one.Vascular Resistance: The force that opposes the flow of BLOOD through a vascular bed. It is equal to the difference in BLOOD PRESSURE across the vascular bed divided by the CARDIAC OUTPUT.Predictive Value of Tests: In screening and diagnostic tests, the probability that a person with a positive test is a true positive (i.e., has the disease), is referred to as the predictive value of a positive test; whereas, the predictive value of a negative test is the probability that the person with a negative test does not have the disease. Predictive value is related to the sensitivity and specificity of the test.Magnetic Resonance Imaging: Non-invasive method of demonstrating internal anatomy based on the principle that atomic nuclei in a strong magnetic field absorb pulses of radiofrequency energy and emit them as radiowaves which can be reconstructed into computerized images. The concept includes proton spin tomographic techniques.Tomography, X-Ray Computed: Tomography using x-ray transmission and a computer algorithm to reconstruct the image.Carotid Artery Diseases: Pathological conditions involving the CAROTID ARTERIES, including the common, internal, and external carotid arteries. ATHEROSCLEROSIS and TRAUMA are relatively frequent causes of carotid artery pathology.Ophthalmic Artery: Artery originating from the internal carotid artery and distributing to the eye, orbit and adjacent facial structures.Contrast Media: Substances used to allow enhanced visualization of tissues.Vasospasm, Intracranial: Constriction of arteries in the SKULL due to sudden, sharp, and often persistent smooth muscle contraction in blood vessels. Intracranial vasospasm results in reduced vessel lumen caliber, restricted blood flow to the brain, and BRAIN ISCHEMIA that may lead to hypoxic-ischemic brain injury (HYPOXIA-ISCHEMIA, BRAIN).Endarterectomy, Carotid: The excision of the thickened, atheromatous tunica intima of a carotid artery.Hemodynamics: The movement and the forces involved in the movement of the blood through the CARDIOVASCULAR SYSTEM.Ultrasonics: A subfield of acoustics dealing in the radio frequency range higher than acoustic SOUND waves (approximately above 20 kilohertz). Ultrasonic radiation is used therapeutically (DIATHERMY and ULTRASONIC THERAPY) to generate HEAT and to selectively destroy tissues. It is also used in diagnostics, for example, ULTRASONOGRAPHY; ECHOENCEPHALOGRAPHY; and ECHOCARDIOGRAPHY, to visually display echoes received from irradiated tissues.Vertebral Artery: The first branch of the SUBCLAVIAN ARTERY with distribution to muscles of the NECK; VERTEBRAE; SPINAL CORD; CEREBELLUM; and interior of the CEREBRUM.Functional Laterality: Behavioral manifestations of cerebral dominance in which there is preferential use and superior functioning of either the left or the right side, as in the preferred use of the right hand or right foot.Cerebral Arterial Diseases: Pathological conditions of intracranial ARTERIES supplying the CEREBRUM. These diseases often are due to abnormalities or pathological processes in the ANTERIOR CEREBRAL ARTERY; MIDDLE CEREBRAL ARTERY; and POSTERIOR CEREBRAL ARTERY.Acetazolamide: One of the CARBONIC ANHYDRASE INHIBITORS that is sometimes effective against absence seizures. It is sometimes useful also as an adjunct in the treatment of tonic-clonic, myoclonic, and atonic seizures, particularly in women whose seizures occur or are exacerbated at specific times in the menstrual cycle. However, its usefulness is transient often because of rapid development of tolerance. Its antiepileptic effect may be due to its inhibitory effect on brain carbonic anhydrase, which leads to an increased transneuronal chloride gradient, increased chloride current, and increased inhibition. (From Smith and Reynard, Textbook of Pharmacology, 1991, p337)Monitoring, Physiologic: The continuous measurement of physiological processes, blood pressure, heart rate, renal output, reflexes, respiration, etc., in a patient or experimental animal; includes pharmacologic monitoring, the measurement of administered drugs or their metabolites in the blood, tissues, or urine.Subarachnoid Hemorrhage: Bleeding into the intracranial or spinal SUBARACHNOID SPACE, most resulting from INTRACRANIAL ANEURYSM rupture. It can occur after traumatic injuries (SUBARACHNOID HEMORRHAGE, TRAUMATIC). Clinical features include HEADACHE; NAUSEA; VOMITING, nuchal rigidity, variable neurological deficits and reduced mental status.Pregnancy: The status during which female mammals carry their developing young (EMBRYOS or FETUSES) in utero before birth, beginning from FERTILIZATION to BIRTH.Embolism, Paradoxical: Blockage of an artery due to passage of a clot (THROMBUS) from a systemic vein to a systemic artery without its passing through the lung which acts as a filter to remove blood clots from entering the arterial circulation. Paradoxical embolism occurs when there is a defect that allows a clot to cross directly from the right to the left side of the heart as in the cases of ATRIAL SEPTAL DEFECTS or open FORAMEN OVALE. Once in the arterial circulation, a clot can travel to the brain, block an artery, and cause a STROKE.Time Factors: Elements of limited time intervals, contributing to particular results or situations.Cerebral Veins: Veins draining the cerebrum.Placental Circulation: The circulation of BLOOD, of both the mother and the FETUS, through the PLACENTA.Collateral Circulation: Maintenance of blood flow to an organ despite obstruction of a principal vessel. Blood flow is maintained through small vessels.Hypocapnia: Clinical manifestation consisting of a deficiency of carbon dioxide in arterial blood.Subclavian Steal Syndrome: A clinically significant reduction in blood supply to the BRAIN STEM and CEREBELLUM (i.e., VERTEBROBASILAR INSUFFICIENCY) resulting from reversal of blood flow through the VERTEBRAL ARTERY from occlusion or stenosis of the proximal subclavian or brachiocephalic artery. Common symptoms include VERTIGO; SYNCOPE; and INTERMITTENT CLAUDICATION of the involved upper extremity. Subclavian steal may also occur in asymptomatic individuals. (From J Cardiovasc Surg 1994;35(1):11-4; Acta Neurol Scand 1994;90(3):174-8)Reference Values: The range or frequency distribution of a measurement in a population (of organisms, organs or things) that has not been selected for the presence of disease or abnormality.Angiography, Digital Subtraction: A method of delineating blood vessels by subtracting a tissue background image from an image of tissue plus intravascular contrast material that attenuates the X-ray photons. The background image is determined from a digitized image taken a few moments before injection of the contrast material. The resulting angiogram is a high-contrast image of the vessel. This subtraction technique allows extraction of a high-intensity signal from the superimposed background information. The image is thus the result of the differential absorption of X-rays by different tissues.Laser-Doppler Flowmetry: A method of non-invasive, continuous measurement of MICROCIRCULATION. The technique is based on the values of the DOPPLER EFFECT of low-power laser light scattered randomly by static structures and moving tissue particulates.Treatment Outcome: Evaluation undertaken to assess the results or consequences of management and procedures used in combating disease in order to determine the efficacy, effectiveness, safety, and practicability of these interventions in individual cases or series.Carotid Arteries: Either of the two principal arteries on both sides of the neck that supply blood to the head and neck; each divides into two branches, the internal carotid artery and the external carotid artery.Intracranial Arterial Diseases: Pathological conditions involving ARTERIES in the skull, such as arteries supplying the CEREBRUM, the CEREBELLUM, the BRAIN STEM, and associated structures. They include atherosclerotic, congenital, traumatic, infectious, inflammatory, and other pathological processes.Foramen Ovale, Patent: A condition in which the FORAMEN OVALE in the ATRIAL SEPTUM fails to close shortly after birth. This results in abnormal communications between the two upper chambers of the heart. An isolated patent ovale foramen without other structural heart defects is usually of no hemodynamic significance.Magnetic Resonance Angiography: Non-invasive method of vascular imaging and determination of internal anatomy without injection of contrast media or radiation exposure. The technique is used especially in CEREBRAL ANGIOGRAPHY as well as for studies of other vascular structures.Pyramidal Tracts: Fibers that arise from cells within the cerebral cortex, pass through the medullary pyramid, and descend in the spinal cord. Many authorities say the pyramidal tracts include both the corticospinal and corticobulbar tracts.Infarction, Middle Cerebral Artery: NECROSIS occurring in the MIDDLE CEREBRAL ARTERY distribution system which brings blood to the entire lateral aspects of each CEREBRAL HEMISPHERE. Clinical signs include impaired cognition; APHASIA; AGRAPHIA; weak and numbness in the face and arms, contralaterally or bilaterally depending on the infarction.Portal Vein: A short thick vein formed by union of the superior mesenteric vein and the splenic vein.Scrotum: A cutaneous pouch of skin containing the testicles and spermatic cords.Constriction, Pathologic: The condition of an anatomical structure's being constricted beyond normal dimensions.Arteries: The vessels carrying blood away from the heart.Electromyography: Recording of the changes in electric potential of muscle by means of surface or needle electrodes.Intracranial Hypertension: Increased pressure within the cranial vault. This may result from several conditions, including HYDROCEPHALUS; BRAIN EDEMA; intracranial masses; severe systemic HYPERTENSION; PSEUDOTUMOR CEREBRI; and other disorders.Observer Variation: The failure by the observer to measure or identify a phenomenon accurately, which results in an error. Sources for this may be due to the observer's missing an abnormality, or to faulty technique resulting in incorrect test measurement, or to misinterpretation of the data. Two varieties are inter-observer variation (the amount observers vary from one another when reporting on the same material) and intra-observer variation (the amount one observer varies between observations when reporting more than once on the same material).Anterior Cerebral Artery: Artery formed by the bifurcation of the internal carotid artery (CAROTID ARTERY, INTERNAL). Branches of the anterior cerebral artery supply the CAUDATE NUCLEUS; INTERNAL CAPSULE; PUTAMEN; SEPTAL NUCLEI; GYRUS CINGULI; and surfaces of the FRONTAL LOBE and PARIETAL LOBE.Fetal Diseases: Pathophysiological conditions of the FETUS in the UTERUS. Some fetal diseases may be treated with FETAL THERAPIES.Dominance, Cerebral: Dominance of one cerebral hemisphere over the other in cerebral functions.Homeostasis: The processes whereby the internal environment of an organism tends to remain balanced and stable.Electric Stimulation: Use of electric potential or currents to elicit biological responses.Skull: The SKELETON of the HEAD including the FACIAL BONES and the bones enclosing the BRAIN.Testicular Diseases: Pathological processes of the TESTIS.Phosphenes: A subjective visual sensation with the eyes closed and in the absence of light. Phosphenes can be spontaneous, or induced by chemical, electrical, or mechanical (pressure) stimuli which cause the visual field to light up without optical inputs.Cerebral Hemorrhage: Bleeding into one or both CEREBRAL HEMISPHERES including the BASAL GANGLIA and the CEREBRAL CORTEX. It is often associated with HYPERTENSION and CRANIOCEREBRAL TRAUMA.Intracranial Arteriovenous Malformations: Congenital vascular anomalies in the brain characterized by direct communication between an artery and a vein without passing through the CAPILLARIES. The locations and size of the shunts determine the symptoms including HEADACHES; SEIZURES; STROKE; INTRACRANIAL HEMORRHAGES; mass effect; and vascular steal effect.Spectroscopy, Near-Infrared: A noninvasive technique that uses the differential absorption properties of hemoglobin and myoglobin to evaluate tissue oxygenation and indirectly can measure regional hemodynamics and blood flow. Near-infrared light (NIR) can propagate through tissues and at particular wavelengths is differentially absorbed by oxygenated vs. deoxygenated forms of hemoglobin and myoglobin. Illumination of intact tissue with NIR allows qualitative assessment of changes in the tissue concentration of these molecules. The analysis is also used to determine body composition.Cerebral Palsy: A heterogeneous group of nonprogressive motor disorders caused by chronic brain injuries that originate in the prenatal period, perinatal period, or first few years of life. The four major subtypes are spastic, athetoid, ataxic, and mixed cerebral palsy, with spastic forms being the most common. The motor disorder may range from difficulties with fine motor control to severe spasticity (see MUSCLE SPASTICITY) in all limbs. Spastic diplegia (Little disease) is the most common subtype, and is characterized by spasticity that is more prominent in the legs than in the arms. Pathologically, this condition may be associated with LEUKOMALACIA, PERIVENTRICULAR. (From Dev Med Child Neurol 1998 Aug;40(8):520-7)Follow-Up Studies: Studies in which individuals or populations are followed to assess the outcome of exposures, procedures, or effects of a characteristic, e.g., occurrence of disease.Acute Disease: Disease having a short and relatively severe course.Hepatic Veins: Veins which drain the liver.Hyperventilation: A pulmonary ventilation rate faster than is metabolically necessary for the exchange of gases. It is the result of an increased frequency of breathing, an increased tidal volume, or a combination of both. It causes an excess intake of oxygen and the blowing off of carbon dioxide.Hypercapnia: A clinical manifestation of abnormal increase in the amount of carbon dioxide in arterial blood.Electroencephalography: Recording of electric currents developed in the brain by means of electrodes applied to the scalp, to the surface of the brain, or placed within the substance of the brain.Severity of Illness Index: Levels within a diagnostic group which are established by various measurement criteria applied to the seriousness of a patient's disorder.Vasomotor System: The neural systems which act on VASCULAR SMOOTH MUSCLE to control blood vessel diameter. The major neural control is through the sympathetic nervous system.Retrospective Studies: Studies used to test etiologic hypotheses in which inferences about an exposure to putative causal factors are derived from data relating to characteristics of persons under study or to events or experiences in their past. The essential feature is that some of the persons under study have the disease or outcome of interest and their characteristics are compared with those of unaffected persons.Uterus: The hollow thick-walled muscular organ in the female PELVIS. It consists of the fundus (the body) which is the site of EMBRYO IMPLANTATION and FETAL DEVELOPMENT. Beyond the isthmus at the perineal end of fundus, is CERVIX UTERI (the neck) opening into VAGINA. Beyond the isthmi at the upper abdominal end of fundus, are the FALLOPIAN TUBES.Posterior Cerebral Artery: Artery formed by the bifurcation of the BASILAR ARTERY. Branches of the posterior cerebral artery supply portions of the OCCIPITAL LOBE; PARIETAL LOBE; inferior temporal gyrus, brainstem, and CHOROID PLEXUS.Embolism: Blocking of a blood vessel by an embolus which can be a blood clot or other undissolved material in the blood stream.Microcirculation: The circulation of the BLOOD through the MICROVASCULAR NETWORK.Fetal Growth Retardation: The failure of a FETUS to attain its expected FETAL GROWTH at any GESTATIONAL AGE.Portography: Examination of the portal circulation by the use of X-ray films after injection of radiopaque material.Hand: The distal part of the arm beyond the wrist in humans and primates, that includes the palm, fingers, and thumb.Magnetics: The study of MAGNETIC PHENOMENA.Vertebrobasilar Insufficiency: Localized or diffuse reduction in blood flow through the vertebrobasilar arterial system, which supplies the BRAIN STEM; CEREBELLUM; OCCIPITAL LOBE; medial TEMPORAL LOBE; and THALAMUS. Characteristic clinical features include SYNCOPE; lightheadedness; visual disturbances; and VERTIGO. BRAIN STEM INFARCTIONS or other BRAIN INFARCTION may be associated.Analysis of Variance: A statistical technique that isolates and assesses the contributions of categorical independent variables to variation in the mean of a continuous dependent variable.Cerebrovascular Trauma: Penetrating and nonpenetrating traumatic injuries to an extracranial or intracranial blood vessel that supplies the brain. This includes the CAROTID ARTERIES; VERTEBRAL ARTERIES; MENINGEAL ARTERIES; CEREBRAL ARTERIES; veins, and venous sinuses.Gestational Age: The age of the conceptus, beginning from the time of FERTILIZATION. In clinical obstetrics, the gestational age is often estimated as the time from the last day of the last MENSTRUATION which is about 2 weeks before OVULATION and fertilization.Spermatic Cord: Either of a pair of tubular structures formed by DUCTUS DEFERENS; ARTERIES; VEINS; LYMPHATIC VESSELS; and nerves. The spermatic cord extends from the deep inguinal ring through the INGUINAL CANAL to the TESTIS in the SCROTUM.Electromagnetic Fields: Fields representing the joint interplay of electric and magnetic forces.Endarterectomy: Surgical excision, performed under general anesthesia, of the atheromatous tunica intima of an artery. When reconstruction of an artery is performed as an endovascular procedure through a catheter, it is called ATHERECTOMY.Intraoperative Complications: Complications that affect patients during surgery. They may or may not be associated with the disease for which the surgery is done, or within the same surgical procedure.Ultrasonography, Interventional: The use of ultrasound to guide minimally invasive surgical procedures such as needle ASPIRATION BIOPSY; DRAINAGE; etc. Its widest application is intravascular ultrasound imaging but it is useful also in urology and intra-abdominal conditions.Intracranial Aneurysm: Abnormal outpouching in the wall of intracranial blood vessels. Most common are the saccular (berry) aneurysms located at branch points in CIRCLE OF WILLIS at the base of the brain. Vessel rupture results in SUBARACHNOID HEMORRHAGE or INTRACRANIAL HEMORRHAGES. Giant aneurysms (>2.5 cm in diameter) may compress adjacent structures, including the OCULOMOTOR NERVE. (From Adams et al., Principles of Neurology, 6th ed, p841)Reaction Time: The time from the onset of a stimulus until a response is observed.Diastole: Post-systolic relaxation of the HEART, especially the HEART VENTRICLES.Echocardiography, Transesophageal: Ultrasonic recording of the size, motion, and composition of the heart and surrounding tissues using a transducer placed in the esophagus.ROC Curve: A graphic means for assessing the ability of a screening test to discriminate between healthy and diseased persons; may also be used in other studies, e.g., distinguishing stimuli responses as to a faint stimuli or nonstimuli.Carotid Artery Thrombosis: Blood clot formation in any part of the CAROTID ARTERIES. This may produce CAROTID STENOSIS or occlusion of the vessel, leading to TRANSIENT ISCHEMIC ATTACK; CEREBRAL INFARCTION; or AMAUROSIS FUGAX.Angiography: Radiography of blood vessels after injection of a contrast medium.Imaging, Three-Dimensional: The process of generating three-dimensional images by electronic, photographic, or other methods. For example, three-dimensional images can be generated by assembling multiple tomographic images with the aid of a computer, while photographic 3-D images (HOLOGRAPHY) can be made by exposing film to the interference pattern created when two laser light sources shine on an object.Hepatic Artery: A branch of the celiac artery that distributes to the stomach, pancreas, duodenum, liver, gallbladder, and greater omentum.Renal Artery: A branch of the abdominal aorta which supplies the kidneys, adrenal glands and ureters.Postoperative Complications: Pathologic processes that affect patients after a surgical procedure. They may or may not be related to the disease for which the surgery was done, and they may or may not be direct results of the surgery.Ovarian Cysts: General term for CYSTS and cystic diseases of the OVARY.Embolism, Fat: Blocking of a blood vessel by fat deposits in the circulation. It is often seen after fractures of large bones or after administration of CORTICOSTEROIDS.Electromagnetic Phenomena: Characteristics of ELECTRICITY and magnetism such as charged particles and the properties and behavior of charged particles, and other phenomena related to or associated with electromagnetism.Metacarpophalangeal Joint: The articulation between a metacarpal bone and a phalanx.Cerebrum: Derived from TELENCEPHALON, cerebrum is composed of a right and a left hemisphere. Each contains an outer cerebral cortex and a subcortical basal ganglia. The cerebrum includes all parts within the skull except the MEDULLA OBLONGATA, the PONS, and the CEREBELLUM. Cerebral functions include sensorimotor, emotional, and intellectual activities.Electric Stimulation Therapy: Application of electric current in treatment without the generation of perceptible heat. It includes electric stimulation of nerves or muscles, passage of current into the body, or use of interrupted current of low intensity to raise the threshold of the skin to pain.Image Enhancement: Improvement of the quality of a picture by various techniques, including computer processing, digital filtering, echocardiographic techniques, light and ultrastructural MICROSCOPY, fluorescence spectrometry and microscopy, scintigraphy, and in vitro image processing at the molecular level.Risk Factors: An aspect of personal behavior or lifestyle, environmental exposure, or inborn or inherited characteristic, which, on the basis of epidemiologic evidence, is known to be associated with a health-related condition considered important to prevent.Liver Circulation: The circulation of BLOOD through the LIVER.Fetal Heart: The heart of the fetus of any viviparous animal. It refers to the heart in the postembryonic period and is differentiated from the embryonic heart (HEART/embryology) only on the basis of time.Brain Death: A state of prolonged irreversible cessation of all brain activity, including lower brain stem function with the complete absence of voluntary movements, responses to stimuli, brain stem reflexes, and spontaneous respirations. Reversible conditions which mimic this clinical state (e.g., sedative overdose, hypothermia, etc.) are excluded prior to making the determination of brain death. (From Adams et al., Principles of Neurology, 6th ed, pp348-9)Pregnancy Trimester, Second: The middle third of a human PREGNANCY, from the beginning of the 15th through the 28th completed week (99 to 196 days) of gestation.Parietal Lobe: Upper central part of the cerebral hemisphere. It is located posterior to central sulcus, anterior to the OCCIPITAL LOBE, and superior to the TEMPORAL LOBES.Infant, Newborn: An infant during the first month after birth.Embolization, Therapeutic: A method of hemostasis utilizing various agents such as Gelfoam, silastic, metal, glass, or plastic pellets, autologous clot, fat, and muscle as emboli. It has been used in the treatment of spinal cord and INTRACRANIAL ARTERIOVENOUS MALFORMATIONS, renal arteriovenous fistulas, gastrointestinal bleeding, epistaxis, hypersplenism, certain highly vascular tumors, traumatic rupture of blood vessels, and control of operative hemorrhage.Mesenteric Artery, Superior: A large vessel supplying the whole length of the small intestine except the superior part of the duodenum. It also supplies the cecum and the ascending part of the colon and about half the transverse part of the colon. It arises from the anterior surface of the aorta below the celiac artery at the level of the first lumbar vertebra.Pilot Projects: Small-scale tests of methods and procedures to be used on a larger scale if the pilot study demonstrates that these methods and procedures can work.Systole: Period of contraction of the HEART, especially of the HEART VENTRICLES.Rheology: The study of the deformation and flow of matter, usually liquids or fluids, and of the plastic flow of solids. The concept covers consistency, dilatancy, liquefaction, resistance to flow, shearing, thixotrophy, and VISCOSITY.Oxygen: An element with atomic symbol O, atomic number 8, and atomic weight [15.99903; 15.99977]. It is the most abundant element on earth and essential for respiration.Echocardiography: Ultrasonic recording of the size, motion, and composition of the heart and surrounding tissues. The standard approach is transthoracic.Brain Mapping: Imaging techniques used to colocalize sites of brain functions or physiological activity with brain structures.Psychomotor Performance: The coordination of a sensory or ideational (cognitive) process and a motor activity.Endosonography: Ultrasonography of internal organs using an ultrasound transducer sometimes mounted on a fiberoptic endoscope. In endosonography the transducer converts electronic signals into acoustic pulses or continuous waves and acts also as a receiver to detect reflected pulses from within the organ. An audiovisual-electronic interface converts the detected or processed echo signals, which pass through the electronics of the instrument, into a form that the technologist can evaluate. The procedure should not be confused with ENDOSCOPY which employs a special instrument called an endoscope. The "endo-" of endosonography refers to the examination of tissue within hollow organs, with reference to the usual ultrasonography procedure which is performed externally or transcutaneously.Malaria, Cerebral: A condition characterized by somnolence or coma in the presence of an acute infection with PLASMODIUM FALCIPARUM (and rarely other Plasmodium species). Initial clinical manifestations include HEADACHES; SEIZURES; and alterations of mentation followed by a rapid progression to COMA. Pathologic features include cerebral capillaries filled with parasitized erythrocytes and multiple small foci of cortical and subcortical necrosis. (From Adams et al., Principles of Neurology, 6th ed, p136)Fibrinolytic Agents: Fibrinolysin or agents that convert plasminogen to FIBRINOLYSIN.Evoked Potentials, Somatosensory: The electric response evoked in the CEREBRAL CORTEX by stimulation along AFFERENT PATHWAYS from PERIPHERAL NERVES to CEREBRUM.Synovitis: Inflammation of a synovial membrane. It is usually painful, particularly on motion, and is characterized by a fluctuating swelling due to effusion within a synovial sac. (Dorland, 27th ed)Arteriovenous Malformations: Abnormal formation of blood vessels that shunt arterial blood directly into veins without passing through the CAPILLARIES. They usually are crooked, dilated, and with thick vessel walls. A common type is the congenital arteriovenous fistula. The lack of blood flow and oxygen in the capillaries can lead to tissue damage in the affected areas.Heart Septal Defects: Abnormalities in any part of the HEART SEPTUM resulting in abnormal communication between the left and the right chambers of the heart. The abnormal blood flow inside the heart may be caused by defects in the ATRIAL SEPTUM, the VENTRICULAR SEPTUM, or both.Prognosis: A prediction of the probable outcome of a disease based on a individual's condition and the usual course of the disease as seen in similar situations.Amaurosis Fugax: Transient complete or partial monocular blindness due to retinal ischemia. This may be caused by emboli from the CAROTID ARTERY (usually in association with CAROTID STENOSIS) and other locations that enter the central RETINAL ARTERY. (From Adams et al., Principles of Neurology, 6th ed, p245)Tissue Plasminogen Activator: A proteolytic enzyme in the serine protease family found in many tissues which converts PLASMINOGEN to FIBRINOLYSIN. It has fibrin-binding activity and is immunologically different from UROKINASE-TYPE PLASMINOGEN ACTIVATOR. The primary sequence, composed of 527 amino acids, is identical in both the naturally occurring and synthetic proteases.Photoplethysmography: Plethysmographic determination in which the intensity of light reflected from the skin surface and the red cells below is measured to determine the blood volume of the respective area. There are two types, transmission and reflectance.Hemangioma, Capillary: A dull red, firm, dome-shaped hemangioma, sharply demarcated from surrounding skin, usually located on the head and neck, which grows rapidly and generally undergoes regression and involution without scarring. It is caused by proliferation of immature capillary vessels in active stroma, and is usually present at birth or occurs within the first two or three months of life. (Dorland, 27th ed)Case-Control Studies: Studies which start with the identification of persons with a disease of interest and a control (comparison, referent) group without the disease. The relationship of an attribute to the disease is examined by comparing diseased and non-diseased persons with regard to the frequency or levels of the attribute in each group.Neural Inhibition: The function of opposing or restraining the excitation of neurons or their target excitable cells.Arterial Pressure: The blood pressure in the ARTERIES. It is commonly measured with a SPHYGMOMANOMETER on the upper arm which represents the arterial pressure in the BRACHIAL ARTERY.Leg: The inferior part of the lower extremity between the KNEE and the ANKLE.Pregnancy Trimester, First: The beginning third of a human PREGNANCY, from the first day of the last normal menstrual period (MENSTRUATION) through the completion of 14 weeks (98 days) of gestation.Heart Rate: The number of times the HEART VENTRICLES contract per unit of time, usually per minute.Thoracic Cavity: The region of the thorax that includes the PLEURAL CAVITY and MEDIASTINUM.Fetus: The unborn young of a viviparous mammal, in the postembryonic period, after the major structures have been outlined. In humans, the unborn young from the end of the eighth week after CONCEPTION until BIRTH, as distinguished from the earlier EMBRYO, MAMMALIAN.Hypertension, Portal: Abnormal increase of resistance to blood flow within the hepatic PORTAL SYSTEM, frequently seen in LIVER CIRRHOSIS and conditions with obstruction of the PORTAL VEIN.Motor Skills: Performance of complex motor acts.Movement: The act, process, or result of passing from one place or position to another. It differs from LOCOMOTION in that locomotion is restricted to the passing of the whole body from one place to another, while movement encompasses both locomotion but also a change of the position of the whole body or any of its parts. Movement may be used with reference to humans, vertebrate and invertebrate animals, and microorganisms. Differentiate also from MOTOR ACTIVITY, movement associated with behavior.Cerebral Cortex: The thin layer of GRAY MATTER on the surface of the CEREBRAL HEMISPHERES that develops from the TELENCEPHALON and folds into gyri and sulchi. It reaches its highest development in humans and is responsible for intellectual faculties and higher mental functions.Xenon: A noble gas with the atomic symbol Xe, atomic number 54, and atomic weight 131.30. It is found in the earth's atmosphere and has been used as an anesthetic.Venous Thrombosis: The formation or presence of a blood clot (THROMBUS) within a vein.Image Processing, Computer-Assisted: A technique of inputting two-dimensional images into a computer and then enhancing or analyzing the imagery into a form that is more useful to the human observer.Heart Valve Prosthesis: A device that substitutes for a heart valve. It may be composed of biological material (BIOPROSTHESIS) and/or synthetic material.Veins: The vessels carrying blood away from the capillary beds.Reperfusion: Restoration of blood supply to tissue which is ischemic due to decrease in normal blood supply. The decrease may result from any source including atherosclerotic obstruction, narrowing of the artery, or surgical clamping. It is primarily a procedure for treating infarction or other ischemia, by enabling viable ischemic tissue to recover, thus limiting further necrosis. However, it is thought that reperfusion can itself further damage the ischemic tissue, causing REPERFUSION INJURY.Tilt-Table Test: A standard and widely accepted diagnostic test used to identify patients who have a vasodepressive and/or cardioinhibitory response as a cause of syncope. (From Braunwald, Heart Disease, 7th ed)Transducers: Any device or element which converts an input signal into an output signal of a different form. Examples include the microphone, phonographic pickup, loudspeaker, barometer, photoelectric cell, automobile horn, doorbell, and underwater sound transducer. (McGraw Hill Dictionary of Scientific and Technical Terms, 4th ed)Posture: The position or attitude of the body.Intracranial Thrombosis: Formation or presence of a blood clot (THROMBUS) in a blood vessel within the SKULL. Intracranial thrombosis can lead to thrombotic occlusions and BRAIN INFARCTION. The majority of the thrombotic occlusions are associated with ATHEROSCLEROSIS.Pulse: The rhythmical expansion and contraction of an ARTERY produced by waves of pressure caused by the ejection of BLOOD from the left ventricle of the HEART as it contracts.Vagina: The genital canal in the female, extending from the UTERUS to the VULVA. (Stedman, 25th ed)Brain Diseases: Pathologic conditions affecting the BRAIN, which is composed of the intracranial components of the CENTRAL NERVOUS SYSTEM. This includes (but is not limited to) the CEREBRAL CORTEX; intracranial white matter; BASAL GANGLIA; THALAMUS; HYPOTHALAMUS; BRAIN STEM; and CEREBELLUM.Vena Cava, Inferior: The venous trunk which receives blood from the lower extremities and from the pelvic and abdominal organs.Trophoblastic Neoplasms: Trophoblastic growth, which may be gestational or nongestational in origin. Trophoblastic neoplasia resulting from pregnancy is often described as gestational trophoblastic disease to distinguish it from germ cell tumors which frequently show trophoblastic elements, and from the trophoblastic differentiation which sometimes occurs in a wide variety of epithelial cancers. Gestational trophoblastic growth has several forms, including HYDATIDIFORM MOLE and CHORIOCARCINOMA. (From Holland et al., Cancer Medicine, 3d ed, p1691)Migraine with Aura: A subtype of migraine disorder, characterized by recurrent attacks of reversible neurological symptoms (aura) that precede or accompany the headache. Aura may include a combination of sensory disturbances, such as blurred VISION; HALLUCINATIONS; VERTIGO; NUMBNESS; and difficulty in concentrating and speaking. Aura is usually followed by features of the COMMON MIGRAINE, such as PHOTOPHOBIA; PHONOPHOBIA; and NAUSEA. (International Classification of Headache Disorders, 2nd ed. Cephalalgia 2004: suppl 1)
... and cerebral circulatory arrest. The tests are possibly useful for perioperative monitoring and meningeal infection. The ... Transcranial Doppler (TCD) and transcranial color Doppler (TCCD) are types of Doppler ultrasonography that measure the velocity ... Stroobant, N; Vingerhoets, G (2000). "Transcranial Doppler ultrasonography monitoring of cerebral hemodynamics during ... Carotid Doppler machine Arterial resistivity index Transcranial pulsed ultrasound "Transcranial Doppler: An Overview of its ...
... and cerebral circulatory arrest. The tests are possibly useful for perioperative monitoring and meningeal infection. The ... Transcranial Doppler (TCD) and transcranial color Doppler (TCCD) measure the velocity of blood flow through the brain's blood ... or as an image using color Doppler (directional Doppler) or power Doppler (non directional Doppler). This Doppler shift falls ... Doppler ultrasonography is medical ultrasonography that employs the Doppler effect to generate imaging of the movement of ...
... and demonstration of loss of cerebral blood flow (cerebral angiography, transcranial doppler ultrasonography, or cerebral ... "cessation of circulatory and respiratory functions under conditions in which those functions cannot return on their own and ... criteria for death are met when a physician determines that efforts to restart a stopped heart during cardiac arrest are futile ... and other confounding factors may also produce cerebral electric silence on EEG. van der Lugt A (November 2010). "Imaging tests ...
The posterior cerebral artery (PCA) is one of a pair of blood vessels that supply oxygenated blood to the posterior aspect of the brain (occipital lobe) in human anatomy. It arises near the intersection of the posterior communicating artery and the basilar artery and connects with the ipsilateral middle cerebral artery (MCA) and internal carotid artery via the posterior communicating artery (PCommA). The development of the PCA in fetal brain comes relatively late and arises from the fusion of several embryonic vessels near the caudal end of the PCommA supplying the mesencephalon and diencephalon of the fetus. The PCA begins as such, as a continuation of the PCommA in the fetus with only 10-30% of fetuses having a prominent basilar origin. The fetal carotid origin of the PCA usually regresses as the vertebral and basilar arteries develop with the PCommA reducing is size. In most adults, the PCA sources from the anterior portion of the basilar artery. Only about 19% of adults ...
Propagation velocity of the seismic waves through solid rock ranges from approx. 3 km/s (1.9 mi/s) up to 13 km/s (8.1 mi/s), depending on the density and elasticity of the medium. In the Earth's interior, the shock- or P-waves travel much faster than the S-waves (approx. relation 1.7:1). The differences in travel time from the epicenter to the observatory are a measure of the distance and can be used to image both sources of quakes and structures within the Earth. Also, the depth of the hypocenter can be computed roughly. In the upper crust, P-waves travel in the range 2-3 km (1.2-1.9 mi) per second (or lower) in soils and unconsolidated sediments, increasing to 3-6 km (1.9-3.7 mi) per second in solid rock. In the lower crust, they travel at about 6-7 km (3.7-4.3 mi) per second; the velocity increases within the deep mantle to about 13 km (8.1 mi) per second. The velocity of S-waves ranges from 2-3 km (1.2-1.9 mi) per second in light sediments and 4-5 km (2.5-3.1 mi) per second in the Earth's ...
A supersonic expansion fan, technically known as Prandtl-Meyer expansion fan, is a centred expansion process that occurs when a supersonic flow turns around a convex corner. The fan consists of an infinite number of Mach waves, diverging from a sharp corner. When a flow turns around a smooth and circular corner, these waves can be extended backwards to meet at a point. Each wave in the expansion fan turns the flow gradually (in small steps). It is physically impossible for the flow to turn through a single "shock" wave because this would violate the second law of thermodynamics.[1] Across the expansion fan, the flow accelerates (velocity increases) and the Mach number increases, while the static pressure, temperature and density decrease. Since the process is isentropic, the stagnation properties (e.g. the total pressure and total temperature) remain constant across the fan. The theory was described by Theodor Meyer on his thesis dissertation in 1908, along with his advisor Ludwig Prandtl, who ...
TIA症狀過後主要是判斷病因,並且根據病因治療。並不是經常能立刻鑑別病人患的是TIA還是腦血管意外(中風)。 大多數在急診被診斷為TIA的病人(在症狀消失後)被送回家並且被囑咐要與自己的醫生聯繫並安排之後的檢查。 心電圖可以顯示心房纖顫(一種TIA的常見病因),或者心律不齊(可以造成腦部栓塞)。超聲心動圖(echocardiogram)可以發現心房/心室內的血栓。這樣就可以對這樣的病人實施抗凝治療。 如果是由於頸動脈病變造成的TIA,經顱多普勒超聲檢查(TCD)可以作為頸動脈狹窄的旁證。對於頸動脈狹窄超過70%的病人,可以推薦手術去除動脈粥樣硬化斑塊(頸動脈內皮切除術)。 一部分病人還應酌量服用抗凝藥,如潘生丁或者氯吡格雷。 ...
A Doppler fetal monitor is a hand-held ultrasound transducer used to detect the fetal heartbeat for prenatal care. It uses the Doppler effect to provide an audible simulation of the heart beat. Some models also display the heart rate in beats per minute (BPM). Use of this monitor is sometimes known as Doppler auscultation. The Doppler fetal monitor is commonly referred to simply as a Doppler or fetal Doppler. It may be classified as a form of Doppler ultrasonography (although usually not technically -graphy but rather sound-generating). Doppler fetal monitors provide information about the fetus similar to that provided by a fetal stethoscope. One advantage of the Doppler fetal monitor over a ...
Many materials have a well-characterized refractive index, but these indexes depend strongly upon the frequency of light. Standard refractive index measurements are taken at the "yellow doublet" sodium D line, with a wavelength of 589 nanometers. There are also weaker dependencies on temperature, pressure/stress, etc., as well on precise material compositions (presence of dopants, etc.); for many materials and typical conditions, however, these variations are at the percent level or less. Thus, it is especially important to cite the source for an index measurement if precision is required. In general, an index of refraction is a complex number with both a real and imaginary part, where the latter indicates the strength of absorption loss at a particular wavelength-thus, the imaginary part is sometimes called the extinction coefficient ...
Like all triptans, almotriptan has a high and specific affinity for serotonin 5-HT1B/1D receptors. Binding of the drug to the receptor leads to vasoconstriction of the cranial (brain) blood vessels and thus affects the redistribution of blood flow. Almotriptan significantly increases cerebral blood flow and reduces blood flow through extracerebral cranial vessels. Even though it affects cranial blood vessels a single standard dose of almotriptan has no clinically significant effect on blood pressure or heart rate in both young and elderly healthy volunteers. Larger doses seem to slightly increase blood pressure but not beyond clinical relevance.[3] ...
... is a form of hypoxia (reduced supply of oxygen), specifically involving the brain; when the brain is completely deprived of oxygen, it is called cerebral anoxia. There are four categories of cerebral hypoxia; they are, in order of severity: diffuse cerebral hypoxia (DCH), focal cerebral ischemia, cerebral infarction, and global cerebral ischemia. Prolonged hypoxia induces neuronal cell death via apoptosis, resulting in a hypoxic brain injury. Cases of total oxygen deprivation are termed "anoxia", which can be hypoxic in origin (reduced oxygen availability) or ischemic in origin (oxygen deprivation due to a disruption in blood flow). Brain injury as a result of oxygen deprivation either due to hypoxic or anoxic mechanisms are generally termed hypoxic/anoxic injuries (HAI). Hypoxic ischemic encephalopathy (HIE) is a condition that occurs when the entire brain is deprived of an adequate oxygen supply, but ...
The posterior cerebral artery (PCA) is one of a pair of blood vessels that supply oxygenated blood to the posterior aspect of the brain (occipital lobe) in human anatomy. It arises near the intersection of the posterior communicating artery and the basilar artery and connects with the ipsilateral middle cerebral artery (MCA) and internal carotid artery via the posterior communicating artery (PCommA). The development of the PCA in fetal brain comes relatively late and arises from the fusion of several embryonic vessels near the caudal end of the PCommA supplying the mesencephalon and diencephalon of the fetus. The PCA begins as such, as a continuation of the PCommA in the fetus with only 10-30% of fetuses having a prominent basilar origin. The fetal carotid origin of the PCA usually regresses as the vertebral and basilar arteries develop with the PCommA reducing is size. In most adults, the PCA sources from the anterior portion of the basilar artery. Only about 19% of adults ...
Usually, the gamma-emitting tracer used in functional brain imaging is 99mTc-HMPAO (hexamethylpropylene amine oxime). 99mTc is a metastable nuclear isomer that emits gamma rays that can be detected by a gamma camera. Attaching it to HMPAO allows 99mTc to be taken up by brain tissue in a manner proportional to brain blood flow, in turn allowing cerebral blood flow to be assessed with the nuclear gamma camera. Because blood flow in the brain is tightly coupled to local brain metabolism and energy use, the 99mTc-HMPAO tracer (as well as the similar 99mTc-EC tracer) is used to assess brain metabolism regionally, in an attempt to diagnose and differentiate the different causal pathologies of dementia. Meta-analysis of many reported studies suggests that SPECT with this tracer is about 74% sensitive at diagnosing Alzheimer's disease vs. 81% sensitivity for clinical exam (cognitive testing, etc.). More recent studies have shown the accuracy of SPECT in Alzheimer's diagnosis may be as high as ...
The arteriovenous oxygen difference, or a-vO2 diff, is the difference in the oxygen content of the blood between the arterial blood and the venous blood. It is an indication of how much oxygen is removed from the blood in capillaries as the blood circulates in the body. The a-vO2 diff and cardiac output are the main factors that allow variation in the body's total oxygen consumption, and are important in measuring VO2. The a-vO2 diff is usually measured in millilitres of oxygen per 100 millilitres of blood (mL/100 mL). The arteriovenous oxygen difference is usually taken by comparing the difference in the oxygen concentration of oxygenated blood in the femoral, brachial, or radial artery and the oxygen concentration in the deoxygenated blood from the mixed supply found in the pulmonary artery (as an indicator of the typical mixed venous supply). Put in simple terms: a-vO2 diff = Ca - Cv where: Ca = the oxygen concentration of arterial blood (oxygenated blood) Cv = the oxygen concentration of ...
In both animals and humans, mTBI can alter the brain's physiology for hours to years,[42][43] setting into motion a variety of pathological events.[44] As one example, in animal models, after an initial increase in glucose metabolism, there is a subsequent reduced metabolic state which may persist for up to four weeks after injury.[10] Though these events are thought to interfere with neuronal and brain function, the metabolic processes that follow concussion are reversible in a large majority of affected brain cells; however, a few cells may die after the injury.[45] Included in the cascade of events unleashed in the brain by concussion is impaired neurotransmission, loss of regulation of ions, deregulation of energy use and cellular metabolism, and a reduction in cerebral blood flow.[45] Excitatory neurotransmitters, chemicals such as glutamate that serve to stimulate nerve cells, are released in excessive amounts.[46] The resulting cellular excitation causes neurons to fire ...
自然形成的氙共由7種穩定同位素組成,在各元素中排第二位。第一位是錫,其穩定同位素共有10個。穩定同位素數量高於7個的元素只有錫。[69]同位素134Xe根據預測能夠進行雙重β衰變,但這未經實驗證明,因此该同位素仍被認為是穩定的。[70]除這些穩定同位素之外,氙還有40多種不穩定同位素。其中壽命最長的為124Xe,它會進行双电子俘获衰變,半衰期為1.8×1022年。[6] 129I在β衰變後,會產生129Xe同位素。該反應的半衰期為1600萬年。另外131mXe、133Xe、133mXe和135Xe都是235U和239Pu的核裂變產物,[68]因此被用作探測核爆炸的發生。[71] ...
Specific intracranial flow patterns indicating cerebral circulatory arrest (CCA) can be visual ... Specific intracranial flow patterns indicating cerebral circulatory arrest (CCA) can be visualized by transcranial Doppler ... The diagnosis and management of a perianesthetic cerebral aneurysmal rupture aided with transcranial Doppler ultrasonography. ... Heiskanen O (1964) Cerebral circulatory arrest caused by acute increase of intracranial pressure. A clinical and ...
Use of Transcranial Doppler Ultrasonography. The Therapeutics and Technology Assessment Subcommittee of the American Academy of ... These include detection of cerebral circulatory arrest and brain death, and monitoring of coronary artery bypass graft ... Neurology has released a guideline on transcranial Doppler ultrasonography (TCD) and transcranial color-coded sonography as a ... "Assessment: Transcranial Doppler Ultrasonography" appears in the May 2004 issue of Neurology and is available online at http:// ...
Cerebral Circulatory Arrest. *Cerebral Vasomotor reactivity. *Intracranial Stenosis. Expand. We aim at spreading smiles of good ... Trans cranial Doppler (TCD) Trans cranial Doppler (TCD) Ultrasonography is the cutting edge in technology used in diagnosis and ... Trans cranial Doppler (TCD) It is a form of ultrasonography and is used in the diagnosis of Stroke along with the CT Scanner, ...
Cerebral monitoring with transcranial Doppler ultrasonography improves neurologic outcome during repairs of acute type A aortic ... deep hypothermic circulatory arrest with retrograde cerebral perfusion or selective antegrade cerebral perfusion. Ann Thorac ... Cerebral metabolic suppression during hypothermic circulatory arrest in humans. Ann Thorac Surg. 1999;67:1895-1899.PubMedGoogle ... Cerebral autoregulation after hypothermic circulatory arrest in operations on the aortic arch. Ann Thorac Surg. 2004;77:72-79. ...
... and cerebral circulatory arrest. The tests are possibly useful for perioperative monitoring and meningeal infection. The ... Transcranial Doppler (TCD) and transcranial color Doppler (TCCD) measure the velocity of blood flow through the brains blood ... or as an image using color Doppler (directional Doppler) or power Doppler (non directional Doppler). This Doppler shift falls ... Doppler ultrasonography is medical ultrasonography that employs the Doppler effect to generate imaging of the movement of ...
... cerebral circulatory arrest, cerebral autoregulation and CO2 reactivity tests, emboli monitoring for stroke etc. They also ... Transcranial Doppler (TCD) Ultrasonography laboratory rotation: Harborview Medical Center has a world-renowned TCD lab and many ... Proficiency in the use of transcranial Doppler ultrasonography. *Proficiency in the use of EEG, somatosensory and brainstem ... Professional Interests: Transcranial Doppler (TCD) Ultrasonography, Cerebrovascular physiology, Traumatic Brain Injury, ...
... and cerebral circulatory arrest. The tests are possibly useful for perioperative monitoring and meningeal infection. The ... Transcranial Doppler (TCD) and transcranial color Doppler (TCCD) are types of Doppler ultrasonography that measure the velocity ... Stroobant, N; Vingerhoets, G (2000). "Transcranial Doppler ultrasonography monitoring of cerebral hemodynamics during ... Carotid Doppler machine Arterial resistivity index Transcranial pulsed ultrasound "Transcranial Doppler: An Overview of its ...
Transcranial Doppler ultrasonography in raised intracranial pressure and in intracranial circulatory arrest // J Neurosurg. - ... Hartman A., Alberti E. Cerebral blood flow and cerebral blood volume in communicating hydrocephalus // Arch Psychiatr Nervenkr ... Hanlo P. W., Gooskens R., Nijhuis I., Faber J., Peters R., Huffelen A, Tulleken C.A., Willemse J. Value of transcranial Doppler ... 3. Behrens A., Lenfeldt N., Ambarki K., Malm J., Eklund A., Koskinen L.O. Transcranial Doppler pulsatility index: not an ...
... and optimization of cerebral oxygenation. In this review, the critical care management of severe TBI will be discussed with ... focus on monitoring, avoidance and minimization of secondary brain insults, and optimization of cerebral oxygenation and CPP. ... Transcranial Doppler Ultrasonography. Transcranial Doppler (TCD) is a non-invasive method to measure CBF velocity. It is ... and cerebral circulatory arrest (brain death). TCD can predict post-traumatic vasospasm prior to its clinical manifestations. ...
... which is visualized with transcranial Doppler as a "pattern of cerebral circulatory arrest". The following are accepted as the ... Humans , Brain Death/diagnosis , Brain Injuries/diagnosis , Ultrasonography, Doppler, Transcranial/methods , Brain Injuries/ ... Transcranial Doppler evaluates cerebral hemodynamics in patients with brain injury and is a useful technical tool in diagnosing ... The basic consensus statements are the following: cerebral circulatory arrest is the final stage in the evolution of ...
... which is visualized with transcranial Doppler as a "pattern of cerebral circulatory arrest". The following are accepted as the ... Female , Humans , Middle Aged , Parkinson Disease , Substantia Nigra , Ultrasonography, Doppler, Transcranial/methods , ... A transcranial Doppler [TCD] velocimeter was used to measure middle cerebral artery blood flow velocity [Vmca] at rest and ... Transcranial Doppler evaluates cerebral hemodynamics in patients with brain injury and is a useful technical tool in diagnosing ...
Transcranial Doppler ultrasonography in raised intracranial pressure and in intracranial circulatory arrest. J Neurosurg. 1988; ... Transcranial Doppler recording of blood velocity from the middle cerebral artery with the intra-aortic balloon pump on standby ... Hassler W, Steinmetz H, Pirschel J. Transcranial Doppler study of intracranial circulatory arrest. J Neurosurg. 1989;71:195-201 ... Transcranial Doppler recording shows blood velocity from the middle cerebral artery while the intra-aortic balloon pump is ...
Application of Transcranial Doppler Ultrasonography for the Diagnosis of Cerebral Circulatory Arrest2013 December;5(1) ... Clinical Application of Transcranial Doppler 2010 October;2(1). Duplex Ultrasonography in Vertebrobasilar System 2009 December; ... Clinical Application of Transcranial Doppler Monitoring for Microembolic Signals2013 December;5(1) ... 신경과 구분을 요하는 구조물은 혈관과 건(tendon)인데, 혈관은 Doppler로 혈류의 방향에 따라 색깔로 표시되기 때문에 비교적 구분이 용이하다. 건은 신경과 달리 많은 평행한 에코발생 선들로 구성되어 섬유구조 형태로 ...
... present a case in which an objective evaluation of a cerebral circulatory compromise was documented using transcranial Doppler ... Objective evidence of cerebral circulatory compromise is often lacking. We ... There was reverberating flow in the left middle cerebral artery (MCA) compatible with cerebral circulatory arrest on that side ... The optic nerve ultrasonography seen on the right side of the figure are corresponding to the side of the middle cerebral ...
Transcranial Doppler can detect microembolic signals which are characterized by unidirectional high intensity increase, short ... Cerebral aneurysm treatment using flow-diverting stents: in-vivo visualization of flow alterations by ... ... Carotid duplex ultrasonography is a noninvasive technique for hemodynamically significant stenosis detection and cardiovascular ... but may present with severe chest pain or cardiac arrest. The introduction of multidetector CT coronary angiography (MDCT-CA) ...
Cerebral microembolism can be monitored by detecting microembolic signals with transcranial Doppler. ... Precordial Doppler ultrasonography, a sensitive technique to detect intracardiac air, is often used during surgical procedures ... Following cardiac arrest, perform immediate delivery if the fetus is ≥23 weeks gestation. In 65% of AFE cases, delivery had not ... Management is directed towards maintenance of oxygenation and circulatory support. Mechanical ventilation and inotropic support ...
Consensus opinion on diagnosis of cerebral circulatory arrest using Doppler-sonography.. Escrito por el personal de Mayo Clinic ... a first stroke by transfusions in children with sickle cell anemia and abnormal results on transcranial Doppler ultrasonography ... The accuracy of transcranial Doppler in the diagnosis of middle cerebral artery stenosis. Alteraciones de la pupila I. ... The accuracy of transcranial Doppler in the diagnosis of middle cerebral artery stenosis. Alteraciones de la pupila I. ...
Transcranial Doppler studies with the patients neck rotated into the left side revealed reduction of flow in his left ... Repair of a penetrating aortic arch injury using deep hypothermic circulatory arrest ... ... BACKGROUND:Lactate fuels cerebral energy-consuming processes and is neuroprotective. The impact of arterial lactate on brain ... dissection of the right internal carotid artery during multidetector 64-row computer tomography and Doppler ultrasonography B- ...
... and transcranial comparative Doppler velocity of the middle cerebral arteries. ... hypothermic circulatory arrest (HCA), antegrade cerebral perfusion (ACP), and retrograde cerebral perfusion (RCP). During the ... and hypothermic circulatory arrest, temporary interruption of brain circulation, transient cerebral hypoperfusion, and ... RCP does not seem to prolong safe brain-ischemia time beyond 30 min, but it appears to enhance cerebral hypothermia by its ...
... and noninvasive confirmation of cerebral circulatory arrest. Improvement in image quality permits novel uses of ultrasonography ... Transcranial parenchymal sonography may assist in the differential diagnosis of movement disorders, while peripheral nerve ... and noninvasive confirmation of cerebral circulatory arrest. Improvement in image quality permits novel uses of ultrasonography ... and noninvasive confirmation of cerebral circulatory arrest. Improvement in image quality permits novel uses of ultrasonography ...
Transcranial Doppler versus angiography in patients with vasospasm due to a ruptured cerebral aneurysm: A systematic review. ... Whole Body Ultrasonography in the Critically Ill 1st ed. 2010 Edition. Acute and Critical Care Echocardiography (Oxford ... Lichtenstein D.A. Lung Ultrasound as the First Step of Management of a Cardiac Arrest: The SESAME-Protocol. In: Lung Ultrasound ... The role of the Glucocorticoid (GC) receptor in circulatory shock. (Sabine Vettorazzi) ...
A. L. Estrera, Z. Garami, C. C. Miller et al., "Cerebral monitoring with transcranial Doppler ultrasonography improves ... E. B. Griepp and R. B. Griepp, "Cerebral consequences of hypothermic circulatory arrest in adults," Journal of Cardiac Surgery ... Surrogate Measures of Cerebral Flow and Metabolism. 11.1. Transcranial Doppler. Transcranial doppler (TCD) is used to measure ... G. Schwarz and G. Litscher, "Transcranial cerebral oximetry, transcranial Doppler sonography, and heart rate variability: ...
The landmark prospective Boston Circulatory Arrest Study reported follow-up in D-TGA survivors at 1, 4, 8 and 16 years of age ( ... Some centers advocate continuous electroencephalography, transcranial Doppler, strict glycemic control, and measurement of ... A reassuring peripheral oxygen saturation level may be associated with paradoxically low cerebral oxygen delivery. Cerebral ... 2013) Accuracy of ultrasonography at 11-14 weeks of gestation for detection of fetal structural anomalies: a systematic review ...
Cerebral blood velocity (Transcranial Doppler), beat-to-beat BP (Finometer), and end-tidal carbon dioxide (ETCO2 , capnography ... and can be measured by transcranial Doppler ultrasonography (TCD). Objective: The aim of this study was to characterize the ... Quantitative CT assessment of lung injury after successful cardiopulmonary resuscitation in a porcine cardiac arrest model of ... A Feasibility Functional Transcranial Doppler Ultrasonography Study.. Lucy C Beishon, Ronney B Panerai, Thompson G Robinson, ...
Transcranial Doppler:. Transcranial Doppler of the cerebral circulation. Transcranial Doppler (TCD) and transcranial color ... and cerebral circulatory arrest. The tests are possibly useful for perioperative monitoring and meningeal infection. The tests ... Doppler Ultrasonography. Doppler ultrasonography at Chandan Hospital is medical ultrasonography that employs the Doppler effect ... Doppler ultrasonography:. Doppler ultrasonography employs the Doppler effect to assess whether structures (usually blood) are ...
  • 1. Aaslid R., Lindegaard K., Sorteberg W., Nornes H. Cerebral autoregulation dynamics in humans // Stroke. (therjn.com)
  • The ideal technique for dynamic cerebral autoregulation (dCA) assessment in critically ill patients should provide considerable variability in blood pressure (BP), but without the need for patient co-operation. (readbyqxmd.com)
  • Furthermore, breakthroughs in the individualization of perfusion targets for patients with HIBI using cerebral autoregulation monitoring represent an attractive area of future work with therapeutic implications. (ubc.ca)
  • Among factors that may be implicated in this secondary injury includereperfusion injury, microcirculatory dysfunction, impaired cerebral autoregulation, hypoxemia, hyperoxia, hyperthermia,fluctuations in arterial carbon dioxide, and concomitant anemia.Clarifying the underlying pathophysiology of HIBI is imperative and has been the focus of considerable research toidentify therapeutic targets. (ubc.ca)
  • Mannitol is a widely accepted in therapy for the treatment of intracranial hypertension (ICHT), as it has positive effect on cerebral perfusion pressure (CPP) and cerebral blood flow (CBF) more so in those patients with focal injury (vs. diffuse), those with lesions on the brain imaging, and those in whom the CPP is at or below the auto regulation threshold (Brown et al. (springeropen.com)
  • Recent advances point to important roles of anemia, carbon dioxide perturbations, hypoxemia, hyperoxia, and cerebral edema as contributing to secondary injury after HIBI and adverse outcomes. (ubc.ca)
  • Resumen Objetivo: Describir los hallazgos en resonancia magnética (RM) de encéfalo en pacientes menores de 65 años que fueron estudiados por Doppler transcraneal (DTC) con contraste de microburbujas, con antecedentes de accidente cerebrovascular (ACV) criptogénico y sospecha de foramen oval permeable (FOP). (bvsalud.org)
  • Las alteraciones de la velocidad del FSC en el ultrasonido doppler transcraneal (UDTC) fueron: 11 (22 por ciento) pacientes con velocidades mayores de 170 cm/s, 6 (12 por ciento) con un flujo entre 170 - 199 cm/s, y 5 (10 por ciento) mayor de 200 cm/s. (bvsalud.org)
  • Manual de Doppler Transcraneal. (andreev-life.ru)
  • The fellows will gain the cognitive and psychomotor skills required for rationale selection and skillful utilization of various monitors and procedures including jugular bulb catheters, fiberoptic intubations, intraoperative evoked potentials monitoring (somatosensory, motor, visual and brainstem evoked potentials), and transcranial Doppler (TCD) ultrasonography. (washington.edu)
  • Ultrasonography has found a place as a noninvasive screening test and bedside technique that provides estimates of the degree of stenosis as well as hemodynamic and structural information about intracranial and extracranial vessels in real time. (elsevier.com)
  • Similar to other neuroimaging techniques such as functional magnetic resonance imaging (fMRI) and positron emission tomography (PET), fTCD is based on a close coupling between regional cerebral blood flow changes and neural activation. (wikipedia.org)
  • 2. Bakker S.L., Boon A.J., Wijnhoud A.D., Dippel D.W., Delwel E.J., Koudstaal P.J. Cerebral hemodynamics before and after shunting in normal pressure hydrocephalus // Acta Neurologica Scandinavica 2002 - Volume 106. (therjn.com)
  • Because of this confusion and lack of standards in the various laboratories, the sonographer must understand the underlying acoustic physics of color Doppler and the physiology of normal and abnormal blood flow in the human body (see Red shift). (wikipedia.org)
  • Objetivo: conocer la frecuencia de niños con AD que tienen alteraciones en la velocidad del flujo sanguíneo cerebral, relacionar estas alteraciones con los eventos clínicos y los datos de laboratorio y evaluar la evolución en el tiempo de los pacientes con alteraciones y su asociación con el uso de hidroxiurea. (bvsalud.org)
  • Se determinaron las alteraciones del flujo sanguíneo cerebral (FSC) y su asociación con otros elementos clínicos y hematológicos. (bvsalud.org)
  • Once the desired blood vessel is found, blood flow velocities may be measured with a pulsed Doppler effect probe, which graphs velocities over time. (wikipedia.org)
  • This begins with primary injury to the brain caused by the immediate cessation of cerebral blood flow following CA. Thereafter, the secondary injury of HIBI takes place in the hours and days following the initial CA and reperfusion. (ubc.ca)
  • The major advantages of pulsed Doppler over continuous wave is that distance information is obtained (the time between the transmitted and received pulses can be converted into a distance with knowledge of the speed of sound) and gain correction is applied. (wikipedia.org)