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Ultrasound analysis of cerebral hemodynamics - arteries and veins
Ultrasound as a simple, cost-effective and non-invasive diagnostic method is particularly suitable to study function and regulatory mechanisms of blood supply to the healthy as well as to the diseased brain (physiology and pathophysiology). Our research group established for instance normal values of blood flow velocity in different intra- and extracranial veins and sinuses e.g. the basal vein of Rosenthal, the vertebral veins, the inferior petrosal sinus and the cavernous sinus and we reported changes of these values in patients with cerebral venous disease. Based on our special knowledge of the venous cerebral ultrasound anatomy we developed a method to analyse the global cerebral circulation time. This is the time interval, the blood needs to pass the brain from the internal carotid artery to the internal jugular vein, assessed by echo-contrast bolus tracking. This method can for instance be used to detect cerebral arteriovenous malformations (angiomas or dural fistulas) or to monitor the patients treatment progress. Combining cerebral blood volume flow and circulation time we described for the first time an ultrasonographic method to calculate the global cerebral blood volume.
Ultrasound in acute stroke
The knowledge of the status of the brain supplying arteries is todays basis for acute interventional stroke treatment strategies. Ultrasound is compared to CTA, MRA and angiography a diagnostic technique, particularly suitable for bedside and repeated analysis. However, in many already applied fields sufficient evidence based ultrasound studies are missing. Within this field we are interested in acute vascular diagnostics, the analysis of collateral blood flow patterns and its improvement, e.g. by active blood pressure modulation. We were able to show, that catecholamine induced increase of blood pressure leads to a measurable blood flow velocity rise in patients with proximal vessel occlusion and distal impaired collateral function. Currently we are extending our abilities to directly measure blood flow within the brain parenchyma (perfusion). Stroke, however is not only caused by vessel occlusions but also by vessel ruptures which lead to intracranial hemorrhages. The new ultrasound - fusion - imaging technology allows - in contrast to earlier ultrasound approaches - to visualize and monitor intracranial hemorrhages with higher sensitivity.
Ultrasound in Neurological intensive care
Within the field of intensive care medicine ultrasound can quickly help to answer specifically arising questions, for instance to assess the vascular status in critically ill patients who cannot be moved away from the ward. Such a condition may for instance arise in patients after subarachnoid hemorrhage, after a brain operation or in cases of suspected cerebral circulatory arrest. Also the questions of a developing pneumothorax, of the cardiac filling and cardiac pump function can be answered and ultrasound can also be used for guided punctures. Within our research group we are working to improve our diagnostic algorhythms and to increase the field of ultrasound applications.
B-Mode-ultrasound allows to assess and analyze brain structures like ventricles, basal ganglia and brain parenchyma which may be altered by different neurological diseases. Especially in movement disorders the echogenicity of certain brain structures can be used for diagnostic differentiation and are currently intensively studied. In co-operation with the movement disorders unit we have gained a specific expertise within the field of substantia nigra ultrasound analysis in Parkinson's disease.
Ultrasound – fusion - imaging
A new development within the field of neurological ultrasound is the use of a combined ultrasound-MRT/CT-fusion – technique. This technique allows a real time combination of a pre-registered CT or MRT-data set with a current live ultrasound image. The method therefore allows to analyses and compare any chosen ultrasound image with its corresponding MRI or CT image, which is in plane and position exactly matched to the chosen ultrasound image plane. The technique can be applied for intracranial ultrasound but also to study extracranial organs, for instance muscles and nerves. The technique is therefore particularly interesting for any disease with initial radiological imaging and the need for monitoring over time or in conditions where direct comparison of methods would be desirable. Our ultrasound lab works in cooperation with ESAOTE Biomedica Germany GmbH and ESAOTE headquarters, Genova, Italy, functioning as a reference lab for fusion imaging, actively contributing to the development and improvement of the already commercially available technology and studying the fields of its clinical application. Besides the application of fusion – imaging within specific research projects, the technology is also used as a teaching tool in our regular ultrasound courses as well as within an annual user seminars of ultrasound – fusion - imaging at the Charité.
Ultrasound of muscle and peripheral nerves
Because of the recent technical developments and advances in high-resolution imaging, ultrasound has become more important for diagnosis of muscle and peripheral nerve disease. In our research group we are using the ultrasound – fusion – imaging technology for comparative studies in peripheral muscle disease and peripheral nerves, for instance before a planned intervention. Furthermore, in cooperation with our electromyography / electroneurography laboratory we are studying peripheral nerves in different types of polyneuropathic diseases.