$368 Journal of Biomechanics 2006, Vol. 39 (Suppl 1) Oral Presentations

between the tubes represents the cerebrospinal fluid (CSF). Similar approxi- mation had been used previously by this and other authors [1-3]. Propagation of pressure pulses was considered using a small-amplitude linearized wave theory. A three-dimensional axisymmetric formulation was used for the tissue of the spinal cord which was modelled as a linear viscoelastic solid. The CSF was modelled as a viscous incompressible fluid. After developing expressions for the phase speed in terms of critical parameters, the propagation of a pressure disturbance introduced in the middle of the spinal column (eg. due to coughing [2]) was considered for the cases with and without communication between the cranial and spinal spaces. Results and Discussion: The results, which are preliminary, suggest that when the movement of the CSF through the foramen magnum is obstructed, wave reflections are intensified at both ends of the spinal cord. This may lead to larger than normal wall movements in the terminal ventricle. Currently, efforts are being made to use the existing model to formulate a one-dimensional theory which will allow the modelling of nonlinear effects.

References [1] S. Cirovic, C. Walsh, W.D. Fraser. Wave propagation through a system of coaxial

tubes: A model of pulse propagation in the intracranial arteries. Journal of Fluids and Structures 2002; 1029-1049.

[2] Lockey E, Poots G., Williams B. Theoretical aspects of the attenuation of pressure pulses within cerebrospinal-fluid pathways. Med. Biol. Eng. 1975; 861- 869.

[3] Berkouk K, Carpenter PW, Lucey AD. Pressure wave propagation in fluid-filled co-axial elastic tubes part 1 : basic theory. J. Biomech. Eng. 2003; 852~356.

7787 Tu, 17:00-17:15 (P25) Visualization of basic flow pattern in a subarachnoid hemorrhage model and measurement of influence due to variant kinetic applications

D. H~nggi 1 , M. Stock 2, J. Galdeano 3, K. Affeld 3, H.-J. Steiger 1 , D. Liepsch 2. 1Department of Neurosurgery, Heinrich-Heine-University, DEtsseldorf, Germany, 2Department of Supply Engineering 05, Laboratory of Biofluid Mechanics, Munich University of Applied Sciences, Germany, 3Laboratory of Biofluid Mechanics, Department of Cardiovascular Surgery, Chadt6 - Universit#tsmedizin Berlin, Germany

Goal of the study is to visualize and analyze the subarachnoid flow of the central cerebrospinal fluid (CFS) after subarachnoid hemorrhage (SAH) com- plications. Cerebral vasospasm remains a devastating medical complication of aneurysmal SAH. It is associated with morbidity and mortality even after the aneurysm has been secured surgically or endovascular. We constructed a silicon rubber model of the subarachnoid space of the central nervous system which is based on digital data of a CISS-MRT sequence of a healthy volunteer. First, basic flow pattern of CSF was measured to evaluate dynamic base line. The CSF was visualized by adding Titaniumoxid tracer particles using a video camera. In a second step the subarachnoid hemorrhage was visualized by adding further particles at typical subarchnoid areas. These pictures were compared with the base line flow pattern. In a third step the model was moved in three different rotational patterns and the influence on CSF flow and clot clearance was visualized and analyzed. The study demonstrates that application of different rotational motion patterns causes effects on subarachnoid fluid flow after experimental subarachnoid hemorrhage. This effect might influence wash-out of subarachnoid blood clots. These findings may be beneficial for patients after subarachnoid hemorrhage in the clinical application of such techniques.

18.3. Imaging 6448 Mo, 14:00-14:15 (P11) Diffusion tensor imaging data in brain tumor surgery

G. Schackert 1 , H. Kitzler 2, W. Benger 3, A. Werner 2, R. v. Kummer 2. 1Department of Neurosurgery and 2Department of Neuroradiology, University of Technology, Dresden, Germany, 3Center for Computation & Technology at Louisiana State University (CCT/LSU), Baton Rouge, Lousiana, USA

Introduction: The goal of modern neurosurgery is to implement functional data into neurosurgical procedures. Planning of surgical approaches has therefor to combine morphological and functional data. Diffusion Tensor Imaging (DTI) provides a tool to visualize fiber tracts. Integrated into neuronavigation DTI data can support glioma surgery in the definition of tumor margins. The development of a three-dimensional representation of white matter texture might improve our knowledge and the reliability of fiber visualization. Method: Forty patients with low and high grade gliomas in the vicinity of the pyramidal tract (PT) have been analyzed with respect to dislocation, edema, infiltration, and disruption. Preoperative analysis of the mean fractional anisotropy has been evaluated with respect to neurological deficits. The intraoperative verification of the PT has been approached by intraoperative subcortical stimulation. In addition, a novel 3D visualization of DTI data (Diffu- sion Tensor Pattern method) has been used allowing six degrees of freedom

to visualize tensor parameters compared to only two degrees of freedom of common techniques. This is expected to provide important information of the reliability of the DT datasets. Results: Evaluation of the data revealed a correlation to the clinical symptoms only in a presumed disruption of the PT, averaging about 50%. Presumed infiltration of the tracts could not predict clinical symptoms. Intraoperative stimulation of the PT was difficult to interpret with brain shift and edema causing unsolved problems. The Diffusion Tensor Pattern method is a promising tech- nique to visualize the white matter texture in explorative 3D datasets providing a holistic perception of the tumor adjacent tissue. Conclusion: DTI provides important information for the planning of surgical approaches in brain tumors. The reliability of visualized data could be improved by novel visualization techniques and statistic approaches in future applica- tions. The diffusion tensor pattern method might be appropriate for gaining a depiction that approximates the real morphological situation.

7755 Mo, 14:15-14:30 (P l l ) Functional brain imaging N. Ward. National Hospital for Neurology and Neurosurgery, Institute of Neurology, University College London, UK

Imaging neuroscience is concerned with describing the functional organization of the human brain at the level of large neuronal groupings and networks. This systems level approach addresses how integrated brain functions are embodied in the physical structure of the brain. Magnetic resonance imaging is currently the technique of choice for the study of cerebral structure-function relationships and the analysis of structural and functional brain images can now be carried out automatically using statistical parametric mapping. The resultant ability to perform clinical-functional-anatomical correlative studies objectively with unparalleled sensitivity is providing powerful new opportunities for studying the relationship between brain structure and function. Furthermore, brain imaging and neurophysiological techniques have developed to the point where a detailed appreciation of the anatomy of pathological change and the function of the remaining brain areas is also possible. Recent activation studies have provided interesting information about the brain's capacity to reorganize after injury and in association with practice and learning. The emerging studies of brain plasticity and its modulation by drugs and other therapies indicate potentially useful approaches to the rehabilitation of adults with brain damage, including damage resulting from cerebral ischaemia. Brain maps must therefore be viewed as dynamic, changing with development, disease progression, normal learning and in parallel with the recovery of function after acute injury. The dynamic plasticity of functional brain maps provides an exciting opportunity to study these processes.

4327 Mo, 14:30-14:45 (P l l ) Brain tumor imaging with [18F]fluoroethyI-L-tyrosine and PET

K.-J. Langen 1,5, F. Floeth 2, G. Stoffels 1,5, G. Reifenberger 3, M. Sabel 2, K. Hamacher 4,5, H.H. Coenen 4,5, D. Pauleit 1,5. 1Institute of Medicine, Research Center JEtlich, JEtlich, Germany, 2Department of Neurosurgery, Heinrich-Heine-University, D~sseldorf, Germany, 3Department of Neuropathology, Heinrich-Heine-University, D~sseldorf, Germany, 4Institute of Nuclear Chemistry, Research Center JEtlich, JEtlich, Germany, 5Brain Imaging Center West, Research Center J~lich, J~lich, Germany

Radiolabeled amino acids and positron emission tomography (PET) have shown great potential for more accurate diagnostis of cerebral gliomas. O- (2-[lSF]Fluoroethyl)-L-tyrosine (FET) is a new tracer for PET which can be produced with high efficiency and distributed according to a satellite concept like the widely used 2-[lSF]fluoro-2-deoxy-D-glucose (FDG). In a prospective study, PET with FET and MRI was performed in 31 patients with suspected cerebral gliomas. Neuronavigated biopsies were taken from lesions with both abnormal MR signal and increased FET uptake, as well as from areas with abnormal MR signal but normal FET uptake. MRI alone yielded a sensitivity of 96% for the detection of tumor tissue but a specifity of only 53%, and combined use of MRI and FET PET in patients with gliomas yielded a sensitivity of 93% and a specificity of 94%. Thus, combined use of MRI and FET PET in patients with cerebral gliomas significantly improves the identification of cellular glioma tissue and allows definite histological tumor diagnosis. Nevertheless, increased regional uptake of FET in the brain is not absolutely specific for glioma tissue and some exceptions have been reported. In a further study FET PET was combined with single-voxel magnetic resonance spec- troscopy (MRS) in a series of 50 consecutive patients with newly diagnosed intracerebral lesions supposed to be diffuse gliomas on contrast-enhanced MRI. Results of MR spectroscopy were considered positive when the neuronal marker N-acetyl aspartate (NAA) was decreased in conjunction with an ab- solute increase of the cell proliferation marker choline (Cho). The accuracy of distinguishing neoplastic and nonneoplastic tissue could be increased from