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  • 1
    Digitale Medien
    Digitale Medien
    Haemodynamic stress in lateral saccular aneurysms (1987)
    Springer
    Acta neurochirurgica 86 (1987), S. 98-105 
    Details
    ISSN: 0942-0940
    Schlagwort(e): Cerebral aneurysm ; fluid dynamics ; haemodynamic stress ; wall shear stress ; viscoelastic fluid ; experimental aneurysm
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The flow velocities in lateral glass and silastic aneurysm models were quantitatively measured with the non-invasive laser Doppler method. The influences of the elasticity of the wall, the pulse wave and the properties of the perfusion medium on the intra-aneurysmal circulation were investigated. As shown previously, the inflow into the aneurysm arose from the downstream lip and was directed toward the centre of the fundus. Backflow to the parent vessel took place along the walls of the fundus. With non-pulsatile perfusion, flow velocities in the centre of the standardized aneurysms varied between 0.4 and 2% of the maximum velocity in the parent vessel. With pulsatile perfusion, flow velocities in the centre of the fundus ranged between 8 and 13% of the flow velocity in the axis of the parent vessel. Flow velocities in the aneurysms were slower with a macromolecular perfusion medium with blood like properties compared to a glycerol/water solution. Flow velocity measurements near the aneurysmal wall allowed the estimation of the shear stresses at critical locations. The maximum shear stresses at the downstream lip of the aneurysm were in the range of the stresses measured at the flow divider of an arterial bifurcation. The present results suggest that in human saccular aneurysms intra-aneurysmal flow and shear stress on the wall are directly related to the pulsatility of perfusion,i.e. the systolic/diastolic pressure difference and that the tendency to spontaneous thrombosis depends on the viscoelastic properties of the blood, namely the haematocrit.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01402292
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  • 2
    Digitale Medien
    Digitale Medien
    Haemodynamic stress in terminal aneurysms (1988)
    Springer
    Acta neurochirurgica 93 (1988), S. 18-23 
    Details
    ISSN: 0942-0940
    Schlagwort(e): Cerebral aneurysm ; experimental aneurysm ; haemodynamic stress ; laser-Doppler-anemometer ; wall shear stress
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The flow velocities in glass and silastic aneurysm models located at bifurcations were quantitatively determined using the non-invasive laser-Doppler method. The geometrical relation between aneurysm and parent vessels was found to be the primary factor governing the intra-aneurysmal flow pattern. Flow was stagnant in straight terminal models, with the aneurysm forming an extension of the afferent vessel, as long as the outflow through the branches of the bifurcation was balanced. Average flow velocities in the fundus were small but turbulent flow fluctuations of high amplitudes were observed. Asymmetric outflow through the branches of the bifurcation induced a rotatory intra-aneurysmal circulation from the dominant to the subordinate branch. The circulation in angled terminal aneurysms with the aneurysmal axis at a 45 degree angle to the plane of the bifurcation was a vortex, which was a natural consequence of the excentric inflow from the afferent vessel. Maximum flow velocities measured in the centre plane of the angled terminal aneurysms were in the range of 50 to 80% of the axial velocity in the afferent vessel. The elasticity of the models did not affect the global turnover rates but it damped the intra-aneurysmal pulse wave. On the basis of the measured velocity gradients near the walls maximum shear stresses on the wall of human terminal aneurysms were estimated to be in the order of 50 dynes/cm2 (5 Pascal), a value that is similar to the maximum wall shear stresses estimated for lateral aneurysms.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01409897
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  • 3
    Digitale Medien
    Digitale Medien
    Book reviews (1988)
    Springer
    Acta neurochirurgica 93 (1988), S. 71-73 
    Details
    ISSN: 0942-0940
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01409906
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  • 4
    Digitale Medien
    Digitale Medien
    German-austrian multicenter trial for aggressive non-Hodgkin lymphomas: COP-BLAM/IMVP-16 chemotherapy with randomized adjuvant radiotherapy (1988)
    Springer
    Annals of hematology 56 (1988), S. 139-142 
    Details
    ISSN: 1432-0584
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00320022
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  • 5
    Digitale Medien
    Digitale Medien
    Radical resection of superior sagittal sinus meningioma with venous interposition graft and reimplantation of the rolandic veins (1989)
    Springer
    Acta neurochirurgica 100 (1989), S. 108-111 
    Details
    ISSN: 0942-0940
    Schlagwort(e): Parasagittal meningioma ; superior sagittal sinus ; cerebrovascular surgery ; saphenous vein graft
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary A case of a 48 year old women is reported in whom a haemangiopericytic meningioma involving the middle third of the superior sagittal sinus was radically excised. The sinus was replaced by a saphenous vein graft and the Rolandic veins were reinserted. During clamping of the sinus the patient was heparinized and hypothermia, hypotension and barbiturates were used to prevent swelling of the brain. The postoperative course was uncomplicated and patency of the graft was demonstrated 2 weeks after the operation by Doppler sonography performed through a midline burr hole. The technical details of the operation and the pertinent physiology of cerebral venous flow are discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01403595
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  • 6
    Digitale Medien
    Digitale Medien
    Low frequency flow fluctuations in saccular aneurysms (1986)
    Springer
    Acta neurochirurgica 83 (1986), S. 131-137 
    Details
    ISSN: 0942-0940
    Schlagwort(e): Cerebral aneurysm ; aneurysm growth ; rupture ; turbulence
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Intra-operative Doppler recordings were carried out on cerebral saccular aneurysms in 12 patients. Distinct fluctuations of flow superimposed on the pulse wave were seen in 6 patients. The fluctuations appeared to be periodic with measured period lengths of 60 to 150 msec. In 3 other patients flow irregularities could be discerned acoustically but a definite periodicity could not be visualized on screen. In 3 patients flow appeared smooth during the entire pulse cycle, acoustically as well as visually. Concomitant flow observations in glass model aneurysms also revealed flow instabilities in certain aneurysm types at a Reynold's number of 300. All observed irregularities of flow were observed in zones of deceleration of flow in the models. Signs of fully developed turbulence were not found, neither in human aneurysms nor in the glass models. It appears likely that the fluctuations of flow induce vibrations of the aneurysmal wall and contibute to aneurysm progression and eventual rupture.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01402392
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  • 7
    Digitale Medien
    Digitale Medien
    Growth of aneurysms can be understood as passive yield to blood pressure (1989)
    Springer
    Acta neurochirurgica 100 (1989), S. 74-78 
    Details
    ISSN: 0942-0940
    Schlagwort(e): Cerebral aneurysm ; pathogenesis ; growth ; rupture ; yield stress ; stress relaxation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The strength of aneurysm walls obtained intraoperatively or at autopsy immediately after death was evaluated by measurements of the force response to one-directional stretch and compared to the walls of intracranial arteries. The maximum stress that aneurysm tissue could tolerate was found slightly lower than in arteries, which is most probably due to the amount of immature forms of collagen. The stress resistance of aneurysms and arterial tissue decayed over a period of several hours. The relaxation curve could be approximated by the sum of 2 exponential terms. The half decay times of these terms were found identical in aneurysms and arteries, they appear to be collagen characteristics. The strength measured in vitro was compared to the stress in vivo, which was calculated on the basis of blood pressure and aneurysm radius. The stress tolerated by aneurysm walls over a period of 24 hours was found to be in the range of the stress that is imposed in vivo by the mean blood pressure. Arteries resisted stresses corresponding to pressures 10 to 20 times higher than physiological values. The thickness of the aneurysm walls correlated with the aneurysm radius in a linear fashion. It is suggested that aneurysm growth can be understood as passive yield to blood pressure, and reactive healing and thickening of the wall with increasing aneurysm diameter.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01405279
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  • 8
    Digitale Medien
    Digitale Medien
    Results of microsurgical carotid endarterectomy (1989)
    Springer
    Acta neurochirurgica 100 (1989), S. 31-38 
    Details
    ISSN: 0942-0940
    Schlagwort(e): Carotid endarterectomy ; transcranial Doppler sonography ; EEG monitoring ; cerebral protection
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary 100 consecutive carotid endarterectomies in a total of 93 patients were performed using the operative microscope. Cerebral perfusion and activity were monitored with simultaneous transcranial Doppler (TCD) and EEG. Thiopentone for cerebral protection was given prior to carotid clamping in 11 cases when an insufficient collateral circulation was suspected on the basis of the pre-operative TCD or angiography and if temporary intraluminal shunting was to be avoided because of a high bifurcation, long stenosis or associated carotid artery kinking. A temporary intraluminal shunt was inserted electively if the mean middle cerebral artery flow velocity fell after cross-clamping below 30–40%. Direct closure of the arteriotomy was preferred over a patch graft, which was performed only in cases with concomitant stricture of the arterial wall. No peri-operative strokes occurred in the present series. Two patients died due to medical complications in the post-operative period. During the mean follow-up of 15 months, 1 patient suffered a lethal stroke ipsilateral to the treated carotid artery and another patient had a minor contralateral stroke. Two patients died of unrelated causes during follow-up. Two patients suffered a single reversible neurologic deficit corresponding to the treated carotid territory. Four other patients had a single contralateral hemispheric or retinal reversible ischaemic attack during follow-up.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01405270
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  • 9
    Digitale Medien
    Digitale Medien
    Accuracy of high resolution computed tomography in direct diagnosis of cerebral aneurysms (1987)
    Springer
    Neuroradiology 29 (1987), S. 152-159 
    Details
    ISSN: 1432-1920
    Schlagwort(e): Cerebral aneurysms ; Computed tomography ; Cerebral angiography ; Subarachnoid hemorrhage
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary With high resolution computed tomography (CT) of the skull, performing rapid series of 1.5 mm slices during an intravenous bolus injection of contrast medium, an angiography-like image (angio-CT) of the basal cerebral arteries can be obtained. From 76 consecutive angiographically or autopsy-verified cerebral aneurysms of vaious size down to 3 mm in diameter, 74 (97.4%) were shown up by the angio-CT. One ruptured and one incidental aneurysm escaped CT visualization. Besides the correct localization of the aneurysms, angio-CT provides information concerning the size and main direction of the aneurysms and yields, in addition, a coronal view of the aneurysms and their surrounding structures. Pitfalls for mis-diagnosis can be the following: Aneurysms of below 5 mm in diameter, located at the supraclinoid part of the carotid artery, multiple or non-ruptured aneurysms, bony or movement artefacts, poorly contrasted vessels due to wrong injection technique of contrast medium or vasospasm, and incorrect interpretation.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00327540
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