Interventionelle Behandlungsoptionen bei vaskulären Malformationen

2019 ◽  
Vol 144 (24) ◽  
pp. 1675-1680
Author(s):  
René Müller-Wille ◽  
Moritz Wildgruber ◽  
Walter A. Wohlgemuth
Keyword(s):  
Interventionelle Therapie ◽  
Slow Flow ◽  
Chirurgische Resektion ◽  
Interventionelle Verfahren ◽  
Fast Flow ◽  
Vaskuläre Malformationen

Was ist neu? Klassifikation von vaskulären Malformationen Während Hämangiome zu den vaskulären Tumoren zählen, sind vaskuläre Malformationen angeboren und bilden sich von selbst nicht zurück. Sie werden nach der ISSVA-Klassifikation unterschieden. Indikation zur Therapie Ziele der Therapie von Gefäßmalformationen sind die Linderung der Symptome, der Organerhalt und die Verhinderung von Krankheitsprogress und Komplikationen. Nichtinvasive Therapieoptionen Die Kompressionstherapie sowie physiotherapeutische Maßnahmen zählen zu den wichtigsten konservativen Therapieoptionen. Invasive Therapieoptionen Die chirurgische Resektion, die oberflächliche Lasertherapie und die interventionelle Therapie stellen die invasiven Therapieoptionen dar. Für die Behandlung symptomatischer Gefäßmalformationen stehen mittlerweile zahlreiche minimalinvasive interventionelle Verfahren zur Verfügung. Slow-Flow-Malformationen können relativ komplikationsarm mittels perkutaner Sklerotherapie behandelt werden, die zu einem zeitversetzten entzündlichen Verschluss der Läsion führt. Dysplastische Venen wie die Marginalvene können mittels endoluminaler Verfahren erfolgreich verödet werden. Die zumeist Katheter-gesteuerten Embolisationsverfahren mittels Flüssigembolisaten, Plugs und Coils erlauben den Verschluss von Fast-Flow-Gefäßmalformationen.

scholarly journals Peripheral Vascular Anomalies – Essentials in Periinterventional Imaging

2019 ◽  
Vol 192 (02) ◽  
pp. 150-162 ◽  
Author(s):  
Maliha Sadick ◽  
Daniel Overhoff ◽  
Bettina Baessler ◽  
Naema von Spangenberg ◽  
Lena Krebs ◽  
...  
Keyword(s):  
Therapeutic Approach ◽  
Vascular Malformations ◽  
Vascular Anomaly ◽  
Flow Dynamics ◽  
Vascular Anomalies ◽  
Vascular Tumors ◽  
Slow Flow ◽  
Peripheral Vascular ◽  
Fast Flow ◽  
Selection Of

Background Peripheral vascular anomalies represent a rare disease with an underlying congenital mesenchymal and angiogenetic disorder. Vascular anomalies are subdivided into vascular tumors and vascular malformations. Both entities include characteristic features and flow dynamics. Symptoms can occur in infancy and adulthood. Vascular anomalies may be accompanied by characteristic clinical findings which facilitate disease classification. The role of periinterventional imaging is to confirm the clinically suspected diagnosis, taking into account the extent and location of the vascular anomaly for the purpose of treatment planning. Method In accordance with the International Society for the Study of Vascular Anomalies (ISSVA), vascular anomalies are mainly categorized as slow-flow and fast-flow lesions. Based on the diagnosis and flow dynamics of the vascular anomaly, the recommended periinterventional imaging is described, ranging from ultrasonography and plain radiography to dedicated ultrafast CT and MRI protocols, percutaneous phlebography and transcatheter angiography. Each vascular anomaly requires dedicated imaging. Differentiation between slow-flow and fast-flow vascular anomalies facilitates selection of the appropriate imaging modality or a combination of diagnostic tools. Results Slow-flow congenital vascular anomalies mainly include venous and lymphatic or combined malformations. Ultrasound and MRI and especially MR-venography are essential for periinterventional imaging. Arteriovenous malformations are fast-flow vascular anomalies. They should be imaged with dedicated MR protocols, especially when extensive. CT with 4D perfusion imaging as well as time-resolved 3D MR-A allow multiplanar perfusion-based assessment of the multiple arterial inflow and venous drainage vessels of arterio-venous malformations. These imaging tools should be subject to intervention planning, as they can reduce procedure time significantly. Fast-flow vascular tumors like hemangiomas should be worked up with ultrasound, including color-coded duplex sonography, MRI and transcatheter angiography in case of a therapeutic approach. In combined malformation syndromes, radiological imaging has to be adapted according to the dominant underlying vessels and their flow dynamics. Conclusion Guide to evaluation of flow dynamics in peripheral vascular anomalies, involving vascular malformations and vascular tumors with the intention to facilitate selection of periinterventional imaging modalities and diagnostic and therapeutic approach to vascular anomalies. Key Points:  Citation Format

scholarly journals Comparison of Quantitative Autoradiographic and Xenon-133 Clearance Methods: Correlation of Gray and White Matter Cerebral Blood Flow with Compartmental Blood Flow Indices

1986 ◽  
Vol 6 (4) ◽  
pp. 481-485 ◽  
Author(s):  
U. I. Tuor ◽  
W. Fitch ◽  
D. I. Graham ◽  
A. D. Mendelow
Keyword(s):  
Blood Flow ◽  
White Matter ◽  
Gray Matter ◽  
Slow Flow ◽  
Stable Measure ◽  
Flow Component ◽  
Primate Brain ◽  
Xenon 133 ◽  
Fast Flow ◽  
Clearance Methods

The relationships between CBF in gray and white matter to those of the fast and slow components of xenon-133 clearance curves remain uncertain. CBF was measured in 13 anaesthetized baboons under a variety of conditions, using both the xenon-133 clearance technique and [14C]iodoantipyrine quantitative autoradiography. There was a linear relationship between CBF, as determined by the stochastic (height/area) analysis of the clearance curve, and mean CBF determined from the autoradiograms ( r = 0.94, p < 0.001, slope = 0.86 ± 0.09). There was also a linear correlation between the fast-flow component (measured with xenon-133) and blood flow in the cerebral gray matter (measured with [14C]iodoantipyrine) ( r = 0.92, p < 0.001, slope = 0.69 ± 0.15) and between the slow-flow component (with xenon-133) and blood flow in white matter (with [14C]iodoantipyrine) ( r = 0.79, p < 0.01, slope = 0.81 ± 0.10). In the primate brain, the fast- and slow-flow indices therefore appear to be representative of CBF in gray matter and white matter, respectively, whereas the stochastic analysis provides a stable measure of mean CBF within the tissue monitored.

scholarly journals Effects of passive storage on modelling hydrological function and isotope dynamics in a karst flow system in southwest China

2021 ◽  
Author(s):  
Guangxuan Li ◽  
Xi Chen ◽  
Zhicai Zhang ◽  
Lichun Wang ◽  
Chris Soulsby
Keyword(s):  
Southwest China ◽  
Flow System ◽  
Hydrodynamic Dispersion ◽  
Slow Flow ◽  
Model Structure ◽  
Tracer Transport ◽  
Coupled Flow ◽  
Heterogeneous Aquifers ◽  
Improved Model ◽  
Fast Flow

Abstract. Representing passive storage in coupled flow-isotope models can facilitate simulation of mixing and retardation effects on tracer transport in many natural systems, such as catchments or rivers. However, the effectiveness of incorporating passive storages in models of complex karst flow systems remains poorly understood. In this study, we developed a coupled flow-isotope model that conceptually represents both “fast” and “slow” flow processes in heterogeneous aquifers to represent hydrological connections between hillslopes and low-lying depression units in cockpit karst landscapes. As this model originally included a varying number of passive storages at different positions of the flow system (e.g. fast/slow flow reservoirs combined with different hillslope/depression units), the model structure and relevant parameters were optimized using a multi-objective optimization algorithm. This was used to match detailed observational data of hydrological processes and isotope concentration in the Chenqi catchment in southwest China. Results show that the optimal structure for a coupled flow-isotope model incorporated only two passive storages in fast flow and slow flow paths of the hillslope unit. Using fewer or greater numbers of passive stores in the model could lead to under- or over-mixing of isotope signatures. This optimized model structure could effectively improve simulation accuracies for outlet discharge and isotope signatures, with > 0.65 of the modified Kling-Gupta efficiency. Additionally, the optimal tracer-aided model yields reasonable parameter values and estimations of hydrological components (e.g. more than 80 % of fast flow in the total discharge). Furthermore, results imply that the solute transport is primarily controlled by advection and hydrodynamic dispersion in steep hillslope unit, which is a remarkable phenomenon in the karst flow system. The study resulted in new insights, more realistic catchment conceptualizations and improved model formulation.

Estimation of baseflow recession constants and effective hydraulic parameters in the karst basins of southwest China

2012 ◽  
Vol 43 (1-2) ◽  
pp. 102-112 ◽  
Author(s):  
Xi Chen ◽  
Yan-fang Zhang ◽  
Xianwu Xue ◽  
Zhicai Zhang ◽  
Lingna Wei
Keyword(s):  
Southwest China ◽  
Low Permeability ◽  
Hydraulic Parameters ◽  
Slow Flow ◽  
Drought Period ◽  
Near Surface ◽  
Aquifer Characteristics ◽  
Break Points ◽  
Fast Flow ◽  
Basin Area

By analysing the hydrographs of karst basin outflow, it is possible to identify aquifer characteristics and, accordingly, the main features of a karst basin. In this study, 19 basins with daily observed flow discharges during drought periods between October and April 1973–1983 were selected to analyse the master recession curve (MRC). During a drought period, the MRCs were separated into segments of fast flow exponential recession and slow flow exponential recession. Break points of the fast and slow recession segments were identified and the recession constants α were determined. Relationships between α and basin area were identified. According to the estimated baseflow recession constants, hydraulic parameters including aquifer thickness and hydraulic conductivity were estimated. Hydraulic conductivities in the near-surface epikarst aquifer are of the order 10−3 m s−1, much larger than 10−5 m s−1 in the low-permeability aquifer.

Turbulent axially directed flow of plasma containing rt-PA promotes thrombolysis of non-occlusive whole blood clots in vitro

2004 ◽  
Vol 91 (03) ◽  
pp. 487-496 ◽  
Author(s):  
Gregor Tratar ◽  
Mitja Štrukelj ◽  
Urša Mikac ◽  
Igor Serša ◽  
Aleš Blinc
Keyword(s):  
Whole Blood ◽  
Spin Echo ◽  
Slow Flow ◽  
Directed Flow ◽  
Specific Lysis ◽  
Magnetic Resonance Contrast ◽  
Blood Clots ◽  
Dynamical Spin ◽  
Fast Flow

SummaryThe rate of thrombolysis markedly decreases after a thrombosed vessel is partly recanalized and the remaining clot poses serious risk for rethrombosis. We studied in vitro how thrombolysis depends on penetration of plasma containing thrombolytic agents – 0.2 μg/ml rt-PA or 250 IU/ml streptokinase (SK) nd the magnetic resonance contrast agent Gd-DTPA (at 1 mmol/l) into non-occlusive clots under conditions of fast (turbulent) or slow (laminar) axially directed flow. Cylindrical non-retracted (fresh) or retracted (aged) whole blood clots were pierced lengthways and connected to a perfusion system. Dynamical spin-echo MRI was used for measuring the penetration of labeled plasma into clots and for assessing the remaining clot size. In both types of clots fast flow enhanced the penetration of Gd-DTPA-labeled plasma into clots in comparison to slow flow. In non-retracted clots, lysis with rt-PA and to a lesser extent also lysis with SK followed the path of plasma penetration into clots. After 40 minutes of fast axially directed flow rt-PA resulted in almost complete lysis and SK left only about a third of the clot undissolved, whereas with slow flow lysis was much slower (undissolved clot: 86 ± 5 % with rt-PA and 95 ± 1 % with SK). In retracted clots, substantial lysis was possible only with rt-PA and rapid flow (53 ± 28% of the clot undissolved after 60 min), whereas the use of SK or slow flow precluded meaningful lysis. We conclude that rapid (turbulent) axially directed flow of plasma along non-occlusive blood clots causes forceful exchange of serum inside the clot with outer plasma which enhances both fibrin-specific and non-fibrin-specific lysis of fresh clots. Dissolution of non-occlusive retracted (aged) clots occurs only under fibrin-specific conditions combined with adequate transport of rt-PA into clots.

Anion and cation leaching through large undisturbed soil cores under different flow regimes. 1. Experimental results

Soil Research ◽  
1999 ◽  
Vol 37 (4) ◽  
pp. 711 ◽  
Author(s):  
L. K. Heng ◽  
R. W. Tillman ◽  
R. E. White
Keyword(s):  
Unsaturated Flow ◽  
Water Flux ◽  
Flow Regimes ◽  
Breakthrough Curves ◽  
Slow Flow ◽  
Exchange Reactions ◽  
Flow Core ◽  
Sodic Soils ◽  
Undisturbed Soil ◽  
Fast Flow

The movement of anions and cations under different unsaturated flow regimes was studied in 2 large undisturbed cores from a soil under pasture. Sequential leaching of calcium sulfate (CaSO4) and potassium bromide (KBr) solutions was carried out at water fluxes which ranged from a normal 5–20 mm/h rate in one core (the slow flow core), to unusually high values up to 350 mm/h in the other (the fast flow core). The objective was to examine the leaching behaviour of the applied cations and anions under these contrasting flow conditions, and determine the relative influence of soil physical and chemical processes in governing ion movement. A better understanding of this behaviour should help in the development of improved practices to reclaim saline soils, ameliorate sodic soils, and minimise unwanted leaching of nutrients. In the slow flow core, miscible displacement breakthrough curves (BTCs) were observed for bromide, with sulfate movement retarded relative to the bromide. Cation exchange reactions occurred in the slow flow core, with calcium generally the dominant cation balancing anions during their movement through the soil. When KBr solution was substituted for CaSO4, potassium ions replaced calcium ions on the exchange sites, resulting in an increase in the calcium concentration in the effluent. In the fast flow core, however, flow was highly preferential and the water flux very variable. The surface-applied solutes appeared very rapidly in the effluent, irrespective of whether they were cations or anions. Under these conditions, solution cation/anion interactions with the soil surfaces did not appear to approach equilibrium, so that the leaching process was dominated by the soil’s water flow characteristics and showed little influence of surface chemical reactions.

scholarly journals Storage dynamics, hydrological connectivity and flux ages in a karst catchment: conceptual modelling using stable isotopes

2018 ◽  
Author(s):  
Zhicai Zhang ◽  
Xi Chen ◽  
Chris Soulsby ◽  
Qinbo Cheng
Keyword(s):  
Stream Flow ◽  
Heavy Rain ◽  
High Temporal Resolution ◽  
Hydrological Connectivity ◽  
Slow Flow ◽  
Water Age ◽  
Catchment Scale ◽  
Karst Terrain ◽  
Landscape Unit ◽  
Fast Flow

Abstract. We integrated unique high temporal resolution hydrometric and isotope data to calibrate a catchment-scale conceptual flow-tracer model representing the two main landscape units of hillslopes, and depressions (with fast and slow flow systems) for cock-pit karst terrain. The model could track hourly water and isotope fluxes through each landscape unit, and we could estimate the associated storage and water age dynamics. This inferred that the fast flow reservoir in the depression had the smallest storage, the hillslope unit was intermediate, and the slow flow reservoir had the largest. The estimated mean ages of the hillslope unit, fast and slow flow reservoirs were 137, 326 and 493 days, respectively. Marked seasonal variability in hydroclimate conditions and associated water storage dynamics were the main drivers of non-stationary hydrological connectivity between the hillslope and depression. Meanwhile, the hydrological connectivity between the slow and fast slow reservoirs had reversible directionality, which was determined by the hydraulic head within each medium. Sinkholes can make an important hydrological connectivity between surface water and underground stream flow in the fast reservoir after heavy rain. New water recharges the underground stream via sinkholes, introducing younger water in the underground stream flow.

scholarly journals Storage dynamics, hydrological connectivity and flux ages in a karst catchment: conceptual modelling using stable isotopes

2019 ◽  
Vol 23 (1) ◽  
pp. 51-71 ◽  
Author(s):  
Zhicai Zhang ◽  
Xi Chen ◽  
Qinbo Cheng ◽  
Chris Soulsby
Keyword(s):  
Model Uncertainty ◽  
Flow System ◽  
Water Storage ◽  
Western China ◽  
Low Flow ◽  
High Temporal Resolution ◽  
Model Parameters ◽  
Hydrological Connectivity ◽  
Slow Flow ◽  
Fast Flow

Abstract. We developed a new tracer-aided hydrological model that disaggregates cockpit karst terrain into the two dominant landscape units of hillslopes and depressions (with fast and slow flow systems). The new model was calibrated by using high temporal resolution hydrometric and isotope data in the outflow of Chenqi catchment in Guizhou Province of south-western China. The model could track hourly water and isotope fluxes through each landscape unit and estimate the associated storage and water age dynamics. From the model results we inferred that the fast flow reservoir in the depression had the smallest water storage and the slow flow reservoir the largest, with the hillslope intermediate. The estimated mean ages of water draining the hillslope unit, and the fast and slow flow reservoirs during the study period, were 137, 326 and 493 days, respectively. Distinct seasonal variability in hydroclimatic conditions and associated water storage dynamics (captured by the model) were the main drivers of non-stationary hydrological connectivity between the hillslope and depression. During the dry season, slow flow in the depression contributes the largest proportion (78.4 %) of flow to the underground stream draining the catchment, resulting in weak hydrological connectivity between the hillslope and depression. During the wet period, with the resulting rapid increase in storage, the hillslope unit contributes the largest proportion (57.5 %) of flow to the underground stream due to the strong hydrological connectivity between the hillslope and depression. Meanwhile, the tracer-aided model can be used to identify the sources of uncertainty in the model results. Our analysis showed that the model uncertainty of the hydrological variables in the different units relies on their connectivity with the outlet when the calibration target uses only the outlet information. The model uncertainty was much lower for the “newer” water from the fast flow system in the depression and flow from the hillslope unit during the wet season and higher for “older” water from the slow flow system in the depression. This suggests that to constrain model parameters further, increased high-resolution hydrometric and tracer data on the internal dynamics of systems (e.g. groundwater responses during low flow periods) could be used in calibration.

scholarly journals Vascular Anomalies (Part II): Interventional Therapy of Peripheral Vascular Malformations

2018 ◽  
Vol 190 (10) ◽  
pp. 927-937 ◽  
Author(s):  
René Müller-Wille ◽  
Moritz Wildgruber ◽  
Maliha Sadick ◽  
Walter Wohlgemuth
Keyword(s):  
Vascular Malformations ◽  
Treatment Strategies ◽  
Interventional Therapy ◽  
Vascular Anomalies ◽  
Vascular Tumors ◽  
Interventional Treatment ◽  
Slow Flow ◽  
Peripheral Vascular ◽  
Percutaneous Sclerotherapy ◽  
Fast Flow

Background The International Society for the Study of Vascular Anomalies (ISSVA) categorizes vascular anomalies into vascular tumors and vascular malformations. Vascular malformations are further divided into slow-flow (venous, lymphatic, and capillary malformation) and fast-flow malformations (arteriovenous malformation and arteriovenous fistula). This interdisciplinary classification has therapeutic implications. Methods The objective of this article is to provide concise information about the current terminology and treatment strategies of peripheral vascular malformations, based on the currently available literature, with a focus on interventional therapy of venous malformations (VM), lymphatic malformations (LM), arteriovenous malformations (AVM) and arteriovenous fistulae (AVF). Results and Conclusion Accurate classification is crucial for appropriate therapy of peripheral vascular malformations. Modern imaging technologies and refined interventional treatment strategies are now central parts in the multidisciplinary management of these patients. Slow-flow and fast-flow vascular malformations can be treated successfully by percutaneous sclerotherapy and endovascular embolotherapy as first-line interventions. Key points:  Citation Format

Stellar Evolution

1962 ◽  
Vol 11 (02) ◽  
pp. 137-143
Author(s):  
M. Schwarzschild
Keyword(s):  
Solar System ◽  
Stellar Evolution ◽  
Space Craft ◽  
New Techniques ◽  
Substantial Body ◽  
Individual Stars ◽  
The Past ◽  
Evolution Of Galaxies ◽  
History Of ◽  
Fast Flow

It is perhaps one of the most important characteristics of the past decade in astronomy that the evolution of some major classes of astronomical objects has become accessible to detailed research. The theory of the evolution of individual stars has developed into a substantial body of quantitative investigations. The evolution of galaxies, particularly of our own, has clearly become a subject for serious research. Even the history of the solar system, this close-by intriguing puzzle, may soon make the transition from being a subject of speculation to being a subject of detailed study in view of the fast flow of new data obtained with new techniques, including space-craft.

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