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See detailHybrid extended equal-area criterion for fast transient stability assessment with detailed power system models
Zhang, Y.; Rousseaux, Patricia ULiege; Wehenkel, Louis ULiege et al

in Proceedings of the IFAC Symposium on Control of Power Plants and Power Systems (1995)

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See detailThe Hybrid Finite Element Mixing Cell Method: A New Flexible Method for Modelling Mine Ground Water Problems
Brouyère, Serge ULiege; Orban, Philippe ULiege; Wildemeersch, Samuel ULiege et al

in Mine Water & the Environment (2009), 28(2), 102-114

Dewatering operations often stop at mine closure. The ground water rebound can have undesirable consequences, which numerical models can help one understand and manage. However, classical modelling ... [more ▼]

Dewatering operations often stop at mine closure. The ground water rebound can have undesirable consequences, which numerical models can help one understand and manage. However, classical modelling techniques are relatively unsuitable to these contexts. While spatially-distributed and physically-based models suffer difficulties due to the lack of data and the complexity of geological and hydrogeological conditions, black-box models are too simple to deal with the problems effectively. A new modelling method is proposed to simulate ground water environments in which water flows through mined (exploited) and unmined (unexploited) areas. Exploited zones are simulated using a group of mixing cells possibly interconnected by pipes. Unexploited zones are simultaneously simulated using classical finite elements. This combined approach allows explicit calculation of ground water flows around the mine and mean water levels in the exploited zones. Water exchanges between exploited zones and unexploited zones are simulated in the model using specifically-defined internal boundary conditions. The method is tested on synthetic cases of increasing complexity, and first results from a real case study are presented. [less ▲]

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See detailThe Hybrid Finite-Element Mixing-Cell method: a candidate for modelling groundwater flow and transport in karst systems
Brouyère, Serge ULiege; Wildemeersch, Samuel ULiege; Orban, Philippe ULiege et al

in Bertrand, C.; Carry, N.; Mudry, J. (Eds.) et al Proc. H2Karst, 9th Conference on Limestone Hydrogeology (2011, September)

Groundwater flow and contaminant transport modelling in karst systems remains a challenge because of the complexity of the geology made of caves, voids, conduits of various sizes and forms and interacting ... [more ▼]

Groundwater flow and contaminant transport modelling in karst systems remains a challenge because of the complexity of the geology made of caves, voids, conduits of various sizes and forms and interacting matrix. Such heterogeneous structures cause complex hydraulic conditions for groundwater flow and transport processes. Despite the progresses in field investigation techniques and experiments, detailed knowledge and characterization of the karst system geometry and connectivity remains inaccessible and pragmatic modelling approaches have to be used. Groundwater models of different complexities have been developed for karst systems, ranging from transfer functions and linear reservoir models to spatially distributed models. Here, a new flexible modelling approach, the Hybrid Finite-Element Mixing-Cell method (HFEMC), has been developed that allows combining in a single model, and in a fully interacting way, different mathematical approaches of various complexities for groundwater modelling in complex environments. This includes linear reservoirs, distributed reservoirs, groundwater flow in variably saturated equivalent porous media, with possibilities to consider by-pass flows along preferential flow paths, internal boundary conditions between the karstic features and the surrounding rock mass matrix background and drainage by surface waters. This method has been implemented in the groundwater flow and solute transport numerical code SUFT3D. The objective of this communication is to present the modelling concepts and to discuss the potentials and advantages of the HFEMC method for modelling groundwater flow in karst systems over existing more classical modelling approaches. The discussion is supported by illustrative “synthetic” examples representative of karst systems and a real modelling application to the case of groundwater rebound and water inrush in a closed underground coal mine which presents a very similar geometrical and hydrological context to a karst, with cavities, drains and interacting rock mass. [less ▲]

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See detailThe Hybrid Finite-Element Mixing-Cell method: a new flexible method for large scale groundwater modelling
Orban, Philippe ULiege; Brouyère, Serge ULiege; Wildemeersch, Samuel ULiege et al

Conference (2008)

Interest of end-users and policy makers for understanding and managing water systems at the regional scale has increased for years. At this scale, groundwater models of different complexity ranging from ... [more ▼]

Interest of end-users and policy makers for understanding and managing water systems at the regional scale has increased for years. At this scale, groundwater models of different complexity ranging from black-box models to physically based distributed models have been used in various hydrogeological conditions. Black-box models, such as transfer functions, have been applied for example to model groundwater in large scale hydrological models, to model karstic systems, in particular for the interpretation of isotopic data. Their concepts are simple and attractive because they require relatively few data. The main drawbacks are however that modelling results are not spatially distributed and their predictive capability is questionable due to the semi-empirical nature of process descriptions. On the contrary, due to a more advanced description of ongoing processes, physically-based distributed models are expected to have better predictive capabilities than black-box models. However, because such models require more data, they are generally applied for case studies that are better characterized from a hydrogeological point of view, for which the distribution of water levels or solute concentrations in the groundwater systems are needed. For large-scale modelling purposes, black-box models and physically-based distributed models have both proved their utilities and have their own justifications, advantages and disadvantages. However, few attempts have been made to combine the advantages of these two categories of approaches in a unified modelling application. A new flexible modelling approach, the Hybrid Finite-Element Mixing-Cell method (HFEMC), has been developed that allows combining in a single model, and in a fully integrated way, different mathematical approaches of various complexities for groundwater modelling in complex and large scale environments. This method has been implemented in the groundwater flow and solute transport numerical code SUFT3D. The approach has been first tested and illustrated using basic and advanced “synthetic” examples that allow validating and discussing its advantages over existing modelling concepts. The HFEMC approach is now applied for the development of a large scale groundwater flow and solute transport model in different groundwater basins in Belgium. [less ▲]

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See detailThe Hybrid Finite-Element Mixing-Cell method: a new flexible method for modelling mine water problems
Brouyère, Serge ULiege; Orban, Philippe ULiege; Wildemeersch, Samuel ULiege et al

in Rapantova, N.; Hrkal, Z. (Eds.) Mine Water and the Environment Proceedings of IWMA 2008 (2008)

Mine closure is often accompanied by a stop in dewatering operations. This generally induces groundwater rebound in the mined rock system with short and long term consequences that may be disastrous: soil ... [more ▼]

Mine closure is often accompanied by a stop in dewatering operations. This generally induces groundwater rebound in the mined rock system with short and long term consequences that may be disastrous: soil instabilities such as landslides and subsidence reactivation, flooding, flooded basement and acid mine drainage. Modelling tools can be very advantageous and efficient in helping understanding and managing such problems, however, classical modelling approaches have proved to be relatively unsuited to such contexts. Because of the former mining operations, the underground geological system is strongly disturbed (excavated, fractured and collapsed zones, galleries, large shafts, etc.). Using complex spatially distributed modelling approaches such as 3D finite elements usually lead to strong difficulties related to the lack of data, the complexity of geological and hydrogeological conditions (complex geometry, non Darcian fluxes…). On the other hand, using a simplified approach such as black-box models often leads to oversimplification of the reality: particularly when interactions between the mined system and its surrounding geological and hydrogeological environment are very important. A new modelling approach is developed for simulation of the groundwater flow in such complex environments. It combines, in a single fully integrated simulator, a representation of the unmined area by a classical finite element modelling technique, together with conceptualisation of the worked areas and galleries by a group of mixing cells connected by pipes. The whole assembled groundwater flow model allows an accurate estimation and representation of (a) water infiltration (precipitations, river losses …) through the unsaturated zone reaching the exploited area (recharge of boxes) and (b) water exchanges with adjacent aquifers. The model can estimate the flow of groundwater in and around the minefield and the mean water level in the boxes. It is also capable of considering water exchanges between different mined zones, through connection pathways such as old roadways galleries and shafts. Modelling concepts and equations are described and illustrated using basic and advances validation examples. A real case application corresponding to an abandoned coalfield in the region of Liège (Belgium) is used to illustrate the suitability and efficiency of the approach. [less ▲]

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See detailHybrid Fire Testing: A new approach for fire labs
Sauca, Ana ULiege; Gernay, Thomas ULiege; Mergny, Elke ULiege et al

Poster (2017, May 02)

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See detailHybrid functional study of prototypical multiferroic bismuth ferrite
Goffinet, Marco ULiege; Hermet, Patrick ULiege; Bilc, Daniel ULiege et al

in Physical Review. B, Condensed Matter and Materials Physics (2009), 79(1),

We report a systematic comparison of various exchange-correlation functionals for the prediction of the structural, magnetic, electronic, and dynamical (phonons and Born effective charge tensors ... [more ▼]

We report a systematic comparison of various exchange-correlation functionals for the prediction of the structural, magnetic, electronic, and dynamical (phonons and Born effective charge tensors) properties of bismuth ferrite, a prototypical multiferroic compound. We have not only considered the usual approximations to density-functional theory such as the local-density approximation (LDA), generalized (GGA), and LDA+U, but also hybrid approaches such as B3LYP and B1. The recent B1-WC hybrid functional of Bilc [Phys. Rev. B 77, 165107 (2008)], with the GGA functional of Wu and Cohen and an exact exchange mixing parameter of 0.16, provides very good overall agreement with experiments and can be considered as a valuable alternative to LDA, GGA, and DFT+U for the study of bismuth ferrite. This does not only allow a reliable interpretation of the physical properties of this specific compound but also opens perspectives for further and more predictive first-principles investigations of multiferroic materials. [less ▲]

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See detailHybrid gamma Doradus-delta Scuti Pulsators: New Insights into the Physics of the Oscillations from Kepler Observations
Grigahcène, Ahmed; Antoci, V.; Balona, L. et al

in Astrophysical Journal (2010), 713

Observations of the pulsations of stars can be used to infer their interior structure and test theoretical models. The main-sequence γ Doradus (Dor) and δ Scuti (Sct) stars with masses 1.2-2.5 M [SUB ... [more ▼]

Observations of the pulsations of stars can be used to infer their interior structure and test theoretical models. The main-sequence γ Doradus (Dor) and δ Scuti (Sct) stars with masses 1.2-2.5 M [SUB]sun[/SUB] are particularly useful for these studies. The γ Dor stars pulsate in high-order g-modes with periods of order 1 day, driven by convective blocking at the base of their envelope convection zone. The δ Sct stars pulsate in low-order g- and p-modes with periods of order 2 hr, driven by the κ mechanism operating in the He II ionization zone. Theory predicts an overlap region in the Hertzsprung-Russell diagram between instability regions, where "hybrid" stars pulsating in both types of modes should exist. The two types of modes with properties governed by different portions of the stellar interior provide complementary model constraints. Among the known γ Dor and δ Sct stars, only four have been confirmed as hybrids. Now, analysis of combined Quarter 0 and Quarter 1 Kepler data for hundreds of variable stars shows that the frequency spectra are so rich that there are practically no pure δ Sct or γ Dor pulsators, i.e., essentially all of the stars show frequencies in both the δ Sct and the γ Dor frequency range. A new observational classification scheme is proposed that takes into account the amplitude as well as the frequency and is applied to categorize 234 stars as δ Sct, γ Dor, δ Sct/γ Dor or γ Dor/δ Sct hybrids. [less ▲]

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See detailA Hybrid Hardware Architecture for High-speed IP Lookups and Fast Route Updates
Luo, Layong; Xie, Gaogang; Xie, Yingke et al

in IEEE/ACM Transactions on Networking (2013)

As network link rates are being pushed beyond 40 Gb/s, IP lookup in high-speed routers is moving to hardware. The ternary content addressable memory (TCAM)-based IP lookup engine and the static random ... [more ▼]

As network link rates are being pushed beyond 40 Gb/s, IP lookup in high-speed routers is moving to hardware. The ternary content addressable memory (TCAM)-based IP lookup engine and the static random access memory (SRAM)-based IP lookup pipeline are the two most common ways to achieve high throughput. However, route updates in both engines degrade lookup performance and may lead to packet drops. Moreover, there is a growing interest in virtual IP routers where more frequent updates happen. Finding solutions that achieve both fast lookup and low update overhead becomes critical. In this paper, we propose a hybrid IP lookup architecture to address this challenge. The architecture is based on an efficient trie partitioning scheme that divides the forwarding information base (FIB) into two prefix sets: a large disjoint leaf prefix set mapped into an external TCAM-based lookup engine and a small overlapping prefix set mapped into an on-chip SRAM-based lookup pipeline. Critical optimizations are developed on both IP lookup engines to reduce the update overhead. We show how to extend the proposed hybrid architecture to support virtual routers. Our implementation shows a throughput of 250 million lookups per second (equivalent to 128 Gb/s with 64-B packets). The update overhead is significantly lower than that of previous work, the memory consumption is reasonable, and the utilization ratio of most external TCAMs is up to 100%. [less ▲]

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See detailA hybrid human-computer approach for large-scale image-based measurements using web services and machine learning
Marée, Raphaël ULiege; Rollus, Loïc ULiege; Stevens, Benjamin ULiege et al

in Proceedings IEEE International Symposium on Biomedical Imaging (2014, May)

We present a novel methodology combining web-based software development practices, machine learning, and spatial databases for computer-aided quantification of regions of interest (ROIs) in large-scale ... [more ▼]

We present a novel methodology combining web-based software development practices, machine learning, and spatial databases for computer-aided quantification of regions of interest (ROIs) in large-scale imaging data. We describe our main methodological choices, and then illustrate the benefits of the approach (workload reduction, improved precision, scalability, and traceability) on hundreds of whole-slide images of biological tissue slices in cancer research. [less ▲]

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See detailHybrid inventory, gravimetry and altimetry (HIGA) mass balance product for Greenland and the Canadian Arctic
Colgan, W.; Abdalati, W.; Citterio, M. et al

in Remote Sensing of Environment (2015), 168

We present a novel inversion algorithm that generates a mass balance field that is simultaneously consistent with independent observations of glacier inventory derived from optical imagery, cryosphere ... [more ▼]

We present a novel inversion algorithm that generates a mass balance field that is simultaneously consistent with independent observations of glacier inventory derived from optical imagery, cryosphere-attributed mass trends derived from satellite gravimetry, and ice surface elevation trends derived from airborne and satellite altimetry. We use this algorithm to assess mass balance across Greenland and the Canadian Arctic over the Sep-2003 to Oct- 2009 period at 26 km resolution. We evaluate local algorithm-inferred mass balance against forty in situ point observations. This evaluation yields an RMSE of 0.15 mWE/a, and highlights a paucity of in situ observations from regions of high dynamic mass loss and peripheral glaciers. We assess mass losses of 212 ± 67 Gt/a to the Greenland ice sheet proper, 38 ± 11 Gt/a to peripheral glaciers in Greenland, and 42 ± 11 Gt/a to glaciers in the Canadian Arctic. These magnitudes of mass loss are dependent on the gravimetry-derived spherical harmonic mass trend we invert. We spatially partition the transient glacier continuity equation by differencing algorithm-inferred mass balance from modeled surface mass balance, in order to solve the horizontal divergence of ice flux as a residual. This residual ice dynamic field infers flux divergence (or submergent flow) in the ice sheet accumu- lation area and at tidewater margins, and flux convergence (or emergent flow) in land-terminating ablation areas, which is consistent with continuum mechanics theory. [less ▲]

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See detailHYBRID INVESTIGATION OF AIR TRANSPORT PROCESSES IN MODERATELY SLOPED STEPPED SPILLWAY FLOWS
Valero Huerta, Daniel ULiege; Bung, Daniel B.

E-print/Working paper (2015)

In stepped spillway flows, a self-aerated flow region is often found where large quantities of air may be entrained into the water body. This air is then mixed with the water phase leading to an air-water ... [more ▼]

In stepped spillway flows, a self-aerated flow region is often found where large quantities of air may be entrained into the water body. This air is then mixed with the water phase leading to an air-water mixture flow with different characteristics than the clear water flow. Thus, air entrainment is an important flow feature which needs to be considered for safe design of these hydraulic structures. Advances in the development of new air-water measurement techniques and numerical modeling capabilities allow addressing these complex problems. Computational Fluid Dynamics (CFD) modeling can be a powerful supplement for physical model tests. In the presented study, the self-aeration process and the subsequent air transport in the aerated flow region of a stepped spillway model is investigated by means of both, new experimental and numerical methods. The slope of the spillway model is 1:2 and different flow rates are considered involving a skimming flow regime. For the physical model tests, a double-tip conductivity probe and ultrasonic sensors are used to evaluate air-water flow properties and flow depths, respectively. Additionally, high-speed camera recordings help to qualitatively analyze the air-water transport. In the numerical model, the same stepped spillway is simulated with identical flow conditions. A RANS approach coupled with RNG k-ε turbulence modeling and a VOF technique for free surface tracking is used. The determination of the inception point and the entrained air quantities are estimated employing a subscale model. To verify the numerical model, results are compared to the laboratory air-water measurements. The comparison of results from both techniques helps to identify their capabilities and limitations. [less ▲]

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See detailA Hybrid IP Lookup Architecture with Fast Updates
Luo, Layong; Xie, Gaogang; Xie, Yingke et al

in Annual International Conference on Computer Communications (2012, March)

As network link rates are being pushed beyond 40 Gbps, IP lookup in high-speed routers is moving to hardware. The TCAM (Ternary Content Addressable Memory)-based IP lookup engine and the SRAM (Static ... [more ▼]

As network link rates are being pushed beyond 40 Gbps, IP lookup in high-speed routers is moving to hardware. The TCAM (Ternary Content Addressable Memory)-based IP lookup engine and the SRAM (Static Random Access Memory)- based IP lookup pipeline are the two most common ways to achieve high throughput. However, route updates in both engines degrade lookup performance and may lead to packet drops. Moreover, there is a growing interest in virtual IP routers where more frequent updates happen. Finding solutions that achieve both fast lookup and low update overhead becomes critical. In this paper, we propose a hybrid IP lookup architecture to address this challenge. The architecture is based on an efficient trie partitioning scheme that divides the Forwarding Information Base (FIB) into two prefix sets: a large disjoint leaf prefix set mapped into an external TCAM-based lookup engine and a small overlapping prefix set mapped into an on-chip SRAM-based lookup pipeline. Critical optimizations are developed on both IP lookup engines to reduce the update overhead. We show how to extend the proposed hybrid architecture to support virtual routers. Our implementation shows a throughput of 250 million lookups per second (MLPS). The update overhead is significantly lower than that of previous work and the utilization ratio of most external TCAMs is up to 100%. [less ▲]

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See detailHybrid lamellar silica: Combined template extraction and hydrophilic silanation
Toussaint, Gilles ULiege; Brisbois, Magali ULiege; Grandjean, Jean ULiege et al

in Journal of Colloid & Interface Science (2009), 329(1), 120-126

The surface modification of lamellar silica prepared by liquid crystal templating has been investigated. Two hydrophilic surface modifier agents, 2-glycidoxypropyltrimethoxysilane and 2-[methoxy ... [more ▼]

The surface modification of lamellar silica prepared by liquid crystal templating has been investigated. Two hydrophilic surface modifier agents, 2-glycidoxypropyltrimethoxysilane and 2-[methoxy(polyethyleneoxy)propyl)] trimethoxysilane, have been tested. Characterizations of the modified silica include thermal analysis, C-13 and Si-29 solid state NMR, transmission electron microscopy (TEM) and X-ray diffraction (XRD). The different characterizations confirmed the preservation of the lamellar morphology and the Successful surface modification with both silanes along with the template elimination. The results also indicate that the structure and length of the silanes influence the final lamellar organization as well as the grafting yields and mechanisms. (C) 2008 Elsevier Inc. All rights reserved. [less ▲]

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See detailHybrid Lens for Solar Concentration: Optimization of the Multilayer Diffractive Lens
Languy, Fabian ULiege; Habraken, Serge ULiege

Poster (2012)

Manufacture process degrades the ideal shape of multilayer diffractive lens due to draft angle, half radius tool and slope error. We show some shape improvements using an extended scalar theory.

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See detailHybrid magnetic equivalent circuit - finite element modelling of transformer fed electrical machines
Gyselinck, Johan; Dular, Patrick ULiege; Legros, Willy ULiege et al

in Compel-the International Journal for Computation and Mathematics in Electrical and Electronic Engineering (2003), 22(3), 643-658

This paper deals with the modelling of transformer supply in the two-dimensional (2D) finite element (FE) simulation of rotating electrical machines. Three different transformer models are compared The ... [more ▼]

This paper deals with the modelling of transformer supply in the two-dimensional (2D) finite element (FE) simulation of rotating electrical machines. Three different transformer models are compared The reference one is based on two 2D FE models, considering a cross-section either parallel or perpendicular to the laminations of the magnetic core. The parameters of the two other transformer models, a magnetic equivalent circuit and an electrical equivalent circuit, can be derived from the reference model Particular attention is paid to some common features of the transformer models, e.g. with regard to the inclusion of iron losses. The three models are used in the 2D FE simulation of the steady-state load operation and the starting from stand-still of an induction motor. [less ▲]

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See detailHybrid material for electromagnetic absorption
Detrembleur, Christophe ULiege; Molenberg, Isabel; Huynen, Isabelle et al

Patent (2012)

The present invention relates to a hybrid material (10) for absorbing electromagnetic radiation (60) and a method for making such a material. The hybrid material (10) comprises at least one grid panel (20 ... [more ▼]

The present invention relates to a hybrid material (10) for absorbing electromagnetic radiation (60) and a method for making such a material. The hybrid material (10) comprises at least one grid panel (20) of thickness t 1 having holes (25) traversing said thickness t 1 , at least one polymer composite material (30) of thickness t 2 filling at least partially the holes (25) of the at least one grid panel (20), said at least one polymer composite material (30) including a polymer matrix (40) and conductive particles (50) dispersed into said polymer matrix (40), characterized in that the internal surface of the holes (25) of the at least one grid panel (20) is metallic. [less ▲]

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See detailHybrid material for electromagnetic absorption
Detrembleur, Christophe ULiege; Huynen, Isabelle; Thomassin, Jean-Michel ULiege et al

Patent (2012)

The present invention relates to a hybrid material (10) for absorbing electromagnetic radiation (60) and a method for making such a material. The hybrid material (10) comprises at least one grid panel (20 ... [more ▼]

The present invention relates to a hybrid material (10) for absorbing electromagnetic radiation (60) and a method for making such a material. The hybrid material (10) comprises at least one grid panel (20) of thickness t 1 having holes (25) traversing said thickness t 1 , at least one polymer composite material (30) of thickness t 2 filling at least partially the holes (25) of the at least one grid panel (20), said at least one polymer composite material (30) including a polymer matrix (40) and conductive particles (50) dispersed into said polymer matrix (40), characterized in that the internal surface of the holes (25) of the at least one grid panel (20) is metallic. [less ▲]

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See detailHybrid MicroPET Imaging for Dosimetric Applications in Mice: Improvement of Activity Quantification in Dynamic MicroPET Imaging for Accelerated Dosimetry Applied to 6-[ 18 F] Fluoro- L -DOPA and 2-[ 18 F]Fluoro- L -Tyrosine
Bretin, Florian ULiege; Mauxion, T; Warnock, G et al

in Molecular Imaging and Biology (2014), 16(3), 383-394

Purpose: Dynamic microPET imaging has advantages over traditional organ harvesting, but is pronetoquantificationerrorsinsmallvolumes.Hybridimaging,wheremicroPETactivitiesarecross- calibrated using post ... [more ▼]

Purpose: Dynamic microPET imaging has advantages over traditional organ harvesting, but is pronetoquantificationerrorsinsmallvolumes.Hybridimaging,wheremicroPETactivitiesarecross- calibrated using post scan harvested organs, can improve quantification. Organ harvesting, dynamic imaging and hybrid imaging were applied to determine the human and mouse radiation dosimetry of 6-[18 F]fluoro-L-DOPA and 2-[18 F]fluoro-L-tyrosine and compared. Procedures: Two-hour dynamic microPET imaging was performed with both tracers in four separate mice for 18 F-FDOPA and three mice for 18 F-FTYR. Organ harvesting was performed at 2, 5, 10, 30, 60 and 120 min post tracer injection with n=5 at each time point for 18 F-FDOPA and n=3 at each time point for 18 F-FTYR. Human radiation dosimetry projected from animal data was calculated for the three different approaches for each tracer using OLINDA/EXM. S- factors for the MOBY phantom were used to calculate the animal dosimetry. Results: Correlations between dose estimates based on organ harvesting and imaging was improved from r=0.997 to r=0.999 for 18 F-FDOPA and from r=0.985 to r=0.996 (p<0.0001 for all) for 18 F-FTYR by using hybrid imaging. Conclusion: Hybrid imaging yields comparable results to traditional organ harvesting while partially overcoming the limitations of pure imaging. It is an advantageous technique in terms of number of animals needed and labour involved. [less ▲]

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