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A Grid Architecture for Medical Applications. Anca Bucur, Rene Kootstra Philips Research Eindhoven. Robert Belleman University of Amsterdam. The GAMA Research Goals.
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A Grid Architecture for Medical Applications Anca Bucur, Rene Kootstra Philips Research Eindhoven Robert Belleman University of Amsterdam
The GAMA Research Goals • Design an adaptive architecture that would enable several relevant compute-intensive medical applications to use Grid technologies, for • improved performance • cost-effective access to large numbers of various resources (computational, data, information, special instruments, etc.) • Study the common and differentiating characteristics of the applications to which this architecture applies, in order to identify classes of healthcare applications fitting the architecture
Our Approach • Investigated relevant computationally challenging medical applications suited for parallelization through decomposition • Identified patterns of compute-intensive applications, based on their decomposition paradigm • Designed an adaptive architecture for solving compute-intensive medical applications (fitting at least one of the patterns) using Grid technology • Chose several medical applications fitting these patterns for which to develop Grid-enabled prototypes complying to the defined architecture
A B A B C D C D The Application Patterns Three patterns of compute-intensive applications Domain decomposition Computational decomposition Functional decomposition
The GAMA Architecture (I) • Targets computationally challenging applications • Suitable for applications with a large degree of spatial and time locality • Adaptive to applications fitting the decomposition patterns • Simultaneously provides different sets of services to multiple users and applications • Uses Grid resources for improved performance • Minimally invasive: Running on Grid as an alternative, easy fall back to local versions
Client Gateway LAN LAN DutchGrid Resources WindowsIDL, Pride LinuxGlobus The GAMA architecture (III) • Windows-based interface in the hospital, the compute-intensive part is placed in the Unix-based Grid environment • Uses Grid resources and technology (e.g. Globus) • Client-server architecture, single interface solution between client(s) and server • One access point (GAP), sends requests from client(s) to server and returns results
The GAMA Case-Study Functional Brain Imaging and White Matter Fiber Tractography • Uses Diffusion Weighted MRI • Fibers visualize anisotropic diffusion of water molecules in brain: • White matter tracts, areas active for different tasks • Connecting pathways between brain structures • ROIs used to select areas of interest • Clinical relevance: surgical planning, stroke detection, psychiatry
The Fiber Tracking Application (I) • Performance gain from distributing the computational part over Grid resources, computational decomposition • Runtime may depend on: the number of starting points, the algorithm, the size of the data set, the number of ROIs • Quick Fiber Tracking: Starting points in the ROIs • Full Volume Fiber Tracking: • Starting points evenly distributed in the entire domain • Detects splitting and crossing fibers, large number of fibers • May result in a clogged image • High computational needs
The Fiber Tracking Application (II) • FVFT amounts to over 10 hours for small voxels • Too few starting points - missing relevant fibers • Too many starting points - crowded image Solution: • Improved throughput: parallelization • Improved accuracy : careful selection of the ROIs. Grid solution: FVFT with good throughput and good accuracy
The DAS-2 System Experiments performed on: • DAS-2 (Distributed ASCI Supercomputer), a wide-area distributed cluster system designed by the Advanced School for Computing and Imaging (ASCI). • The DAS-2 is used for research on parallel and distributed computing. • Five clusters, located at five universities. One with 72 nodes, the other four with 32 nodes • 200 nodes with 400 CPUs in total. The system was built by IBM.
Scalability Results (I) • Tracking long fibers takes much longer, fibers are grouped in bundles • Round Robin distribution, slices of width equal to voxel size • For FVFT the number of ROIs has little influence on performance 1ROI: NGFT 448.69s (Tw = 20ms) Tc32=2.1s, Tc16=1.9, Tc8=1.2s, Tc4=0.9s 4 ROI: NGFT 461.34s • Experiments for large step of tracking fibers • Improved throughput
Scalability Results (II) (almost) linear speed-up, improved performance for up 32 processors • Figures compare two interpolation steps • Limit the speed-up (large influence): • The interpolation algorithm • The execution time for tracking the longest fiber, the communication time • The distribution of starting points • Implement a workpool-based solution
Future Work • Identify other relevant medical applications fitting the decomposition patterns • Apply the GAMA architecture to applications fitting domain and functional decomposition • Investigate other medical applications with different decomposition characteristics