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FMT-XCT Workpackage 2 Project advancement

FMT-XCT Workpackage 2 Project advancement. Holger Br ue nner Marek Karolczak. Marco Brambilla Véronique Rebuffel. Outline. Work-package 2 objectives and tasks X-ray CT system design (task 2.1) Dual-energy XCT system development (task 2.2) XCT prototype development On-bench CT at LETI

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FMT-XCT Workpackage 2 Project advancement

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  1. FMT-XCT Workpackage 2 Project advancement Holger BruennerMarek Karolczak Marco Brambilla Véronique Rebuffel

  2. Outline • Work-package 2 objectives and tasks • X-ray CT system design (task 2.1) • Dual-energy XCT system development (task 2.2) • XCT prototype development • On-bench CT at LETI • Dual energy protocol definition and optimization • Work-package advancement • Revised planning

  3. WP 2 objectives Hybrid imaging system for small animal XCT FMT XCT module should: provide adequate accommodation of the optical components, eliminate X-ray interference with optical components, offer improved contrast between organs as is important for optimal use of XCT information as priors in the FMT inversion procedure (WP4). PARTNERS: CEA-LETI (No.2, lead) CEA-LIME (No.2) VAMP (No.7) FIHGM (No.5) + UZH (No.6) + HMGU (No.1) Enhanced contrast XCT strategies: Dual-energy XCT Use of X-ray contrast agents

  4. D D D D D M M M Year 1 Year 2 WP 2 tasks, deliverables & milestones 7 Deliverables: • D2.1 / due month 1: XCT design • D2.2 / due month 15: Dual energy prototype • D2.3 / due month 15: Dual energy processing software • …D2.4 to 2.7: due month 18, 21, 24 Significant milestone (n°5) : selection of an appropriate XCT technology for FMT-XCT system (by the executive committee) -> Month 18: preliminary recommendation / Month 24: official decision

  5. Task 2.1: XCT system design (1/2) Report “WP2: XCT design”, november 2008, issued by CEA-LETI and VAMP, approved by HMGU, distributed to the Consortium. Remark: this report fulfils most of the objectives of the task 2.7 « optimal XCT design », this was decided because of the (long) delivery time of the system key components. Geometrical configuration Appropriate X-ray tube and detector Mechanics Safety and normative requirements Electrical design

  6. Task 2.1: XCT system design (2/2) Oxford instruments UltraBright 80 Watts power, 20-90kV, down to 13µm focal spot size Non-continuous rotation mode. 1200 acquisitions in 4mn per energy scan. Expected resolution 0.1 mm 400 mm Detector: Hamamatsu C7943 (CsI scintil. + CMOS photo. array), 100μm pixel size, 1248x1248 pixels, 7 frames per second

  7. Task 2.2: XCT prototype development Under development at VAMP. First parts have been constructed and others ordered (parts in stock can be used). Status of detector: up to now, VAMP have not yet received positive feedback from Hamamatsu approving our specifications to the chosen detector

  8. Task 2.2: On-bench CT at LETI Versatile tool, in order to help Dual Energy development and validation. Vertical tomographic axis

  9. Radiography • Measure of x-rays attenuation • μ = μ(E, material) • Contrast depends on: • object composition • incident beam spectrum • transversed length of each material • Tomography • volume reconstruction by means of filtered backprojection algorithm • GL → μ(E, material) • Contrast depends only on object materials source i0 object i detector Dual-energy imaging / Theory (1/4) X-Rays imaging principle μ → l Ideal Model (linear detector, no scatter…)

  10. E1 E2 Dual-energy imaging / Theory (2/4) X-Rays dual energy principle μ = μ(E, material) Image the same object with x-rays of different energies (2 or >) Obtain quantitative information on chemical composition of the object Contrast enhancement

  11. Dual-energy imaging / Theory (3/4) X-Rays dual energy principle Project (a1, ..., an) measurement into (l1, l2) representation • (l1, l2) basis functions: • in principle: any • in pratice, often: • attenuation spectra of two base materials • projected values: base materials equivalent lengths • Single material images or combined • “closer” basis: • contrast enhancement • noise amplification • Many applications in NDT, security and medicine

  12. bone LE (75kV) Soft tissue Dual-energy imaging / Theory (4/4) An example: bone/soft tissue separation

  13. Dual-energy protocol for FMT-XCT (1/5) Biological tissues analysis • The absorption curves are all enclosed between those of cortical bone and adipose tissue. • Plexiglass is almost superimposed to adipose tissue. • All the other soft tissues are indeed indistinguishable from water • Breast tissue is the only one which differs from water (probably due to high adipose tissue content) • May adipose tissue act as a contrast agent ? ICRU-44 data of human tissue (hopefully not too different from mouse’s ones) Possible base materials: water and plexiglas.

  14. Dual-energy protocol for FMT-XCT (2/5) Energy couple determination • Multiparametric problem • x-rays generator kV and mA • x-rays filters: material and thickness • duration of irradiation for LE and HE acquisitions • By means of a simulation software: • simulated all the dual energy chain trying different combinations of the parameters • find the combination with best figure of merit • Find a figure of merit to optimize equivalent length contrast • Tried different FOMs and different levels of simulation accuracy • Only very realistic simulations give affordable results • Validate results with phantom and animal study

  15. Dual-energy protocol for FMT-XCT (3/5) Energy couple determination • RESULTS • Best contrast configuration: • LE: • Generator: 40kV-6mA • Filter: 60um Sn • 2.4 mAs • HE: • Generator: 70kV-2mA • Filter: 100um Pb • 0.8 mAs • Angles: • θ1,θ2 ~ 1.5° • θ3 ~ 3.1° θ1 θ3 θ2

  16. Dual-energy protocol for FMT-XCT (4/5) Energy couple validation • Phantom measurements • 35mm cylindrical container filled with: • 1 quail's leg • 1 Plexiglas cylinder • 1 piece of lamb liver • water • Mouse measurements • 1 euthanized mouse • Measurement parameters from optimization • LE: 40kV, 6mA, 50um Tin filter • HE: 70kV, 2mA, 100um Lead filter • “low” resolution: 360 projections @ 1° step; binned images

  17. Dual-energy protocol for FMT-XCT (5/5) Energy couple validation • Reconstructed volume • 300x300x420 @ 200um/voxel

  18. Task 2.2: Remaining sub-tasks • Dual-energy data processing • decomposition in data domain or reconstructed volume? • enhanced contrast reconstruction • Dual-energy acquisition protocol • Validate chosen acquisition sequence: • Dual-energy calibration protocol • CEA-LETI bench is different from final prototype • more intense x-rays source • detector with higher resolution but less sensitivity → Repeat optimization process for FMT-XCT system • Evaluate scattering effects • from a first estimation: 15-20% in projections • assess contrast reduction in reconstructed volumes (both LE & HE) • consider the possibility of using anti-scattering grids

  19. WP 2: Revised planning To be approved by the Consortium….

  20. WP 2: Other tasks • Optimization of the delivered dose (Task 2.3) • to the animal • flat panel detector → minor problem (no need for scans) • diffused • adequate external shielding already reckoned • main problem: the optical chain →design suitable protections Minimization of X-ray interference (task 2.4) Dual-energy contrast (task 2.5) Use of X-ray contrast agents (task 2.6) To provide an optimal XCT design (task 2.7) CEA-LETI, VAMP, HMGU CEA-LETI, CEA-LIME, HMGU Month 18 CEA-LETI, FIHGM, UZH, HMGU Month 24 CEA-LETI, VAMP

  21. WP 2: Training session • Organized by CEA-LETI in Grenoble • Open to all FMT-XCT partners • Date: ~ second part of june (to be confirmed) • Program to be discussed: • X-ray imaging (theory, experimental demonstration) • Prototype demonstration • Simulation software tool presentation • Tour of facilities (X-ray and optical) • Duration: 1.5, 2, 2.5 days ?

  22. Thanks for you attention

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