1 / 16

Overview of Geant4 Use and Issues in Imaging: Emission Tomography (PET and SPECT)

Overview of Geant4 Use and Issues in Imaging: Emission Tomography (PET and SPECT). Assen S. Kirov Department of Medical Physics Memorial Sloan-Kettering Cancer Center New York. Why simulate imaging systems and scans ?.

viho
Télécharger la présentation

Overview of Geant4 Use and Issues in Imaging: Emission Tomography (PET and SPECT)

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Overview of Geant4 Use and Issues in Imaging:Emission Tomography (PET and SPECT) Assen S. Kirov Department of Medical Physics Memorial Sloan-Kettering Cancer Center New York

  2. Why simulate imaging systems and scans ? • Better understand and model phenomena affecting image quality and accuracy • Optimize scan imaging and processing parameters • Calculate parameters needed for improved image reconstruction

  3. Basis of this talk Membership in the OpenGATE collaboration ( www.opengatecollaboration.org ) Whose goal is • the creation of an elaborate and flexible Monte Carlo program that allows realistic simulation of the physical processes, detector geometry and all factors affecting emission tomography applications • realistic modeling of patient and small animal anatomy - based on GEANT4

  4. Basis of this talk • Product of OpenGATE : GATE(GEANT4 Application for Tomographic Emission) • Widely used for • PET • SPECT • Potential for CT (why not ?) • Potential for Radioimmunotherapy and Nuclide Therapy dosimetry Jan et al, PMB 49 (2004) 4543

  5. Use of GEANT4 prior to GATE for imaging • GEANT3 and GEANT4 based codes • example Jan S (Thesis) : GePETos • Summary of other codes: • Buvat and Castiglioni (Q J Nuc Med, 46, p 48-61, 2002)

  6. GATE architecture User Layer Application Layer Core Layer GEANT 4 Jan et al, PMB 49 (2004) 4543

  7. User Layer • -Verbosity and visualization • Geometry • Digitizer • Physics • Sources • Outputs • Experiment … /gate/block/daughters/name crystal /gate/block/daughters/insert box /gate/crystal/placement/setTranslation 0.0 0.0 0.0 mm /gate/crystal/geometry/setXLength 30.0 mm /gate/crystal/geometry/setYLength 4.4 mm /gate/crystal/geometry/setZLength 4.75 mm /gate/crystal/setMaterial BGO …

  8. GATE systems • Geometry organization: Hierarchical structures • For realistic signal processing organization • Simplifies geometry input GATE system: {Hierarchically organized geometry + corresponding LMF output} 5 GATE systems SPECT - 1 PET – 3 (2 block based, 1 pixelated) Generic -1 Jan et al, PMB 49 (2004) 4543

  9. GATE time and movements Needed for: - Patient and organ motion - Scanner rotation - Activity distribution changes GEANT4 limitations: - geometry: static during simulation - no source movements Solutions in GATE: - Geometry updated between simulation time steps - The source is confined to a smaller volume moving inside a larger emission volume Santin et al, 2003 Strul et al, 2003 Jan et al, PMB 49 (2004) 4543

  10. GATE physics • Sources • Particle type, position (volume), direction (solid angle), energy (spectrum), activity • Modified GEANT4’s RDM – virtual clock defines absolute time used to initialize GEANT4’s internal tracking time • Multiple, voxelized sources • e+ emission (Jan 2002): • b+ spectra parametrization - faster • annihilation photon noncolinearity • GEANT4’s interaction processes and cuts Jan et al, PMB 49 (2004) 4543

  11. GATE digitization • Resolution blurring, spatial blurring, crosstalk • Parallelizable and non-parallelizable dead times • Coincidence processing • Post simulation processing of output files stored before digitization

  12. GATE validation • PET at least 5 patient and microPET scanners energy spectra, sensitivity, resolution, scatter faction, count rates, image quality, contrast recovery • SPECT at least 5 systems energy spectra, sensitivity, resolution,… • Prototype at least 4 systems energy spectra, sensitivity, resolution… More than 15 references in Jan et al, PMB 49 (2004) 4543 and at www.opengatecollaboration.org

  13. GE Advance/ DLS PET scanner

  14. MC based coincidence count rates for IQ phantom Randoms Trues Scattered NECR See Schmidtlein et al, SU-EE-A4-03 Mod. Poster at this meeting

  15. Other issues • CT simulations – GATE could handle the geometry, not tested yet • Optical imaging – very promising field for GEANT4 : small animal; 3D dosimetry (see Kirov et al, SU-FF-T-229 at this meeting), etc. • Worst GATE/GEANT4 problem for imaging • Very time consuming simulations 35 CPU days on 2 GHz !!

  16. Conclusions • GEANT4 with GATE - powerful, flexible, convenient for use and accurate tool for nuclear medicine imaging applications • GEANT4 without GATE: worth pursuing only if a new approach can drastically improve performance • Efficiency: work needed

More Related