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O AK R IDGE N ATIONAL L ABORATORY U.S. DEPARTMENT OF ENERGY

O AK R IDGE N ATIONAL L ABORATORY U.S. DEPARTMENT OF ENERGY. Royal Prince Alfred Hospital. U.S. DEPARTMENT OF ENERGY. Image Reconstruction of Restraint-Free Small Animals with Parallel and Multipinhole Collimation: Progress and Plans. Key Personnel for Image Reconstruction.

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O AK R IDGE N ATIONAL L ABORATORY U.S. DEPARTMENT OF ENERGY

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  1. OAK RIDGE NATIONAL LABORATORY U.S. DEPARTMENT OF ENERGY Royal Prince Alfred Hospital U.S. DEPARTMENT OF ENERGY Image Reconstruction of Restraint-Free Small Animals with Parallel and Multipinhole Collimation: Progress and Plans

  2. Key Personnel for Image Reconstruction • Jefferson Lab - Mark Smith, Tim Tran • Oak Ridge National Laboratory - Shaun Gleason, Jim Goddard • Royal Prince Alfred Hospital - Steve Meikle

  3. Image Reconstruction Flowchart LIST-MODE SINGLE PHOTON DATA time-stamp detector head index x, y coordinates of projection pixel gantry rotation angle TRACKING DATA FILE time-stamp raw data from small animal tracking system LIST-MODE SINGLE PHOTON DATA, SMALL ANIMAL REFERENCE FRAME (SARF) time-stamp x, y, z coordinates of projection pixel in SARF pinhole locations in SARF TRANSFORMATION DATA FILE time-stamp coordinate transformation (translation and rotation) from gamma camera reference frame to small animal reference frame HEAD MOTION FILE time-stamp head linear velocity function head angular velocity function IMAGE RECONSTRUCTION edit data as desired (e.g. if excessive head velocity) list-mode iterative MLEM reconstruction in SARF

  4. • • • • • • • • • • • • • • • • • • • • multipinhole mask scintillation array List-Mode Iterative MLEM Image Reconstruction with Animal Motion Transform Pinhole and Projection Pixel Coordinates To SARF for Reconstruction Small Animal Reference Frame (SARF) SPECT Acquisition with Animal Motion list-mode iterative MLEM update equation source voxel j sum over N detected events sum over M mouse poses probability for detection in projection pixel k at mouse pose m of emission from source voxel j predicted counts projection pixel ki , mouse pose mi

  5. Major Challenges • Implementation of animal motion into list-mode image reconstruction Two detector strategy • single or multipinhole collimator: better resolution and sensitivity but with image truncation or projection data multiplexing • parallel hole collimator: sacrifice resolution and sensitivity for full field of view • Quality control and calibration parameters • registration between reconstruction, detector, tracking reference frames • orientation of detector and collimator in SPECT reference frame • calibration phantom development with ORNL (Bequé et al. analysis) - focal length, distance to AOR, mech. offset, electrical shifts, tilt, twist • Computation time • (15 poses/sec ) x (1200 sec)=18,000 poses for 20 min scan • One- or few-pass list-mode MLEM algorithm (Reader et al.)

  6. Multipinhole Collimatorsfor Small Animal SPECT brain ph1 ph5 ph13a ph13b Side view of the small animal imaging system Simulated Projections 3 mCi dose, 30 min acquisition, 120 angles Mouse Model brain and body activity ph1 ph5 ph13a ph13b Single and multipinhole masks

  7. Multipinhole Image Reconstructions Mouse Model, No Motion, OSEM (10 subsets) Coronal SNR and Contrast for the High (H) and Low (L) Activity 2.5 mm diam. Cylinders in Mouse Brain Transaxial C=(H-L)/(H+L) SNR=(H-L)/s(H+L) ph1 2 iterations ph5 4 iterations ph13a 6 iterations ph13b 6 iterations

  8. RPAH: micro Deluxe Resolution Phantom 1 pinhole on detector A 1 pinhole on detector A, 2 pinholes on detector B 1 pinhole on detector A, 4 pinholes on detector B aperture projection image

  9. Simulation of a Moving Mouse Parallel (ideal) Parallel (detector blur)

  10. Moving Line Source Acquisitions Parallel Pinhole

  11. Next Steps • Image reconstruction code implementation and testing for simulated moving mouse studies • use simulated list-mode data with different activity levels • Acquisition and analysis of QC calibration data for parallel hole and pinhole collimation • Incorporation of complete set of QC parameters into reconstruction code • Image reconstruction of simple geometric phantoms with motion • line source, mouse-sized Schramm phantom • Image reconstruction of mice • possibly ex-vivo mice with 3-D motion • unanesthetized, unrestrained live mice

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