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Generation of multiple respiratory phases in PET/CT A phantom study

European Institute. of Molecular Imaging. Generation of multiple respiratory phases in PET/CT A phantom study. Mohammad Dawood, M Fieseler , F Büther , M Schäfers , KP Schäfers European Institute of Molecular Imaging University of Münster , Germany. Motivation. PET, Minutes.

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Generation of multiple respiratory phases in PET/CT A phantom study

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  1. European Institute ofMolecular Imaging Generation of multiple respiratory phases in PET/CT A phantom study Mohammad Dawood, M Fieseler, F Büther, M Schäfers, KP Schäfers European Institute of Molecular Imaging University of Münster, Germany

  2. Motivation PET, Minutes CT, Seconds

  3. Problem CT based attenuation of PET data at inspiration CT based attenuation of PET data at expiration Non-Corresponding PET and CT Corresponding PET and CT Difference MyocardialUptake: NCAT phantomdata

  4. Proposed solution Use PET data to estimate motion with optical flow methods Apply motion vectors to the given CT to generate 4D-CT respiratory phases

  5. Generating FDG PET data using NCAT Simulation of 10 respiratory gates @ 30 mm diaphragm motion 10 emission and 10 attenuation maps Emission map Emission sinogram Attenuatedemissionsinogram Noisyemissionsinogram Attenuationmap Attenuationsinogram → EM reconstruction (20 iterations):

  6. Motion estimation Optical flow As a voxel at position 1 moves to position 2 its gray value remains the same: I : Gray value (Activity) x,y,z,t : Position Brightness consistency constraint V : Flow (Motion)

  7. Global smoothness Localconsistency Motion estimation Discontinuity PreservingAlgorithm Local Consistency + Global smoothness + Organ boundaries Dawood, Büther, Jiang, Schäfers: Motion correction in 3d PET/CT with advanced optical flow algorithms. IEEE Trans Med Imaging, 2008; 27(8):1164-75. PET patientdatawithout AC Coronal slice from 3D volume FDG, 1 h p.i.

  8. Application to the given CT respiratory phase Ground truth NCAT phantom data Generated respiratory phases by the proposed method

  9. Results: Position of the diaphragm Ground truth Generated

  10. Lungvolumeanalysis (volume in liters)

  11. Results: Myocardial uptake in LV on NCAT phantom data 100 90 80 70 60 50 40 30 20 10 0 Artifacts are removed if corresponding PET/CT phases are used for attenuation correction Difference between generated and ground truth: Average 0.5%, Maximum = 4.3% PET : Exp. GroundTruth CT : Exp. 100 90 80 70 60 50 40 30 20 10 0 4.5 4 3.5 3 2.5 2 1.5 1 0.5 0 - = PET : Insp. Generated CT : Insp. PET : Insp. GroundTruth CT : Insp. Difference

  12. Results: Myocardial uptake on patient data PET : Insp. CT : Insp. PET : Exp. CT : Insp. PET : Exp. CT : Exp. (generated)

  13. Conclusions • Respiratory motion leads to artifacts during attenuation correction • up to 20% in this case • Corresponding respiratory phases are required • An optical flow based method is proposed to solve this problem • Studies on NCAT phantom data showed encouraging results • uptake error reduced to 0.5% on average, 4.3% max • correlation with ground truth 98.6% • lung volumes corresponded 99.4% with ground truth data • position of diaphragm same • Further studies on patient data to be conducted soon

  14. Thankyou ! EIMI - Technology team Torsten Budumlu Florian Büther Katharina Büscher Björn Czekalla Mohammad Dawood Michael Fieseler Fabian Gigengack Thomas Kösters Klaus Schäfers Sönke Schmid Daniel Tenbrinck Susanne Zeglin

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