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Real-Time MRI – Outline

Real-Time MRI – Outline. Technical Considerations - Data Acquisition - Image Reconstruction Preliminary Applications - Joint Movements, Swallowing, Speaking - Heart Function A First Extension - Cardiovascular Blood Flow 3D MRI Movies ?!

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Real-Time MRI – Outline

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  1. Real-Time MRI – Outline Technical Considerations - Data Acquisition - Image Reconstruction Preliminary Applications - Joint Movements, Swallowing, Speaking - Heart Function A First Extension - Cardiovascular Blood Flow 3D MRI Movies ?! - An (Almost) Unbelievable Story … Biomed NMR JF11/59

  2. Real-Time MRI – Robust, Fast, and Continuous Echo-Planar and Spiral Imaging - Limited Spatial Resolution (single-shot version) - Not Continuous (unless gradient-echo version with low flip angle) - T2* and Off-Resonance Problems Fast Spin-Echo (RARE) MRI - High SAR (high field), Not Continuous STEAM MRI - Low SNR, Not Continuous FLASH MRI - Very Short TR/TE (high bandwidth), Low SAR, Continuous - Fast? Undersampling! Biomed NMR JF11/52

  3. Real-Time MRI – Radial vs Cartesian Encoding Cartesian Simple Image Reconstruction - Inverse Fourier Transformation Radial Robust Against Motion - No Phase Encoding - Central Sampling of k Space Equivalence of Individual Spokes - Tolerance Against Undersampling - Minor Loss of Spatial Resolution Biomed NMR JF11/42

  4. Parallel MRI as Regularized Nonlinear Inverse Problem M Uecker et al, MagnReson Med 60:674-682, 2008;MagnReson Med 63:1456-1462, 2010 Biomed NMR JF11/65

  5. Real-Time MRI – Outline Technical Considerations - Data Acquisition - Image Reconstruction Preliminary Applications - Joint Movements, Swallowing, Speaking - Heart Function A First Extension - CardiovascularBlood Flow 3D MRI Movies ?! - An (Almost) Unbelievable Story … Biomed NMR JF11/59

  6. Real-Time MRI of the Knee Reconstructions Using Nonlinear Inversion Lifting of the Lower Leg in Prone Position Central Section Lateral Section Refocused Radial FLASH, TR/TE = 4.4/2.3 ms, 25o , 0.75 × 0.75 × 5 mm3 75 Spokes, 256 × 256 Matrix, Acquisition Time 333 ms, 3 Frames per Second Biomed NMR JF11/51

  7. Real-Time MRI of the Temporomandibular Joint Reconstructions Using Nonlinear Inversion Voluntary Opening and Closing of the Mouth Refocused Radial FLASH, TR/TE = 4.3/2.2 ms, 20o , 0.75 × 0.75 × 5 mm3 77 Spokes, 256 × 256 Matrix, Acquisition Time 333 ms, 3 Frames per Second Collaboration: N GersdorffBiomed NMR JF11/44

  8. Real-Time MRI of Normal Swallowing Reconstructions Using Nonlinear Inversion Voluntary Swallowing of 5 ml Pineapple Juice RF-Spoiled Radial FLASH, TR/TE = 2.17/1.44 ms, 5o, 1.5 × 1.5 × 10 mm3, FOV 192 × 192 mm2 19 Spokes, 128 × 128 Matrix, Acquisition Time 41.2 ms, 24 Frames per Second S Zhang et al, 2011 Biomed NMR JF11/46

  9. Real-Time MRI of Speaking – Sentences Reconstructions Using Nonlinear Inversion “You are watching a presentation about MRI in real time …” RF-Spoiled Radial FLASH, TR/TE = 2.22/1.44 ms, 5o, 1.5 × 1.5 × 10 mm3, FOV 192 × 192 mm2 15 Spokes, 128 × 128 Matrix, Acquisition Time 33 ms, 30 Frames per Second A Niebergall et al, 2011 Biomed NMR JF11/45

  10. Real-Time MRI of the Heart – Short-Axis View Reconstructions Using Nonlinear Inversion 15 Spokes 11 Spokes 30 ms 22 ms RF-Spoiled Radial FLASH, TR/TE = 2.0/1.3 ms, 8o, 2 × 2 × 8 mm3, FOV 256 × 256 mm2 15 / 11 Spokes, 128 × 128 Matrix, Acquisition Time 30 / 22 ms, 33 / 45 Frames per Second M Uecker et al, NMR Biomed 23:986-994, 2010 Biomed NMR JF11/53

  11. Real-Time MRI of the Heart – Short-Axis View Reconstructions Using Nonlinear Inversion 9 Spokes 7 Spokes 18 ms 14 ms RF-Spoiled Radial FLASH, TR/TE = 2.0/1.3 ms, 8o, 2 × 2 × 8 mm3, FOV 256 × 256 mm2 9 / 7 Spokes, 128 × 128 Matrix, Acquisition Time 30 / 22 ms, 55 / 71 Frames per Second M Uecker et al, NMR Biomed 23:986-994, 2010 Biomed NMR JF11/54

  12. Real-Time MRI of the Heart – 100 Frames per Second Reconstructions Using Nonlinear Inversion 5 Spokes 5 Spokes Short-Axis View Three-Chamber View RF-Spoiled Radial FLASH, TR/TE = 2.0/1.3 ms, 8o, 2 × 2 × 8 mm3, FOV 256 × 256 mm2 5 Spokes, 128 × 128 Matrix, Acquisition Time 10 ms, 100 Frames per Second M Uecker et al, NMR Biomed 23:986-994, 2010 Biomed NMR JF11/55

  13. Real-Time MRI of the Heart – 1.5 mm Resolution Reconstructions Using Nonlinear Inversion 15 Spokes, 34 ms 15 Spokes, 34 ms Short-Axis View Three-Chamber View RF-Spoiled Radial FLASH, TR/TE = 2.28/1.46 ms, 8o, 1.5 × 1.5 × 6 mm3, FOV 256 × 256 mm2 15 Spokes, 176 × 176 Matrix, Acquisition Time 34 ms, 30 Frames per Second M Uecker et al, NMR Biomed 23:986-994, 2010 Biomed NMR JF11/56

  14. Real-Time MRI – Outline Technical Considerations - Data Acquisition - Image Reconstruction Preliminary Applications - Joint Movements, Swallowing, Speaking - Heart Function A First Extension - CardiovascularBlood Flow 3D MRI Movies ?! - An (Almost) Unbelievable Story … Biomed NMR JF11/59

  15. Real-Time MRI of the Heart – Turbulent Flow Reconstructions Using Nonlinear Inversion 18 ms 18 ms Four-Chamber View Two-Chamber View RF-Spoiled Radial FLASH, TR/TE = 2.0/1.3 ms, 8o, 2 × 2 × 8 mm3, FOV 256 × 256 mm2 9 Spokes, 128 × 128 Matrix, Acquisition Time 18 ms, 55 Frames per Second S Zhang et al, J CardiovascMagnReson 12:39, 2010 Biomed NMR JF11/57

  16. Velocity-Encoded Phase-Contrast MRI in Real Time Reconstructions Using Nonlinear Inversion Two Acquisitions Using Highly Undersampled Radial FLASH (interleaved or sequential) with Two Bipolar Phase-Contrast Gradients Gvencof Opposite Polarity (through-plane flow) AA Joseph et al, NMR Biomed, 2011 Biomed NMR JF11/41

  17. Velocity-Encoded Phase-Contrast MRI in Real Time Reconstructions Using Nonlinear Inversion Ascending Aorta, Through-Plane Flow, venc = 150 cm s-1 Anatomy Magnitude Image RF-Spoiled Radial FLASH, TR/TE = 3.44/2.76 ms, 10o, 1.8 × 1.8 × 6 mm3, FOV 256 × 256 mm2 2 × 7 Spokes, 144 × 144 Matrix, Total Acquisition Time 48 ms, 21 Frames per Second AA Joseph et al, NMR Biomed, 2011 Biomed NMR JF11/37

  18. Velocity-Encoded Phase-Contrast MRI in Real Time Reconstructions Using Nonlinear Inversion Ascending Aorta, Through-Plane Flow, venc = 150 cm s-1 Phase-Contrast Map Velocity Profile (20 Heartbeats) RF-Spoiled Radial FLASH, TR/TE = 3.44/2.76 ms, 10o, 1.8 × 1.8 × 6 mm3, FOV 256 × 256 mm2 2 × 7 Spokes, 144 × 144 Matrix, Total Acquisition Time 48 ms, 21 Frames per Second AA Joseph et al, NMR Biomed, 2011 Biomed NMR JF11/38

  19. Velocity-Encoded Phase-Contrast MRI in Real Time Reconstructions Using Nonlinear Inversion Ascending Aorta, Through-Plane Flow, venc = 150 cm s-1 Dynamic Velocities During Single Heartbeat (12 Frames =512 ms) RF-Spoiled Radial FLASH, TR/TE = 3.05/2.29 ms, 10o, 1.8 × 1.8 × 6 mm3, FOV 256 × 256 mm2 2 × 7 Spokes, 144 × 144 Matrix, Total Acquisition Time 42.5 ms, 23 Frames per Second AA Joseph et al, NMR Biomed, 2011 Biomed NMR JF11/76

  20. Real-Time MRI – Outline Technical Considerations - Data Acquisition - Image Reconstruction Preliminary Applications - Joint Movements, Swallowing, Speaking - Heart Function A First Extension - CardiovascularBlood Flow 3D MRI Movies ?! - An (Almost) Unbelievable Story … Biomed NMR JF11/59

  21. Spatially Encoded Phase-Contrast MRI 3D MRI of 2D Objects Using 2 Projection Images Two Acquisitions of a Projection Image (nonselective RF excitation) with Two Monopolar Phase-Contrast Gradients Gpcof Opposite Polarity (perpendicular encoding) KD Merboldt et al, MagnReson Med 66:950-957, 2011 Biomed NMR JF11/25

  22. Spatially Encoded Phase-Contrast MRI 3D MRI of 2D Objects Using Two Projection Images Three-Dimensional Visualization of the 2D Phase-Contrast Projection Map 2D Phase-Contrast Projection Map Using Radial FLASH (color = phase difference) KD Merboldt et al, MagnReson Med 66:950-957, 2011 Biomed NMR JF11/26

  23. Spatially Encoded Phase-Contrast MRI in Real Time 3D MRI of the Acting Human Hand – 40 ms Resolution Reconstructions Using Nonlinear Inversion and Phase Difference RF-Spoiled Radial FLASH, TR/TE = 2.88/2.25 ms, 5o (nonselective), 2 × 2 mm2, FOV 256 × 256 mm2 2 × 7 Spokes (FOV 256 mm), 128 × 128 Matrix, Total Acquisition Time 40 ms, 25 Frames per Second KD Merboldt et al, MagnReson Med 66:950-957, 2011 Biomed NMR JF11/47

  24. Spatially Encoded Phase-Contrast MRI in Real Time 3D MRI of 1D Objects Using 3 MRI Signals Reconstructions Using Fourier Transformation and Phase Difference Three Acquisitions of a Frequency-Encoded MRI Signal (nonselective RF excitation) Two Orthogonal Monopolar Phase-Contrast Gradients Gpc1 and Gpc2 (two phase-encodings) KD Merboldt et al, MagnReson Med 66:950-957, 2011 Biomed NMR JF11/27

  25. Spatially Encoded Phase-Contrast MRI in Real Time 3D MRI of a Rotating Water-Filled Tube – 5 ms Resolution Reconstructions Using Fourier Transformation and Phase Difference Frequency-Encoded Gradient Echoes, TR/TE = 1.68/1.15 ms, 12o (nonselective), 2 × 2 mm2 3 Gradient Echoes, 128 × 128 Matrix, Total Acquisition Time 5 ms, 200 Frames per Second KD Merboldt et al, MagnReson Med 66:950-957, 2011 Biomed NMR JF11/22

  26. Real-Time MRI – Summary Data Acquisition – Low-Flip Angle Gradient Echo MRI (FLASH) - Radial Encoding with Pronounced Undersampling - Multi-Coil Data for Parallel MRI Image Reconstruction – Regularized Nonlinear Inversion - Joint Estimation of Image Content and Coil Sensitivities - Regularization with Previous Frame - Temporal and Spatial Filtering Current Projects - Reduction of Reconstruction Time (GPU Implementation) - Adaptation of Post-Processing Software (Cardiovascular MR) - Improvement of the Algorithm (Regularization, Filtering) - Many More Applications and Extensions Biomed NMR JF11/58

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