1. Real-Time Motion Correction for High-Resolution Imaging of the Larynx: Implementation and Initial Results Presentation: Thursday @ 2pm # 5036 Electrical Engineering Stanford University Joëlle K. Barral Juan M. SantosDwight G. Nishimura

2. # 5036Real-Time Motion Correction for Larynx Imaging -- J.K. Barral et al.2/38 In a Nutshell We propose a real-time algorithm to combat the main types of motion that corrupt high- resolution larynx imaging. Our algorithm combines navigator-based motion correction with a reacquisition strategy.

3. MOTIVATION

4. # 5036Real-Time Motion Correction for Larynx Imaging -- J.K. Barral et al.4/38 The Larynx Thyroid cartilage Sagittal http://www.antiquescientifica.com -- Drawing courtesy of Julie C. DiCarlo Axial Thyroid cartilage Anterior commissure Cricoid cartilage Vocal cords

5. # 5036Real-Time Motion Correction for Larynx Imaging -- J.K. Barral et al.5/38 Laryngeal Motion Healthy volunteer Real-time acquisition: 13 frames per second Notice swallowing at time t = 18 s!

6. # 5036Real-Time Motion Correction for Larynx Imaging -- J.K. Barral et al.6/38 Laryngeal Motion Cancer patient : Outliers (Sporadic motion) : Bulk motion (Drift) High-frequencies: Respiration, 14 cycles per min Motion detected by Cartesian navigators

7. # 5036Real-Time Motion Correction for Larynx Imaging -- J.K. Barral et al.7/38 Laryngeal Motion Types  How to mitigate their effects  Intermittent, sporadic motion: –Swallowing, coughing, jolting  Alternative ordering schemes  Continuous motion: –Flow (carotid arteries)  Phase encodes L/R –Bulk motion (drift)  Physical restraints; Coaching; Navigators –Respiration  Diminishing Variance Algorithm (DVA) If a continuous drift happens, DVA never converges.

8. # 5036Real-Time Motion Correction for Larynx Imaging -- J.K. Barral et al.8/38 Diminishing Variance Algorithm (DVA) Sachs, MRM 34: 412-422, 1995 -- Sachs, IEEE-TMI19: 73-79, 2000

9. METHODS

10. # 5036Real-Time Motion Correction for Larynx Imaging -- J.K. Barral et al.10/38 Proposed Approach We propose to first correct the data based on the shift information. We then reacquire encodes whose projections could not be properly corrected.

11. # 5036Real-Time Motion Correction for Larynx Imaging -- J.K. Barral et al.11/38 Implementation 1.5 TRTHawk Santos, IEEE-EMBS 2: 1048-1051, 2004

12. # 5036Real-Time Motion Correction for Larynx Imaging -- J.K. Barral et al.12/38 Pulse Sequence Fast Large Angle Spin Echo = FLASE – Spin echo: immune against flow & off-resonances – 3D: high-resolution – T 1 -weighted contrast Ma, MRM 35:903-910, 1996 -- Song, MRM 41:947-953, 1999

13. # 5036Real-Time Motion Correction for Larynx Imaging -- J.K. Barral et al.13/38 Encodes Ordering Sequential Square spiralPseudo-random kzkz kyky Examples with 32 phase encodes and 16 slice encodes Elliptical (concentric) Wilman, MRM 38: 793-802, 1997 -- Bernstein, MRM 50: 802-812, 2003

14. # 5036Real-Time Motion Correction for Larynx Imaging -- J.K. Barral et al.14/38 Reconstruction Pipeline Barral, ISMRM Motion Workshop 2010, p. 18 The user stops the scan when satisfactory image quality is obtained.

15. # 5036Real-Time Motion Correction for Larynx Imaging -- J.K. Barral et al.15/38 GUI XYZ S S

16. # 5036Real-Time Motion Correction for Larynx Imaging -- J.K. Barral et al.16/38 Experimental Parameters FOV 12 cm - Matrix size 256x128x32 - TR/TE = 80/10 ms Sequential encodes order Three-coil larynx dedicated array First pass (full acquisition: 4096 encodes): 5 min 28 s Each additional pass (64 encodes reacquired): 5 s Phantom (orange) scans: coronal acquisitions In vivo (larynx) scans: axial acquisitions Barral, ISMRM 2009, p. 1318 -- Coil picture courtesy of Marta G. Zanchi

17. PHANTOM EXPERIMENTS

18. # 5036Real-Time Motion Correction for Larynx Imaging -- J.K. Barral et al.18/38 No Motion  An orange was scanned. Phantom Experiment 1:

19. # 5036Real-Time Motion Correction for Larynx Imaging -- J.K. Barral et al.19/38 No Motion One pass = Full acquisition  As expected, image and corrected image are identical Phantom Experiment 1:

20. # 5036Real-Time Motion Correction for Larynx Imaging -- J.K. Barral et al.20/38 DVA  Non-rigid motion was simulated by switching from the coronal acquisition to an axial acquisition towards the middle of the scan, for several seconds. Phantom Experiment 2:

21. # 5036Real-Time Motion Correction for Larynx Imaging -- J.K. Barral et al.21/38 DVA Pass # 1 = Full acquisition: 4096 encodes acquired  As expected, motion correction fails  Motion detection successful  Shift information meaningless Phantom Experiment 2:

22. # 5036Real-Time Motion Correction for Larynx Imaging -- J.K. Barral et al.22/38 DVA Pass # 1 Pass # 6  When corrupted encodes are reacquired, a motion-free image is obtained. Phantom Experiment 2:

23. # 5036Real-Time Motion Correction for Larynx Imaging -- J.K. Barral et al.23/38 Motion Correction  Towards the middle of the scan, the table was manually translated. It was brought back to its original position several seconds later. Phantom Experiment 3:

24. # 5036Real-Time Motion Correction for Larynx Imaging -- J.K. Barral et al.24/38 Motion Correction Pass # 1 = Full acquisition: 4096 encodes acquired  As expected, motion correction works Phantom Experiment 3:

25. # 5036Real-Time Motion Correction for Larynx Imaging -- J.K. Barral et al.25/38 Motion Correction  Blurry: the final position of the table did not perfectly match the original position. Phantom Experiment 3: Pass # 1 Pass # 4

26. # 5036Real-Time Motion Correction for Larynx Imaging -- J.K. Barral et al.26/38 Combined Algorithm  Non-rigid motion was simulated by switching to an axial acquisition towards the middle of the scan, for several seconds. The table was then manually translated. Phantom Experiment 4:

27. # 5036Real-Time Motion Correction for Larynx Imaging -- J.K. Barral et al.27/38 Combined Algorithm Pass # 1 = Full acquisition: 4096 encodes acquired  Motion correction successfully accounts for the translation Phantom Experiment 4:

28. # 5036Real-Time Motion Correction for Larynx Imaging -- J.K. Barral et al.28/38 Combined Algorithm Pass # 1 Pass # 6  Reacquisition needed to correct for non-rigid motion Phantom Experiment 4:

29. IN VIVO EXPERIMENTS

30. # 5036Real-Time Motion Correction for Larynx Imaging -- J.K. Barral et al.30/38 Without Instructions  A healthy volunteer was scanned. In Vivo Experiment 1:

31. # 5036Real-Time Motion Correction for Larynx Imaging -- J.K. Barral et al.31/38 Without Instructions One pass = Full acquisition Slice 20/32 X Y In Vivo Experiment 1: Slice 26/32

32. # 5036Real-Time Motion Correction for Larynx Imaging -- J.K. Barral et al.32/38 Without Instructions Sagittal reformat In Vivo Experiment 1:

33. # 5036Real-Time Motion Correction for Larynx Imaging -- J.K. Barral et al.33/38 With Instructions  A healthy volunteer was scanned. He was asked to swallow at will and to accentuate motion when the center of k-space was being acquired. For this experiment, 192 encodes were reacquired each additional pass. In Vivo Experiment 2:

34. # 5036Real-Time Motion Correction for Larynx Imaging -- J.K. Barral et al.34/38 With Instructions Pass # 1 = Full acquisition: 4096 encodes acquired X Y In Vivo Experiment 2:  Swallowing properly detected  Only bulk motion corrected by motion-correction

35. # 5036Real-Time Motion Correction for Larynx Imaging -- J.K. Barral et al.35/38 With Instructions  When corrupted encodes are reacquired, motion correction is needed to account for bulk shift (drift) that happened between passes. In Vivo Experiment 2: Pass # 1 Pass # 3

36. WRAP-UP

37. # 5036Real-Time Motion Correction for Larynx Imaging -- J.K. Barral et al.37/38 Conclusion & Future Work  Our real-time algorithm corrects for rigid- body motion and reacquires encodes that could not be corrected.  Additional scans are needed to validate the robustness of the method in vivo.  Future work will improve the flexibility of the algorithm and improve the user interface.

38. # 5036Real-Time Motion Correction for Larynx Imaging -- J.K. Barral et al.38/38 Thank you! Contact: jbarral@stanford.edu On larynx imaging, see also posters # 2410 and 2416!