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# 5036. Presentation: Thursday @ 2pm. Real-Time Motion Correction for High-Resolution Imaging of the Larynx: Implementation and Initial Results. Juan M. Santos. Dwight G. Nishimura. Joëlle K. Barral. Electrical Engineering Stanford University. In a Nutshell. - PowerPoint PPT Presentation
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Real-Time Motion Correction for High-Resolution Imaging of the Larynx: Implementation and Initial
Results
Presentation: Thursday @ 2pm#
5036
Electrical EngineeringStanford University
Joëlle K. Barral Juan M. Santos Dwight G. Nishimura
# 5036 Real-Time Motion Correction for Larynx Imaging -- J.K. Barral et al.
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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.
MOTIVATION
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The Larynx
Thyroid cartilage
Sagittalhttp://www.antiquescientifica.com -- Drawing courtesy of Julie C. DiCarlo
Axial
Thyroid cartilage
Anterior commissure
Cricoid cartilage
Vocal cords
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Laryngeal Motion
Healthy volunteer
Real-time acquisition: 13 frames per secondNotice swallowing at time t = 18 s!
QuickTime™ and aYUV420 codec decompressor
are needed to see this picture.
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Laryngeal Motion
Cancer patient
: Outliers (Sporadic motion)
: Bulk motion (Drift)
High-frequencies: Respiration, 14 cycles per min
Motion detected by Cartesian navigators
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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.
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Diminishing Variance Algorithm (DVA)
Sachs, MRM 34: 412-422, 1995 -- Sachs, IEEE-TMI19: 73-79, 2000
METHODS
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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.
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Implementation
1.5 TRTHawk
Santos, IEEE-EMBS 2: 1048-1051, 2004
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Pulse Sequence
Fast Large Angle Spin Echo = FLASE– Spin echo: immune against flow & off-
resonances– 3D: high-resolution
– T1-weighted contrast
Ma, MRM 35:903-910, 1996 -- Song, MRM 41:947-953, 1999
QuickTime™ and aYUV420 codec decompressor
are needed to see this picture.
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Encodes Ordering
Sequential
Square spiral
Pseudo-random
kz
ky
Examples with 32 phase encodes and 16 slice encodes
Elliptical (concentric)
Wilman, MRM 38: 793-802, 1997 -- Bernstein, MRM 50: 802-812, 2003
QuickTime™ and aYUV420 codec decompressor
are needed to see this picture.
QuickTime™ and aYUV420 codec decompressor
are needed to see this picture.
QuickTime™ and aYUV420 codec decompressor
are needed to see this picture.
QuickTime™ and aYUV420 codec decompressor
are needed to see this picture.
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Reconstruction Pipeline
Barral, ISMRM Motion Workshop 2010, p. 18
The user stops the scan when satisfactory image quality is obtained.
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GUI
X Y Z
S
S
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Experimental ParametersFOV 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
PHANTOM EXPERIMENTS
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No Motion
An orange was scanned.
Phantom Experiment 1:
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No MotionOne pass = Full acquisition
As expected, image and corrected image are identical
Phantom Experiment 1:
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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:
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DVAPass # 1 = Full acquisition: 4096 encodes acquired As expected, motion correction fails
Motion detection successful Shift information meaningless
Phantom Experiment 2:
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DVAPass # 1
Pass # 6
When corrupted encodes are reacquired, a motion-free image is obtained.
Phantom Experiment 2:
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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:
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Motion CorrectionPass # 1 = Full acquisition: 4096 encodes acquired
As expected, motion correction works
Phantom Experiment 3:
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Motion Correction
Blurry: the final position of the table did not perfectly match the original position.
Phantom Experiment 3:
Pass # 1
Pass # 4
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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:
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Combined Algorithm
Pass # 1 = Full acquisition: 4096 encodes acquired
Motion correction successfully accounts for the translation
Phantom Experiment 4:
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Combined Algorithm
Pass # 1
Pass # 6
Reacquisition needed to correct for non-rigid motion
Phantom Experiment 4:
IN VIVO EXPERIMENTS
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Without Instructions
A healthy volunteer was scanned.
In Vivo Experiment 1:
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Without Instructions One pass = Full acquisition
Slice 20/32
X
Y
In Vivo Experiment 1:
Slice 26/32
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Without Instructions
Sagittal reformat
In Vivo Experiment 1:
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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:
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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
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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
WRAP-UP
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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.
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Thank you!
Contact:
On larynx imaging, see also posters # 2410 and 2416!
