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© NIH National Center for Image-Guided Therapy
NCIGT Project Week
Fast Imaging Library
V E R I TAS
W. Scott Hoge and Bruno Madore
© NIH National Center for Image-Guided Therapy
Overview
• Fast Imaging: reconstruct MR images from limited data• MR applications limited by time
– Reduce data aquired == reduce acquisition time– Can be used to increase spatial resolution, temporal resolution,
or both.
• Aims to ‘fill the gaps’ left by scanner manufacturers• Library currently supports:
– Parallel MR Imaging (SENSE, GRAPPA, …)– Temporal Processing (UNFOLD)– plus additional utility functions (Partial Fourier, DICOM, …)
• Linux, Windows, and Mac distributions available• Link from stand-alone C/C++ applications or call from
Matlab scripts
© NIH National Center for Image-Guided Therapy
Library Functions: Parallel Imaging
• pMRI: Parallel MR Imaging employs spatial encoding to complement Fourier encoding and reduce image data requirements.
• SENSE and GRAPPA are widely known variants
• Library supports:– Variable-density sampling– Sophisticated regularization– 2D and 3D acquisitions
© NIH National Center for Image-Guided Therapy
Library Functions: UNFOLD
• Temporal encoding can “tag” acquisition artifacts• One can then suppress the artifacts by applying
temporal filters to an image series.
• Library provides both time domain and frequency domain Fermi filters for UNFOLD
© NIH National Center for Image-Guided Therapy
Library Functions: Utility Routines
• Partial Fourier reconstruction (homodyne)• Basic building blocks
– FFT, SVD, Conjugate Gradient, LSQR• Magnetic field corrections (GradWarp)• Basic DICOM reader/editor/writer
© NIH National Center for Image-Guided Therapy
Applications
• A wide variety of applications have been supported to date:– Accelerated Cardiac Perfusion CINE– Real-time cardiac imaging– Accelerated temperature monitoring– Real-time self-calibrated EPI– Accelerated PROPELLER EPI for
perfusion imaging
© NIH National Center for Image-Guided Therapy
App: Cardiac Perfusion
• Utilizing library building blocks, one can mix-and-match algorithms for best image quality
UNFOLD+ SPACE RIP (lo)+ SPACE RIP (mid)
UNFOLD+ GRAPPA (lo)+ GRAPPA (mid)
UNFOLD+ GRAPPA (lo)+ SPACE RIP (mid)
3.5x acceleration, 8 channel cardiac coil, 1.5T, SSFP sequence
Credit: B. Madore
© NIH National Center for Image-Guided Therapy
App: Real-time Cardiac Tracking
• 3.2x acceleration, 128x128, 8 channel coil, SSFP
• Completely self-referenced
• 6 images/sec with 1 frame of latency
Credit: E. Samset, R. Chu
© NIH National Center for Image-Guided Therapy
App: Temperature Monitoring
• 8x acceleration using 2DRF, SENSE+UNFOLD
8 times 8 times accelerationacceleration
Heating Result (20w for 60sec)
1/81/8FOVFOV
Before SENSE+UNFOLD
After enhanced reconstruction
Reconstructed phase image
Gel Phantom
Transducer
Water tank
Phantom after 2DRF Excitation
Reduced FOVReduced FOV
Pha
se d
irect
ion
Focus of Heating
2DRF Excitation Profile4.3 msec RF pulse
Credit: C-S Mei, J. Yuan, N. McDannold, L. Panych, B. Madore
© NIH National Center for Image-Guided Therapy
App: Real-time self-cal EPI
• Phase-labeling w/ UNFOLD for Nyquist ghost correction
• 3.2x acceleration, 128x128, SS-GE-EPI, 1.5T
• Completely self-referenced with low latency
1x: 3.2x:
Credit: H.Tan, B. Kraft (WFU)
note ReducedDistortion
© NIH National Center for Image-Guided Therapy
App: PROPELLER EPI for Perfusion
2007: before collaboration
No parallel imaging
Blade dimension = 32 x 128Number of blades = 64
2009: with Fast Imaging Library
Acceleration factor = 2x, GRAPPA
Blade dimension = 96 x 128Number of blades = 64with distortion correction.Credit: H.Tan, B. Kraft (WFU)
© NIH National Center for Image-Guided Therapy
What’s in the Package?
• Linkable binary library file• Documentation (via Doxygen)
– Quick Start Guide– Function Reference Manual
• Demos– Matlab MEX functions w/ test data– C/C++ demos: FFT, data I/O, DICOM tag
editing
© NIH National Center for Image-Guided Therapy
Quick Setup Example
• Download from
http://www.ncigt.org/pages/Downloads
“Imaging Toolkit”• Unzip into working directory• Start Matlab• Build MEX files• Run Matlab demo scripts
© NIH National Center for Image-Guided Therapy
Acknowledgements
• Funding provided by NCIGTNIH U41 RR019703-01A2 (PI:Jolesz)
• For more information:[email protected]