SMASH%20and%20SENSE

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Parallel Imaging

• SMASH and SENSE
• High field advantage
• Pros and cons
• But first, review of last few homework assignments

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Bibliography parallel imaging

• Original SMASH and SENSE papers
• Griswold MA, Jakob PM, Chen Q, Goldfarb JW,
  Manning WJ, Edelman RR, Sodickson DK (1999).
  Resolution enhancement in single-shot imaging
  using simultaneous acquisition of spatial
  harmonics (SMASH). Magn Reson Med. 41(6)1236-45.
  
• Pruessmann KP, Weiger M, Scheidegger MB, Boesiger
  P (1999). SENSE sensitivity encoding for fast
  MRI. Magn Reson Med. 42(5)952-62.
• Additional references
• Sodickson, DK (2000). Tailored SMASH image
  reconstructions for robust in vivo parallel MR
  imaging. Magn Reson Med 44243-251.
• Weiger, M, Boesiger, P, Hilfiker, PR, Weishaupt,
  D, Pruessmann, KP (2005). Sensitivity encoding as
  a means of enhancing the SNR efficiency in
  steady-state MRI. Magn Reson Med 53177-185.
• Griswold MA, Jakob PM, Heidemann RM, Nittka M,
  Jellus V, Wang J, Kiefer B, Haase A. (2002).
  Generalized autocalibrating partially parallel
  acquisitions (GRAPPA). Magn Reson Med.
  47(6)1202-1210.
• Sodickson, DK, McKenzie, CA (2001). A generalized
  approach to parallel magnetic resonance imaging.
  Med Phys 28(8)1629.

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Parallel Imaging simplistic overview
Coil sensitivity maps
Partial k-space data from 2 coils
Reconstructed image


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Undersampled k-space aliased image
Full k-space
Undersampled k-space
Reconstructed image
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Multiple coils information to fix aliasing
Coils with complementary sensitivities
Full k-space
Undersampled k-space
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Parallel Imaging SENSE
RECONSTRUCT
ACQUIRE
COMBINE
Coil sensitivity, partial k-space
Images from each coil
Images from all coils, using coil sensitivity maps
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Parallel Imaging SMASH
RECONSTRUCT
ACQUIRE
COMBINE
Coil sensitivity, partial k-space
Missing lines of k-space, using coil sensitivity
maps
Images from all coils
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SENSE recon idealized example
L1(x,y)
Reconstructed ?
Ln(x,y) Cn(x,y)?(x,y) Cn(x,yNPE/2)?(x,yNPE
/2)
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Pineapple fake 2-channel coil, noise
(with perfect knowledge of coil sensitivity)
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Pineapple fake 2-channel coil, noise
(with imperfect knowledge of coil sensitivity)
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Pineapple fake 2-channel coil, not ind.
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Parallel imaging terminology

• Methods
• iPAT Siemens name for all of its parallel
  imaging implementations
• SENSE
• SMASH
• GRAPPA auto-calibrating SMASH-like technique
• Parameters
• Reduction factor integer describing k-space
  undersampling
• g describes degradation of reconstructed image
  due to lack of independence between coil
  sensitivities (limits useful reduction factor)
• High field advantage
• of course