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Department of Neurology
MSC10 5620
Health Sciences Center
1 University of New Mexico
Albuquerque, New Mexico 87131
Phone: (505) 272-3342
Fax: (505) 272-6692
Department of Neurology
Posse MR Lab
Proton-Echo-Planar-Spectroscopic-Imaging
- PEPSI Research Network
- Pulse Sequence Options
- Raw Data Reconstruction with Water Referencing
- Spectral Quantification
- Partial Volume & Relaxation Correction
- Mapping of J-Coupled Resonances at 4T
- Mapping of J-Coupled Resonances at 3T
- Linear Sensitivity Increase between 1.5 and 7 Tesla with 8-Channel Array
- 3D Glutamate Mapping at 3T using regularized 2D SENSE Acceleration
- Sub-minute 2D Glutamate Mapping with up to 5-fold SENSE acceleration
- PEPSI with ICE Reconstruction Program
P E P S I Research Network
(click chart for an expanded listing)
P E P S I Pulse Sequence Options
- TEmin: 11 msec
- Spatial matrix:
up to 64x64x8 - Digital Spectal Resolution:
1 Hz - Up to 12 outer volume suppression slices
- Frequency drift correction
- 2D spectral encoding
(J-resolved) - Adiabatic refocusing
- Ramp sampling correction
for maximum sensitivity
- Automated spectral
reconstruction with phase
correction in ICE - Compatible with Siemens
Spectroscopy Task Card
(2D and 3D)
(click to expand in a new window)
Raw Data Reconstruction with Water Referencing
(click to expand in a new window)
Spectral Quantification
- LCModel fitting with 16
component simulated basis
set:
Asp, GSH, Ins, GPC, Glc,
Cho,Cr, PCr, Gln, Glu,
GABA,NAA, NAAG,
Lac, PE and Tau - Additional fits using soft
constraints:
MM09, MM12, MM14, MM20 - Water scaling using NWS
scan
Partial Volume & Relaxation Correction
Correction for Tissue Heterogeneity (Gm,Wm,CSF) in Large Spectroscopic Voxels
- FSL-based tissue segmentation using high-res MRI.
Convolution of tissue masks with PEPSI PSF:
- Concentration of MR visible water:
- Relaxation attenuation — literature T1/T2 values: (T1-values at 4T confirmed using long TR scan)
- Relaxation and partial volume correction:
- Where:
Mapping of J-Coupled Resonances at 4 Tesla
8.5 min scan, 1cc, TE: 15 ms.
[24] Posse et al, MRM 2007
Mapping of J-Coupled Resonances at 3 Tesla
TIM TRIO 12 Channel Array 8.5 min scan, 1cc, TE: 15 ms.
[24] Posse et al, MRM 2007
Linear Sensitivity Increase between 1.5
and 7 Tesla with 8-Channel Array
- Linear SNR increase for Cho, Cr and NAA
- Singlet line width decreases slightly with B0
- Expect even larger gains for multiplets
[21] Otazo et al, MRM 2006
3D Glutamate Mapping at 3T using regularized 2D SENSE Acceleration
TE: 15 ms, 32x32x8 spatial matrix, 32 channel array
[25] Otazo et al, MRM 2007
Sub-minute 2D Glutamate Mapping with up to 5-fold SENSE acceleration
3 T, 32-channel array TE: 15 ms, TR: 2 s, 32x32 matrix, 1.1 cc, single average
PEPSI with ICE Reconstruction Program
