mr spectroscopy at 7t - university of pennsylvania spectroscopy at 7t university of pennsylvania...
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MR Spectroscopy at 7TMR Spectroscopy at 7T
University of PennsylvaniaDepartment of Radiology
University of PennsylvaniaDepartment of Radiology
Harish Poptani, Ph.D.Harish Poptani, Ph.D.
RA DI O LO G Y
HUP
GLxmI
mI
NAA
Lac
CrCho
Cr
GLxNAA
Asp
CrCho
mI
Cr
mIGLx Asp
NAA
LacGLx
NAA
Glx
ASP
Increased chemical shift dispersion
3 Tesla
7 TeslaSteam
Steam
NYU, Siemens
Milk phantom
SVS steam, TE = 30 ms 8 cc voxel, 16 ave TA = 24 sec
NYU, Siemens
Single voxel, one acquisition!
Minnesota, Varian
Tkac et al, Minnesota, Varian 7T
Increased SNR at 7T
Scheenen TWJ et al. Magn Reson Mat Phy Biol Med 21:95-101, 2008
3D MRSI, TE 30, 0.14 cc voxel, 10mins, LASER ,Adiabatic pulses, SiemensSurface coil
MRSI of much smaller voxels!
3D MRSI, TE 50, 0.14 cc voxel, 10mins LASER seq, CP head coil
High resolution metabolite maps
NAA Cho Cr
Scheenen TWJ et al. Magn Reson Mat Phy Biol Med 21:95-101, 2008
fMRS at 7T
Minnesota, Varian
fMRS
Minnesota, Varian
Unedited schemes cannot be used for robust detection of Glutathione which is at the shoulder of Creatine.
Creatine
Glutathione
Radhika Srinivasan, UCSF, GE
Detecting GSH
Chemical Shift (ppm)3.5 3.0 2.5 2.0
Cycle 1
Cycle 2
Differencespectra
GSH
3T edited GSH (phantom)
The Aspartyl resonance of NAA (Asp-NAA) co-edits with Glutathione in the difference spectrum
Glutathione using a spectral editing sequence
A) Spectrum without editing pulse
(B) Spectrum with editing pulse
(B-A) Difference spectrum showing GSH at 2.95 ppm.
GSH at 3T
Radhika Srinivasan, UCSF, GE
3.03.5 3.0 2.53.52.5 3.0 2.5 2.03.5PPM PPM PPM
Asp-NAA
Asp-NAA
GSH NOT detected at 3T. The onlyvisible peak corresponds to Asp-NAA
PPM PPM PPM
12.0 12.2 13.2
10.9 12.0 13.3
9.4 10.3 10.9
3.03.5 3.0 2.53.52.5 3.0 2.5 2.03.5
Asp-NAA
GSH
GSH GSH
3T 7T
GSH is detected at 7T (red arrows) withthe SNR indicated in each voxel.
In-vivo detection of GSH at 3T vs 7T
Glutathione was detected at 7T with the same SNR as Glutamate studies at 3T. This level of detection from a metabolite that is present at half the concentration of Glutamate demonstrates the sensitivity of 7T MRSI.
Radhika Srinivasan, UCSF, GE
Glutamate by TE averaged PRESS
Simulation study, Ralph Hurd
1.5T
3.0T
4.0T
7.0T
234
ppm
234ppm
Black: Glutamate Red: Glutamine
TE Averaged PRESSConventional PRESS
JMRI 22 (2005) 279-85
1.5T
7T
Ravinder Regatte, NYU, Seimens
Corn Oil-1.5T vs 7T
JMRI 22 (2005) 279-85
1.5T
Bone marrow
7T
Ravinder Regatte, NYU, Seimens
Skeletal Muscle
1.5T
3.0T
7.0T
Ravinder Regatte, NYU, Seimens
Qiao, H et al, MRI 49:1281-1286, 2006
Surface coil,Varian
4T
7T
31P MRS of the brain
Lei, H et al, MRM 49:199-205, 2003
31P MRS of the brainNOE enhancedPrimary visual cortex7.5 ml, 8 minMinnesota, Varian
Lei, H et al, MRM 49:199-205, 2003
Disadvantages• Static field distortions
– Shimming requirements –strong 2nd order shims• Chemical shift displacement errors
– Increased BW required – higher requirement for achievable peak B1 – adiabatic pulses
• Less homogenous B1– B1 shimming methods, adiabatic pulses
• Short T2 – need for shorter TE’s• SAR