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