Method for magnetic resonance spectroscopic imaging

1. A method for performing spectroscopy using an interleaved readout for at least two species, comprising of:

a) applying a B 0 field;

b) applying a first spatial-spectral (SPSP) position resolved spectroscopy sequence (PRESS) excitation with a sufficiently narrow band to excite a first species without exciting a second species;

c) performing a first readout that measures the first species;

d) applying a second SPSP PRESS excitation with a sufficiently narrow band to excite the second species without exciting the first species;

e) performing a second readout that measures the second species; and

f) generating a spectroscopic output for a portion of k-space from the first readout and the second readout, wherein steps b-e are performed a plurality of times so that the first SPSP PRESS excitation is interleaved with the second SPSP PRESS excitation.

2. The method of claim 1 , wherein the spectroscopic output is a spectrum for the first species and the second species.

3. The method of claim 1 , wherein the spectroscopic output is a spectroscopic image for the first species and the second species from the first and second readouts.

4. The method of claim 3 , wherein the applying a first spatial-spectral (SPSP) position resolved spectroscopy sequence (PRESS) excitation excites a third species, wherein the first readout measures the third species and the spectroscopic image also shows the third species.

5. The method of claim 4 , wherein the first SPSP PRESS excitation comprises:

a SPSP 90° pulse;

a first adiabatic SPSP 180° pulse; and

a second adiabatic SPSP 180° pulse, wherein the SPSP 90° pulse and the first and second adiabatic SPSP 180° pulses each have a spectral profile centered on the resonant frequency for exciting the first and third species and a bandwidth sufficiently narrow to avoid exciting the second species; and

wherein the second SPSP PRESS excitation comprises:

a SPSP 90° pulse;

a first adiabatic SPSP 180° pulse; and

a second adiabatic SPSP 180° pulse, wherein the SPSP 90° pulse and the first and second adiabatic SPSP 180° pulses each have a spectral profile centered on the resonant frequency for exciting the second species and a bandwidth sufficiently narrow to avoid exciting the first and third species.

6. The method of claim 5 , wherein each SPSP 90° pulse has a same spectral profile as the associated first and second adiabatic SPSP 180° pulses.

7. The method of claim 6 , wherein the first species is choline containing compounds, the second species is N-acetyl aspartate, and the third species is creatine/phosphocreatine.

8. The method of claim 7 , wherein the first and second adiabatic SPSP 180° pulses for the first excitation and the second excitation were designed by first creating an adiabatic sech/tanh pulse wherein the amplitude A(t) of the adiabatic sech/tanh pulse is

A ( t ) = A 0 sech(β t )− T/ 2 ≦t ≦T/ 2

and wherein the frequency modulation function Δω(t) of the adiabatic sech/tanh pulse is

Δω( t )=−μβtanh(β t )− T/ 2 ≦t ≦T/ 2

where β is a modulation angular frequency, μis a modulation angular frequency, and T is a pulse duration.

9. The method of claim 8 , further comprising:

a third SPSP PRESS excitation with a sufficiently narrow band to excite a fourth species without exciting the first, second, and third species, and wherein the first and second SPSP PRESS excitations do not excite the fourth species; and

performing a third readout that measures the fourth species.

10. The method of claim 4 , wherein the first species is choline containing compounds, the second species is N-acetyl aspartate, and the third species is creatine/phosphocreatine.

11. The method of claim 1 , wherein the first and second readouts are used to generate spectroscopic outputs for a 2D grid in k-space , and further comprising using the spectroscopic outputs for a 2D grid in k-space to generate, through the use of a Fourier Transform, a spectroscopic image containing spectra from a plurality of voxels.

12. The method of claim 1 , wherein the first SPSP PRESS excitation comprises:

a SPSP 90° pulse;

a first adiabatic SPSP 180° pulse; and

a second adiabatic SPSP 180° pulse, wherein the SPSP 90° pulse and the first and second adiabatic SPSP 180° pulses each have a spectral profile centered on a resonant frequency for exciting the first species and a bandwidth sufficiently narrow to avoid exciting the second species; and

wherein the second SPSP PRESS excitation comprises:

a SPSP 90° pulse;

a first adiabatic SPSP 180° pulse; and

a second adiabatic SPSP 180° pulse, wherein the SPSP 90° pulse and the first and second adiabatic SPSP 180° pulses each have a spectral profile centered on a resonant frequency for exciting the second species and a bandwidth sufficiently narrow to avoid exciting the first species.

13. The method of claim 12 , wherein each SPSP 90° pulse has a same spectral profile as the associated first and second adiabatic SPSP 180° pulses.

14. The method of claim 1 , further comprising:

a third SPSP PRESS excitation with a sufficiently narrow band to excite a third species without exciting the first and second species, and wherein the first and second SPSP PRESS excitations do not excite the third species; and

performing a third readout that measures the third species.

15. The method, as recited in claim 1 , wherein the spectroscopic output comprises interleaved spectral bands, wherein the interleaving allows excitation of a large spectral range without increasing scan time.

16. A computer implemented method, comprising:

a) applying a B 0 field;

b) performing for a plurality of cycles:

applying a first spatial-spectral (SPSP) position resolved spectroscopy sequence (PRESS) excitation with a sufficiently narrow band to excite a first species without exciting a second species, wherein the first SPSP PRESS excitation comprises:

a SPSP 90° pulse;

a first adiabatic SPSP 180° pulse; and

a second adiabatic SPSP 180° pulse, wherein the SPSP 90° pulse and the first and second adiabatic SPSP 180° pulses each have a spectral profile centered on a frequency for exciting the first species and a bandwidth sufficiently narrow to avoid exciting the second species;

performing a first readout that measures the first species;

applying a second SPSP PRESS excitation with a sufficiently narrow band to excite the second species without exciting the first species, wherein the second SPSP PRESS excitation comprises:

a SPSP 90° pulse;

a first adiabatic SPSP 180° pulse; and

a second adiabatic SPSP 180° pulse, wherein the SPSP 90° pulse and the first and second adiabatic SPSP 180° pulses each have a spectral profile centered on a frequency for exciting the second species and a bandwidth sufficiently narrow to avoid exciting the first species; and

performing a second readout that measures the second species; and

c) generating a spectroscopic output for the first species and the second species by interleaving the first and second readouts.

17. The computer implemented method of claim 16 , wherein the spectroscopic output is a spectrum for the first species and the second species.

18. The computer implemented method of claim 16 , wherein the spectroscopic output is a spectroscopic image for the first species and the second species.

19. A magnetic resonance imaging apparatus, comprising:

a magnetic resonance imaging excitation and detection system; and

a controller electrically connected to the magnetic resonance imaging excitation and detection system, comprising:

a display; and

at least one processor configured for implementing a tangible computer readable media, comprising:

computer readable code for applying a B 0 field;

computer readable code for applying a first spatial-spectral (SPSP) position resolved spectroscopy sequence (PRESS) excitation with a sufficiently narrow band to excite a first species without exciting a second species;

computer readable code for performing a first readout that measures the first species;

computer readable code for applying a second SPSP PRESS excitation with a sufficiently narrow band to excite the second species without exciting the first species;

computer readable code for performing a second readout that measures the second species;

computer readable code for generating a spectroscopic image for the first species and the second species by interleaving the first and second readouts; and

computer readable code for displaying the spectroscopic image on the display.

20. The apparatus as recited in claim 19 , wherein the magnetic resonance imaging excitation and detection system may be placed around a human head to allow the generation of a spectroscopic image of a brain.