Claims
- 1. A method of obtaining slice-selective magnetic resonance signals for imaging short T.sub.2 species while suppressing longer T.sub.2 species comprising the steps of
- (a) applying a static magnetic field (B.sub.o) to a body thereby aligning nuclear spins,
- (b) applying an RF pulse to said body, said RF pulse having sufficient amplitude to excite the longer T.sub.2 species but insufficient amplitude to excite the short T.sub.2 species,
- (c) applying a modulated magnetic gradient (G(t)) to said body,
- (d) applying a first RF excitation pulse (B.sub.1 (t)) to said body to tip said nuclear spins,
- (e) detecting first magnetic resonance signals from said body,
- (f) applying a second RF excitation pulse (B.sub.1 (t)) to said body to tip said nuclear spins, said first RF excitation to pulse and said second RF excitation pulse each being half of a conventional slice-selective pulse,
- (g) detecting second magnetic resonance signals from said body, and
- (h) combining said first magnetic resonance signals and said second magnetic resonance signals.
- 2. The method as defined by claim 1 wherein each of said RF excitation pulses is slewed to zero at a slew rate, S, and said modulated magnetic gradient is slewed to zero as each of said RF excitation pulses is slewed to zero.
- 3. The method as defined by claim 2 wherein said modulated magnetic gradient is ##EQU12## and each of said RF excitation pulses is ##EQU13##
- 4. The method as defined by claim 1 wherein step (b) tips the longer T.sub.2 species away from one axis while the short T.sub.2 species remain aligned along said one axis.
- 5. The method as defined by claim 4 wherein step (b) further includes applying a magnetic gradient along said one axis thereby dephasing the longer T.sub.2 species.
- 6. Apparatus for obtaining slice-selective magnetic resonance signals for imaging short T.sub.2 species comprising
- (a) means for applying a static magnetic field (B.sub.o) to a body thereby aligning nuclear spins,
- (b) applying an RF pulse to said body, said RF pulse having sufficient amplitude to excite the longer T.sub.2 species but insufficient amplitude to excite the short T.sub.2 species,
- (c) means for applying a modulated magnetic gradient (G(t)) to said body,
- (d) means for applying a first RF excitation pulse (B.sub.1 (t)) to said body to tip said nuclear spins,
- (e) means for detecting first magnetic resonance signals from said body,
- (f) means for applying a second RF excitation pulse (B.sub.1 (t)) to said body to tip said nuclear spins, said first RF excitation pulse and said second RF excitation pulse each being half of a conventional slice-selective pulse,
- (g) means for detecting second magnetic resonance signals from said body, and
- (h) means for combining said first magnetic resonance signals and said second magnetic resonance signals.
- 7. Apparatus as defined by claim 6 wherein each of said RF excitation pulses is slewed to zero at a slew rate, S, and said modulated magnetic gradient is slewed to zero as each of said RF excitation pulses is slewed to zero.
- 8. Apparatus as defined by claim 7 wherein said modulated magnetic gradient is ##EQU14## and each of said RF excitation pulses is ##EQU15##
- 9. Apparatus as defined by claim 6 wherein said (b) means tips the longer T.sub.2 species away from one axis while the short T.sub.2 species remain aligned along said one axis.
- 10. Apparatus as defined by claim 9 and further including means for applying a magnetic gradient along said one axis after said RF pulse is applied to said body thereby dephasing the longer T.sub.2 species.
- 11. In imaging short T.sub.2 species in a body while suppressing longer T.sub.2 species in the body using magnetic resonance imaging, a method on enhancing image contrast between the short T.sub.2 species and the longer T.sub.2 species comprising the steps of
- (a) applying a static magnetic field (B.sub.o) to the body thereby aligning nuclei along an axis (z),
- (b) applying an RF pulse to said body, said RF pulse having sufficient amplitude to excite the longer T.sub.2 species but insufficient amplitude to excite the short T.sub.2 species, whereby nuclei of the longer T.sub.2 species are tipped away from said axis while the short T.sub.2 species remain aligned along said axis, and
- (c) thereafter detecting magnetic resonance signals for imaging the short T.sub.2 species.
- 12. The method as defined by claim 11 and including after step (b) the step of applying a magnetic gradient along said one axis thereby dephasing the longer T.sub.2 species nuclei.
Parent Case Info
This application is a continuation-in-part of application Ser. No. 07/386,901 filed Jul. 28, 1989 for MAGNETIC RESONANCE IMAGING USING SHORT T.sub.2 SPECIES, now U.S. Pat. No. 5,025,216.
Government Interests
The U.S. Government has rights in the disclosed invention pursuant to National Institute of Health grant #1R01HL34962 to Stanford University.
US Referenced Citations (11)
Continuation in Parts (1)
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386901 |
Jul 1989 |
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