Method for magnetic resonance imaging using inversion recovery with on-resonant water suppression including MRI systems and software embodying same
Featured are methods for magnetic resonance imaging of a volume, such a volume having susceptibility-generating objects or interfaces having susceptibility mismatches therein. Such a method includes selectively visualizing one of susceptibility-generating objects or interfaces having susceptibility mismatches as hyperintense signals, where such visualizing includes controlling variable imaging parameters so as to control a geometric extent of a signal enhancing effect, m more particular aspects of the present invention, such selectively visualizing includes attenuating or essentially suppressing signals from fat and/or water, namely on-resonant water protons, so as to thereby enhance a signal(s) associated with magnetic susceptibility gradient(s). Also featured are MRI systems, apparatuses and/or applications programs for execution on a computer system controlling the MRI data acquisition process embodying such methods.
1. A method for magnetic resonance imaging (MRI) of a volume, such a volume having therein one of susceptibility-generating objects or interfaces having susceptibility mismatches; said MRI method comprising the step(s) of:
attenuating signals from at least one of fat or on-resonant water, so as to thereby enhance a signal(s) associated with magnetic susceptibility gradient(s).
2. The method of claim 1 , wherein said attenuating includes attenuating signals from fat and on-resonant water.
3. The method of claim 2 , wherein said attenuating signals from one of fat or and water includes:
applying a spectral presaturation radio frequency pulse having a predetermined frequency and predetermined bandwidth sufficient to excite both on-resonance water and fat protons.
4. The method of claim 3 , wherein said attenuating signals from one of fat or and water further includes:
applying a crusher gradient to dephase the transverse magnetization created by excitation of protons after such applying a spectral presaturation radio frequency pulse having a predetermined frequency and predetermined bandwidth.
5. The method of claim 3 , wherein said applying a spectral presaturation radio frequency pulse having a predetermined frequency and predetermined bandwidth includes applying a spectral presaturation radio frequency pulse having a predetermined frequency and predetermined bandwidth that does not significantly excite off-resonance protons precessing at frequencies greater than the resonant frequency of water.
6. The method of claim 1 , further comprising the step(s) of:
acquiring image data after said attenuating.
7. The method of claim 1 , wherein said attenuating of the fat signal is established based on one of T 1 nulling or spectral pre-saturation.
8. The method of claim 1 , wherein said attenuating the fat signal includes:
applying radio frequency pulses to the volume being imaged to substantially suppress the fat signal based on its T 1 relaxivity.
9. The method of claim 8 , wherein said applying radio frequency pulses includes applying a series of radio frequency pulses to the volume that are temporally separated to substantially suppress the fat signal based on its T 1 relaxivity.
10. The method of claim 8 , wherein:
said applying radio frequency pulses includes applying a first radio frequency pulse non-selectively to produce a 180° inversion of protons excited in the imaging volume, and
wherein said attenuating the fat signal includes applying a crusher gradient to dephase transverse magnetization that can arise from the excitation of protons from said applying a first radio frequency pulse.
11. The method of claim 10 wherein:
said applying radio frequency pulses includes applying a second radio frequency pulse non-selectively to the imaging volume to produce a 180° inversion of the previously inverted and partially recovered magnetization, and
said attenuating the fat signal includes applying a crusher gradient to dephase transverse magnetization that can arise from the excitation of protons from such applying a second radio frequency pulse.
12. The method of claim 1 , wherein said attenuating the fat signal includes:
applying a spectral presaturation radio frequency pulse with a center frequency at or near a predetermined frequency so as to thereby excite protons within the imaging volume that resonate at frequencies within the bandwidth of the radio frequency pulse, and
applying a crusher gradient to dephase transverse magnetization created by excitation of fat protons following such applying a spectral presaturation radio frequency pulse.
13. The method of claim 12 wherein said applying a spectral presaturation radio frequency pulse includes applying a spectral presaturation radio frequency pulse with a center frequency at or near a resonance frequency of fat protons.
14. A magnetic resonance imaging (MRI) system comprising:
a gradient magnetic sub-system including one or more gradient magnets and a power controller for selectively operating each of the one or more gradient magnets;
an RF transmitter sub-system, including an RF transmitter and one or more antennas operably coupled thereto;
system controller for selectively controlling each of the gradient magnetic subsystem and the RF subsystem, said controller including a microprocessor; and
an applications program for execution on the system controller, said applications program including code segments, instructions and criteria for:
controlling each of the gradient magnetic sub-system and RF subsystem so as to attenuate signals from at least one of fat or on-resonant water, so as to thereby enhance a signal(s) associated with magnetic susceptibility gradient(s).