Method and system for NMR using adiabatic RF pulses producing spatially quadratic phase

A method of obtaining a magnetically resonant excited signal from a sample having a spatially varying frequency in a MRI or NMR system, comprising the steps of:

• providing an adiabatic RF excitation pulse capable of producing a spatially varying phase that is substantially quadratic, and capable of producing a spatially sharp slab profile and an excited signal in a slab of the sample;
• applying read- and phase-encoding gradients to the slab to spatially localize the excited signal;
• and
• detecting the excited signal.

A computer-readable medium having computer-executable instructions to cause a computer to perform a method of obtaining a magnetically resonant excited signal from a sample having a spatially varying frequency in a MRI or NMR system, comprising the steps of:

• providing an adiabatic RF excitation pulse capable of producing a spatially varying phase that is substantially quadratic and capable of producing a spatially sharp slab profile and an excited signal in a slab of the sample;
• applying read- and phase-encoding gradients to the slab to spatially localize the excited signal;
• and
• detecting the excited signal.

In a computer having a processor, a method of forming an MRI image or NMR spectrum of a slab of a sample having a spatially varying frequency arranged in a MRI or NMR system, the method comprising:

• iteratively providing an adiabatic RF excitation pulse capable of forming a spatially sharp slab profile to the slab;
• spatially varying the phase-encoding gradient levels in each iteration to localize excited signals in the slab;
• detecting the excited signals;
• and
• in the processor, processing the excited signals to form the MRI image of the slab or the NMR spectrum of the slab.

A system which performs slab-select 3-D MRI or NMR spectroscopy of a slab in a sample having a spatially varying frequency, comprising:

• means for inducing magnetically resonant excitation in the slab that creates a substantially quadratic phase spatially across the slab arid that creates a spatially sharp slab profile;
• means for detecting excited signals from the magnetically resonant excitation;
• and
• means for processing the excited signals to form a MRI image of the slab or a NMR spectrum of the slab.

A system which performs 3-D MRI or NMR spectroscopy of a slab of a sample having a spatially varying frequency, comprising:

• a magnet that creates a constant magnetic field within the slab;
• gradient coils capable of forming phase-encoding gradient magnetic fields within the slab;
• and
• one or more RF coils in operable communication with the slab and capable of providing thereto adiabatic RF excitation pulses capable of forming a spatially sharp slab profile and a substantially quadratic phase spatially across the slab, and detecting an excited signal from the slab.