Positive contrast MRI using positive and negative field inhomogeneity
AssigneeThe Board of Trustees of the Leland Stanford Junior University
InventorsScott B. Reeder, Garry E. Gold
Life of this patent
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Abstract
The acquisition of multiple images at slightly different time shifts from the spin echo (or from TE=0 for gradient echo sequences), allows the separation of on-resonance spins from off-resonance spins by encoding this information in the received signal. The excitation pulse can be a standard broadband excitation that will excite all spins. The separation of on- and off-resonance spins is then performed on the received signal. The polar and equatorial lobes of a magnetic particle such as SPIO produce signals from excited water molecules near the particle which are frequency offset above and below the frequency of signals from water molecules unaffected by the particle.
Claims19
A MRI method for identifying the presence and location in a body of a contrast agent or an object with magnetic susceptibility sufficient to induce magnetic field inhomogeneity in spins near the agent or object comprising the steps of:
- a) placing the body in a static magnetic field,
- b) applying a sequence of RF excitation and/or refocusing pulses to excite/refocus frequencies for spins containing the contrast agent or the object,
- c) detecting spin signals at a plurality of different times after excitation and/or refocusing pulses, wherein the detected signals are from spins that have a positive off-resonance and spins that have a negative off-resonance, and spins that are on-resonance, wherein the spin signals from the off-resonance spins and on-resonance spins are simultaneously detected;
- d) using a mathematical transform on all detected signals to separate detected signals from spins that have a positive off-resonance from detected signals from spins that have a negative off-resonance and from detected signals from spins that are on-resonance;
- and
- e) identifying the presence and location in the body of the contrast agent or object using the separated detected signals from spins that have a positive off-resonance and/or signal from spins that have a negative off-resonance.
Dependencies are inferred from the claim text.