Nuclear Magnetic Resonance (NMR) Fingerprinting

摘要

Apparatus, methods, and other embodiments associated with NMR fingerprinting are described. One example NMR apparatus includes an NMR logic configured to repetitively and variably sample a (k, t, E) space associated with an object to acquire a set of NMR signals. Members of the set of NMR signals are associated with different points in the (k, t, E) space. Sampling is performed with t and/or E varying in a non-constant way. The varying parameters may include flip angle, echo time, RF amplitude, and other parameters. The NMR apparatus may also include a signal logic configured to produce an NMR signal evolution from the NMR signals, a matching logic configured to compare a signal evolution to a known, simulated or predicted signal evolution, and a characterization logic configured to characterize a resonant species in the object as a result of the signal evolution comparisons.

主权项

1. A method, comprising:
controlling a nuclear magnetic resonance (NMR) apparatus to apply radio frequency (RF) energy to a volume in an object in a series of variable sequence blocks, where a sequence block includes one or more excitation phases, one or more readout phases, and one or more waiting phases,
where the volume contains one or more resonant species,where the RF energy applied during a sequence block is configured to cause the one or more resonant species in the volume to simultaneously produce individual NMR signals, andwhere at least one member of the series of variable sequence blocks differs from at least one other member of the series of variable sequence blocks in at least N sequence block parameters, N being an integer greater than one; controlling the NMR apparatus to acquire the simultaneously produced individual NMR signals; controlling the NMR apparatus to compare the acquired NMR signals to one or more known signal evolutions, and controlling the NMR apparatus to characterize at least one of the resonant species as a function of comparing the acquired NMR signals to the one or more known signal evolutions, where characterizing the resonant species comprises identifying one or more of, T1 relaxation associated with the resonant species, T2 relaxation associated with the resonant species, off-resonance relaxation associated with the resonant species, and diffusion weighted relaxation associated with the resonant species, where the known signal evolutions include a signal selected from a set of signals described by:SE=∑s=1Ns∏i=1NA∏j=1NRFRi(α)RRFij(α,φ)R(G)Ei(T1,T2,D)M0orSE=∑s=1Ns∏i=1NA∏j=1NRFRi(α)RRFij(α,φ)R(G)Ei(T1,T2,D)M0where:
SE is a signal evolution, NS is a number of spins, NA is a number of sequence blocks, NRF is a number of RF pulses in a sequence block, α is a flip angle, φ is a phase angle, Ri(α) is a rotation due to off resonance, RRFij(α, φ) is a rotation due to RF differences, R(G) is a rotation due to a gradient, T1 is spin-lattice relaxation, T2 is spin-spin relaxation, D is diffusion relaxation, Ei(T1,T2,D) is decay due to relaxation differences, and M0 is the default or natural alignment to which spins align when placed in the main magnetic field.