Magnetic resonance fingerprinting (MRF) with echo splitting

Patent metadata

Field	Value
Publication number	US-9568579-B2
Application number	US-201314024999-A
Country	US
Kind code	B2
Filing date	Sep 12, 2013
Priority date	Dec 19, 2012
Publication date	Feb 14, 2017
Grant date	Feb 14, 2017

Abstract

Apparatus, methods, and other embodiments associated with nuclear magnetic resonance (NMR) fingerprinting using echo splitting are described. One example 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 the number of echo splitting pulses, spacings between echo splitting pulses, flip angle of echo splitting pulses, 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, and a characterization logic configured to characterize a resonant species in the object as a result of comparing acquired signals to reference signals.

First claim

What is claimed is:

1. A method for characterizing a property of a material exposed to a nuclear magnetic resonance (NMR) fingerprinting pulse sequence, comprising:
exposing, using an NMR apparatus, the material to the nuclear magnetic resonance (NMR) fingerprinting pulse sequence, where the pulse sequence includes:
an excitation period comprises an initial RF pulse, and one or more echo splitting RF pulses, to produce a magnetization in a resonant species in the material and to divide the magnetization to produce two or more different echo paths,
a readout period including a readout gradient configured to facilitate acquiring two or more echo paths,

characterizing the property by comparing first information associated with NMR signals acquired from the material in response to the pulse sequence to reference information associated with NMR fingerprinting, where the first information includes two or more signal evolutions associated with the two or more different echo paths; and
generating at least one map indicating the characterizing of the property of the material.

2. The method of claim 1 , where the excitation period is configured to repeatedly divide the magnetization into different echo pathways.

3. The method of claim 1 , where the excitation period is configured to divide the magnetization into 3 k echo paths, where k is the number of echo splitting RF pulses, k being an integer.

4. The method of claim 1 , where the one or more echo splitting RF pulses are configured to produce two or more echo paths having different T 1 and T 2 weighting, where T 1 is spin-lattice relaxation and where T 2 is spin-spin relaxation.

5. The method of claim 1 , where generating at least one map includes generating two or more parameter maps simultaneously.

6. The method of claim 5 , where the two or more parameter maps include a T 1 map, a T 2 map, an M 0 map, a proton density map, a field map, a perfusion map, or a diffusion map, where T 1 is spin-lattice relaxation, T 2 is spin-spin relaxation, and M 0 is magnetization.

7. The method of claim 1 , comprising controlling the NMR apparatus to apply a constant readout gradient during the readout period.

8. The method of claim 1 , comprising configuring the pulse sequence to separate echo pathways by increasing the delay between echo splitting RF pulses.

9. The method of claim 1 , comprising controlling the NMR apparatus to apply the NMR fingerprinting pulse sequence.

10. The method of claim 9 , where the pulse sequence includes a series of variable sequence blocks, where a sequence block includes one or more excitation periods and one or more readout periods,
where 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.

11. The method of claim 10 , where the sequence block parameters comprise, the number of echo splitting RF pulses, the time between echo splitting RF pulses, and a flip angle of echo splitting RF pulses.

12. The method of claim 11 , where the excitation period includes at least a first echo splitting RF pulse, a second echo splitting RF pulse, and a third echo splitting RF pulse, and where the spacing between the first echo splitting RF pulse and the second echo splitting RF pulse is less than the spacing between the second echo splitting RF pulse and the third echo splitting RF pulse.

13. The method of claim 12 , comprising, upon determining that a set of echo pathways have been established in response to the pulse sequence, reconfiguring the pulse sequence to have constant spacing between subsequent echo splitting RF pulses.

14. The method of claim 11 , where the sequence block parameters comprise, echo time, flip angle, phase encoding, diffusion encoding, flow encoding, RF pulse amplitude, RF pulse phase, number of RF pulses, type of gradient applied between an excitation portion of a sequence block and a readout portion of a sequence block, number of gradients applied between an excitation portion of a sequence block and a readout portion of a sequence block, type of gradient applied between a readout portion of a sequence block and an excitation portion of a sequence block, number of gradients applied between a readout portion of a sequence block and an excitation portion of a sequence block, type of gradient applied during a readout portion of a sequence block, number of gradients applied during a readout portion of a sequence block, amount of RF spoiling, and amount of gradient spoiling.

15. The method of claim 10 , where N is greater than two and where at least one percent of the members of the series of variable sequence blocks are unique.

16. The method of claim 1 , where flip angles of the one or more echo splitting RF pulses are not an integer multiple of 90° .

17. The method of claim 16 , where the one or more echo splitting RF pulses are configured to split a single path M xy + of arbitrary phase φ, into paths including:
M xy + with unchanged phase φ and inverted phase−φ.
M xy o + with unchanged phase φ and inverted phase−φ.
M z + of phase |φ|.

18. The method of claim 1 , where characterizing the property of the material includes providing information concerning one or more of, T 1 associated with the material, T 2 associated with the material, a diffusion resonant frequency, a diffusion coefficient associated with the material, a spin density associated with the material, a proton density associated with the material, a magnetic field to which the material was exposed, a gradient field to which material was exposed, a tissue type of the material, and an identification of the material, T 1 being spin-lattice relaxation, and T 2 being spin-spin relaxation.

19. The method of claim 18 , where characterizing the property of the material includes one or more of, identifying a portion of the reference information related to the first information, identifying a degree to which a portion of the reference information is related to the first information, and identifying the likelihood that a portion of the reference information is related to the first information.

20. The method of claim 1 , where the first information includes one or more of, the NMR signals acquired from the material in response to the pulse sequence, a signal evolution produced from the NMR signals acquired from the material in response to the pulse sequence, and information derived from the signal evolution produced from the NMR signals acquired from the material in response to the pulse sequence.

21. The method of claim 20 , where the information derived from the signal evolution includes one or more of, information derived by transforming the signal evolution, information derived by combining the signal evolution with one or more other signal evolutions, and information derived by decomposing the signal evolution.

22. The method of claim 1 , where the reference information includes one or more of, a previously acquired NMR signal, a modeled NMR signal, a previously acquired signal evolution, a modeled signal evolution, information derived from a reference signal evolution, and non-signal evolution information.

23. The method of claim 22 , where the information derived from the reference signal evolution includes one or more of, information derived by transforming the reference signal evolution, information derived by combining the refe

Assignees

• Univ Case Western Reserve
• Siemens Ag

Inventors

• Jerecic Renate
• Griswold Mark
• Jiang Yun
• Ma Dan

Classifications

• G01R33/50

  based on the determination of relaxation times {, e.g. T1 measurement by IR sequences; T2 measurement by multiple-echo sequences} · CPC title

• G01R33/5602

  by filtering or weighting based on different relaxation times within the sample, e.g. T1 weighting using an inversion pulse · CPC title

• G01R33/561 Primary

  by reduction of the scanning time, i.e. fast acquiring systems, e.g. using echo-planar pulse sequences · CPC title

• G01R33/56 Primary

  Image enhancement or correction, e.g. subtraction or averaging techniques {, e.g. improvement of signal-to-noise ratio and resolution} · CPC title