NUCLEAR MAGNETIC RESONANCE (NMR) FINGERPRINTING

• US 20120235678A1
• Filed: 03/18/2011
• Published: 09/20/2012
• Est. Priority Date: 03/18/2011
• Status: Active Grant

• Current Assignee: Case Western Reserve University
• Original Assignee: Case Western Reserve University
• Inventors: Griswold, Mark, SEIBERLICH, NICOLE, Ma, Dan, Gulani, Vikas
• Granted Patent: US 8,723,518 B2
• Time in Patent Office: Days
• US Class Current: 324/307
• CPC Class Codes: G01R 33/4828 Resolving the MR signals of different chemical species, e.g. water-fat imaging
• CPC Class Codes: G01R 33/50 based on the determination of relaxation times , e.g. T1 measurement by IR sequences; T2 measurement by multiple-echo sequences
• CPC Class Codes: G01R 33/54 Signal processing systems, e.g. using pulse sequences ; Generation or control of pulse sequences; Operator console
• CPC Class Codes: G01R 33/543 Control of the operation of the MR system, e.g. setting of acquisition parameters prior to or during MR data acquisition, dynamic shimming, use of one or more scout images for scan plane prescription G01R33/546 takes precedence
• CPC Class Codes: G01R 33/56 Image enhancement or correction, e.g. subtraction or averaging techniques , e.g. improvement of signal-to-noise ratio and resolution
• CPC Class Codes: G01R 33/56341 Diffusion imaging

Abstract

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.

Claims

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, and

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;

controlling the NMR apparatus to acquire the simultaneously produced individual NMR signals; and

controlling the NMR apparatus to compare the acquired NMR signals to one or more signal evolutions.

2. The method of claim 1, 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.

3. The method of claim 1, where the sequence block parameters are selected from the group including 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.

4. The method of claim 1, comprising:

controlling the NMR apparatus to vary one or more of, the amount of time between sequence blocks in the series of variable sequence blocks, the relative amplitude of RF pulses in sequence blocks in the series of variable sequence blocks, and the relative phase of RF pulses in sequence blocks in the series of variable sequence blocks.

5. The method of claim 1, comprising controlling the NMR apparatus to configure a member of the series of variable sequence blocks as one of, a TrueFISP pulse sequence, a FLASH pulse sequence, and a TSE pulse sequence.

6. The method of claim 1, where N is greater than two.

7. The method of claim 1, where N is greater than three.

8. The method of claim 1, where N is greater than ten.

9. The method of claim 1, where at least one percent of the members of the series of variable sequence blocks are unique.

10. The method of claim 1, where at least ten percent of the members of the series of variable sequence blocks are unique.

11. The method of claim 1, where at least fifty percent of the members of the series of variable sequence blocks are unique.

12. The method of claim 1, where at least ninety-nine percent of the members of the series of variable sequence blocks are unique.

13. The method of claim 1, comprising:

controlling the NMR apparatus to configure a later member of the series of variable sequence blocks based, at least in part, on an NMR signal acquired in response to applying an earlier member of the series of variable sequence blocks.

14. The method of claim 1, the object being an animal and the one or more resonant species comprising an animal tissue, water, and fat.

15. The method of claim 1, comprising:

controlling the NMR apparatus to apply members of the series of variable sequence blocks according to a partially random acquisition plan configured to under-sample the object at an under-sampling rate R.

16. The method of claim 15, where the rate R is greater than two.

17. The method of claim 1, where the signal evolutions are one or more of, previously acquired signal evolutions, and simulated signal evolutions.

18. The method of claim 1, where the signal evolutions are one or more of, associated with signals acquired from the object, and associated with signals not acquired from the object.

19. The method of claim 1, where the signal evolutions include signals outside the set of signal evolutions characterized by:

SE=A−

Be<sup>−

t/C</sup>

where;

SE is a signal evolution,

A is a constant,

B is a constant,

t is time, and

C is a single relaxation parameter.

20. The method of claim 1, where the known signal evolutions include a signal selected from a set of signals described by:

21. The method of claim 1, comprising:

controlling the NMR apparatus to characterize at least one of the resonant species as a function of comparing the acquired NMR signals to one or more signal evolutions.

22. The method of claim 21, where controlling the NMR apparatus to characterize at least one of the resonant species as a function of comparing the acquired NMR signals to one or more signal evolutions comprises:

controlling the NMR apparatus to compare the acquired NMR signals to members of a multi-dimensional set of NMR signal evolutions,

where a first dimension in the multi-dimensional set is associated with a first set of sequence block parameters, and

where a second dimension in the multi-dimensional set is associated with a second, different set of sequence block parameters.

23. The method of claim 22, where characterizing a 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.

24. The method of claim 1, where signal content of the acquired NMR signals varies directly with N.

25. The method of claim 1, where information content in the acquired NMR signals remains above an information content threshold for at least 5 seconds.

26. The method of claim 1, where information content in the acquired NMR signals remains above an information content threshold for at least 10 seconds.

27. The method of claim 1, where information content in the acquired NMR signals remains above an information content threshold for at least 60 seconds.

28. The method of claim 1, where the signal evolutions include a signal selected from a set of signals described by:

29. A nuclear magnetic resonance (NMR) apparatus, comprising:

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, where members of the set of NMR signals are associated with different points in the (k, t, E) space, where t is time and E includes at least T1, T2, and one other relaxation parameter, T1 being spin-lattice relaxation, and T2 being spin-spin relaxation, and where one or more of, t, and E, vary non-linearly;

a signal logic configured to produce an NMR signal evolution from the set of NMR signals, and

a matching logic configured to compare the produced NMR signal evolution to a known NMR signal evolution.

30. The NMR apparatus of claim 29, where the NMR logic is configured to acquire NMR signals that change in one or more of, amplitude, and phase, during signal acquisition.

31. The NMR apparatus of claim 29, comprising a characterization logic configured to characterize a resonant species in the object based, at least in part, on comparing the produced NMR signal evolution to the known NMR signal evolution.

32. The NMR apparatus of claim 31, where the characterization logic is configured to provide image pixel data suitable for producing a diagnostic image, where the image pixel data is identified from correlations between the produced NMR signal evolution and the known NMR signal evolution and between the known signal evolution and the image pixel data.

33. The NMR apparatus of claim 31, where the characterization logic is configured to provide relaxation parameter data identified from correlations between the produced NMR signal evolution and the known NMR signal evolution and between the known signal evolution and the relaxation parameter data.

34. The NMR apparatus of claim 29, where the (k, t, E) space is a produced as a function of applying RF energy to the object according to two or more different sequence blocks.

35. The NMR apparatus of claim 34, where a sequence block includes one or more excitation phases, one or more readout phases, and one or more waiting phases.

36. The NMR apparatus of claim 34, where at least one member of the two or more sequence blocks differs from at least one other member of the two or more sequence blocks in the number of α

2 pulses in a sequence block.

37. The NMR apparatus of claim 34, where at least one member of the two or more sequence blocks differs from at least one other member of the two or more sequence blocks in at least one of, the number of α

2 pulses in a sequence block, the spacing of α

2 pulses in a sequence block, the phase of α

2 pulses in a sequence block, and the amplitude of α

2 pulses in a sequence block.

38. A non-transitory computer-readable medium storing computer executable instructions that when executed by a computer control the computer to perform a method, the method comprising:

controlling a nuclear magnetic resonance apparatus (NMR) to apply radio frequency (RF) energy suitable to produce nuclear magnetic resonance in a resonant species to a resonant species in a volume,

where the NMR apparatus is controlled to apply the RF energy in at least two different sequence blocks that differ in at least the number of α

2 pulses; and

determining two or more relaxation parameters for the resonant species by pattern matching NMR signals produced by the resonant species to characterizing signal evolutions.

39. The non-transitory computer-readable medium of claim 38, where the method includes controlling the NMR apparatus to apply the RF energy in at least two different sequence blocks that differ in at least two or more of, the number of α

2 pulses, the amplitude of α

2 pulses, the phase of α

2 pulses, and the spacing between α

2 pulses.