METHOD FOR ERROR COMPENSATED CHEMICAL SPECIES SIGNAL SEPARATION WITH MAGNETIC RESONANCE IMAGING

• US 20120268120A1
• Filed: 04/19/2011
• Published: 10/25/2012
• Est. Priority Date: 04/19/2011
• Status: Active Grant

• Current Assignee: Wisconsin Alumni Research Foundation (University of Wisconsin System)
• Original Assignee: Wisconsin Alumni Research Foundation (University of Wisconsin System)
• Inventors: Hernando, Diego
• Granted Patent: US 9,625,549 B2
• Time in Patent Office: Days
• US Class Current: 324/309
• CPC Class Codes: G01R 33/4828 Resolving the MR signals of different chemical species, e.g. water-fat imaging
• CPC Class Codes: G01R 33/56518 due to eddy currents, e.g. caused by switching of the gradient magnetic field

Abstract

A method for producing an image of a subject with a magnetic resonance imaging (“MRI”) system, in which relative signal contributions from a plurality of different chemical species are separated, is provided. A plurality of different echo signals occurring at a respective plurality of different echo times are acquired with the MRI system and a signal model that accounts for relative signal components for each of a plurality of different chemical species is formed for each echo signal. Those echo signals containing errors, such as phase errors, magnitude errors, or errors indicative of a corrupted echo signal, are identified. The relative signal components for each of the plurality of different chemical species are then determined by fitting the echo signals with the signal model. Particularly, those echo signals identified as containing errors are fitted to the signal models in a manner that discards the error-containing information.

Claims

1. A method for producing an image of a subject with a magnetic resonance imaging (MRI) system, the steps of the method comprising:

a) acquiring with the MRI system, a plurality of different echo signals occurring at a respective plurality of different echo times;

b) forming for each of the plurality of different echo signals, a signal model that accounts for relative signal components for each of a plurality of different chemical species;

c) identifying ones of the plurality of different echo signals that contain errors;

d) determining the relative signal components for each of the plurality of different chemical species by fitting the plurality of echo signals acquired in step a) to respective ones of the signal models formed in step b), in which the fitting discards portions of the ones of the plurality of different echo signals identified in step c) as containing errors; and

e) producing an image of the subject using the relative signal components for one of the plurality of different chemical species determined in step d).

2. The method as recited in claim 1 in which the plurality of different chemical species includes at least two of water, fat, silicone, hyperpolarized carbon-13, metabolites containing hyperpolarized carbon-13, hyperpolarized xenon-129, hyperpolarized helium-3, acetone, choline, and lactate.

3. The method as recited in claim 1 in which the plurality of different chemical species comprises water and fat, and in which the signal models formed in step b) account for a fat spectrum having multiple spectral peaks.

4. The method as recited in claim 3 in which the signal models formed in step b) equate a transverse relaxation rate of water with a transverse relaxation rate for fat.

5. The method as recited in claim 1 in which the plurality of different echo signals are acquired in step a) by directing the MRI system to perform a single-shot acquisition pulse sequence.

6. The method as recited in claim 1 in which the plurality of different echo signals are acquired in step a) by directing the MRI system to perform a multiple-shot acquisition pulse sequence.

7. The method as recited in claim 1 in which the errors identified in step c) are phase errors and step d) includes fitting a magnitude of the ones of the plurality of different echo signals identified in step c) to a magnitude of the respective signal model formed in step b).

8. The method as recited in claim 1 in which the errors identified in step c) are magnitude errors and step d) includes fitting a phase of the ones of the plurality of different echo signals identified in step c) to a phase of the respective signal model formed in step b).

9. The method as recited in claim 1 in which the errors identified in step c) are errors indicative of a corrupted echo signal and step d) includes discarding the ones of the plurality of different echo signals identified in step c).

10. The method as recited in claim 1 further comprising:

f) producing a metric using the relative signal components for ones of the plurality of different chemical species determined in step d).

11. The method as recited in claim 10 in which the plurality of different chemical species comprises water and fat, and in which the metric calculated in step f) is a fat fraction.

12. A method for separating relative signal components from a plurality of different chemical species in a subject with a magnetic resonance imaging (MRI) system, the steps of the method comprising:

a) acquiring with the MRI system, a plurality of image data sets by sampling echo signals occurring at a each of a respective plurality of different echo times;

b) forming a system of equations that relates the plurality of image data sets acquired in step a) to a relative signal component for each of the plurality of different chemical species;

c) selecting ones of the plurality of image data sets that contain phase errors; and

d) calculating a relative signal component for each of the plurality of different chemical species by solving the system of equations formed in step b) using a minimization in which phase information from the ones of the plurality of image data sets selected in step c) is discarded.

13. The method as recited in claim 12 in which the plurality of different chemical species includes at least two of water, fat, silicone, hyperpolarized carbon-13, metabolites containing hyperpolarized carbon-13, hyperpolarized xenon-129, hyperpolarized helium-3, acetone, choline, and lactate.

14. The method as recited in claim 12 in which the plurality of different chemical species comprises water and fat, and in which the system of linear equations formed in step b) accounts for a fat spectrum having multiple spectral peaks.

15. The method as recited in claim 14 in which the system of linear equations formed in step b) equates a transverse relaxation rate of water with a transverse relaxation rate of fat.

16. The method as recited in claim 12 in which the plurality of image data sets are acquired in step a) by directing the MRI system to perform a single-shot pulse sequence.

17. The method as recited in claim 16 in which phase information from one of the plurality of image data sets corresponding to a first echo signal acquired at a first echo time is discarded in step c).