Method for fat characterization using MRI images acquired using a multiple gradient-echo sequence with bipolar gradients

Patent metadata

Field	Value
Publication number	US-10646134-B2
Application number	US-201615568839-A
Country	US
Kind code	B2
Filing date	Apr 22, 2016
Priority date	Apr 24, 2015
Publication date	May 12, 2020
Grant date	May 12, 2020

Abstract

It is proposed a method for post-processing images of an region of interest in a subject, the images being acquired with a magnetic resonance imaging technique, the method for post-processing comprising at least the step of: —unwrapping the phase of each image, —extracting a complex signal over echo time for at least one pixel of the unwrapped images, and —calculating fat characterization parameters by using a fitting technique applied on a model, the model being a function which associates to a plurality of parameters each extracted complex signal, the plurality of parameters comprising at least two fat characterization parameters, the magnitude error and the phase error generated by the use of the bipolar readout gradients, the fitting technique being a non-linear least-square fitting technique using pseudo-random initial conditions.

First claim

The invention claimed is:

1. A method for post-processing images of a region of interest in a subject, the images being acquired with a magnetic resonance imaging technique, the magnetic resonance imaging technique involving successive echoes of a multiple-gradient echo sequence with bipolar readout gradients, each image associating to each pixel of the image the amplitude of the measured signal in the magnetic resonance imaging technique and the phase of the measured signal in the magnetic resonance imaging technique, the method for post-processing comprising at least the step of:
unwrapping the phase of each image, to obtain unwrapped images,
extracting a complex signal over echo time for at least one pixel of the unwrapped images, to obtain at least one extracted complex signal, and
calculating fat characterization parameters by using a fitting technique applied on a model,
the model being a function which associates to a plurality of parameters each extracted complex signal, the plurality of parameters comprising at least two fat characterization parameters, the magnitude error generated by the use of the bipolar readout gradients and the phase error generated by the use of the bipolar readout gradients,
the fitting technique being a non-linear least-square fitting technique using pseudo-random initial conditions.

2. The method for post-processing images according to claim 1 , wherein the fat characterization parameters are chosen in the group consisting of the number of double bounds, the number of methylene-interrupted double bounds and the chain length.

3. The method for post-processing images according to claim 1 , wherein the method for post-processing images further comprises the step of:
determining the phase jump in the phase between two images, the first image being acquired at a first echo and the second image being acquired at a second consecutive echo,
comparing the phase jump with a threshold value, and
correcting the phase value when the phase jump is superior or equal to the threshold value.

4. The method for post-processing images according to claim 1 , wherein the model further depends on the complex intensity of water, the complex intensity of fat and a complex field map taking into account the effect of transversal relaxivity rate and the field inhomogeneity in the magnetic field used in the magnetic resonance imaging technique.

5. The method for post-processing images according to claim 1 , wherein the method for post-processing images further comprises the step of:
quantifying the proportion of unsaturated fatty acids and proportion of saturated fatty acids in the region of interest in the subject based on the calculated fat characterization parameters.

6. The method for post-processing images according to claim 5 , wherein the quantifying step comprises determining the proton density fat fraction and the fatty acid composition based on the calculated fat characterization parameters.

7. A method for predicting that a subject is at risk of suffering from an obesity related disease, the method for predicting at least comprising the step of:
carrying out the steps of the method for post-processing images of the subject according to claim 1 , to obtain fat characterization parameters, and
predicting that the subject is at risk of suffering from the obesity related disease based on the fat characterization parameters.

8. A method for diagnosing an obesity related disease, the method for diagnosing at least comprising the step of:
carrying out the steps of the method for post-processing images of the subject according to claim 1 , to obtain fat characterization parameters, and
diagnosing the obesity related disease based on the fat characterization parameters.

9. A method for monitoring the responsiveness of a subject suffering from an obesity related disease to a treatment useful for said disease, the method for monitoring the responsiveness comprising:
carrying out the steps of the method for post-processing images of the subject according to claim 1 , to obtain fat characterization parameters before the treatment,
carrying out the steps of the method for post-processing images of the subject according to claim 1 , to obtain fat characterization parameters during or after the treatment, and
comparing the fat characterization parameters before the treatment with the fat characterization parameters during or after the treatment, a difference between said fat characterization parameters being indicative that the treatment is effective.

10. A method for screening a probiotic, a prebiotic, a chemical compound or a biological compound suitable for obtaining a treatment useful for an obesity related disease using the method for monitoring the responsiveness of a subject according to claim 9 .

11. A method for monitoring the proportion of unsaturated fatty acids and proportion of saturated fatty acids in a region of interest in a subject, the method for monitoring at least comprising the step of:
imaging the region of interest in the subject by using a magnetic resonance imaging technique, the magnetic resonance imaging technique involving successive echoes of a multiple-gradient echo sequence with bipolar readout gradients, to obtain images
carrying out the steps of the method for post-processing the obtained images according to claim 1 , to obtain fat characterization parameters, and
quantifying the proportion of unsaturated fatty acids and proportion of saturated fatty acids in the region of interest in the subject based on the calculated fat characterization parameters.

12. The method for monitoring according to claim 11 , wherein the magnetic resonance imaging technique involves using a magnetic field value comprised between 1.0 T and 11.7 T.

13. A method for identifying a biomarker, the biomarker being a diagnostic biomarker of an obesity related disease, a susceptibility biomarker of an obesity related disease, a prognostic biomarker of an obesity related disease or a predictive biomarker in response to the treatment of an obesity related disease, the method comprising the steps of:
carrying out the steps of the method for post-processing images according to claim 1 , to obtain first fat characterization parameters from a subject suffering from the obesity related disease,
carrying out the steps of the method for post-processing images according to claim 1 , to obtain second fat characterization parameters from a subject not suffering from the obesity related disease, and
selecting a biomarker based on the comparison of the first and second obtained parameters.

14. A non-transitory computer readable medium having encoded thereon a computer program comprising instructions for carrying out a method of claim 1 when said computer program is executed on a suitable computer device.

15. A device for monitoring the proportion of unsaturated fatty acids and proportion of saturated fatty acids in a region of interest in a subject, the device comprising:
a magnetic resonance imaging system adapted to image the region of interest in the subject by using a magnetic resonance imaging technique, the magnetic resonance imaging technique involving successive echoes of a multiple-gradient echo sequence with bipolar readout gradients, to obtain images and
a controller adapted to:
receive the obtained images of the region of interest from the magnetic resonance imaging system, each image associating to each pixel of the image the amplitude of the measured signal in the magnetic resonance imaging technique and the phase of the measured signal in the magnetic resonance imaging technique,
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Assignees

• Inst Nat Sante Rech Med
• Univ Paris Diderot—Paris 7
• Hopitaux Paris Assist Publique
• Univesite De Versailles Saint Quentin En Yvelines
• Univ Versailles Saint Quentin En Yvelines
• Assist Publique Hopitaux Paris Aphp

Inventors

• LEPORQ Benjamin
• Lambert Simon
• Van Beers Bernard

Classifications

• A61B5/4872

  Body fat · CPC title

• G01R33/5615

  Echo train techniques involving acquiring plural, differently encoded, echo signals after one RF excitation, e.g. using gradient refocusing in echo planar imaging [EPI], RF refocusing in rapid acquisition with relaxation enhancement [RARE] or using both RF and gradient refocusing in gradient and spin echo imaging [GRASE] · CPC title

• G01R33/4828

  Resolving the MR signals of different chemical species, e.g. water-fat imaging · CPC title

• A61B5/055 Primary

  involving electronic [EMR] or nuclear [NMR] magnetic resonance, e.g. magnetic resonance imaging · CPC title

• G01R33/56554

  caused by acquiring plural, differently encoded echo signals after one RF excitation, e.g. correction for readout gradients of alternating polarity in EPI · CPC title