Method and device for forming images by nuclear magnetic resonance

• US 4,727,326 A
• Filed: 03/24/1986
• Issued: 02/23/1988
• Est. Priority Date: 03/26/1985
• Status: Expired due to Term

• Current Assignee: Thomson-Cgr
• Original Assignee: Thomson-Cgr
• Inventors: Roux, Georges, Kaplan, Daniel
• Primary Examiner(s): NOLAND, THOMAS
• Application Number:
  US06/843,266
• Time in Patent Office: 701 Days
• Field of Search: 324/309
• US Class Current: 324/309
• 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 33/56 Image enhancement or correction, e.g. subtraction or averaging techniques , e.g. improvement of signal-to-noise ratio and resolution

Abstract

The invention provides a method and device for forming images by nuclear magnetic resonance in which an image is constructed by discrimination of the intrinsic parameters of the tissues examined. The image is formed by putting forward the degrees of attachment and mobility of the nuclei of the tissues. The parameters displayed represent the field heterogeneities at the microscopic and molecular levels. The method consists in acquiring a first image using conventional methods then, after slightly varying the orientater magnetic field, in acquiring another image using the same methods. Then an image of another type is formed by representing the relative variations of the relaxation times between this first and this second image.

Claims

1. A method of forming images by nuclear magnetic resonance comprising the steps of:

acquiring an image of the volume element of a section of a body to be examined by discrimination of the relaxation times of the nucleii of said volume elements in the presence of a first value of a given orientating magnetic field;

reiterating said acquisition step for a second value of said magnetic field; and

forming another type of image of said section by representing for each image element the relative variations of the relaxation times between said step of acquiring and said reiterated step of acquiring.

2. The method as claimed in claim 1, wherein said acquisitions are reiterated a certain number of times, each time for different values of the fields and the image of the section is formed by representing the relative variations of the relaxation times by effecting a statistical estimation of the relative variations.

3. The method as claimed in claim 2, wherein the statistical estimation is established with minimum quadratic deviation.

4. A device for forming images by nuclear magnetic resonance of the type comprising

means for subjecting a body to be examined to an orientating magnetic field,

field gradient means for determining a section of the body,

means for producing a pulsed alternating magnetic field for exciting the nucleii of the volume elements of the section,

means for measuring the relaxation times of these nuclei after excitation,

and means for acquiring an image of the section by representing these relaxation times, which device further comprises

means for storing the image,

means for varying the orientating magnetic field and the frequency of the pulsed magnetic field so as to acquire, using the same procedure, another image of the same section,

and means for forming an image of this section, of another type, by representing the relative variations of the relaxation times between the first and second acquisitions.

5. The device as claimed in claim 4, further comprising means for reiterating the acquisitions a certain number of times, each time for different values of the field, and further comprising means for effecting a statistical estimation of the relative variations of the relaxation times to be represented.

6. The device as claimed in claim 4, or claim 5, wherein the means for subjecting a body to an orientating magnetic field comprises so called Bitter coils through which a pilot controlled electric current flows.