Magnetic resonance image diagnosing apparatus

• US 6,445,183 B1
• Filed: 07/30/2001
• Issued: 09/03/2002
• Est. Priority Date: 12/03/1998
• Status: Expired due to Fees

• Current Assignee: Hitachi Medical Corporation (Hitachi, Ltd.)
• Original Assignee: Hitachi Medical Corporation (Hitachi, Ltd.)
• Inventors: Watanabe, Shigeru, Shimizu, Hiromichi
• Primary Examiner(s): Lefkowitz, Edward
• Assistant Examiner(s): Shrivastav, Brij B.
• Application Number:
  US09/857,304
• Time in Patent Office: 400 Days
• Field of Search: 324/309, 324/307, 324/315, 324/322, 600/410, 600/412, 128/736, 128/653
• US Class Current: 324/309
• CPC Class Codes: A61B 5/055 involving electronic [EMR] or nuclear [NMR] magnetic resonance, e.g. magnetic resonance imaging
• CPC Class Codes: A61B 5/7257 using Fourier transforms
• CPC Class Codes: G01R 33/4804 Spatially selective measurement of temperature or pH

Abstract

A burst wave 91 is applied as an RF magnetic filed in order to excite nuclei of hydrogen, and also a oradient magnetic field 95 along a readout direction is applied so as to excite magnetization in a stripe shape. Thereafter, while a magnetization-inverting RF magnetic field pulse 92 for selecting a slice is applied and a readout gradient magnetic field 96 is applied, a signal 97 is measured. At this time, a time instant when a spin echo is produced is made different from a time instant when a gradient magnetic field echo is produced, so that a phase rotation made by a chemical shift may be reflected on to a signal. The MR signal 97 is processed by a 2-dimensional Fourier-transform, and a phase distribution is calculated from both a real part and an imaginary part of complex data after the 2-dimensional Fourier-transform. Then, this calculated phase distribution is converted into a temperature change so as to display the temperature change. A temperature change in a diseased portion in connection with IVMR can be monitored in real time.

Claims

1. A magnetic resonance image diagnosing apparatus comprising:

magnetic field generating means for generating a static magnetic field, a gradient magnetic field, and a radio-frequency magnetic field in a space where an object under examination is located;

detecting means for detecting a magnetic resonance signal produced from said object under examination;

means for reconstructing an image based upon said detected magnetic resonance signal;

display means for displaying thereon an image; and

control means for controlling each of said means, wherein;

said control means executes the below-mentioned sequences, namely;

1) a burst wave for exciting nuclei of hydrogen is applied as said radio-frequency magnetic field, and at the same time, a gradient magnetic field along at least one direction is applied;

2) after said burst wave has been applied, a magnetization-inverting radio-frequency pulse is applied in combination with a slice-selecting gradient magnetic field;

3) a readout-operating gradient magnetic field is applied in such a manner that a gradient magnetic field echo is produced at such a time instant different from a time instant when a spin echo is produced by applying said radio-frequency pulse;

4) when said burst wave is applied, or said magnetic resonance signal is detected, such a gradient magnetic field which phase-encodes said magnetic resonance signal is applied;

5) the phase-encoded magnetic resonance signal is detected as the gradient magnetic field echo;

6) said detected magnetic resonance signal is Fourier-transformed, and a phase distribution is calculated based upon both a real part and an imaginary part of complex data of the Fourier-transformed magnetic resonance signal; and

7) an image is constructed from said phase distribution, and said constructed image is displayed on said display means.

2. A magnetic resonance image diagnosing apparatus as claimed in claim 1 wherein:

when said control means constructs the image from said phase distribution, a temperature distribution calculated from said phase distribution is constructed as the image.

3. A magnetic resonance image diagnosing apparatus as claimed in claim 1 wherein:

after said burst wave has been applied, said control means applies a gradient magnetic field for phase-encoding the magnetic resonance signal along a slice direction;

while a strength of said gradient magnetic field is changed, said control means repeatedly executes said sequences

     1) to

     5); and

said control means processes the acquired data by way of a 3-dimensional Fourier-transform to thereby form a 3-dimensional phase distribution.

4. A magnetic resonance image diagnosing apparatus as claimed in claim 3 wherein:

every time said control means repeatedly executes the phase encoding operation of said slice direction, said control means changes a frequency of said burst wave so as to sequentially excite different regions, and to repeatedly execute said sequences

     1) to

     5) in repetition time shorter than longitudinal magnetization recovery time.

5. A magnetic resonance image diagnosing apparatus as claimed in claim 1 wherein:

said control means executes said sequences

     1) to

     5) two times, or more at different time instants;

every time said sequences

     1) to

     5) are carried out, said control means acquires a phase distribution; and

said control means calculates a difference among these phase distributions, and then converts said calculated difference into a temperature change so as to display said temperature change.

6. A magnetic resonance image diagnosing apparatus comprising:

magnetic field generating means for generating a static magnetic field, a gradient magnetic field, and a radio-frequency magnetic field in a space where an object under examination is located;

detecting means for detecting a magnetic resonance signal produced from said object under examination;

means for reconstructing an image based upon said detected magnetic resonance signal;

display means for displaying thereon an image; and

control means for controlling each of said means, wherein;

said control means executes the below-mentioned sequences, namely;

1) a burst wave for exciting nuclei of hydrogen is applied as said radio-frequency magnetic field, and at the same time, the gradient magnetic field along at least one direction among three directions is applied;

2) while a gradient magnetic field having a polarity opposite to that of said gradient magnetic field is applied as a readout-operating gradient magnetic field, a magnetic resonance signal is detected as a gradient magnetic field echo;

3) said detected magnetic resonance signal is Fourier-transformed, and a phase distribution is calculated based upon both a real part and an imaginary part of complex data of the Fourier-transformed magnetic resonance signal; and

4) an image is constructed from said phase distribution, and said constructed image is displayed on said display means.

7. A magnetic resonance image diagnosing apparatus as claimed in claim 6 wherein:

when said control means constructs the image from said phase distribution, a temperature distribution calculated from said phase distribution is constructed as the image.

8. A magnetic resonance image diagnosing apparatus as claimed in claim 6 wherein:

after said burst wave has been applied, said control means applies a gradient magnetic field for phase-encoding the magnetic resonance signal along a slice direction;

while a strength of said gradient magnetic field is changed, said control means repeatedly executes said sequences

     1) and

     2); and

said control means processes the acquired data by way of a 3-dimensional Fourier-transform to thereby form a 3-dimensional phase distribution.

9. A magnetic resonance image diagnosing apparatus as claimed in claim 8 wherein:

every time said control means repeatedly executes the phase encoding operation of said slice direction, said control means changes a frequency of said burst wave so as to sequentially excite different regions, and to repeatedly execute said sequences

     1) and

     2) in repetition time shorter than longitudinal magnetization recovery time.

10. A magnetic resonance image diagnosing apparatus as claimed in claim 6 wherein:

said control means executes said sequences

     1) and

     2) two times, or more at different time instants;

every time said sequences

     1) and

     2) are carried out, said control means acquires a phase distribution; and

said control means calculates a difference among these phase distributions, and then converts said calculated difference into a temperature change so as to display said temperature change.

11. In a magnetic resonance image diagnosing apparatus comprising:

magnetic field generating means for generating a static magnetic field, a gradient magnetic field, and a radio-frequency magnetic field in a space where an object under examination is located;

detecting means for detecting a magnetic resonance signal produced from said object under examination;

means for reconstructing an image based upon said detected magnetic resonance signal;

display means for displaying thereon an image; and

control means for controlling each of said means,

said magnetic resonance image diagnosing apparatus is comprised of;

means for applying a burst wave to said object under examination so as to excite a predetermined region of said object under examination;

means for detecting a magnetic resonance signal produced by said burst wave as a gradient magnetic echo;

means for Fourier-transforming the detected magnetic resonance signal and for acquiring a phase distribution from complex data of the Fourier-transformed magnetic resonance signal; and

means for constructing an image from said phase distribution.

12. A magnetic resonance image diagnosing apparatus as claimed in claim 11 wherein:

said image constructing means includes means for constituting a temperature distribution acquired from said phase distribution as an image.

13. A magnetic resonance image diagnosing apparatus as claimed in claim 11 wherein:

said magnetic resonance image diagnosing apparatus is further comprised of;

means for applying a gradient magnetic field used to phase-encode the magnetic resonance signal along a slice direction, and for detecting said magnetic resonance signal while changing a strength of said gradient magnetic field; and

said phase distribution acquiring means includes means for performing a 3-dimensional Fourier transform with respect to the acquired data so as to form a 3-dimensional phase distribution.

14. A magnetic resonance image diagnosing apparatus as claimed in claim 13 wherein:

said means for exciting the object under examination includes means operated in such a manner that every time the phase encode operation along the slice direction is repeatedly carried out, a frequency of said burst wave is changed so as to sequentially excite different regions; and

said magnetic resonance image diagnosing apparatus is further comprised of means for detecting said gradient magnetic echo in repetition time shorter than longitudinal magnetization recovery time.

15. A magnetic resonance image diagnosing apparatus as claimed in claim 11 wherein:

said magnetic resonance image diagnosing apparatus is further comprised of means for performing a sequence used to detect said gradient magnetic echo at different time instants two times, or more;

said phase distribution acquiring means includes means for acquiring a phase distribution every time said sequence is carried out; and

said image displaying means includes means for calculating a difference among said plurality of phase distributions and for converting said calculated difference into a temperature change to display said temperature change.

16. An MR imaging method realized in a magnetic resonance image diagnosing apparatus comprising:

magnetic field generating means for generating a static magnetic field, a gradient magnetic field, and a radio-frequency magnetic field in a space where an object under examination is located;

detecting means for detecting a magnetic resonance signal produced from said object under examination;

means for reconstructing an image based upon said detected magnetic resonance signal;

display means for displaying thereon an image; and

control means for controlling each of said means, wherein;

said MR imaging method is comprised of;

1) a step in which a burst wave for exciting nuclei of hydrogen is applied as said radio-frequency magnetic field, and at the same time, a gradient magnetic field along at least one direction is applied;

2) a step in which after said burst wave has been applied, a magnetization-inverting radio-frequency pulse is applied in combination with a slice-selecting gradient magnetic field;

3) a step in which a readout-operating gradient magnetic field is applied in such a manner that a gradient magnetic field echo is produced at such a time instant different from a time instant when a spin echo is produced by applying said radio-frequency pulse;

4) a step in which when said burst wave is applied, or said magnetic resonance signal is detected, such a gradient magnetic field which phase-encodes said magnetic resonance signal is applied;

5) a step in which the phase-encoded magnetic resonance signal is detected as the gradient magnetic field echo;

6) a step in which said detected magnetic resonance signal is Fourier-transformed, and a phase distribution is calculated based upon both a real part and an imaginary part of complex data of the Fourier-transformed transformed magnetic resonance signal; and

7) a step in which an image is constructed from said phase distribution, and said constructed image is displayed on said display means.

17. An MR imaging method as claimed in claim 16 wherein:

said image displaying step includes a step for constructing the temperature distribution acquired from said phase distribution as an image.

18. An MR imaging method as claimed in claim 16, further comprising:

a step in which after said burst wave has been applied, a gradient magnetic field for phase-encoding the magnetic resonance signal along a slice direction is applied; and

a step in which while a strength of said gradient magnetic field is changed, said steps

     1) to

     5) are repeatedly executed; and

wherein;

said phase distribution calculating step includes a step for performing a 3-dimensional Fourier-transform with respect to the acquired data so as to form a 3-dimensional phase distribution.

19. An MR imaging method as claimed in claim 18, further comprising:

a step in which every time the phase encoding operation of said slice direction is repeatedly executed, a frequency of said burst wave is changed so as to sequentially excite different regions; and

a step for repeatedly executing said steps

     1) to

     5) in repetition time shorter than longitudinal magnetization recovery time.

20. An MR imaging method as claimed in claim 16, further comprising:

a step for executing said steps

     1) to

     5) at different time instants two times, or more; and

wherein;

said phase distribution calculating step includes a step for calculating a phase distribution every time said steps

     1) to

     5) are executed; and

said image displaying step includes a step for calculating a difference among these phase distributions, and for converting said difference into a temperature change so as to display said temperature change.

21. An MR imaging method as claimed in claim 20, further comprising:

a step for executing said steps

     1) and

     2) at different time instants two times, or more; and

wherein;

said phase distribution calculating step includes a step for calculating a phase distribution every time said steps

     1) and

     2) are executed; and

said image displaying step includes a step for calculating a difference among these phase distributions, and for converting said difference into a temperature change so as to display said temperature change.

22. An MR imaging method realized in a magnetic resonance image diagnosing apparatus comprising:

magnetic field generating means for generating a static magnetic field, a gradient magnetic field, and a radio-frequency magnetic field in a space where an object under examination is located;

detecting means for detecting a magnetic resonance signal produced from said object under examination;

means for reconstructing an image based upon said detected magnetic resonance signal;

display means for displaying thereon an image; and

control means for controlling each of said means, wherein;

said MR imaging method is comprised of;

1) a step in which a burst wave for exciting nuclei of hydrogen is applied as said radio-frequency magnetic field, and at the same time, the gradient magnetic field along at least one direction among three directions is applied;

2) a step in which while a gradient magnetic field having a polarity opposite to that of said gradient magnetic field is applied as a readout-operating gradient magnetic field, a magnetic resonance signal is detected as a gradient magnetic field echo;

3) a step in which said detected magnetic resonance signal is Fourier-transformed, and a phase distribution is calculated based upon both a real part and an imaginary part of complex data of the Fourier-transformed magnetic resonance signal; and

4) a step in which an image is constructed from said phase distribution, and said constructed image is displayed on said display means.

23. An MR imaging method as claimed in claim 22 wherein:

said image displaying step includes a step for constructing the temperature distribution acquired from said phase distribution as an image.

24. An MR imaging method as claimed in claim 22, further comprising:

a step in which after said burst wave has been applied, a gradient magnetic field for phase-encoding the magnetic resonance signal along a slice direction is applied;

a step in which while a strength of said gradient magnetic field is changed, said steps

     1) and

     2) are repeatedly executed; and

wherein;

said phase distribution calculating step includes a step for performing a 3-dimensional Fourier-transform with respect to the acquired data so as to form a 3-dimensional phase distribution.

25. An MR imaging method as claimed in claim 24, further comprising:

a step in which every time the phase encoding operation of said slice direction is repeatedly executed, a frequency of said burst wave is changed so as to sequentially excite different regions; and

a step for repeatedly executing said steps

     1) and

     2) in repetition time shorter than longitudinal magnetization recovery time.