Nuclear Magnetic Resonance Imaging Apparatus

• US 20080111546A1
• Filed: 10/27/2005
• Published: 05/15/2008
• Est. Priority Date: 10/29/2004
• Status: Active Grant

• Current Assignee: Hitachi Medical Corporation (Hitachi, Ltd.)
• Original Assignee: Hitachi Medical Corporation (Hitachi, Ltd.)
• Inventors: Takahashi, Tetsuhiko, Goto, Tomohiro
• Granted Patent: US 7,535,226 B2
• Time in Patent Office: Days
• US Class Current: 324/307
• CPC Class Codes: A61B 5/055 involving electronic [EMR] or nuclear [NMR] magnetic resonance, e.g. magnetic resonance imaging
• CPC Class Codes: A61B 5/7285 for synchronising or triggering a physiological measurement or image acquisition with a physiological event or waveform, e.g. an ECG signal A61B6/5205, A61B6/541, A61B8/5207, A61B8/543 take precedence
• CPC Class Codes: G01R 33/4833 using spatially selective excitation of the volume of interest, e.g. selecting non-orthogonal or inclined slices
• CPC Class Codes: G01R 33/5635 Angiography, e.g. contrast-enhanced angiography [CE-MRA] or time-of-flight angiography [TOF-MRA]
• CPC Class Codes: G01R 33/56375 Intentional motion of the sample during MR, e.g. moving table imaging
• CPC Class Codes: G01R 33/56383 involving motion of the sample as a whole, e.g. multistation MR or MR with continuous table motion
• CPC Class Codes: G01R 33/5673 Gating or triggering based on a physiological signal other than an MR signal, e.g. ECG gating or motion monitoring using optical systems for monitoring the motion of a fiducial marker
• CPC Class Codes: G01R 33/5676 Gating or triggering based on an MR signal, e.g. involving one or more navigator echoes for motion monitoring and correction

Abstract

There is provided an MRI apparatus that is capable of imaging ON/OFF in response to a biological gating signal and changing conditions for imaging, even while the moving bed imaging is performed, and further reducing a load on a subject to be examined, which is caused by fluctuations in the bed moving velocity. A controller that controls a bed to transport the examined subject in a static magnetic field and a unit to apply an RF magnetic field and a gradient magnetic field for imaging configures settings so that the bed moving velocity is kept constant considering an entire imaging time, and further controls the magnetic applying unit for applying the RF magnetic field and the gradient magnetic field so that a moving velocity of the FOV (imaging area) in the subject coordinate system is made different from the bed moving velocity.

Claims

1. A nuclear magnetic resonance imaging method that acquires an image of an imaging region of a subject to be examined, in a static magnetic field space of a nuclear magnetic resonance imaging apparatus provided with an FOV being desirable, the imaging region being wider than the FOV, while moving a transport unit having the examined subject thereon, comprising,

a step that moves the examined subject so that the imaging region of the examined subject passes through the space for imaging,

a step that relatively displaces the FOV with respect to the static magnetic field space, in response to information obtained from the examined subject during at least a part of a period when the examined subject is being moved,

a step that executes an imaging pulse sequence while the examined subject is being moved, and collects nuclear magnetic resonance signals from the examined subject, and

a step that reconstructs an image of the wide imaging region of the examined subject, by using the nuclear magnetic resonance signals.

2. The nuclear magnetic resonance imaging method according to claim 1, wherein,

in the step that relatively displaces the FOV,

the information obtained from the examined subject is biological information detected from the examined subject, and

a moving velocity of the FOV for the examined subject is controlled to be different from each other between in a first period and in a second period while acquiring an image of the imaging region, in response to this biological information.

3. The nuclear magnetic resonance imaging method according to claim 2, wherein,

in the step that relatively displaces the FOV,

a direction of the relative displacement is controlled to be different from each other between in the first period and in the second period.

4. The nuclear magnetic resonance imaging method according to claim 1, comprising,

a step that configures settings for a first area and a second area within the imaging region, prior to the step that collects the nuclear magnetic resonance signals,

further comprising in the step that relatively displaces the FOV, a step that acquires positional information of the FOV for the examined subject, wherein,

the information obtained from the examined subject is information indicating reaching that the FOV has reached each of the areas, and

a moving velocity of the FOV for the examined subject is controlled to be different from each other between in the first area and in the second area, in response to the information indicating the reaching.

5. The nuclear magnetic resonance imaging method according to claim 4, wherein,

in the step that relatively displaces the FOV, the direction of the relative displacement is controlled to be different from each other in the first area and in the second area.

6. The nuclear magnetic resonance imaging method according to claim 2, wherein,

in the step that collects the nuclear magnetic resonance signal, imaging of at least a part of the imaging region includes a synchronous imaging by using the biological information, the imaging is executed in the first period in response to the biological information, the imaging is suspended in the second period in response to the biological information, the direction of the relative displacement is opposite to the moving direction of the examined subject in the first period, and the direction of the relative displacement is the same as the moving direction of the examined subject in the second period.

7. The nuclear magnetic resonance imaging method according to claim 6, wherein,

in the step that collects the nuclear magnetic resonance signal, the biological information is acquired from a biological signal obtained from at least one of the electrocardiograph, the sphygmograph, and body motion monitor,

in the step that moves the examined subject, a moving velocity of the transport unit is determined by a total imaging time including the first period and the second period and a distance the transport unit has traveled for acquiring an image of the imaging region,

in the step that relatively displaces the FOV, the moving velocity of the FOV for the examined subject within the first period is determined by the total imaging time when no synchronous imaging is performed, and a distance that the transport unit has traveled for acquiring the image of the imaging region, and the imaging is executed from a position of the FOV at the point when the imaging is suspended, and

in the second period, the moving velocity of the FOV for the examined subject is set to zero and the position of the FOV for the examined subject is not moved.

8. The nuclear magnetic resonance imaging method according to claim 4, wherein,

in the step that collects the nuclear magnetic resonance signals, imaging of the second area includes, collecting of the nuclear magnetic resonance signals required for reconstructing a test object image, and collecting of the nuclear magnetic resonance signal required for detecting a body motion of the examined subject, and

in the step that relatively replaces the FOV, the moving velocity of the FOV for the examined subject is controlled to be lower in the second area than in the first area.

9. The nuclear magnetic resonance imaging method according to claim 4, wherein,

in the step that configures settings of each of the areas, an imaging condition in the first area is set to be different from the imaging condition in the second area, and

in the step that relatively displaces the FOV, the moving velocity of the FOV for the examined subject is controlled to be different from each other between in the first area and in the second area, in response to each of the imaging conditions.

10. The nuclear magnetic resonance imaging method according to claim 9, wherein,

in the step that configures settings of each of the areas, the imaging conditions are set such that the second area should have a spatial resolution higher than the first area, and

in the step that relatively displaces the FOV, the moving velocity of the FOV for the examined subject is controlled to be lower in the second area than in the first area.

11. The nuclear magnetic resonance imaging method according to claim 10, wherein,

in the step that configures settings of each of the areas, the imaging condition for the second area is set in such a manner that at least one of a slice number, a phase encoding number, and a slice encoding number is increased relative to the imaging condition for the first area.

12. The nuclear magnetic resonance imaging method according to claim 9, wherein,

in the step that configures settings of each of the areas, the imaging conditions are set such that the second area should have a higher SN than the first area, and

in the step that relatively displaces the FOV, the moving velocity of the FOV for the examined subject is controlled to be lower in the second area than in the first area.

13. The nuclear magnetic resonance imaging method according to claim 12, wherein,

in the step that configures settings of each of the areas, the imaging conditions are set in such a manner that a number of averaging the nuclear magnetic resonance signals is increased in the imaging condition for the second area, relative to the imaging condition for the first area.

14. The nuclear magnetic resonance imaging method according to claim 9, wherein,

in the step that configures settings of each of the areas, the imaging conditions are set in such a manner that a size of the FOV in the first area and a size of the FOV in the second area are different from each other.

15. The nuclear magnetic resonance imaging method according to claim 4, wherein,

in the step that collects the nuclear magnetic resonance signals includes an imaging using a contrast agent,

in the step that configures settings of each of the areas, the first area and the second area are configured in such a manner that in the second area, the contrast agent moves at a velocity lower than the first area, and

in the step that relatively moves the FOV, the moving velocity of the FOV for the examined subject is controlled to be lower in the second area than in the first area.

16. The nuclear magnetic resonance imaging method according to claim 15, further comprising a step that obtains a mean flow velocity of the contrast agent within the imaging region, prior to the step that configures settings of each of the areas, wherein,

in the step that moves the examined subject, the moving velocity of the transport unit is assumed as the mean flow velocity, and

in the step that relatively displaces the FOV, in order that the moving velocity of the FOV for the examined subject accords with the moving velocity of the contrast agent, a moving direction of the FOV for the examined subject is set to be opposite to the moving direction of the examined subject in the first area, and the moving direction of the FOV for the examined subject is made to be the same as the moving direction of the examined subject in the second area.

17. The nuclear magnetic resonance imaging method according to claim 4, wherein,

in the step that configures settings of each of the areas, the first area and the second area are configured in such a manner that the second area is set in an area where a body axis direction of the examined subject and the moving direction of the examined subject form a larger angle than in the first area, and

in the step that relatively displaces the FOV, the moving velocity of the FOV for the examined subject in the moving direction of the examined subject is controlled to be lower in the second area than in the first area.

18. The nuclear magnetic resonance imaging method according to claim 17, wherein,

in the step that relatively displaces the FOV, the FOV is moved along the body axis direction, and

the moving velocity of the FOV in the body axis direction is made approximately identical between the first area and the second area.

19. The nuclear magnetic resonance imaging method according to claim 1, wherein,

in the step that collects the nuclear magnetic resonance signals from the examined subject, a high-frequency magnetic field is applied for exciting the FOV, and

in the step that relatively moves the FOV, a frequency of the high-frequency magnetic field is controlled so as to control the relative displacement of the FOV.

20. The nuclear magnetic resonance imaging method according to claim 1, wherein,

in the step that moves the examined subject, the moving velocity of the examined subject is kept constant during a period for acquiring an image of the imaging region.

21. The nuclear magnetic resonance imaging method according to claim 2, wherein,

in the step that moves the examined subject, the moving velocity of the examined subject is controlled to be different from each other between in the first period and in the second period.

22. The nuclear magnetic resonance imaging method according to claim 1, wherein,

in the step that reconstructs the image, an image of a part of the imaging region is reconstructed based on the nuclear magnetic resonance signals that have been obtained so far within at least a part of the period for acquiring an image of the imaging region.

23. A nuclear magnetic resonance imaging apparatus comprising,

a transport unit that transports a subject to be examined within a static magnetic field space including a desired FOV,

an information obtaining unit that obtains information from the examined subject,

a magnetic field application unit that applies a high-frequency magnetic field and a gradient magnetic field to the examined subject,

a control means that controls the transport unit and the magnetic field application unit, and

a signal processing unit that receives nuclear magnetic resonance signals generated from the examined subject to construct an image, wherein,

in the nuclear magnetic resonance imaging apparatus that acquires the nuclear magnetic resonance signals while the examined subject is moved by the transport unit, and acquires an image of an imaging region wider than the FOV,

the control unit controls the magnetic field application unit in such a manner that the FOV is relatively displaced with respect to the static magnetic field space, in response to the information from the examined subject, during at least a part of a period when the examined subject is moving.

24. The nuclear magnetic resonance imaging apparatus according to claim 23, wherein,

the information obtaining unit that obtains information from the examined subject, obtains biological information from the examined subject, and

the control unit controls the magnetic field application unit, in response to the biological information, in such a manner that the moving velocity of the FOV for the examined subject is made different from each other between in a first period and in a second period, while an image of the imaging region is acquired.

25. The nuclear magnetic resonance imaging apparatus according to claim 23, wherein,

the information obtaining unit that obtains information from the examined subject, further obtains positional information of the FOV for the examined subject, and finds information indicating reaching that the FOV has reached the first area and the second area within the imaging region configured in advance, and

the control unit controls the magnetic field application unit, in response to the information indicating the reaching, in such a manner that the moving velocity of the FOV for the examined subject is made different from each other between in the first period and in the second period.

26. The nuclear magnetic resonance imaging apparatus according to claim 24, wherein,

the information obtaining unit that obtains the biological information is at least one of an electrocardiograph, a sphygmograph, and a body motion monitor, and

the control unit controls the magnetic field application unit in such a manner that the imaging is executed during the first period in response to the biological information, and the imaging is suspended during the second period in response to the biological information.

27. The nuclear magnetic resonance imaging apparatus according to claim 25, wherein,

the information obtaining unit that obtains the positional information of the FOV comprises an encoder provided on the transport unit, and obtains the positional information of the FOV on the examined subject based on information from the encoder and a frequency of the high-frequency magnetic field.